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THE JOURNAL

OF

ANIMAL BEHAVIOR

VOLUME 5, 1915

EDITORIAL BOARD

Madison Bentley

University of Illinois

Harvey A. Carr

The University of Chicago
Editor of Reviews

Gilbert V. Hamilton

Santa Barbara, California

Samuel J. Holmes

The University of California

Walter S. Hunter

The University of Texas

Herbert S. Jennings

The Johns Hopkins University

Edward L. Thorndike

Teachers College, Columbia University

Margaret F. Washburn

Vassar College

John B. Watson

The Johns Hopkins University

William M. Wheeler

Harvard University

Robert M. Yerkes, Harvard University

Managing Editor

Published Bi-monthly

at Cambridge, Boston, Mass.

HENRY HOLT & COMPANY

34 West 33d Street, New York

G. E. STECHERT & CO., London, Paris and Leipzig, Foreign Agents

Entered as second-class matter March 7, 1911, at the post-office at Cambridge, Boston,
Massachusetts, under the act of March 3, 1879

^

30

CONTEXTS OF VOLUME 6, 191 5
Number i, January-February

pages

Vincent, Stella B. The white rat and the maze problem.

I. The introduction of a visual control 1-24

Yerkes, Robert M., assisted by Eisenberg, A. M. Prelimi-
naries to a study of color vision in the ring dove Tutor
risorius 25_43

White, Gertrude M. The behavior of brook trout em-
bryos from the time of hatching to the absorption of
the yolk sac 44-60

Bittner, L. H., Johnson, G. R., and Torrey, H. B. The

earthworm and the method of trial 61-65

Hubbert, Helen B. Elimination of errors in the maze. . . . 66-72

McDermott, F. Alex. Note on the reaction of the house-
fly to air currents 73_74

Financial statement for 1914

Number 2, March- April

Coburn. Charles A., and Yerkes, Robert M. A study of
the behavior of the crow Corvus Americanus And. by

the multiple choice method 75-114

DeVoss, J. C, and Ganson, Rose. Color blindness of cats, 115-130
Vincent, Stella B. The white rat and the maze problem.

II. The introduction of an olfactory control 140-157

Cole, L. W. The Chicago experiments with raccoons. . . . 158-173

Number 3, May-June

Vincent, Stella B. The white rat and the maze problem.

III. The introduction of a tactual control 175-184

Yerkes, Robert M., and Coburn, Charles A. A study of

the behavior of the pig Sits scrofa by the multiple choice .

method 185-225

Schwartz, Benjamin, and Safir, S. R. Habit formation in

the fiddler crab 226-239

Rau, Phil. The ability of the mud-dauber to recognize

her own prey (Hymen) 240-249

(JHo b

CONTENTS iii

Hargitt, Charles W. Observations on the behavior of

butterflies 250-257

Yerkes, Robert M. The role of the experimenter in com-
parative psychology 258

Number 4, July-August
Walton, Arthur C. The influences of diverting stimuli

during delayed reaction in dogs 259-291

Barber, Alda Grace. The localization of sound in the

white rat 292-31 1

Hunter, Walter S. The auditory sensitivity of the white

rat 3I2-329

Dodson, J. D. The relation of strength of stimulus to

rapidity of habit-formation in the kitten 330~336

Turner, C. H. The mating of Lasius nigcr L 337~340

Number 5, September-October

Mast, S. O. The behavior of fundulus, with especial refer-
ence to overland escape from tide-pools and locomotion
on land 341-350

Sturtevant, A. H. Experiments on sex recognition and

the problem of sexual selection in drosophila 35I-366

Vincent, Stella B. The white rat and the maze problem.
IV. The number and distribution of errors — a com-
parative study 36/-374

Redfield, Elizabeth S. P. The grasping organ of Dendro-
cocluni lacteum 375-38o

Essenberg, Christine. The habits and natural history of

the backswimmers Notonectidae 381-390

Shepherd, W. T. Some observations on the intelligence

of the chimpanzee 39x-396

Essenberg, Christine. The habits of the water-strider

Gcrris remiges 397_4°2

Yerkes, Robert M. Maternal instinct in a monkey 403-405

Hunter, Walter S. A reply to Professor Cole 406

Number 6, November-December
Holmes, S. J. Literature for 1914 on the behavior of the

lower invertebrates 407~4I4

iv CONTENTS

Turner, C. H. Literature for 1914 on the behavior of

spiders and insects other than ants 415-445

Vincent, Stella B. Literature for 1914 on the behavior of

vertebrates 446-461

Thorndike, E. L., and Herrick, C. Judson. Watson's

" Behavior " 462-470

Herrick, C. Judson. Dunlap's " An Outline of Psycho-
biology " 471-472

Hunter, Walter S. Hachet-Souplet's " De l'Animal a

l'Enfant 473-474

Hunter, Walter S. Kafka's " Einfiihrung in die Tiers-

psychologie " 475-479

Rahn, Carl. Cesaresco's psychology and training of the
horse 480-481

Subject and Author Index

VOLUME 5

Original contributions are marked by an asterisk (
lexander, C. P. Biology of flies, 441.

Allee. W. C. Reactions of isopods,
407, 413,

* Amphibians, literature on, 449.
Andrews, E. A. The Bottle- Animal-
cule, 408, 413.

*Ant, mating in, 337.
fApe. intelligence of, 391.

* Association, literature on, 440.
Aubin, P. A. The buzzing of diptera,

436, 441.

R

ack. Life history of melon-flv, 441.

Banta, A. M. Sex recognition in frog,
454, 460.
*Barber, A. G. Audition in rat, 292.

Basset, G. C. Habit formation in rat,
456, 460.

Baumberger, J. P. Longevity of in-
sects, 438, 441.

Baunacke, W. Function of statocyst,
408, 413.

Becker, G. G. Migration in Seiara,
433, 441.

Beutel-Eeepen, v. Senses of bees, 416,

441;
ancestry of bees, 428, 441.
Bingham, H. C. Definition of form,
446, 460.
*Bird, literature on, 450.
*Bittner, L. H. Habit in earthworm,
61.
Bloeser, W. Life history of Siphona,
429, 441;
a parasite of Siplwna, 435, 441.
Boving, A. Larva of Hydroscapha,

441.
Branch, H. E. The biologv of Entyla,

427, 441.
Bromlev, S. W. Food of asilids, 429,

44i.
Browne, F. B. Life history of beetle,

441.
Buddenbrock. W. v. Orientation of
crab, 408, 413.
^Butterfly, behavior of, 250.

Cameron, A. E. Biology of leaf-
miner, 441.
Campion, H. Dragon flies, 429, 441.
Carr, H. Selection in animal learning,

459, 460.
*Cat, color-blindness in, 115;
*habit formation in, 330.
Cesaresco, E. M. " Psvchologv of

Horse," 480.
Chapman, T. A. Life history of Agri-
ades, 442.
"Chimpanzee, intelligence of, 391.
Coad, B. R. Behavior of boll weevil.
429, 442.
*Coburn, C. A. Behavior of crow, 75 ;
*behavior of pig, 185;
behavior of crow, 450, 460.
*Cole, L. W. Experiments with rac-
coons, 158;
*reply to, 406.
Comstock, A. B. Cricket music, 436,

442.
Cowles, E. P. Reactions of starfish,
408, 413.
*Cral). tiddler, habit in, 226.
Craig, W. Doves reared in isolation,
454, 460.
*Crow, behavior of, 75.
Cummins, H. A mite in the cat, 435,
442.

Davidson, J. Habits of Aphis, 439,
442.
^Delayed reaction, in dog, 259.
Demuth, G. S. Temperature of honey

cluster, 438, 443.
*DeVoss, J. C. Color-blindness in cat,

115.
Dice, L. R. Movements of daphnia,

408, 413.
Disease, relation of insects to, 434;
*spreading, literature on, 434.
*Dodson, J. D. Habit formation in kit-
ten, 330.
*Dog, delayed reaction in, 259.
Draper, B. M. Box for insects, 440,
442.
*Drosophila, sex recognition in. 351.
Dunlap, K. " Psychobiology," 471.

VI

INDEX

"Duration of life, literature on, 438.
Dyer, H. G. Life history of caterpil-
lar, 442.

"[7 arthworm, habit

formation in, 61.

*Eisenberg, A. M. Color vision of ring-
dove. 25.
Emery, W. T. Biology of Simulium,
429, 442.
"Essenberg, C. Habit in backswimmers,
381;
"habit in water-strider, 397.
Ewald, W. F. Light reactions of in-
vertebrates, 409, 413.

Fabre, J. H. The mason-bee, 426,
442.
Fasten. X. Fertilization in the cope-

pod, 409, 414.
Ferton, C. Instinct of bee, 442.
"Fish, behavior of, 44, 341.

literature on, 449.
*Fly, reaction of, 73.
Frevtag, F. Vision in animals, 449,

*460.
Frohawk, F. W. Sleeping attitude of
butterflies, 439, 442.

Galiano, F. F. Chemotaxis of Para-
mecium, 409, 414.
*Ganson, R. Color-blindness in cat,

115.
Gates, B. N. Temperature of bee col-
ony, 439, 442.
Girault, A. A. North American in-
sects, 429, 442.
Graham-Smith, C. 8. Flies in relation

to disease, 434, 442.
Guvenot, E. Behavior of fruit fly,
' 429. 442.

k

*T J abit, formation of, in earthworm.
11 61;

*in fiddler crab, 226;
*and strength of stimulus, 330 ;
*in hemiptera, 381 ;
*in water-strider, 397;
"literature on, 453.
Haehet-Souplet, P. " From Animal to

Child," 473.
Haempel, O. Vision in fishes, 449, 460.
Haenel, II. Elberfeld horses, 458, 460.
Hahn, W. L. Hibernation, 454, 460.
Hamilton, G. V. Sexual tendencies in

monkeys, 453, 460.
Hanliam, A. \Y. Flowers and insects,
442.

"Hargitt, ('. W. Behavior of butterfly,
250.
Harms. B. Insects and diseases, 434,

442.
Hartung, YV. J. Life history of melon

fly, 428, 444.
Hays, G P. Orientation of Porcellio,

' 413, 414.
Headlee, T. J. Temperature, moisture,
and insects, 442.
*Hearing, in rat,' 292, 312;
"literature on, 419, 451.
Heath, E. F. Food of phalangid, 429,
442.
"Herrick, C. J. Watson's " Behavior,"
462;
*Dunlap"s " Psychobiology," 471.
Herrick, G. W. ' Apple pest, 428, 442.
Herwerden, M. A. v. Vision in daph-

nia, 409, 414.
Hess, C. Vision in invertebrates, 409,

414.
Hewitt, G. Habits of Scatophagy 42'.>.

442.
"Hibernation, literature on, 4oi..
"Holmes, S. J. Behavior of lower in-
vertebrates, 407.
Houser, J. S. Life history of Con-

wentzia, 429, 442.
Howard, S. M. Honey bees, 439. 442.
"Hubbert, H. B. Errors in maze. 66;
time and distance in learning, 458,
460.
Hudson, G. V. Memory and reasoning

in wasp, 440, 442.
Hueguenin, J. C. Insectivorous larva,

430, 443.
Hungerford, H. B. Notes on coleop-

tera, 427, 445.
Hunter, S. J. Sand fly and Pellagra,

435, 443.
"Hunter. W. S. Hearing in rat. 312;
"reply to Cole, 406;
hearing in white rat, 451, 460;
"Haehet-Souplet's " From Animal to

Child," 473;
"Kafka's " Introduction to Animal
Psychology," 475.
Huxlev. J. Courtship of grebe, 454,

460.
Hyde, R. B. Inheritance of length of
life, 442.

*T deational behavior, in crow, 75;

"in pig, 185;
*in dog, 259.
"Insects, sex recognition in. 351;
-natural history of, 3S1 ;

INDEX

vn

•literature on, 415.
"Instinct, mating, in ant, 337 ;

*sex recognition, 351;

*maternal, in monkey, 403 ;

*mating, 426;

*defensive, 429;

•literature on, 453.
"Intelligence, of chimpanzee, 391.
"Invertebrates, literature on, 407.
Isley, D. Biology of wasp, 427, 443.

Jennings, A. H. Insects in relation
to Pellagra, 443.
•Johnson, G. R. Habit in earthworm,
61.
Johnson, H. M. Form perception, -±46,

460.
Jones, T. H. Life history of Lauron,

443.
Jordan, H. Beflexes of Holothurians,

410, 414.
Just, E. E. Habits of worm, 410, 414.

Kafka, G. Animal psychology, 410,
414;
" Introduction to Animal Psychol-
ogy," 475.
Kanda, S. Orientation of paramecium,
410, 414;
geotropism of worm, 411, 414.
Kellogg, C. E. Graphic maze, 458,

461.
King, L. A. L. Habits of mites, 426,

443.
Kolmer, W. Vision in fishes, 449, 460.
Kiihn, W. Biology of snail, 411, 414.

Lashley, K. S. Persistence of an in-
stinct, 454, 460.
Laurens, H. Reactions of amphibian

larvae, 449, 460.
•Learning, literattire on, 456.
Lillie, F. E. Habits of butterfly, 432,

443.
Lloyd, L. Insects and disease, 434,

443.
Lohner, L. Death feigning in arthro-
pods, 411, 414.
Lovell, J. H. Oligotropism of bee, 417,

443;

vision in bees, 424, 443.
Ludlow. C. S. Insects and disease,

434, 443.
Lund, E. J. Food of Bursaria, 411,

414.

MacGregor
learning

acGregor, M. Learning and re-
lg in mice and rats, 456,
460.
Maday, S. v. Tbinking in man and

horse, 451, 460.
*Mast, S. O. Behavior of fundulus,
341;
orientation in Euglena, 412, 414.
•Mating instinct, in ant, 337.
•Maze, for rat, 1, 140, 175, 367;

•errors in, 66.
•McDermott, F. A. Reaction of house
fly, 73;
vision, in insects, 426, 443.
Mclndoo, N. E. Smell in insects, 421,

443.
•Memory, literature on, 440.
Merrill, D. E. Food of Clerid larva,

430, 443.
Metalnikov, S. Choice of food by Para-
mecium, 412, 414.
•Method, maze, 1, 140, 175, 367;

*in comparative psychology, 258.
•Migration, of fundulus, 341.
Moekel, P. The Mannheim dog, 457,
460.
•Monkey, maternal instinct, in, 403.
Morgulis, S. Hearing in dog, 451, 460;
Pawlow's theory of nerve functions,
459, 460.
Muir, F. Insect parasitism, 435, 443.
•Multiple choice method, for crow, 75 ;
•for pig, 185;
Murphv, R. C. Reactions of spider,
443.

'N

atural history, of wasp, 240;
•of backswimmer, 381.
^Nicholson, C. Respiration of insects,

443.
Noyes, A. A. Biology of trichoptera,
432, 443.

0

'Kane, C. Experience with insectary,
440, 443.

Orton, J. H. Food-taking mechanisms,
412, 414.

Palmer, M. A. Life history of lady
beetle. 429, 443.
^Parasitism, literature on, 435.
Parker, J. R. Life history of root

louse, 443.
Pax, F. Natural history of actinians,

412. 414.
Peairs, L. M. Temperature ana insect

life. 438, 444.
Pearl, R. The brooding instinct, 455,
460.

Vlll

INDEX

Pearse, A. S. Habits of fiddler crab,

412, 414.
Pemberton. Life history of melon fly,

441.
Phillips, E. F. Temperature of honey

cluster, 438, 443.
*Phototropism, in earthworm, 61.
Pieron, H. Thinking animals, 458,

460.
*Pig, behavior of, 185.
Poulton, E. B. Marriage in wasp, 444.
Powers, E. B. Reactions of crayfish,

412, 414.

Putter, A. Sensibility of protozoans,

413, 414.

•R.

.accoons, experiments with, 158.
*Rahn, C. Cesaresco's " Psychology of

Horse," 480.
*Eat, reactions to maze, 1, 140, 176,
367;
•hearing in, 292, 312.
*Rau, P. Behavior of wasp, 240.
Ran, P. and N. Longevity of moth,

438, 444.
Reasoning, in wasp, 440, 442.
*Redfield, E. S. P. Grasping organ in

dendrocoelum, 375.
Regen, J. Sex behavior of cricket, 436,

444.
Rilev, W. A. Insects and disease, 434,
"444.
*Ring-dove, color vision in, 25.
Risser, J. Smell in amphibians, 452,

461.
Robertson, C. Oligotrophy of bee, 416,

444.
Rogers, St. A. Scent of butterflies,
444.

Oafir, S. R. Habit in crab, 226.
Sanderson, E. D. Temperature and in-
sect life, 438, 444.
Schinz, J. Learning and relearning in

mice and rats, 456, 460.
Schmidt, P. Catalepsy in Pliasmides,

444.
Schroeder, C. The reckoning horses,

458, 461.
"Schwartz, B., Habit in crab, 226.
Schwarz, E. Hearing in moths, 419,

444.
Severin, H. H. P. and H. C. Reactions

of fruit-fly, 415, 444.
*Sex recognition, 351.
Shannon, R. C. Habits of Tachimdae,

444.

bnarp, R. G. Nervous system of in-
fusoria, 413, 414.
Shelford, V. E. Evaporation and in-
sect behavior, 439, 444;
modification of behavior, 452, 461;
animal community, 433, 444.
^Shepherd, W. T. Intelligence of chim-
panzee, 391;
hearing in cats, 451, 461.
Sherman, A. Feeding humming birds,
455, 461.
•Smell, in rat, 140;

•literature on, 421, 452.
*Sound production, literature on, 436.
*Spiders, literature on, 415.
Strand, E. Nest of wasps, 427, 444.
Strong, R. M. Behavior oi Herring-
gull, 456, 461.
•Sturtevant, A. H. Sex recognition in
drosophila, 351.
Szymanski. J. S. Habit formation in
rat, 447, 461.

Tashiro, S. Reactions of isopods,
407, 413.
*Thorndike, E. L. Watson's - Be-
havior," 462.
*Torrev, H. B. Habit in earthworm,
61.
orientation of Porcellio, 413. 414.
*Touch, in rat, 176.
Tower, D. G. Life history of Prose-

paltella, ^4l.
Triggerson, C. J. Courtship of Dryo-
phanta, 426, 444.
*Tropisins, literature on, 415.
•Trout, behavior of, 24.
Trowbridge, C. C. Flocking habits of

birds, 455, 461.
Tugman, E. F. Vision in sparrow,
450, 461.
^Turner, C. H. Mating in ant, 337;
•behavior of spiders and insects, 415;
hearing in moths, 419, 444.
Tyler, W. M. Nest life of brown
creeper, 456, 461.

u

rban, C. Life history of Kaefer,
444.

Venerables, E. P. Food habits of
saw-fly, 430, 444.
•Vertebrates, literature on, 446.
*Vincent, S. B. White rat in maze, 1,
140, 175, 367;
•behavior of vertebrates, 446.
*Vision, of rat, 1 ;

*color, in ring-dove, 25;
•color-blindness, in cat, 115;

INDEX

IX

in invertebrates, 400, 414;
"literature on, 424.

Wadsworth, J. T. Life history of
gall-fly, 444.
* Walton, A. C. Delayed reaction in
dog, 250.
Wardle, R. A. Life history of Zen-
tilla. 444.
'""Wasp, behavior of, 240.

Waterson, J. Bird lice, 4:50. 444.
*Water-strider, habits of, 397.
Watson, J. B. Circular maze with
camera lucida, 45!>. 4til ;
" Behavior." 402.
"Webster, R. L. Life history of Cono-

trachelus, 434, 445.
Weiss, H. B. Pain in insects, 416,
445;
eggs of Paratenodera, 427, 445.
Welch. P. S. Life history of Hydro-

myza, 420, 445.
Wevland, If. Chemotaxis oi Colpi-
' (limn. 413, 414.

*White, <L M. Behavior of trout. 44.
Williams, I'". X. Habits of wasps. 427,

445.
Wolcott, (J. X. Life history of wasp.

434, 445.
Wolff, P. Temperature reactions of

butterflies. 440, 445.
"Worm, grasping organ in, 375.
Wradatsch, G. Hibernation of Kaefer,

445.

*\t erkes, P. M. Color vision of ring-
1 dove, 25 ;
*behavior of crow, 75;
"liehavior of pig, 185;
*role of the experimenter, 258;
"instinct in monkey, 403;
Franklin Field-Station, 450, 461;
the graphic maze, 458, 461.

Zagorowski, I'. Thermotaxis in Para-
mecium. 413, 414.
Zetck. J. Fly and disease, 434, 445.

JOURNAL OF ANIMAL BEHAVIOR

Vol. 5 JANUARY-FEBRUARY, 1915 No. 1

THE WHITE RAT AND THE MAZE PROBLEM
I. THE INTRODUCTION OF A VISUAL CONTROL

STELLA B. VINCENT

From the Psychological Laboratory of the University of Chicago

WITH EIGHT FIGURES

Small1 was the first to emphasize the importance of the kin-
aesthetic sensations in the life of the rat, while Professor Wat-
son,2 by eliminating the senses one by one, showed that in learn-
ing the maze, at least, senses other than the kinaesthetic and
tactual can easily be dispensed with. The natural conclusion
was drawn that in such problems these animals use vision,
hearing, olfaction, etc., but slightly if at all.

The recognition of the functional value of the kinaesthetic
sensations and the dominant part which they play in such a
bit of learning as this has been of the greatest possible value.
The question is immediately raised, however, of what intrinsic
value are eyes, ears, etc., if not for learning. Or, the question
might be put in this way: Is this motor co-ordination and the
mode of learning entirely different from those other habits which
the rat acquires naturally in its usual environment.

Professor Watson himself anticipated further work when he
says, " We have supported everywhere the negative conclusions
of Small. We, no more than he, offer positive evidence that
the kinaesthetic are the only necessary factors in the maze
association. Both of us alike used the method of elimination
We feel that we are now in a position to begin the

1 Small, W. S. Development of the Young White Rat. Am. Jour. Psychol.,

vol. 11, p. 234. 1899.

2 Watson, J. B. Kinaesthetic and Organic Sensations. Psychol. Rev. Mon.

Sup., vol. 8, no. 2. 1907.

2 STELLA B. VINCENT

study of the positive aspects of the problems offered by the
behavior of the rat in forming the maze association." 3

It was this positive aspect of the situation which formed the
basis for this study. Our contention was that other senses
might enter into the learning of such a problem and modify it.
We believed that the true path and the false in the maze might
be made to differ so in brightness, in olfactory qualities, in
tactual values, etc., as to affect the establishment of the habit.
Our object was to find out if the learning process was thus
affected and in what particular ways. The first experiments
were concerned with an attempt to introduce sight as a control
in the formation of this habit. The maze as ordinarily con-
structed and as used by Professor Watson is all of wood and of
one color and is not favorable for the use of vision. The sides
of the runways are high enough to prevent any visual help from
outside unless from above. It has been shown many times that
human subjects under such conditions find it difficult to obtain
or to use visual clues. Ours was not the first attempt to intro-
duce visual control in the maze. Others had tried the same
thing in different ways but the stimuli which they used were
ineffective and the investigators did not carry their experiments
far enough to make any final statements. Although so much
has been done with rats the proof of their ability to use vision
in any exact way was not very conclusive.

PREVIOUS WORK

The previous lines of experimental evidence as to the effective-
ness of vision are several: first, the comparison of the time of
learning and speed in running of normal rats trained and tested
in the dark and light respectively; second, a comparison in the
same respects of normal and blind animals.

Professor Watson based his conclusions, as to the uselessness
of vision in the maze, upon the fact that normal rats trained in
the light could run the maze as quickly in the dark ; that normal
rats could learn the maze in the dark and acquire as rapid speed
as in the light ; and that blind rats could learn the maze and run
it with a speed equal to that of their normal companions. It
has been shown by others that it is scarcely fair, in such a situ-
ation, to make speed the sole criterion of the learning process.

3 Ibid, p. 96.

THE WHITE RAT AND THE MAZE PROBLEM 3

It must also be remembered that many experimenters who have
attacked this problem fail to separate in their detailed results
and conclusions the typical learning process, which is shown
chiefly in the first few trials, and the perfecting of the automa-
tism, the acquisition of speed, which follows. Possibly Pro-
fessor Watson's work may bear this criticism.

The third line of evidence comes from attempts to introduce
visual clues at critical points in the maze. Small fixed colored
posts at such places and also varied the direction of the light
which fell upon the maze. He concluded that the use of vision
was not shown by any discrimination or recognition.4 Miss
Allen marked the path for another rodent, the guinea pig, with
colored cards but her results were negative.5 Professor Watson,
in the case of one rat, used colored lights with no perceptible
effect.6 All of these objects were stationary. It is possible
that moving objects might have been better. Rats are hyper-
metropic and such animals may well fail to respond to near
objects in any discriminating way.

The fourth form of attack upon the visual powers of these
animals consists in observations of the animals and experiments
with them in the dark and in the light respectively and noting
the amount of activity and the accuracy of movement. Opin-
ions differ slightly here. Slonaker shows in his studies of the
activity of the white rat that its greatest period is during the
night, beginning with the first shadows of afternoon. He says
that the average distance traveled is five miles per night as
against one-tenth of a mile per day and concludes that light
normally does have an influence upon the animal's activity.7
A few of Yerkes' dancers seemed somewhat disturbed by tests
in the darkness.8 Miss Allen found that her guinea pigs made
more random movements in the darkness than in the light.9
So far as I know no one has followed this lead further. It
would be an interesting bit of experimental work.

4 Op. cit.

5 Allen, Jessie. Association in the Guinea Pig. Jour. Comp. New. and Psy-

chol, vol. 14. 1904.

6 Op. cit., p. 43.

7 Slonaker, J. P. The Normal Activity of the White Rat at Different Ages.

Jour. Comp. Nenr. and Psychol., vol. 17, p. 342. 1907.

8 Yerkes, R. M. The Dancing Mouse. P. 189. 1907.

9 Op. cit.

4 STELLA B. VINCENT

The fifth line of proof lies in the comparison of blind and
normal animals as to their accuracy of movement. In the
experiments reported in Orientation in the Maze where, by
means of a removable section, the maze could be lengthened
and shortened there was a blind animal which had trouble with
turns which the normal rats made correctly. The authors say
of some other (normal) animals, ' Since two out of the eight
animals made eight out of the nine unquestioned immediate
orientations we are willing to admit the possibility of the use
of distance sense data in their cases." 10 Miss Richardson in
some jumping tests with rats, where both direction and dis-
tance of the jump were varied independently of each other and
also varied from habitually established norms, concluded that
the visual stimulus furnished a control as to the direction of
the jump but failed to afford any accommodation to changes
in distance. Concerning some tests with problem boxes, she
says they afforded no conclusive evidence as to the functioning
of visual impulses. ' The lack of vision, however, was disad-
vantageous in proportion as the problem demanded finely co-
ordinated and narrowly localized movements." "

The sixth method of investigation is more directly concerned
with the sense itself. The Watsons concluded from experiments
with spectral lights that there is good if not conclusive evidence,
since green was not used, that the responses were made to differ-
ences in intensity and not quality. Similarly Miss Weidensall
showed in a critique of discrimination that in experiments with
black and white the white was twice as effective as the black
and that in most discrimination experiments with two objects
only one of the objects may have any regulative control, the
other being neglected.

The use of sight by some animals, as birds and monkeys, is
admitted in connection with such problems but we have con-
fined this report to rodents whose vision is of a common type.

The following views are held as to the place of vision in the
labyrinth problem: (a) The control is kinaesthetic par excel-
lence, coupled probably with tactual and static and possibly
with organic sensations; (b) Vision may have a tonic stimulating

10Carr, Harvey, and Watson, J. B. Orientation in the White Rat. Jour.

Comp. Neur. and Psychol., vol. 18, p. 27. 1908.
11 Richardson, Florence. A Studv of the Sensory Control in the Rat. Psy-

chol. Rev. Mon. Sup., vol. 12. 1910.

THE WHITE RAT AND THE MAZE PROBLEM 5

effect or it may serve merely for general orientation; (c) Vision
is not for perceptual purposes — ' The rat does not hang his
associations upon gross and obvious (visual) objects;" (d) Sight
may lessen random movements; (e) It may give general direc-
tion if not accurate distance; (f) Vision may even be a hin-
drance in such problems.

In a previous paper12 facts have been given which show that
the rat's vision is weak. It may be possible that a rat does
not discriminate stationary objects and it is probable that bright-
ness is the most effective factor. In this work, however, there
was no attempt made to substantiate such opinions or to eval-

n

■L

FOOD BOX

J

Fig. 1. Plan of maze

uate the visual sense. The only interest lay in the attempt
to see whether vision could not be introduced into the laby-
rinth problem as a control and if this could be done then to
determine what was its effect upon the establishment of the
automatism.

APPARATUS AND MODE OF EXPERIMENTATION

The maze used was the modified Hampton Court Maze which
Professor Watson describes in " Kinaesthetic and Organic Sen-
sations." 13 Indeed it was one of the same mazes which he used
in his experiments. The only change in the construction was

"Vincent, S. B. The Mammalian Eye. Jour, of Animal Behavior, vol. 2,

no. 4, pp. 249-255. 1912.
13 For detailed description see "Kinaesthetic and Organic Sensations," op. cit.,
p. 16-18.

6 STELLA B. VINCENT

the blocking of pathway "C" at the farther end to make it a
blind alley instead of a longer way around (Fig. 1). The essen-
tial difference, however, was the fact that the true pathways
and the blind alleys were made to differ as far as possible in
brightness. Black cardboard lined and covered the one and a
very white paper lined the other. In the later experiments
black and white enamel paint was used on the floor and sides
while black cardboard covered the top of the black pathway.

The problem box for the discrimination tests was a paste-
board box 12' x 12' x 9', with round tubes inserted at the floor
level in opposite sides. One tube was white, with white oiled
paper pasted in the upper third to increase the brightness, the
other tube was black. The tubes were not straight but were
bent in the middle at right angles to prevent any entering light
from the end of the open tube from giving a clue. Only the
tube of the brightness for which the animal was being trained
remained open at the end. The box was turned in an irregular
order to prevent choice by position.

The only stimulus to the activity was the reward of food at
the completion of a successful run in the maze or the choice of
the right exit in the problem box. Five animals usually consti-
tuted a group.

Some records were first made upon the maze as it originally
stood with walls and floor of unpainted pine. A group of un-
trained rats was given 50 trials covering a period of 18 days.
These rats were then taken over to the problem box where they
were given 50 trials. Then another group of rats which had
previously been given 50 trials on the problem box was put in
the maze for 50 trials. Ten trials a day were given in the prob-
lem box, but on the maze only 3. These records are referred to
as the normal records and furnish the standard for comparison.

The maze was then made black and white, the true path black
(see dotted line, Fig. 1) and the blind alleys white. Two other
groups of rats learned both it and the problem box in alternation
as above. This maze is sometimes spoken of as the black maze.

The third change consisted in making the true path white
and the cul de sacs black and using two new groups of animals
in the manner described above. This maze is occasionally re-
ferred to as the white maze.

In brief the experiments upon which this discussion is based
are as follows:

THE WHITE RAT AND THE MAZE PROBLEM 7

1. Normal maze records — (a) rats trained; (b) rats untrained;
(c) discrimination experiment for (a) ; (d) discrimination experi-
ment for (b).

2. Black-white maze records, true path black — (a) rats trained;
(b) rats untrained; (c) discrimination experiment for (a); (d)
discrimination experiment for (b).

3. Black-white maze records, true path white — (a) rats
trained; (b) rats untrained; (c) discrimination experiment for
(a) ; (d) discrimination experiment for (b) .

The reason for the use of the two pieces of apparatus was
this: After the first group of animals had learned the black
and white maze we wished to see whether it was really bright-
ness to which the animals were reacting. The other experiment
— the box with the black and white exits — was devised, there-
fore, to see whether the brightness experience carried over.
Then the suggestion arose that the differences which were seen
in the conduct of the rats might not be due to brightness alone
but that some of the changed results might be a general effect
of training. To meet this criticism not only were the experi-
ments doubled by the use of both maze and box, but groups
of animals trained upon the box afterward learned the maze
and animals trained upon the maze learned the box. In order
to make the normal group comparable the training also had to
be included in their case although the maze was uniform in
brightness.

It may be objected that the contact values of the two media,
paper and cardboard, used in the first experiments differed and
that the air pressure, sound qualities, etc., were not the same
in the two paths. The work will have to face that criticism.
The training tests upon the problem box and the succeeding
experiments upon it seemed to show, however, that it was really
brightness to which the animals were reacting. The six blind
animals used upon the black-white maze furnished a further
control. If there were other sensory elements fused with vision
it does not affect the value of the experiment since this is nor-
mally true and since it was the visual element which was the
variable one.

The tables submitted show only the time of a total reaction
and the errors. Leaving the true path, entering a cut de sac,
was counted as one error. Returns could not be counted as
errors since part of the maze was covered. For the same reason

8

STELLA B. VINCENT

we can say nothing about the total distance traversed. All of
the tables upon which this discussion is based would gladly be
given but it is impossible within the limits of this paper. The
results will be shown by means of graphs upon which the dis-

is

10

IS

Fig. 2. Learning curves of 10 rats on the normal maze
Time, Errors

cussion will be based and only such other additional data will
be given as is necessary.

Four months' work was put upon this problem in 1907.
Nothing more was attempted until it was resumed in 1910.
None of the first experimentation is reported here, since it was
all repeated in the later series under stricter control and with
similar results.

THE WHITE RAT AND THE MAZE PROBLEM 9

NORMAL MAZE

There is no need in this place of giving a long description of
the general behavior or giving the individual details of the
experimentation with the groups of rats in the normal maze.
The conduct differed in no respect from that noted by so many-
others. The curve of learning may be seen in Fig. 2. The
description of the mode of plotting this curve may be found in
my monograph on the tactile hair.14 The actual time and the
number of errors for the first 10 trials are given in Table 1.
These records are made from the combined records of two
groups of animals, one of which had been previously trained
upon a black- white discrimination box. As this training proved
to have so little effect upon the subsequent maze record these
pages will not be burdened with the numerical results.

TABLE 1

Time and Error Records, First Ten Trials, on Normal and

Black-white Mazes

Time Errors

Normal Black-white
Trial Maze Maze

1 1804 sec. 1342 sec.

2

966

3

542

4

847

5

233

6

193

7

63

8

49

9

37

10

33

Normal

Black-white

Maze

Maze

14.9

7.5

11.9

4.3

10.4

3.

7.4

3.

4.1

1.6

3.5

1.

1.6

.5

1.4

.2

1.5

.5

1.1

.4

413
254
211

98

72

37

48

54

39

The training upon the box, on the whole, seemed slightly
disadvantageous to the group of animals which later learned
the original maze. There was not so high a degree of accuracy
as evidenced by the number of errors and the average time
taken per trial was longer than that of the other group which
had had no training. To account for this is not difficult when
we consider that the problems are distinctly different. In the
one case there is an immediate reaction, in time too brief to be
taken, to a situation which offers but two alternatives and in
which brightness is the determining factor. In the other case

14 Vincent, S. B. The Function of the Vibrissae in the Behavior of the White
Rat. Behavior Mon., vol. 1, no. 5, p. 15. 1912.

10 STELLA B. VINCENT

there is a devious way to learn which involves many turns and
the possibility of many false turns. The final escape to food takes
a time which varies from two hours per trial at the beginning
to ten seconds when the problem is learned. The habits set up
by the brightness contrast, whether depending upon discrimi-
nation or not, clearly cannot be carried over advantageously to
a situation where the contrast does not exist. It may easily
be conceived also that the motor habits involved in the simpler
reactions described above for the problem box which bring the
rat immediately to the presence of its food might be disastrous
and delay the acquisition of a reaction depending upon the
co-ordination of a long series of acts and extending over a con-
siderable period of time.

As the learning of this maze has been so fully and freely dis-
cussed before all mention of it will be neglected here and any
facts of interest concerning it will be brought out in the com-
parison of the two mazes which will follow later.

BLACK AND WHITE MAZE

The outcome of the tests on the black and white maze was
noticeably unlike that of the normal maze. The differences were
seen in the behavior of the animals and appear in the numerical
results and the graphs plotted from them. They were con-
firmed and checked by the data furnished by the blind animals
and by the facts brought out in the box experiments.

Success in .such a problem has several measures: (a) the time
taken relative to the total distance, i.e., speed; (b) the number
and distribution of the errors, i.e., accuracy; (c) the time of
learning, i.e., the number of trials in learning; (d) the surplus
values of time and errors; (e) the rate of elimination, i.e., dis-
tribution of effort; (f) the form of the learning curve — a picture
which reveals some of the complex relationships existing among
the various factors. In this paper the burden of proof will be
put upon accuracy and speed, since it was in these two respects
that the greatest divergence was seen. The other criteria, how-
ever, will not be entirely neglected.

In the interest of clearness as well as of time and space, the
results from the four groups of animals, trained and untrained,
for the black and for the white maze, will be combined and
presented as a whole. The differences were unessential. Any
evidence of training being carried over from the box to the

THE WHITE RAT AND THE MAZE PROBLEM 11

black- white maze was so slight that it may be neglected. This
is due, doubtless, to the fact that the two problems were so
dissimilar and that the time on the box was so brief. On the
contrary, there was decided evidence of the effect of training
in animals which went from the black-white maze to the box
but that will be mentioned in another connection. The results
also, when the true path was white and when it was black,
agreed entirely in the essential details and hence they may be
massed. The minor differences will be used only by way of
explanation or illustration.

SPEED

Speed is time as measured by the distance traversed. In
this case it is impossible to state the total distance since the
returns, in the part of the maze which was covered cannot be
counted. However, some evidence can be offered. One of the
first lines of proof is the observed conduct of the animals.

The behavior in the black-white maze was very unlike that
in the normal maze. In the beginning trials there was less
activity, more sluggishness of movement, fewer errors, yet slow
runs. Time and again I find in my notes such expressions as:
" Slow start." "A very slow walk around although without
error." " Very little rapid running." " Slow movement com-
pared with normal maze." " No running and little sniffing at
food-box or anywhere else." " Little running but much actual
sitting still." " Few errors but little running." " Do not seem
at all frightened or curious." " Do not apparently use covered
ways as places of refuge." " Errors do not seem attractive and
there is no blind running which would make the animals blunder
into errors." There was more hesitation seen in these rats.
Even long after the problem was learned they slowed up or
wavered in their running when they came to a cul de sac. Some
typical records, where every move which could be seen was
entered with the time which it took, may serve to indicate the
lesser activity better than a general description.

First Two Records of Rat "1"

May 10th and 11th:
1st trial:
To first corner and back — 10 sec.
About entrance 55 sec.
To first corner 10 sec.
Here 2 min. 30 sec.
Home — remains 9 min. 30 sec.
First corner 15 sec.

12 STELLA B. VINCENT

Second corner 30 sec.

Reaches error "2" in 15 sec*

Reaches error "3': in 5 sec.

Stays here 1 min. 15 sec.

Reaches food box 15 sec.

Reaches error "4" 15 sec.

Reaches error "4" 15 sec.

Reaches error "6" 11 sec.

Reaches error "7" 20 sec.

Back to "6" 1 min.

Back to "4" 10 sec.

Back to food box 10 sec.

Returns to "4" 30 sec.

Returns to "6" 20 sec.

On to "7" 1 min. 45 sec.

Back to "6", here 5 min. 15 sec.

Back to "4" 30 sec.

In "4" and out. Sits here 30 sec.

On to "6" 15 sec.

On to "7" 1 min.

Sits at "7" 3 min. 30 sec.

In "7" and out 30 sec.

Sits here 7 min.

On to food box 15 sec.

Total time 40 min. 22.6 sec.

Errors 2.

2nd trial, rat "1":
Slow start.

Reaches 2nd corner 5 sec.
Reaches error "2" 10 sec.
In and out error "2" 20 sec.
In and out error "3" 10 sec.
Reaches food box 30 sec.
* Reaches error "4" 15 sec.

In and out "4" 30 sec.
Reaches "6" 5 sec. Here 20 sec.
On a short way 30 sec.
Returns to "6". Here 15 sec.
Back to "3" 1 min. 30 sec.
Returns to food box and back to "3" 1 min.
To food box. Here 3 min. 30 sec.
Back to "3". Here 30 sec.
To food box 1 min.
To "4" 15 sec.

Reaches "6" 15 sec. Here 15 sec.
In and out "6" 30 sec.
In alley near 1 min. 45 sec.
Back to "6". Here 45 sec.
Back to "4", to food box, to "3", 30 sec.
Back to "2". Here 1 min.
Back to food box 30 sec. Here 9 min. 30 sec.
On to "4", back to food box 30 sec.
On to "4", back to food box 15 sec.
On to "4", in and out 1 min.
On to "6" 15 sec.
On to "7" 45 sec.
On to food box 15 sec.

Total time 29 min.

Errors 4.

* "2", "3", etc., are the numbers of the blind alleys in the Maze. See Fig. 1.

THE WHITE RAT AND THE MAZE PROBLEM

13

These individual records show the type of behavior described
above, which clearly is not like that seen in the normal maze
in the first and second trials. There, the rats cover three or
four times the distance and make twice the number of errors.
Here, the total distance traversed in the true path in trial one
was 93 ft., making the rate about 2 ft. per minute. It is true
that the rats were not moving all of the time but neither were
the rats in the normal maze although they are far more active.
The total distance covered in the true path in the second trial

Fig. 3.

Learning curves of 20 rats on the black-white maze
Time, Errors

was 135 ft. The rate, therefore, was but little less than 5 ft.
per minute. If the activity had been evenly distributed over
the maze, this rat, in its first trial, should have been in the
false path 18 minutes and in its second trial 13 minutes.

From the figures of the rats in the normal maze I took those
of the rat whose time and error records most nearly approached
the average and computed the total distance, etc., for the first
and second trials in the same way as above. This rat's time was
a little low, so the speed is probably a little high for the first
trial. The first trial showed a total distance covered of 313 ft.
of which 190 ft. was in the true path and 123 ft. was in the

14 STELLA B. VLNCENT

blind alleys. The average speed for the entire distance was a
little over 15 ft. per minute. The total distance for the second
trial was 184 ft. of which 106 ft. was in the true path and 78
ft. in the cut de sacs. The speed then was 27 ft. per minute.
Notice the distribution of the activity in this maze and com-
pare it with that of the black-white maze above.

This slowness might be made more evident by another illus-
tration. The average time of the first trial made without error
for the rats on the normal maze was 45 sec. The average time
of the 20 rats on the black-white maze for the same errorless
trip was 122 sec. It took the latter group over four times as

Fig. 4. Time curves for black-white and normal mazes, last 10 trials
Normal, Black-white

Fig. 5. Error curve for black-white and normal mazes, last 10 trials
Normal, Black-white

long. Returns were not counted in either case but so far as I
can tell they were very few and fairly comparable.

But besides these individual records there are the combined
group averages. The numerical data for the first ten trials has
already been referred to (Table 1). The curves plotted reveal
the same characteristics (Fig. 3). The time curve begins much
lower in the black-white maze but that is because of the fewer
number of errors which decreases the total distance of the run.
These curves do not show the actual number of trials nor the
exact average time for any particular trial. The first two-thirds
of the distance shows the learning process, the last third an
automatism. The ordinary curve where one trial is the unit

THE WHITE RAT AND THE MAZE PROBLEM 15

resembles this in main outlines but the automatic period is
greatly extended. Curves plotted with one minute as the unit
of time do not reveal really significant fluctuations since the
maze can be run in ten seconds. An increase of ten or twenty
seconds scarcely shows on the curve, although the rats are taking
two or three times longer to run. The end of a graph, in which
one trial is the unit, has been magnified and the last ten runs
of the fifty are revealed in a more significant fashion (Figs. 4
and 5). The time curve for the normal maze is considerably
lower than that for the black- white maze. The records show
that the average speed of the last five trials of the rats in the
normal maze is ten seconds better than the speed of the rats in
the black- white maze for the corresponding trials.

Thus the evidence, from the behavior notes, from typical
individuals, from the average speed in the first trials without
error, from the actual speed of individual animals in the true
path, from the numerical results and plotted curves, confirms
the original assertion. Rats in the black- white maze, in experi-
ments continued long past the learning period, maintain a slower
speed than rats in the normal maze. The significance or cause
of this will be discussed later. We will now consider the criterion
of accuracy.

ACCURACY

One of the first things to attract the attention of the observer
who was watching these experiments day by day was the very
few errors which were made. No one who had had any experi-
ence with other mazes could fail to be impressed by it. A number
of animals made their way around several times without error on
the second trial. They went slowly, to be sure, but accurately.
There were no signs of marked avoidance but neither was there
any evidence of direct discrimination. Slow as these animals
were they did not enter many cut de sacs. If a rat by chance
entered one of these blind alleys it did not seem in any hurry
to get out but neither did it linger in it. One rather expected
that the rats would tend to hide or tarry in the side-paths,
especially when the covered ways were the cut de sacs.

The accuracy was apparent from the very beginning and was
not a virtue of slow growth. Whatever influence was at work
it was there from the first. The rats on the normal maze made

10

STELLA B. VINCENT

an average of 14.9 errors the first trial while those on the black-
white maze made only half as many, 7.5.

Notice the difference in the initial height of the error curves
of the two mazes (Figs. 2 and 3). The error curve of the black-
white maze is not like any error curve made for a normal maze
and it is a direct expression of the accuracy. The time curve
which accompanies it, as has been said, is low because of the
fewer errors and not because of more rapid speed.

There is a great decrease in total as well as in beginning errors
from the mark set by the normal maze. The latter maze has to
its credit an average of 66.6 errors per animal or 1.48 per trial
for each rat while the black-white maze gives only 35.6 errors

Fig. 6. Graph showing the point at which the animals made their first trial with-
out error. Each vertical bar represents an animal.' The black represents
those of the black-white maze. This is superimposed upon the white, which
represents the animals in the normal maze.

per animal or .8 per trial. The accuracy is nearly twice as great
in the black-white maze.

' One would naturally expect then, what really is the case,
that the error curve for the black-white maze (Fig. 3) would
reach its lowest level much sooner than the error curve for the
other maze — that the automatism would be more quickly estab-
lished. The figures show that the rats on the black- white maze
made their average first trip without error on the 4.2 trial but
the average for this trip on the normal maze was 8.5. If we
take the first ten trials and compare them we find that the rats
in the black- white maze have an average of 4.2 perfect trips to
their credit while the normal maze has only half that number, 2.
The graph seen in Fig. 6 is made from the records of 20 animals

THE WHITE RAT AND THE MAZE PROBLEM 17

in the black-white maze and of 17 in the normal maze. It shows
the trial at which the zero point was reached and the number
making it at each point. It is perhaps more striking than the
ordinary error curve.

If the errors are so few in the beginning, if the co-ordination
is acquired so quickly, why is it that there is not a greater differ-
ence in the total errors ? This is a question which requires an
answer. The answer is that the final accuracy is less. See the
curves, Figs. 2, 3 and 5. The normal error curve is regularly at
the end of 50 trials below the black-white. What the causes
are which produce this greater final variability is a question
for our future inquiry. The three main points to be emphasized
here are the few beginning errors, the rapid drop to the zero
point and the persistence of errors to the very end.

SURPLUS TIME AND RATE OF ELIMINATION OF TIME

AND ERRORS

Professor Carr argues at length for the value of the rate of
elimination of surplus time and errors as one of the elemental
components of the learning curve which varies independently
from the other components.15 The curves which show elimina-
tion in the experiments here reported are seen in Fig. 7. The
rate of elimination is very similar in the two mazes. There
are, however, some points of contrast.

The time curve for the normal groups exhibits a fairly steady
rate of decline to the 24th trial. Here the final limit is reached,
.4%. The time curve for the black- white group reaches its
final limit of 1.8% on the 9th trial. It then follows the same
course as the curve for the normal maze but with greater varia-
bility. The curve for the black- white maze reaches its level
much sooner but cannot maintain it with the same constancy;
neither can it reach, in the limits of the experiment, the same
low level which the normal curve so easily reaches and maintains.

The error curve of the black-white maze indicates a much
quicker rate of elimination than that of the normal maze. There
is a steady drop till the 6th trial. From this point on there is
only 6% of the errors left to eliminate. It will be remembered
that the black-white maze had fewer errors to eliminate at the

15 Hicks, Vinnie, and Carr, H. A. Human Reactions in the Maze. Jour, of
Animal Behavior, vol. 2, no. 2, p. 98. 1912.

18

STELLA B. VINCENT

beginning. From the 6th trial on, however, the rate of elimi-
nation is below that of the normal maze. For the twenty suc-
ceeding trials the average is slightly above 6% and is only 1%
less than this at the end.

The errors are eliminated more slowly in the normal maze.
This curve does not reach the 6% level until the eleventh trial.

100

10

to

V

bo

SO

HO

3o

2P

10

RATE OF ETU AW/VAT I C/V, TIME AND ERRORS

B/ac/<-W/wt£, Ti'Tne.
A/orm*] 77 n«-

l^ilds.- S

45"

r-^f

So

Fig. 7. Curves showing the rate of time and error elimination in the
black-white and the normal mazes

From here on, however, there is a regular decline until, in the
eighteenth trial, there is only 1% left to be eliminated. The
curve wavers above and below 1% but this is practically the
final level. The black- white maze has five times as much left
to eliminate at the end as the normal maze.

THE WHITE RAT AND THE MAZE PROBLEM 19

BRIGHTNESS

But it may be argued that although the reactions of the rats
in the black-white maze differ from those made in the normal
maze in respect to speed and accuracy, the contributing cause
may not have been the brightness of the runways. In reply it
can only be said that no other difference can be seen in the
experimental conditions. The maze was the same in every
experiment and it stood in the same place. The animals were
from the same breeding cages, were given the same care and
were used by the same person throughout. Tests to prove that
it was the brightness factor, however, were introduced.

The blind animals furnished the best means of control. These
animals were of the same original stock as the others and during
the entire period of experimentation were kept in the cage with
the others. They ran the maze daily with the other rats. They
were put through the box problem but could not learn this as
the rats with vision did. When taken over to the maze they
behaved just as the blind rats in the normal maze behave. The
learning curve for these rats has been plotted and may be seen
in Fig. 8. Compare this curve with that made for the rats in
the normal maze, Fig. 2, and see how nearly identical they are.
Neither resembles at all the curve for the black-white maze, Fig.
3. These blind rats were in good physical condition, active
and strong, and the only observable difference from their com-
panions was in their lack of vision. Is not the conclusion fair
that the contrast in behavior and the different numerical results
of the two groups of animals used in this part of the experiment
were due to the visual situation in the maze ?

The second control was the use of the problem box. Rats
taken from the box over to the normal maze showed no favor-
able effect of general training. The training if anything resulted
unfavorably. The reasons have already been given. Rats
trained on the box when taken to the black-white maze exhib-
ited no unfavorable effects of training but gave some slight
indications that the brightness experience had been an aid.
The slightness of this effect was probably due to the differences
in the essential nature of the two problems and the briefness
of the time in which the animals were in the box.

From the black-white maze to the box, however, the effect
was different. The experience certainly did carry over. The

20

STELLA B. VINCENT

number of trials in learning was one-third less and the total
number of errors was reduced in the same proportion. The
brightness situation must have been responsible for these con-
trasting results. The lengthened period of training on the maze
before attempting the problem box may account for its greater
effectiveness in this case.

Although the conduct described above was influenced by

Fig. 8.

Curves of the blind rats in the black-white maze
Time, Errors

brightness, may there not have been a preference, either in-
stinctive or acquired, for black or for white ? It must be
remembered that the animals in the experiments described may
have been reacting to one color only regardless of any changes
in the maze.

We do not think the reactions were due to preference. If
they had been, there would have been greater differences be-
tween the results of the experiments where the true path was

THE WHITE RAT AND THE MAZE PROBLEM 21

white and those where it was black. The following figures,

taken from many others, show the similarity of the conduct

in the two cases.

Black White

Speed in first 5 trials 8.1 ±4 min. 7.1 ± 3. min.

Final speed .36 ± .1 min. .44 ± .14 min.

Surplus time 46.4 ± 17.6 min. 47.6 ± . 16 min.

Errors in first 5 trials 18.4 ± 4.4 16.5 ± 4.6

Total errors 30 ± 6.4 39.2 ±10.5

There are variations, as will be seen in the above table, but the
balance is now on one side, now on the other side of the scale.

If there were a preference for either black or white the ob-
served behavior would have shown it. There would have been
a lingering in one path rather than the other, a choosing or
avoidance of the covered way, more errors in the one case than
the other. There was no observable conduct which would indi-
cate such a preference either for black or for white. There
must be some other explanation than that of preference.

It is quite possible, even when it is granted that these results
are not due to an instinctive preference, that there may have
been a difference in the relative stimulative effectiveness of the
black and the white paths. Since the effects of training were
the same for both black and white the two groups may be com-
pared directly irrespective of the minor grouping for training.
The results are very similar. The differences are slight indeed
in comparison with the larger differences which were seen be-
tween the black-white and the normal mazes and may be due
to chance.

The white true path seems to give a better initial direction
for the first trials. The animals constituting this group stayed
in the true path more consistently than those of the group where
the true path was black. But the black cut de sacs proved more
attractive in the end, for while following the white path more
total and more average errors were made than while following
the black. A greater number of trials was also necessary in
learning. The white path gave the lowest initial time and the
the lowest final time although the total time of the two mazes
was about equal. Thus while the white path probably gave a
better beginning both in speed and accuracy and the speed as
a whole was better, the record for total and final accuracy was
less than that of the maze when the true path was black.

22 STELLA B. VINCENT

CONCLUSIONS

The conclusion seems justified that such a contrast in bright-
ness between two roads is exceedingly effective with these ani-
mals as they learn the maze. It gives increased accuracy, as
is shown both in initial and total decrease of errors, and in a
decrease of total time. So far it seems advantageous, yet there
was a final inaccuracy greater than normal and a lesser final
speed.

There were no outward signs of discrimination such as marked
avoidance, quick reaction, noticeable change of behavior with
change of stimulus. There was no lingering in one path or
another which might indicate an instinctive preference. There
was only a slower, perhaps a more cautious, activity in which
random movements were inhibited in both initial and early
trials prior to any effects of learning.

If the difference is not due to discrimination, and we have
no evidence from the behavior or the nature of the curve as
ordinarily interpreted that it is, what has caused the different
character of the learning ? All who have worked with animals
know that a stimulus may be effective although not discrimi-
nated. In such a case as this, where two widely differing degrees
of brightness were used, one may have been more directive,
more potent, more attractive than the other. Professor Carr
suggests the phrase ' dominance of a stimulus." This would
tend to attract the animal's attention either to the white or to
the black pathway.

It was said above that the different behavior was seen " prior
to any effect of learning." It must be remembered, however, that
such a problem is solved not by one act but by a series of acts
and hence there may be learning within the trial itself. If the
second trial is influenced by the first, if learning has begun,
where did it begin ? Learning the maze is not at all like a
single act, jumping a certain distance, for example. In a prob-
lem of this kind, which takes so long a time, it clearly may
begin in the first attempt. As the animals enter this maze they
are in the true path be it black or white. The first error, to
the right, is barred almost immediately, probably by kinaes-
thesis. It is seldom made again except in times of great con-
fusion. The true path includes first, a run to the left half way
across the maze, then a turn, and then a clear run across one

THE WHITE RAT AND THE MAZE PROBLEM 23

side. In this side there is the possibility of an error, but not
one into which the animal runs headlong. Hence from the
very first there is a safe experience of a definite sensory sort
which extends over a considerable period of time. Because it
is the first experience, because it proves safe, because the ani-
mal, on the whole, is more in this path than the other, because
his returns are made on this path, these may be some of the
reasons why this path proved more potent, more dominant,
more directive than the other and indicate one way in which
learning may possibly begin.

The term learning needs 'more careful definition. Certainly
there was little evidence of discriminative learning here. If
there was any, it must have occurred chiefly within the first
trial. This possibility may be referred to in a later paper. The
curve showing the rate of elimination of time and errors furnishes
a slight indication of learning to use vision in the interval between
the fifth and the tenth trials, Fig. 7.

If the mere strength of the visual stimulus was the effective
cause of the reinforcement or modification of the usual controls,
then we shall have to conclude that the white path was, on
the whole, the more dominant one. The entire matter then
would hang upon the supposition that the brightness factor in
a certain path had the power to hold or compel the attention
of the animal.

The time taken per trial depends of course upon the speed
and the accuracy. The more errors an animal makes, the more
blind alleys he explores, the longer the time per trial. Thus
the fewer errors would largely account for the lessened initial
time. The contrast between black and white, as will be re-
membered, was as strong as could be produced. The final
inaccuracies might have been due to this contrast effect which
persisted to the end and attracted the attention of the rats
when they were momentarily distracted and thus led them into
errors. The stimulating power of this contrast was no doubt
responsible for the late development of the kinaesthetic con-
trol. But the slow change, when it did come, from reliance
upon vision to the automatism of kinaesthesis left vision free
to be caught, to be attracted by these contrasts, and led the
animals into errors.

The decrease of final speed might have been due to the greater

24 STELLA E. VINCENT

number of errors, yet this is probably not sufficient to account
for the result since the speed was less in cases where there were
no errors. The slower speed was caused, perhaps, by a natural
hesitation because of the attractiveness of the errors and this
was made possible by the slighter kinaesthetic automatism.

Our final conclusion is then that if animals are given two
contrasting paths side by side, differing in brightness, the one
path may prove more dominant and favor accuracy and because
of accuracy a shorter time in the early trials. After the problem
is learned, in the slow turning over to kinaesthesis, when atten-
tion is freed, these sensory factors may still retain their potency
in times of momentary distraction. The result is a less perfect
automatism and a slower speed.

PRELIMINARIES TO A STUDY OF COLOR VISION
IN THE RING-DOVE TURTUR RISORIUS^

ROBERT M. YERKES

Assisted by A. M. EISENBERG

From the Harvard Psychological Laboratory

At the present moment a thorough study of the visual reac-
tions of a few types of birds and mammals is highly desirable.
This paper presents an account of observations on the reactions
of the ring-dove in the Watson- Yerkes color vision apparatus.
The ring-dove was chosen as a subject because of its easy adap-
tation to laboratory conditions and its convenient size. It was
hoped that it might prove an ideal bird for the intensive study
of vision.

As a preparation for the study of color discrimination, the
limits of the spectrum, and the stimulating values of various
waye-lengths, observations were first made on the response of
the bird to achromatic stimuli. The apparatus used throughout
the preliminary work here reported was the Watson- Yerkes
spectral color vision device, as described in volume one of the
Behavior Monographs.2 A Bausch and Lomb automatic arc
lamp was used as a source of light, and a selenium cell, as de-
scribed in the monograph (pp. 79-81) served as a means of
measuring the energy of the stimuli employed. For the simple
reaction-box shown as W in figure 7 of the monograph, the
box represented in figure 1 of this paper was substituted, and
instead of having two reflecting surfaces, M and L of figure 7
above referred to, fixed on the experiment-box and moving
laterally with it, three reflecting surfaces were employed. These
remained fixed while the experiment-box moved sufficiently to
reverse the position of the two photic stimuli.

1 This work has been made possible by a grant from the Bache Fund of the
National Academy of Arts and Sciences, which enabled the author to complete
the construction of a spectral apparatus and install a selenium cell outfit to
measure chromatic stimuli. Grateful acknowledgment is made to the trustees
of the Fund and to the Committee in charge, for the facilitation of this research.

2 Yerkes, Robert M., and Watson, John B. Methods of studying vision in
animals. Behavior Monographs, 1911, vol. 1.

25

26 ROBERT M. YERKES

The general apparatus need not be redescribed in detail. The
reader who is unfamiliar with it is referred to the above-men-
tioned monograph and to Watson's more recent book.3 In
brief, it consists of a source of light which, by means of a system
of lenses, prisms, and slits, is made to supply chromatic stimuli
in any desired quality or intensity. Two stimuli are presented
to the subject simultaneously. The position of these stimuli
may be reversed at the will of the experimenter. The subject
is required to distinguish the stimuli and react differently to
the two.

Assuming, now, that the reader has a general knowledge of
the mechanism by which the chromatic stimuli are obtained,
controlled, and measured, we may consider our method of pro-
cedure in its relations to the reaction-box of figure 1. This
consists of an entrance chamber (A) in which, at the beginning
of a series of observations, the subject is placed by the experi-
menter, and from which it passes, when the door (D) is raised,
into compartment B, which may be designated the discrimina-
tion compartment. A sliding partition (M) enables the experi-
menter to avoid delay because of the unwillingness of the subject
to enter B, for by raising the door (D) and drawing M slowly
and steadily backward toward the rear of compartment A, the
subject may, without disturbance, be compelled to enter the
discrimination compartment. Once in B, the subject faces the
two stimuli S, S. These are presented either with or without
general overhead illumination, and they appear as illuminated
surfaces, either chromatic or achromatic, 7 cm. long by 1.8
cm. wide. These two stimuli are separated by the partition
P, of figure 1.

On the floor of each stimulus-box, E, are electrodes by means
of which electric shocks may be given as punishment for failures
to distinguish and properly to react to the two stimuli. The
doors F, F, leading from the stimulus compartments into the
alleys G, G, may be raised by the experimenter by means of
the cords shown in the figure. When the subject enters the
compartment which contains the stimulus selected by the ex-
perimenter as the positive stimulus, the appropriate door F is
immediately raised, the slide-door, H, of the same side opened,
and the subject thus permitted to pass by way of the alley G,

3 Watson, J. B. Behavior. New York, 1914, p. 70.

A STUDY OF COLOR VISION IN THE RING-DOVE

27

back to the starting point at A, where is it allowed to feed for
a definite interval. In case, however, the subject enters the
other compartment, it is not allowed to pass into the alley,
but instead, either with or without the use of the electric shock,
according to the experimenter's previous decision, it is required
to retrace its steps and again attempt to distinguish the stim-

FlG. 1. Reaction-box for Ring-doves. A, entrance chamber; B, discrimination
compartment; D, screen-door; M, sliding partition moving in A and B; E, E,
stimulus compartments; P, partition between E and E; F, F, doors between
stimulus compartments and alleys G, G,; H, H, slide-doors between G and A;
I, I, pulleys for cords attached to F, F; S, S, stimulus apertures.

ulus which demands positive reaction from that which demands
negative reaction.

In the case of the observations about to be described, achro-
matic stimuli were obtained by placing a two candle power
carbon incandescent lamp 86 cm. from the stimulus area. Thus,

28 ROBERT M. YERKES

the one of the stimulus areas presented to the subject was always
illuminated, whereas the other was entirely unilluminated, except
as general illumination was employed in the experiments. Natur-
ally, as the experiment-box was shifted from side to side, the
more intense achromatic stimulus was presented now in the
stimulus compartment on the right of the subject, now in the
one on the left.

The writer is convinced that wherever possible the inter-
ference of the experimenter in the course of an animal's reaction
should be obviated by the use of automatic or subject-actuated
devices. It was not feasible, however, in the present investiga-
tion, to introduce such devices, — consequently the use of the
slide-doors, as shown in figure 1. These, it should be stated,
proved surprisingly satisfactory in the case of the ring-dove,
which is easily startled and which would not react well in a
subject-actuated apparatus unless everything could be made to
work steadily, quietly, and fairly slowly. It is, however, beyond
question that our efforts in studies of behavior should be to
eliminate, as far as possible, the necessity, during the course of
reaction, of movements by the experimenter which tend to
modify the behavior of the subject. It has repeatedly appeared
that even the experienced investigator is liable, unconsciously,
to supply cues to his subject which facilitate proper reaction,
or even serve as the sole basis for what appears to be discrimi-
nation.

The birds used for the present work were obtained from a
Boston dealer. All that could be learned about them was that
they were young We are therefore under the disadvantage
of being unable to give a satisfactory description. It is
obviously desirable in all such investigations that the origin
and exact age, as well as the sex and history of each subject,
should be known. But this is somewhat less essential, it must
be admitted, in the case of preliminary observations than in
that of continuation-work. Four birds were used. Of these,
two, supplied as male and female by the dealer, in reality both
males, appear as numbers 1 and 2 in this report. They were
used over a period of several weeks by Mr. A. M. Eisenberg.
The others appear as number 3, a female, and number 4, a male.
During a period of five months these birds were used in the
visual experiment by the writer. The results obtained with

A STUDY OF COLOR VISION IN THE RING-DOVE 29

numbers 1 and 2 will be' presented only in contrast with those
of numbers 3 and 4, since the conditions of use varied some-
what, and the experiments conducted by Mr. Eisenberg were
not carried so far as those of the writer. The descriptions of
general behavior in this paper will be based almost wholly upon
the observations made on doves 3 and 4.

At the outset, it was assumed that the ring-dove would react
satisfactorily in the discrimination apparatus, that it would
exhibit a fair degree of docility, breed rapidly in captivity, be
easy to handle, and endure close confinement well. It must
be admitted that these assumptions have not all been justified,
for the birds did not quickly adapt themselves to the experi-
mental situations, and in docility they rank low. Indeed, their
slowness in acquiring the discrimination habit demanded in this
work was a great surprise to the writer. He is now somewhat
uncertain as to whether it is desirable to attempt an intensive
study of visual response with a subject which demands such a
large amount of training.

Work was initiated by feeding the birds in the entrance cham-
ber of the experiment-box, with all of the doors of the box open
so that the subject might wander about at will. This was con-
tinued for a week, with the occasional variation of opening and
closing the doors as the bird passed from compartment to com-
partment, so that it might become accustomed to the operating
of the simple mechanisms and learn the route from the entrance
chamber, by way of the stimulus chamber, back to the starting
point.

During the second week of the preliminary observations, the
birds were sufficiently tame and accustomed to the apparatus
to work fairly well. They were regularly each morning required
to make the trip through the apparatus three or four times,
and they were rewarded for so doing with food. It was dis-
covered that they would not make the trip quickly unless they
were very hungry, and even in that condition their attention
to the situation was very variable, and they were so easily
distracted by slight noises or jars that the whole process was a
very tedious one. It thus became apparent that unless an
additional motive for discrimination and progress through the
experiment-box could be discovered, the work would be most
tedious. Consequently, at the beginning of the third week,

30 ROBERT M. YERKES

the electric shock was introduced as a means of compelling
attention to the visual stimuli and of encouraging careful com-
parison and appropriate reaction. Even from the start, the
electric stimulus served this purpose admirably. It at once
rendered the birds more alert, careful, attentive, and active.
The writer's notes record, " In two weeks the doves apparently
have learned nothing, but to-day as the result of four trials
with electrical stimulation, each seemed to attempt to discrim-
inate between the light and the dark chambers.

It was decided, on the basis of the preliminary observations,
that the doves should be required to choose the lighter rather
than the darker of the two compartments.

Number 3, the female, was at the outset much less wild and
more timid than number 4, the male. It was much easier for
the experimenter to catch her in the living-cage than to catch
him, but when in the experiment-box, she was very much more
disturbed, excitable, and liable to discouragement than he. By
contrast, then, the' female may be described as tame and timid,
the male as wild and bold. But it should be added that neither
bird was sufficiently wild to be difficult to handle.

On February 28th, 1914, systematic, regular experiments were
begun, with the use of both food and the electric shock. Both
birds worked well in the six trials which were given. Only one
bird was used at a time, and it was given its trials in succession,
with from one-half to one minute interval for feeding between
choices. In comment on this day's reactions, the writer's notes
state that " The use of the electric shock discreetly and infre-
quently has transformed the birds from time-wasting and care-
less subjects to active, alert, constantly moving reactors. This
modification of method evidently means a saving of an immense
amount of time to the experimenter. It enables him to command
the attention of his subject instead of having to beg for it by
the offering of food. Food, however, is serving an excellent
purpose in the work, for each bird comes to its task hungry
and usually feeds between trials."

On March the 2nd, the number of trials for each bird was
increased to ten, and it was subsequently found that as many
as fifteen or even twenty trials could be given in succession
without overfatiguing the subjects and with excellent results.

Table 1 presents two sample detailed records of the daily

A STUDY OF COLOR VISION IN THE RING-DOVE

31

trials from the writer's note-book. The first portion of the
table gives the results of an early series of ten choices, those
of March 4th. The remainder of the table presents, by con-
trast, the results of a later series of fifteen trials in which the
birds were practically perfect in their discrimination. This series
was given on April 19th. The table indicates, in the first col-
umn, the position of the positive stimulus, that is the stimulus
indicative of the chamber to be entered. In the second column,
the letters R and W designate, respectively, correct and incor-
rect choices.

TABLE 1

Examples of Detailed Daily Records

March 4, 1914, 10:10 A. M. With general illumination. Stimulus-lamp 86 cm*
from stimulus area. Coil at 1 cm. for female and 2 cm. for male.

Positive

Female, No. 3

Male, No. 4

Trial

stimulus

Reaction

Remarks

Reaction

Remarks

1

Left

W

Shocked?

W

Shocked?

2

11

W

a

W

«

3

ii

W

a

W

Shocked

4

Right

R

Direct

W

«

5

Left

W

Shocked?

R

Discrimination

6

Right

R

R

Anxious

7

it

W

R

11

8

a

W

Shocked

R

Eager

9

Left

R

W

No shock

10

Right

W

W

Shock

Summary :

4 R:6 R

4 R:6 W

April 19, 1914, 9:50 A. M. With general illumination. Stimulus-lamp 126 cm.
from stimulus area. Coil at 2 cm. for both.

Left

Female, No. 3

Male, No. 4

1

R

Near-mistake

R

Exc. disc.

2

Right

R

Direct

R

3

u

R

a

R

4

a

R

a

R

5

u

R

it

R

6

Left

R

a

R

7

a

R

Good disc.

R

8

a

R

ii

R

9

it

R

Near-mistake

R

Careful

10

Right

R

Eager

R

11

Left

R

R

12

Right

R

Direct

R

13

U

R

ii

R

14

Left

R

Near-mistake

R

15

a

W

Careless

R

Summary :

14 R:l W

15 R:0 W

32 ROBERT M. YERKES

TABLE 2

Summary of Results of Training in Light-dark Discrimination.

Electrically Illuminated Area Versus Unilluminated Area.

Electric Shock Used as Punishment.

Dove Number 3

.?

Dove Number 4

. &

Date

Conditions

00

bo

C

£

Date

Conditions

DO

Ofl

c

2

s

£

5

£

Feb. 28 Gen.

ill., elect, stim

3

3Feb.28 Gen.

ill., elect

. stim

4

2

Mar. 1

No gen. ill.,

elect, stim.

3

3Mar. 1

No gen. ill., elect, stim.

4

2

" 2

u

a a

a

it

8

2

a

2

a

(i a

a

tt

5

5

" 3 Mixed ilium.

a

tt

9

1

tt

3 Mixed ilium.,

u

tt

5

5

" 4 Gen.

ilium.,

u

tt

4

6

it

4 Gen.

ilium.,

a

tt

4

6

" 5

u

ff

a

it

6

4

it

5

it

»

u

ti

6

4

" 6

a

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it

tt

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6

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6

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7

3

" 7

it

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:. "

a

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it

it

9

1

" 13

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a

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6

4

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2

■ 14 Gen.

ilium.,

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5

5

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14 Gen.

ilium.,

tt

tt

8

2

" 15

a

a

u

ti

3

7

a

15

it

u

tt

tt

6

4

" 16 No. i

gen. ill.,

tt

it

4

6

u

16 No gen. ill.,

tt

it

6

4

" 17 Gen.

ilium.,

a

tt

5

5

a

17 Gen.

ilium.,

ti

it

5

5

" 26

a

ft

a

it

3

7

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26

ti

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" 27

it

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" 28

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" 31

a

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4

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31

tt

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5

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Apr. 1

u

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11

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5

10

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tt

14

1

" 14

u

a

tt

u

14

1

it

14

u

It

tt

tt

13

2

" 15

a

if

tt

tt

10

5

a

15

u

tt

tt

tt

13

2

" 16

tt

a

tt

it

12

3

u

16

a

tt

u

tt

14

1

" 17 Stim

. less,

a

a

11

4

a

17

Stim

. less,

u

it

15

0

" 18

it

«

tt

it

13

2

it

18

u

it

ti

it

14

1

■ 19

it

a

a

a

14

1

tt

19

a

tt

it

tt

15

0

" 20

tt

u

a

it

12

3

ti

20

u

tt

it

tt

14

1

The general results of the several series of reactions required
for doves number 3 and number 4 appear in table 2, under
their appropriate dates. A brief statement is given in the second
column of the table of the important conditions of reaction. It
is stated, for example, whether general illumination was used

A STUDY OF COLOR VISION IN THE RING-DOVE 33

TABLE 3

;summary of results of training in llght-dark discrimination.
Electrically Illuminated Area Versus Unilluminated
Area. Electric Shock Not Used

Date

Mar. 2
" 3

I

Ger

»

a
it
ti
u
u
it
a
u
a

No

it
a
it
it

No

tt
a

ti
u
a

No

a

Gen

a

u
a
tt

ll

u
it
tt
u
ti
a
tt
it
it
it
u
it
u
u
u
u
it
u
u

Dove Number 1
Conditions

i. ilium

u

. d1

+->
Xi
b/0

s

3
5

4

1

2

0

3

3

3

4

0

1

1

1

2

1

2

2

3

2

2

3

4

5

2

6

1

4

8

5

5

2

5

5

4

7

5

2

3

10
6
1

10

10

10

10
6
9
6

r

g Date

7Mar. 3 Gen

5 " 4 "

6 " 7 "

4 " 9 "

3 " 10 "

5 " 11 "
2 " 12 "
2 " 13 "

2 " 14 "

1 " 16 "

5 " 17 No j

4 " 18 "
4 " 19 "
4 " 20 "

3 " 21 "

4 " 23 No i
3 " 24 "

3 " 25 "

2 " 26 "

3 " 27 "

3 " 28 "
2 " 30 "

6 " 31 "
5Apr. 1 Gen.

8 " 2 "

4 " 3 "

9 " 4 "
6 " 6 "

2 " 8 "

5 " 9 "
5 " 10 "
8 " 11 "
5 " 13 "

5 " 14 "

6 " 16 "

3 " 17 "
5 " 18 "

8 " 20 *

7 " 21 "
0 " 23 "

4 " 24 "

9 " 25 "
0 " 27 "
0 " 28 "
0 " 29 "

0 " 30 "
4May 1 "

1 " 2 "

4 " 2 "
a 4 it

It g u

u n a
it U «

)ove Nu
Condi

. ilium

it

it
u
ii
it
it

mber 2,
tions

&

-t-J

H

"So

2
2
2
2
2
2
2
0
2
2
1
2
2
1
2
1
2
1
5
4
4
4
5
5
5
6
7
4
6
4
4
5
6
5
5
5
7
4
7
3
10
5
9
6
9
5
6
10
10
10
9
8
5

G

2

3
3
3
3
3
3
3
5
3
3
4
3

" 4

ii

" 7

it

" 9

u

" 10

u

" 11

u

" 12

u

it

" 13

It

it

" 14

ll

a

" 16

ll

?en. illui
a it

it it

ii ti

ti it

?en. ill.,
it it

U ll

ll ll
ll ll
ll It
ll It
a it

ilium

n

" 17

gen. ilium
it ii

u it

n it

ii ii

gen. ill., el

it it

ti it
ti it
ii it
u ii

gen. ilium.

ti it

. ilium. . . .

tt

■ 18

3

4

3

4

3

4

5

6

6

6

5

5

5

4

3

6

4

6

6

5

4

5

5

5

3

6

3

7

0

5

1

4

1

5

4

0

0

n

" 19

" 20

" 21

elect, stim.
a it

it ti

it ti

it it

ti ti

ti ti

it ti

" 23
" 24
" 25
" 26
" 27
" 28
" 30
" 31

lect.

it

it

stim.

tt

it
it
it
ii

Apr. 1

ii

" 2

it

" 3

it

it

" 4

it

it

" 6

it

u

" 8

ti

a

" 9

it

u

" 10

it

u

" 11

u

u

" 13

ti

it

« 14

it

it

" 17

it

u

" 18

it

ti

" 20

u

ti

" 21

it

it

" 23

ii

it

" 24

it

ti

" 25

u

it

" 27

ti

it

" 28

it

a

" 29

u

u

" 30

ti

ti

May 9

ti

ii

" 11

ii

it

" 14

ti

ii

a

it

l

u

2

it

5

34 ROBERT M. YERKES

or not, and it is indicated that in a few series of observations
the conditions of illumination were mixed, that is, for some of
the reactions general illumination was employed, whereas in
others it was lacking. Throughout the regular experiments the
electric stimulus was employed. On April 17th, as is indicated,
the intensity of the visual stimulus was lessened, thus dimin-
ishing the difference in the stimuli to be distinguished.

Table 3 presents the comparable results for doves number 1
and number 2. The chief difference in the conditions for these
results and those obtained with doves numbers 3 and 4 is the
absence of the electric stimulus in the case of the former. With
the exception of one week, March 23rd to March 28th, Mr.
Eisenberg trained number 1 and number 2 to achromatic dis-
crimination on the basis of food as a reward without the use
of the electric shock as punishment for mistakes. His results,
therefore, may be compared with those of the writer, with a
view to discovering the value of punishment as contrasted with
reward in this experiment with ring-doves.

Such comparison indicates, in the first place, that it is pos-
sible to make a larger number of observations per series with
punishment than without it. Thus, the writer by the aid of
the electric stimulus was able to make ten, fifteen or even twenty
observations per series. Whereas, Mr. Eisenberg, without the
electric stimulus, could not satisfactorily make more than ten
observations, and during a considerable portion of the training
he made only five. Second, the time required for the work
varied much more widely when punishment was not used than
when it was used. As appears from tables 2 and 3, all of the
doves acquired the ability to discriminate with a reasonable
degree of certainty, and to react appropriately. The course of
habit formation in case of each of the four subjects is surprising.
Instead of being steady, regular, and fairly rapid, as the writer
had anticipated, it proved to be irregular and extremely slow.
One day the experimenter would feel confident that his subjects
were acquiring the habit, and the next day he would find them
utterly unable to react properly.

In table 4 the choices are presented by groups of fifty, and
the course of habit formation is indicated with the daily varia-
tions eliminated. This table shows that as the result of three
hundred trials, no one of the four doves had acquired the ability

A STUDY OF COLOR VISION IN THE RING-DOVE

35

TABLE 4

Reactions in Light-dark Training Grouped in Fifties to Show Slowness
of Improvement and Irregularities

Dove 1, J1

Dove 2, c?

Dove 3, 9

Dove 4, tf

Right

Wrong

Right

Wrong

Right

Wrong

Right

Wrong

1 -50

18

32

18

32

32

18

27

23

51-100

18

32

20

30

23

27

29

21

101-150

22

28

21

29

23

27

35

15

151-200

23

27

28

22

25

25

25

25

201-250

20

30

25

25

27

23

22

28

251-300

25

25

26

24

30

20

29

21

301-350

37

13

36

14

34

16

34

16

351-400

36

9

41

9

41

9

46

4

401-450

27

8

38

12

47

3

451-500

30

5

33

2

to react properly. Between the three hundredth and the four
hundredth trials, all of them, however, showed marked im-
provement. Were it not that two experimenters were involved
and the conditions of observation thoroughly controlled, it might
fairly be suspected that the doves finally discovered some other
basis for reaction than the difference in the intensity of illumi-
nation. We are convinced, however, that this was not the
case and that the results satisfactorily prove that the ring-dove
is extremely slow, under the conditions described, in learning to
react appropriately to achromatic stimuli, even though they
differ very markedly. It must be admitted, however, that there
are certain features in table 3 which are puzzling. Number 1
discriminated perfectly on April 23rd, and number 2 on April
24th, whereas on both the preceding and the following days they
did poorly. This suggests to the writer that they had happened
upon some means of choosing other than that intended by the
experimenter.

From a careful comparison of the data of tables 2, 3, and 4,
it is clear that by the use of the electric stimulus, it is possible
to develop a visual discrimination habit in the dove much more
quickly, and consequently with less labor, than by the employ-
ment of the food getting desire alone.

All of the foregoing observations are merely preparatory to
the work with chromatic stimuli. It therefore seems unneces-

36 ROBERT M. YERKES

sary to burden the reader with further details of conditions or
results, except possibly with respect to the general illumination
and its relation to the reactions. In some of the series, general
illumination was not employed, and it was naturally apparent
that the doves could distinguish the stimuli much more easily
than when the surroundings were illuminated. It was deemed
desirable to use general illumination in order to guard against
choice on the basis of the visibility of the sides and floor of the
stimulus chambers, for naturally enough, this differed greatly
in the light and the dark chambers in the absence of general
illumination. On the whole, it seemed very much more satis-
factory to conduct experiments in the general illumination pro-
duced by a two candle power frosted carbon incandescent lamp,
at a distance of 110 cm. above the center of the partition be ween
the stimulus chambers.

As an aid to rapid reaction, the alleys of the experiment-box
were kept dark except at the moment of entrance of the dove.
In each alley was placed a low-power lamp which could be turned
on the instant the door F was raised, and turned off the instant
the door H was opened. This served to induce the dove to enter
the alley- way and to hasten through it to the food-box. After
a few daily series, the birds made the trip quickly and volun-
tarily, seldom loitering in the passageways and usually passing
from entrance chamber to discrimination chamber rapidly.

The food placed in the entrance chamber as a motive for
return to that portion of the experiment-box was milk-soaked
bread, with a small quantity of cracked corn added. During
a large portion of the series, the birds ate little, unless they were
practically deprived of food while in the living-cage. It is thus
fair to say that the process of habit formation in the case of
doves 3 and 4 depended almost solely upon punishment, whereas
the process in the case of birds 1 and 2 depended solely upon
reward.

As in the writer's previous use of punishment, the induced
current was used by means of a Porter inductorium with a
number 6 Columbia dry cell as source of current. In the early
experiments, no attempt was made to keep the feet of the birds
moist, and as a consequence, the secondary coil had to be placed
well over the primary. Its position was varied somewhat from

A STUDY OF COLOR VISION IN THE RING-DOVE 37

day to day, but in general it was placed at 1 cm. for the female
and at 3 cm. for the male. This, of course, means that the male
responded to a very much weaker electric stimulus than did the
female, but it is probable that this indicates not so much a
difference in sensitiveness to the stimulus as the result of differ-
ence in weight, for the male bird was much heavier than the
female. During March it was found difficult to get satisfactory
responses, even when the maximum current was used, and the
experimenter finally hit upon the device of placing a square
piece of moist blotting paper before the food-box in the entrance
chamber. This was found to yield very satisfactory results.
The secondary now had to be set at 2 cm. for the female and
2\ for the male. The settings proved satisfactory throughout
the remainder of the work, and whereas previously the responses
to the electric stimulus had varied extremely, they subsequently
were very constant.

RESULTS WITH CHROMATIC STIMULI

Doves 3 and 4, having been trained to practically perfect
discrimination of a bright area from a dark area of the same
size, were tested for preference of spectral red and green. The
value of the red stimulus was 626 to 640/*/^, while that of the
green was 498 to 510/*/*. In energy, as measured by the selenium
cell, the red stood slightly above the green, but they were so
nearly the same that it seemed needless to attempt to equate
them more closely for these preliminary experiments.

Table 5 presents in summary the results of the chromatic
reactions of doves 3 and 4. From this table it appears that
on April 21st, when given an opportunity to choose either the
red or the green chamber, without punishment, number 3 chose
the one as often as the other, whereas number 4 chose the red
eight times, the green twice. On April 22nd, in the absence
of general illumination and with a period of two minutes for
darkness adaptation before the series was commenced, the
results were entirely different, for number 3 selected the green
nine times out of ten, while number 4 chose it five times out of
ten. On the following day, the original conditions of April 21st
were reinstated and the responses were similar to those of that

38

ROBERT M. YERKES

date. On April 28th, by the elimination of general illumination,
darkness adaptation was effected, and the results again, as on
April 22nd, favored the green.

TABLE 5
Results of Experiments with Chromatic Stimuli
Dove Number 3, 9 Dove Number 4, tf

Date

Conditions

T3

4J

Date

Conditions

13

c

«

o

«

6

Apr.

21

Preference for

Apr.

21

Preference for

a

22

red or

u u

green

5
1

5
9

u

22

red or

ii a

green

ii

8
5

2
5

a

23

(darkness

a it

3 adaptation)

a

3

7

a

23

(darkness adaptation)

ii ii ii

7

3

u

28

(gen. ilium.)

11 11 It

(no gen. ilium.)

4

6

a

28

(gen. ilium.)

ii ii ii

(no gen. ilium.)

5

5

Apr.

a

29
30

Red-black training. . .

II u

11
16

9

4

Apr.

29
30

Red-black training. . .

ii ii

18
12

2

8

May

1

a

u

13

7

May

1

ii

ii

18

2

u

2

a

a

13

7

i<

2

ii

ii

19

1

u

3

a

u

10

10

it

3

ii

ii

20

0

tt

4

it

a

17

3

it

4

a

ii

20

0

tt

5

a

u

18

2

it

5

ii

ii

17

3

u

6

a

a

17

3

H

6

ii

it

19

1

tt

7

a

u

19

1

ii

7

a

ii

19

1

a

8

a

u

18

2

a

8

ii

it

17

3

May

«

9 Red-green training. . .
10

14
10

6
10

May

9 Red-green training . . .
10

16
20

4
0

it

11

it

a

10

10

ii

11

a

u

15

5

U

12

a

a

13

7

«

12

a

II

16

4

a

13

11

a

15

5

u

13

ii

II

15

5

a

14

a

it

13

7

tt

14

ii

11

13

7

a

15

it

a

14

6

II

15

ii

11

17

3

u

16

u

tt

14

6

II

16

it

II

13

7

a

17

u

tt

14

6

II

17

!!

II

16

4

a

18

a

tt

13

7

II

18

11

II

15

5

tt

19

a

it

16

4

II

19

II

II

18

2

u

20

a

tt

16

4

II

20

11

II

18

2

tt

21

a

u

15

5

II

21

II

II

19

1

a

22

a

tt

17

3

II

22

Ii

II

19

1

tt

23

u

tt

14

6

II

23

11

II

14

6

tt

24

u

tt

14

6

II

24

11

II

16

4

a

25

u

n

18

2

II

25

II

II

17

3

11

26

a

it

18

2

II

26

II

II

18

2

u

27

»

u

20

0

II

27

II

II

18

2

tt

28

a

tt

20

0

II

28

II

II

20

0

From these four series of ten reactions with doves numbers
3 and 4, it may be inferred that under the condition of general
illumination in which these doves had been trained to distin-
guish the light stimulus patch from the dark and to react posi-

A STUDY OF COLOR VISION IN THE RING-DOVE 39

tively to the lighter of the two, the spectral red and green stimuli
appeared of about the same intensity to the female dove, whereas
to the male, the red appeared the more intense. One naturally
infers that both birds, as a result of their previous training,
would go to the stimulus patch which appeared the lighter of
the two, supposing that an appreciable difference existed. The
series of observations on April 22nd and 28th with darkness
adaptation indicate that green appeared considerably lighter for
both birds than without adaptation. Green was chosen more
frequently by number 3 than by number 4, apparently because
the two stimuli were of more nearly the same value in general
illumination for this bird than for the male.

From these few observations, and naturally only a few obser-
vations could be made of preference, we may conclude that
spectral red and green stimuli of approximately the same energy
values did not appear markedly different to the female dove
in general illumination, whereas without general illumination the
green seemed the more intense. For the male, on the contrary,
the red seemed somewhat more intense than the green, and
darkness adaptation rendered the two of practically the same
intensity.

Hess4 has already demonstrated the Purkinje phenomenon in
chickens and doves, by a method radically different from that
of the writer, while Lashley5 has more recently demonstrated
it in the game bantam by the method of this investigation.
There seems to be no reason for doubting that the observations
described above also constitute a satisfactory demonstration of
the modification of stimulating value by adaptation.

A series of observations was now instituted, beginning on
April 29th, on the development of the ability to distinguish
red from black and of the habit of reacting positively to red and
negatively to black. Supposing that red appeared light and
black dark, it would seem that both doves, merely as the result
of their light-dark training with colorless stimuli, should select
red uniformly and avoid the black. The results, however, as
they appear in table 5, do not wholly justify this expectation.

4 Hess, C. Untersuchungen iiber das Sehen und uber die Pupillenreaction von
Tag- und Nachtvogeln. Archiv. fur Augenheilkunde, 1908, Bd. 59, S. 143.

. Vergleichende Physiologie des Gesichtssinnes. Jena, 1912,

Bd. 4, S. 9.

5 Watson, J. B. Behavior. New York, 1914, p. 350.

40 ROBERT M. YERKES

Instead, they seem to indicate that for the female dove, the
red was so dark that it tended to be confused with the black,
or at least was not accepted as the equivalent of the light area
which the bird had previously learned to choose.

In this red-black training, it was possible to give each dove
twenty trials in succession. As a result of one hundred and
forty trials, number 3 was reacting properly ninety per cent of
the time. Curiously enough, the male, number 4, chose the red
eighteen times out of twenty in his first series, and showed
throughout his reactions, in the red-black training, ability to
respond to these two stimuli much as he had to the light and
dark achromatic stimuli. This is, of course, wholly in agree-
ment with the results of the preference tests, which clearly indi-
cated that the red stimulus for some reason possessed a higher
stimulating value for the male than for the female.

It is, of course, impossible to say, on the basis of the red-
black results, that either bird responded to the chromatic differ-
ence instead of to the intensity difference of the stimuli. It is
doubtless safer to assume that the latter alone was the basis
of choice.

Beginning on May 9th both doves were presented with the
red and green stimuli which on April 21st had been offered as
a basis for preference reactions, with the difference that now
they were required to choose the red and to avoid the green on
penalty of electric stimulation. Again, each daily series con-
sisted of twenty successive trials. The female exhibited, at
first, slight ability to distinguish the two stimuli and to respond
appropriately, but after three hundred and eighty trials, she
was reacting perfectly. The male, on the contrary, reacted
perfectly even from the first, his second series of twenty trials
including no mistakes. It is thus fairly clear that he responded
to the intensity difference of the two chromatic stimuli, and it
seems wholly probable, in view of the gradual development of
the habit, that she also acquired the ability to respond to the
same difference.

From these preliminary observations, it seems safe to con-
clude that for the ring-dove a red and a green from the spec-
trum of the carbon arc, of the wave lengths designated above,
and of approximately the same energy, as measured by the
selenium cell, are sufficiently unlike in stimulating value to be

A STUDY OF COLOR VISION IN THE RING-DOVE 41

readily distinguished by certain individuals and with difficulty
by others. The particular results in hand suggest that the red
has a higher stimulating value for the male than for the female.

The next step in the experiment would naturally enough
have been observation of the responses of the subjects to varied
energy values (intensities) of the two chromatic stimuli. Un-
fortunately, the investigation had to terminate at the end of
May and the laborious preparation for these final observations
was unavoidably wasted. The writer had fully expected and
hoped, within the period of six months at his disposal when the
investigation was undertaken, to ascertain whether the ring-
dove can distinguish a red from a green stimulus throughout a
wide range of energy or intensity values. This he did not suc-
ceed in doing, and consequently this report must be entitled
' Preliminaries to a study of color vision in the ring-dove."

The principal conclusions wThich may safely be drawn from
these observations have been suggested in the course of the
presentation, but by way of summary and review, they may
be enumerated here.

1. It is fairly obvious that the ring-dove is not sufficiently
docile to be an ideal subject for the study of color vision by
means of the method which Watson and I have developed.

2. It is indicated that the value of a certain red and a certain
green may be very different for two ring-doves, and it is pos-
sible that this difference is correlated with sex, the red having
a higher stimulating value for the male than for the female.

3. As has already been demonstrated by the writer in the
case of a number of animals, the use of the electric stimulus as
a means of compelling attention to an experimental situation
and of promoting habit formation is desirable in work with the
ring-dove.

4. Ring-doves differ markedly in temperament. The pair used
by the writer throughout this work presented differences which
must be considered if one is to understand the results. To
begin with, the ♦male was somewhat wild, but at the same time
fairly bold, whereas the female was tamer but more timid. Be-
cause of this contrast in timidity, the male almost from the
start proved the better subject. He was not so easily disturbed
or distracted, reacted therefore more steadily, and chose more
certainly. With constant handling he became quite as tame as

42 ROBERT M. YERKES

the female and lost almost entirely his timidity in the apparatus.
She, however, continued to be rather timid throughout the sev-
eral months of work, although she was perfectly tame. The
differences in the nature of the reactions, as recorded in the
experimenter's record-book, can be appreciated only in the light
of these temperamental facts.

The sex contrasts indicated in the above paragraphs one dare
not emphasize very strongly on the basis of observations on
two individuals, but they at least suggest the desirability of
further study of the sexes. It is the writer's opinion that they
agree sufficiently closely with the results obtained in the case
of other animals to justify their provisional acceptance.

As has been repeatedly noted with other animals, there are
good and bad days in experimental work with ring-doves, — days
which are good or bad, not, so far as one may tell, because of
variation in the experimenter or his manipulation of the appa-
ratus, but chiefly because of variations in the condition of the
subjects. The experiments described in this paper were made
at about the same hour each morning, and it was quite impos-
sible for the experimenter to predict the outcome of a series
in the light of previous series, for the attention of the doves to
the situation seemed to vary independently of any conditions
or group of conditions which the experimenter could take into
account. There are animals which can be relied upon to work
steadily and fairly predictably. The ring-dove is not one of them.

The writer has been led to reflect, because of the outcome of
this series of observations, on the possible relation of the sim-
plicity of the experimental situation to the results. He was
compelled to devote several weeks to the establishment of a
simple habit in two ring-doves, a habit which was next to value-
less except as a preparation for further observations. It is
natural that during this long period of preparation he should
frequently wonder whether the desired end might not be gained
more quickly by a different method. It seems probable that a
complex situation would have proved more favorable, and that
had the two stimuli varied in other respects than in intensity,
the animal's attention would more readily have been directed to
them and more steadily held upon them. The matter is men-
tioned here because it is obviously of extreme importance to

A STUDY OF COLOR VISION IN THE RING-DOVE 43

students of behavior to discover the most efficient means of
developing preparatory habits in animals.

In concluding this paper, the writer can not refrain from
calling attention to the waste of time which results from the
sacrificing of trained animals at the end of an investigation.
It should be possible, through exchange, to make the same
subject serve in various experiments. And different experi-
menters, supposing our methods to be reasonably standardized,
might study quite different problems on the basis of similar
preparatory habits. Thus, for example, the doves which in this
investigation have been trained to certain visual reactions, might
perfectly well be employed for other forms of visual response,
or even to greater advantage for studies of the relation of the
central nervous system to the acquired responses. It is sug-
gested, therefore, that American investigators who are actively
engaged in studies in animal behavior keep in close touch and
develop a system of reporting their experiments while in pro-
gress, which may serve as a basis for the serviceable exchange of
trained subjects. The writer happens to have on hand at the
moment of writing three tame crows which are highly trained
in certain modes of response. The labor of taming and training
them would have to be valued at several hundred dollars. It
is impossible, under present conditions, to make use of these
birds, and unless some other investigator can be found who
can take advantage of this preparation, they will have to be
either set at liberty or otherwise sacrificed.

THE BEHAVIOR OF BROOK TROUT EMBRYOS FROM
THE TIME OF HATCHING TO THE ABSORPTION

OF THE YOLK SAC

GERTRUDE M. WHITE
Zoological Laboratories, University of Wisconsin

WITH FOUR FIGURES

CONTENTS

PAGE

a. INTRODUCTION 44

b. EXPERIMENTS AND OBSERVATIONS 46

1. Hatching 46

2. Swimming movements 48

3. Reactions to mechanical jars 49

4. Reactions to touch 49

5. Reactions to current 49

6. Reactions to light 52

7. Reactions to current and light 53

8. Carbon dioxide and light 54

9. Reactions to shadows ' 55

10. Feeding reactions 55

c. GENERAL DESCRIPTION OF THE EARLY LIFE OF THE

BROOK TROUT 56

d. SUMMARY 59

e. BIBLIOGRAPHY 60

A. INTRODUCTION

Although certain senses of mature fishes have been carefully
studied, little work has been done upon the reactions of embryos.
The investigations of the adult fish have been made chiefly with
reference to the senses of smell, taste, sight, and hearing. Her-
rick ('03) found that some fishes possess taste buds located in
the skin, by which they habitually discover their food, while
other fishes have the sense of taste confined to the mouth. That
the catfish has a true olfactory sense, which is distinct from
gustatory, was shown by Parker ('10). The sense of hearing
has also been studied by Parker ('05, '08, '11), who believes
that some fishes are stimulated by sounds of slow vibration.
Bernoulli ('10), on the other hand, maintains that the fishes
with which he worked do not hear, but respond through tactual

44

THE BEHAVIOR OF BROOK TROUT EMBRYOS 45

and visual stimulation, when at all, to the mechanical motion
of the water.

The work of Paton ('07), who describes some of the reactions
of fish embryos, is of particular interest. He believes that the
early attempts of fish embryos to lie upon the ventral side are
not due to the influence of the nervous system, but rather to
the position in which they lie in the egg, and the shape of the
body, combined with the propulsion of the water. Even embryos
of thirteen and fourteen millimeters show a tendency to right
themselves when they swim.

This author found that trout embryos of fifteen millimeters often
swam once or twice around a dish five centimeters in diameter,
but in all fishes progression was possible long before this, even
at nine or ten millimeters. Squeezing or pricking the yolk sac
of the trout caused exaggerated movements in the young fish.
The head was found to be less sensitive to touch than the body;*
the eye in all stages examined was rather insensitive to touch.
Prompt and unmistakable responses to thermal stimuli appeared
at an early age. The rate of the heart beat at ten millimeters
was twenty-five or twenty-eight, and at fifteen millimeters was
seventy-five or eighty.

Since the information concerning the reactions of fish embryos
is so meagre, it seems desirable that the kinds of stimulation to
which various types of fish react, and the age at which such
reactions begin, should be ascertained and possible applications
to economic problems considered. The present paper is an
attempt to give a connected account of the life activities of the
Brook Trout, Salvelinus fontinalis, from the time of hatching to
the absorption of the yolk sac.

The Brook Trout is usually found in clear, cold spring water,
and prefers brooks or streams flowing over gravelly bottoms.
It pushes from the rivers into the smaller streams, seeking the
head-waters, where it rests in the deep pools and eddies. Under
natural conditions it is seldom found in water over 60° F. to
65° F. The Brook Trout spawns in autumn as the temperature
of the water falls. The season, which usually lasts about two
months, begins earlier in the northern latitudes, in the Lake
Superior region in September, or even in August, while in New
York, New England, and Lower Michigan, it commences about
the middle of October. The time necessary for developing the

46 GERTRUDE M. WHITE

eggs is dependent upon the temperature of the water, varying
from about 125 days at 37° F. to about 50 days at 50° F.

The experiments here described were performed in the Zo-
ological Laboratories of the University of Wisconsin. About
five hundred embryos were used, eggs being obtained at the
Madison Fish Hatchery, and brought to the laboratory in four
different batches, so that embryos of various stages could be
observed at the same time. The youngest stages were kept in
a wire tray in a trough of running water (from Lake Mendota)
while the older individuals were placed in glass dishes and set
in running water to keep them cool. About one hundred Rain-
bow Trout, Salmo irideus, of two different stages and a number
of young German Brown Trout, Salmo fario, which swam freely
in the trough, were kept under observation.

During the experiments the temperature of the water ranged
from 5° C. to 10° C. Most of the experiments were performed
in a dark room, the temperature of which was usually about
19° to 20° C. The fish were handled with a feather or with a
spoon made of bent wire with netting stretched across it. Al-
though theie was a high rate of mortality (due to gas-bubble
disease, fungi, algae which crept into the gills, and persistent
handling), several of the Brook Trout survived during the whole
period. All experimental data refer to the Brook Trout unless
otherwise stated.

This work was accomplished under the direction of Professor
A. S. Pearse, for whose helpful suggestions and encouragement
it gives me great pleasure to express my appreciation.

B. EXPERIMENTS AND OBSERVATIONS
1. Hatching

The egg of the Brook Trout is small and nearly colorless,
measuring about four millimeters in diameter. The embryo,
which is about three times as long as the diameter of the egg,
lies curled around its yolk sac with the tip of the tail beside
the head. The eyes and head are visible through the thin shell.
The hatching is initiated by movements starting at the head
and later extending through the whole length of the body, so
that the position of the embryo in the egg is somewhat changed.
Such movements continue at intervals, varying from a quarter
of a minute to an hour or more, until the shell is so strained

THE BEHAVIOR OF BROOK TROUT EMBRYOS

47

that a slit appears. There does not seem to be any distinction
as to which part of the embryo comes out first, for in the twenty-
three cases observed, eight embryos appeared head first, one
tail first, and in fourteen cases the yolk sac broke through before
the body. The final shedding of the egg case is sometimes brought

Fig. 1. Egg of a Brook Trout shortly before hatching. Magnified six and

two-third times. (Drawn by Miss Wakeman)

Fig 2. Embryo hatching head first. Magnified six and two-third times

about by a violent movement of the body, but in nearly all the
instances observed it was a gradual process lasting from three-
quarters of an hour to five or six hours, during which the initial
slit was slowly enlarged by the rhythmical motions of the body
and the respiratory movements. If the anterior end is to be

^Z^

Fig. 3.

Dorsal view of an embryo three weeks old (15 mm.). Magnified
six and two-thirds times

the first to appear, the violent contraction of the embryo raises
the head until the strain splits the shell far enough to free the
region bearing the pectoral fins, which immediately begin to
move. The front of the head soon follows. Whether the tail
or the yolk sac comes out first, the length of time required is

48 GERTRUDE M. WHITE

nearly the same, and the details of the process differ very little.
Unless the animal is disturbed, it may lie quiet for hours while
the egg case slips off, but if the fish is jarred, a violent contrac-
tion almost invariably results, thus hastening the loss of the
egg case. In nature, where there are great numbers of fish
hatching simultaneously, they undoubtedly touch one another
continually, shortening the time required for hatching.

The Brook Trout makes its appearance as a pretty, delicate,
translucent creature about twelve centimeters long. Its most
conspicuous features are its enormous eyes, which occupy almost
the whole head, its huge yolk sac covered with a fine network
of bloodvessels leading to the heart, the beating of which can
plainly be seen. Along the back is a strip of pigment extending
from the head to the tip of the slender tail.

Fig. 4. Lateral view of an embryo three weeks old. Magnified six and

two-thirds times

2. Swimming Movements

Although the Brook Trout spends most of the first six weeks
of its larval life lying quietly on its side, it is perfectly capable
of swimming as soon as the egg case is lost. In fact, Paton
('07), who worked on trout among other varieties of fish, states
that definite progression is possible when the embryo is nine
or ten millimeters long. In the present experiments, if a fish
which had just hatched was suddenly touched, it would whirl
round and round as if its cumbersome yolk sac formed a movable
pivot. By the fourth day the movements are still rotatory, but
the fish swim in larger circles and can go straight ahead for a
greater distance. There is also more darting about, the tail
being always the most active part of the body. The trout which
is one week old (14-15 millimeters) swims in a spiral course. As
the yolk sac diminishes in size, the fish is better able to control
its movements. It lies upon its ventral side like an adult at the
age of six weeks in most cases, and in swimming, continually
darts about, turning first one way, then the other.

THE BEHAVIOR OF BROOK TROUT EMBRYOS 49

3. Reaction to Mechanical Jars

Possibly the first stimulus to which a developing trout reacts
is that of mechanical jars. Often before the embryo has com-
pletely left the shell, the shaking of the dish or currents in the
water cause it to contract, and if the tail is free, to swim about
with the head still encased. This sensitiveness to mechanical
vibrations continues throughout the larval life. Even so slight
a vibration as that caused by blowing on the water makes the

fish dart about.

4. Reactions to Touch

The sense of touch is well developed when the trout hatches*
but it is impossible to predict what response will be given to
a stimulus in any particular part of the body. Embryos in
nearly all stages of development from the time of hatching until
the yolk sac was lost, were touched systematically with a slender,
pointed stick, and with bristles to determine whether one part
of the body was more sensitive than another. I found, as
Paton ('07) did, that although it is very difficult to localize the
tactile areas, the head is much less sensitive than the body, and
the eye is quite insensitive. Judged by such responses, the tail
seems to be the most sensitive part of the body. It was found
that the trout avoided a brush much more vigorously than they
did a pointed stick or a single bristle. This is probably because
the brush stimulates them at more points.

If touched persistently the embryos swim about, turning

rapidly in all directions. When they are eventually fatigued,

the responses become less marked, the trout may then merely

move its tail or increase the rate of movement of its fins. It

may even become absolutely quiet for a time, after which the

reactions take place as before. The young trout show some

measure of adaptability, for they grow somewhat accustomed

to being handled, and particularly in the case of the oldest fish

(three months old), those which had been repeatedly picked up

were slightly easier to catch than those which had never been

touched.

5. Reactions to Current

Since Brook Trout live in swift flowing streams, one would
expect them to react to currents. In order to test this matter.
a trough was constructed in which they could be tested. The
apparatus was fifty inches long by two and one-fourth inches

50

GERTRUDE M. WHITE

wide and three inches deep with straight sides. A piece of
rubber tubing connecting with a faucet was attached to the
center of one end, in such a way that a current of uniform in-
tensity flowed through the whole length of the trough; at the
other end, was an outlet covered with netting to prevent the
loss of the fish.

After testing various strengths of current, the one which
brought about the greatest number of reactions was found to
be that which carried carmine solution the length of the trough
in half a minute. Therefore, this strength of current was used
in most of the experiments. Since all tests were made in a
dark room, it was a simple matter to turn on the faucet a cer-
tain distance with the room in total darkness, in that way elim-
inating all reactions to light. Nevertheless, since it was found
that the daylight had little effect on the results, the room was
not darkened for all the experiments.

Nearly all stages of young Brook Trout from the time of hatch-
ing to the absorption of the yolk sac were tested. Table 1 shows
some of the results.

TABLE 1
Showing the Reactions of Brook Trout to Current

Number

of ex-
periment

Number

of fish

used

Age

of

fish

Condition

of

light

Number

of fish

positive

Number

of fish

negative

Number

of fish

indifferent

Per cent

of fish

positive

1
2
3

4

25
25
20
20

4 days

4 days

34 days

42 days

day
dark
day
day

Trout rea(

22

21
17
16

0
0
0
0

3

4
3

4

88%
84%
85%
80%

Total np.rr.p.ntacfp of Rronk

'ting positi

velv

84.25%

The fish were placed in the trough one at a time in most cases,
with right and left sides alternately toward the current before
the water was turned on. The fact that the older trout showed
a slightly smaller percentage of positive reactions is probably
not significant, as there appears to be no difference in their
reactions, except such as would be caused by their greater
activity and strength. Although it is not recorded in table 1,
embryos which had just been hatched were found to react posi-

THE BEHAVIOR OF BROOK TROUT EMBRYOS 51

tively to current. But they were usually unable to swim more
than a few centimeters, or able merely to orient themselves,
owing to the size of the yolk sac.

While none of the Brook Trout were persistently negative
in their reactions to current, there were always a few which did
not give a definite positive response. Since it was noted that
a fish was sometimes carried backward farther than it was able
to advance, the four embryos in experiment number two which
did not react definitely- were tested later in the light, where
they could be watched. One fish did not swim at all. Three
fish were carried backward, but oriented toward the source of
the current. They struggled to advance, but were unable to
do so. Therefore, these were actually positive.

Of the twenty-one which are marked positive, five were evi-
dently weak; their condition somewhat resembling the three
just mentioned. Since these were found on being tested in the
light to be clearly positive, and on the third trial in the dark
progressed decidedly toward the current, they were included
with the trout which had just been observed to move definitely
against the current.

In order to discover whether surrounding objects affect the
reaction to current, a striped paper was passed back and forth,
beneath and at the sides of the glass dish containing Brook
Trout about three weeks old. No reaction resulted. Brook
Trout were also placed in a round glass dish set within another
dish and a current of water made to run between the dishes.
To this also the fish failed to react. Hence during the first
few months, the sense of sight appears to have little or no rela-
tion to the reaction of Brook Trout to current. This does not
agree with what Lyon ('04) believed to be true regarding the
fishes with which he worked.

Positive rheotropism was also exhibited by a school of German
Brown Trout two or three months old, that were almost invari-
ably found resting or swimming about near the source of the
current in the trough where they were kept. On testing Rain-
bow Trout three days old, when the yolk sac is enormously
large, forty or fifty per cent were observed to be positive to
current, while sixty per cent were indifferent, the latter either
lying quiet or whirling about without orienting themselves when
stimulated.

52

GERTRUDE M. WHITE

6. Reactions to Light

That young Brook Trout are negatively phototropic has been
recognized by the fish-hatchers who, finding that the trout seek
the dark corners, keep the troughs covered. Their phototropism,
however, was tested more accurately in the following manner:
A Nernst lamp was placed within a large box (75 cm. wide x
120 cm. long x 120 cm. high) blackened inside and out, and
having an opening (6 cm. x 9 cm.) at one end. A narrow glass
dish, 4 cm. through, containing water was placed before the
hole to absorb the heat rays; at right angles to this was an
oblong glass dish with rectangular sides (38 cm. long x 10 cm.
wide x 8 cm. high) in which the fish were placed.

Brook Trout of nearly every age, from those which had just
hatched to those two months old, were placed in the dish singly
or in groups and left for varying lengths of time. Table 2 shows
the results.

TABLE 2
Showing the Light Reactions of Brook Trout

Age of trout

Number

of

trout

Strength of light

Number
of trout
negative

Number
of trout
positive

2 days

2 days

2 days

21 days

21 days

21 days

25
25
5
10
10
10

1.5 candle meters
2.3 candle meters
7.7 candle meters
2.3 candle meters
7.7 candle meters
16 candle meters

14
21
4
7
8
8

0
2
0
2
0
2

Totals

85

62

6

Totals.

Number

of trout

indifferent

11
2
1

1
2
0

17

Per cent
of trout
negative

56%
84%
80%
70%
80%
80%

75%

Per cent
of trout
positive

0

8%

0
20%

0
20%

8%

Per cent

of trout

indifferent

44%

8%
20%
10%
20%

0

17%

THE BEHAVIOR OF BROOK TROUT EMBRYOS 53

In the experiments tabulated the trout were placed in the
center of the dish with right and left sides alternately toward
the light, so as to eliminate complication from a propensity to
turn toward a particular side of the body. Each fish was ob-
served for five minutes. The strengths of the lights given are
approximately what the fish actually encountered in the center
of the dish. It may be noted that a somewhat greater percentage
reacted negatively to a light 2.3 candlemeters than to a light
1.5 candlemeters. Above 2.3 candlemeters, however, the in-
crease in the strength of light seems to make little difference.
Brook Trout less than a week old in general react more strongly
to a weak light (2.3 candlemeters) than to a strong one (16
candlemeters). With the older fish this does not seem to be
true.

The conclusion that young Brook Trout larvae are negatively
phototropic was corroborated by other incidental observations.
When a dish containing fish was placed before a window, they
almost invariably sought the side of the dish away from the
light. The same was true of the Rainbow Trout.

In order to discover whether a Brook Trout is photokinetic,
a Nernst lamp was suspended about eighteen inches above a
dish containing them. When the light was first turned on, the
trout darted about vigorously, many seeking the corners of the
dish. After a few minutes' exposure, however, they came to rest
quietly as before. The same experiment was tried with Rain-
bow Trout with like results. It was observed that the raising
of a window curtain suddenly allowing the sunlight to fall on a
dish of Rainbow Trout, stimulated them to unusual activity
for several minutes.

From these experiments it is evident that Brook Trout are
photokinetic and negatively phototropic.

7. Light and Current

It has been shown that Brook Trout are negative to light
and positive to current. It is desirable to know how they react
when the two stimuli conflict. Fish-hatchers claim that when
a light is placed at the head of the current, the trout go away
from the light, thus reversing the usual reaction to current.
In order to study this matter, the trough used for the current
experiments was entirely covered except for an opening 3 cm.

54 GERTRUDE M. WHITE

x 4 cm. at the end where the water entered. Opposite this open-
ing was placed a Nernst lamp having an intensity of about
ten candlemeters in the center of the trough.

Trout about one week old were placed in the center of the
trough, four at a time in most instances, since the trough was
found to be large enough to hold that many without inter-
ference. Their positions were noted just before the water was
turned on and again five minutes later. Twenty-five Brook
Trout were used. Of these twenty-three moved away from
the light and two fish did not change their positions.

This seems to show that Brook Trout become negative to
current when a light is placed at the head of the stream. This
probably means that in natural conditions, when they have to
choose between shelter and cool water, they seek shelter.

8. Carbon Dioxide and Light

Since an excess of Carbon Dioxide is a condition which a
growing fish is likely to meet, the way in which a Brook Trout
responds to it and the effect it has upon its light reactions is
very important in determining whether or not the trout is to
escape from the unfavorable conditions, and swim into purer
water, where there is more oxygen.

For the purpose of discovering the effect of an excess of carbon
dioxide upon the response to light, fifty individuals were tested
separately in the apparatus used for the light experiments in
a five per cent solution of carbonated water.1 The strength
of the light for one-half the fish was two candlemeters, for the
other half about eight candlemeters. The results of the two
were similar.

Almost immediately after a trout was placed in the carbo-
nated water, the fins began to move more rapidly and the mouth
to open and close with a gulping motion. Shelf ord ('14) de-
scribes this same condition in the fish that he tested in an excess
of carbon dioxide. In the present experiments, the trout were
stimulated to great activity, swimming continually from one end
of the dish to the other with no apparent reference to the light.
They were as likely to stop at the end of the dish toward the
light as at that away from it. Excess of carbon dioxide appar-
ently causes the Brook Trout to be indifferent to light.

1 The solution of carbonated water was made by adding carbonated water from
a siphon to the ordinary city water, which is taken from Lake Mendota.

THE BEHAVIO OF BROOK TROUT EMBRYOS 55

A ten per cent solution of carbonated water was also tried,
but this was found to partially anesthetize the Brook Trout
in from three to five minutes, and therefore no reactions re-
sulted. The young trout were able to endure a five per cent
solution for two or three hours without apparent injury; at
the end of such a period of time they seemed somewhat slug-
gish. A two and a half per cent solution also had a stimulating
effect. A twenty or twenty-five per cent solution caused all
swimming movements to stop almost immediately, and made
the heart beat of a trout three weeks old fall within about
eight minutes from an average of eighty beats a minute to
thirty-seven. Death ensued very soon after that. This was
tried in several other cases with similar results.

9. Reaction to Shadows

As was stated in the discussion of rheotropism, the Brook
Trout three weeks old does not respond to moving objects out-
side the water. This seems to be true of objects in the water
also, provided they do not cause mechanical jars. This absence
of reaction to shadows continues until the embryo is about six
weeks old, when the greater part of the yolk sac is absorbed.
At this time the trout suddenly begin to respond; the waving
of a hand above the dish causes them to dart about in all direc-
tions. If such a movement is made repeatedly, however, they
soon become accustomed to it and cease to react for a time.

The reaction to shadows is, therefore, not present at hatch-
ing, but becomes apparent at the time when the yolk sac is
greatly reduced in size and shortly before the feeding reactions
begin. It would be interesting to know whether there is a change
in the eye or the nerve connections at this period, which brings
about this new response, or whether it is merely due to in-
creased swimming power.

10. Feeding Reactions

The feeding reactions begin when the Brook Trout are about
two months old. At this time the larvae appear to develop a
sudden curiosity concerning everything about them. They swim
to the top more frequently and often explore the bottom. The
fish studied were fed liver chopped very fine and put into the
water with a dropper. For several days the trout did not appear

56 GERTRUDE M. WHITE

to notice it, at least they were not observed to eat. A stream
of meat juice directed against the body was avoided in the
same manner as a jet of clean water. After a week or less,
however, the trout began to take bits of food into their mouths
as they chanced upon them and often to swallow them. From
this time on they were observed to dart after pieces of meat
floating about in the water, although they often rested directly
upon meat lying on the bottom without appearing to pay any
attention to it. They were also seen to chase bubbles and bits
of filter paper, and to take them into their mouths, but they
never swallowed them. The fish were fed in dishes with black
or white bottoms. The trout were found to take food more
eagerly from the dishes with black bottoms where the food was
more plainly visible, although they would also eat pieces of
meat over the white backgrounds. This fact is made use of by
the fish-hatchers who feed the larvae in blackened troughs.

In order to discover what part is played by the chemical
sense in helping the Brook Trout to find its food, a bag con-
taining meat was placed in the water; this was nosed by the
trout and one fish bit at it. At other times two bags, one with
food and one without it, were set in the dish. The trout inves-
tigated both bags, but they bit at neither. They were appar-
ently unable to discover meat hidden under a paper in the
bottom of the dish. Although they wandered over it as they
swam about, it was not noted that its presence had any effect
upon the fish.

The Brook Trout apparently first react through sight to the
presence of food, since they were often observed to leave pieces
of meat near them to dart after bits farther away, which would
not be the case, were it the chemical sense which was most
strongly stimulated. The gustatory sense appears to determine
whether or not the food is swallowed.

C. GENERAL DESCRIPTION OF THE EARLY LIFE OF THE

BROOK TROUT

Let us follow a developing Brook Trout on the pebbly bottom
of a swift flowing stream. During the first six weeks of its
existence it does not move far from the spot where it was hatched,
but lies quietly in the shadows among the stones, out of sight
of its enemies. It is not affected by objects passing over head.

THE BEHAVIOR OF BROOK TROUT EMBRYOS 57

If someone throws a stone into the water the jar startles the
little fish into swimming about rapidly for a few seconds, after
which it sinks again into some shady nook. Here it rests, until a
sudden eddy caused by an animal swimming through the water,
makes it dart a few inches into the current. Other tiny fish
touch and jostle it continually. If the water becomes filled
with carbon dioxide, it becomes more active, and overcoming
its impulse to avoid the light, swims about restlessly from place
to place- until it comes into purer water, where it again sinks
down beneath the stones. Thus far its responses have been
largely avoiding reactions, serving to keep it from unfavorable
conditions.

When the trout is about six weeks old, it becomes more sen-
sitive to objects outside itself. The sight of other animals pas-
sing by sends it scurrying under the cover of moss and stones.
Shortly after this it begins to be curious, nosing nearly every
object which it sees. It swims to the top of the water in pursuit
of a bubble. It explores the bottom of the stream, often swim-
ming head downward, passing in and out among the rocks,
stones, and algae. Many particles on the bottom or floating
above are taken into the mouth. If found to be good to eat,
they are swallowed; if not, they are expelled. As the fish eats,
it takes food more and more eagerly until it is satisfied, when it
ceases to react, and hides in the algae.

Throughout its larval life the Brook Trout is reacting to
external and internal stimuli, responding to nearly every cur-
rent, object, or ray of light that strikes it.

In general, the behavior suits the needs of the fish. As long
as the trout are very young, and are encumbered with the large
yolk sac, which renders them unable to swim any distance,
their reactions are such as would naturally tend to keep them
lying quietly out of the sight of their enemies. They exhibit
no curiosity, but avoid the light, hiding beneath the rocks and
stones, reacting to current just enough to keep them from being
carried down stream. The trout appear not to notice external
objects, except as their approach jars the fish, making them
struggle to regain their equilibrium.

As was previously stated, an excess of carbon dioxide renders
them temporarily indifferent to light, so that they swim about
restlessly until they reach a place where the water is purer.

58 GERTRUDE M. WHITE

When the Brook Trout grow larger, lose the yolk sac, and
become strong enough to escape their enemies by swimming
away, they begin to notice moving objects inside and outside
of the water. The approach of any object sends them darting
about in all directions in search of a hiding place. Just before
the trout are old enough to commence eating, they show great
interest in every object in the water, and begin to try taking
any small object from a bubble or a bit of alga to a piece of
meat into their mouths, though they appear to swallow only
such as are edible.

From the consideration of the facts of behavior one is natur-
ally led to ask what are the artificial conditions which best
suit the needs and instincts of the young trout. In other words,
what is the economic importance of the experiments discussed
in this paper. One easily concludes from the observation of
the natural conditions of Brook Trout and their reactions to
current and carbon dioxide, that the first essential is cool run-
ning water with plenty of oxygen. The water should be free
from algae of a sort which is apt to get into the gills. If a
fungus attacks the young trout, the disease spreads rapidly,
unless the infected and dead fish are removed, since the fish
knock against each other as they swim about.

The fact that Brook Trout are so strongly negative to light
seems to indicate that hatching troughs should be covered,
or if the fish are in ponds or streams, that the trout should have
natural covers, such as rocks, stones, or water plants, under
which to hide. By living beneath these they may often escape
predaceous animals which prey upon them.

Since it requires nearly a week for Brook Trout to learn to
eat, they should be carefully watched when they are near the
feeding stage, for if they do not learn to take food before the
yolk sac is entirely absorbed, they will die of starvation. Shortly
before the trout are two months old, they commence to swim
to the top frequently and to exhibit curiosity, which indicates
that they will soon begin to eat. Meat ground or chopped
very fine should then be introduced into the water, so that the
fish may take particles of it into their mouths by chance, as
they wander about, and thus become accustomed to it before
it is necessary for them to eat.

THE BEHAVIOR OF BROOK TROUT EMBRYOS 59

D. SUMMARY

1. The Brook Trout which has just hatched swims with a
whirling movement. About the fourth day after hatching, the
trout commences to swim in a spiral course, and from then on,
the movements become gradually better co-ordinated, the trout
swimming in larger circles and going straight ahead for greater
distances.

2. The Brook Trout reacts to touch and mechanical jars
immediately after hatching. The head is the least sensitive
to touch of any part of the body, the eye being insensitive.
The reaction is more marked when the trout is stimulated at
a number of points, than when it is touched with a single bristle.

3. Positive rheotropism becomes apparent as soon as the trout
has hatched.

4. The Brook Trout is photokinetic and negatively photo-
tactic.

5. Directive light from a lamp at the source of the current
reverses the usual rheotropic reaction, showing that Brook
Trout are more strongly negative to light than they are posi-
tive to current.

6. An excess of carbon dioxide up to a certain point stimu-
lates Brook Trout; a very strong solution depresses them. A
five per cent solution stimulates trout to move about continu-
ally and makes them indifferent to light. Stimulation is also
brought about by a two and a half per cent solution. A twenty
or twenty-five per cent solution causes a rapid fall in the rate
of the heart beat, then death.

7. Brook Trout begin to respond to shadows about the fifth
week after hatching, when the yolk sac is greatly diminished
in size.

8. Feeding reactions commence when Brook Trout are about
two months old. The sense of sight seems to cause the trout
to take small objects into the mouth, the gustatory sense to
decide whether or not they are edible.

9. Before the yolk sac is absorbed the reactions of the young
trout are protective, afterward they are exploratory and ag-
gressive.

60 GERTRUDE M. WHITE

BIBLIOGRAPHY

Bernoulli, A. L. Zur Frage des Horvermogens der Fische. Arch. f. d. ges.

1910. Physiol, vol. 134, pp. 633-644.
Clark, Frank N. The Brook Trout. U. S. Com. oj Fish and Fisheries. Revised

1900. edition, pp. 80-90.
Herrick, C. J. The Organ and Sense of Taste in Fishes. U. S. Commission

1902. Bulletin for 1902, pp. 237-272.
Lyon, E. P. On Rheotropism: I. Rheotropism in Fishes. Am. Jour. Physiol.,

1904. vol. 12, pp. 149-170.
Parker, G. H. Influence of the Eyes, Ears, and Other Allied Sense Organs on

1909. the Movements of the Dogfish Mustelus canis (Mitchill). Bull.
U. S. Fisheries, vol. 29, pp. 45-47.

1910. Olfactory Reactions in Fishes. Jour. Exper. Zool., vol. 8, no. 4, pp.

535-542.
Paton, S. The Reaction of the Vertebrate Embryo to Stimulation and the Asso-
1907. ciated Changes in the Nervous System. Mitteil. a. d. Zool. Stat. z.
Neapel, Bd. 18. Heft 2 und 3, pp. 535-581, Taf. 23-25.
Shelford, V. E., and Allee, W. C. Rapid Modification of the Behavior of Fishes
1914. by Contact with Modified Water. Jour. Animal Behav., vol. 4,
no. 1, pp. 1-30.

THE EARTHWORM AND THE METHOD OF TRIAL

L. H. BITTNER, G. R. JOHNSON, AND H. B. TORREY

Reed College, Portland, Oregon

About ten years ago Jennings attempted to clarify existing
conceptions of the behavior of the lower organisms by sub-
stituting for what he believed to be an inadequate theory of
tropisms a conception that rested on what has come to be
known as the " method of trial."

Tropism hypotheses have existed at various times that have
differed in various respects. There is no doubt that in one
respect or another, some of these hypotheses have been open
to just criticism. That the method of trial affords an escape
from such criticism, however, is becoming less and less apparent
with the passage of time.

Notwithstanding their differences, all tropism hypotheses
agree in excluding the conception of orientation by trial reac-
tions. Fundamental to them all is the conception of orienta-
tion by means of movements that, with reference to a given
source of stimulation, are predictable as to direction. However
cogent, then, the criticism of a particular variety of tropism
hypothesis in other respects, it can hardly affect the funda-
mental characteristic which they all possess in common.

Some months ago, an analysis of the behavior of Porcellio
scaber showed that the method of trial was incompetent to inter-
pret the orientation of this organism under photic stimulation.1
In the present paper we shall consider the orientation, under
similar stimulation, of the earthworm (Allolobophora sp.), an
organism of some complexity -of structure, whose behavior has
seemed to some observers to lend support to the method of
trial. These critics have based their conclusions in part on
observations,2 in part on the identification of "random" with

1 Torrey and Hays. The Role of Random Movements in the Orientation of
Porcellio scaber to Light. Jour. Animal Behav., 1914, 4, p. 110.

2 See especially Holmes. The Selection of Random Movements as a Factor in
Phototaxis. Jour. Comp. Neur. Psych., 1905, 15, p. 98.

61

62 L. H. BITTNER, G. R. JOHNSON, AND H. B. TORREY

"trial" movements, a source of confusion that has already been
discussed in the paper on Porcellio to which we have just
referred.

The earthworm comes midway between the sow bug (Porcel-
lio) and the leech in the freedom with which it bends its body
when reacting to light. It has been shown3 that the first move-
ments of Porcellio after stimulation are away from the source of
light. The body moves stiffly as a whole. The photoreceptors
are anteriorly placed paired eyes. Holmes cites observations on
the leech Glossosiphonia that show a wide range of mobility in its
response to light, dependent upon its characteristic locomotion.
The earthworm does not react stiffly, like Porcellio, nor are
more than a very few anterior segments concerned in what-
ever random movements may be observable under photic stim-
ulation. Holmes was led to believe that the method or orienta-
tion of the leech is, in principle, the same as that of the earth-
worm. He calls especial attention to the characteristic waving
of the body, preliminary to fixation of the anterior end. Our
observations, however, encourage us to place emphasis on the
resemblance of the reactions of the earthworm to the behavior
rather of Porcellio than of Glossosiphonia. The random move-
ments of the earthworm have thus appeared to us to be less
significant elements in its orientation to light than the obser-
vations of Holmes indicated.

It is characteristic of the earthworm when advancing in dif-
fused light, to protrude its anterior end first on one side and
then on the other, with successive extensions, in fairly regular
alternation. A distinct tendency thus exists for this end, when
bent to one side, to bend to the opposite side at the next exten-
sion. Mechanical causes, such as tensions in muscles and skin,
are probably responsible for it. It is natural to expect evidence
of this tendency in experiments on earthworms where relatively
low intensities of light are employed unilaterally. Mast, indeed,
asserts that in active worms, " the anterior end is simply turned
sharply in the direction opposite to that in which it is when it
receives the stimulus. . . . Thus it is turned toward the
light about as often as from it, regardless of the light inten-
sity."4 Sluggish individuals, however, reacted quite differently.

3 Torrey and Hays, 1914.

4 Light and the Behavior of Organisms. 1910, p. 200.

THE EARTHWORM AND THE METHOD OF TRIAL 63

From what we judge to have been a neutral position, six slug-
gish individuals, in one hundred and fifty trials, turned toward
the light in but ten of them. In certain other cases there " was
no evidence of even the slightest preliminary turning toward the
source of light." (P. 201.)

From this evidence ours differs in that our active individuals
behaved in the low intensities of light used very much like the
sluggish individuals of Mast. Whatever the ultimate signifi-
cance of this distinction, we have been forced to conclude, as
Mast appears to have concluded, that under some conditions,
earthworms respond to photic stimulation by orienting reactions
that are in no sense trial or random movements. Nevertheless,
in our figures, there was unmistakable evidence of that tendency
which has been mentioned of the anterior end to swing from
side to side. This did not appear, however, in our first series
of experiments.

In our first series, sixteen active individuals, taken from
darkness, were each subjected to one hundred exposures in
quick succession to a very low light intensity. The worm under
observation crawled over a moist slate. When, in very weak
diffused light, the anterior end was pointed straight forward,
the light of a small pocket lamp was flashed upon it from a
distance of 50 mm. at an angle of ninety degrees with the body
axis. The results are shown in the accompanying table.

From these figures it appears that our earthworms exhibited
a marked disposition to react without trial negatively to the
light used.

Our second series of observations was taken under somewhat
different conditions, and shows very clearly the tendency to
which we have alluded above. Each of ten worms was sub-
jected to a total of but thirty trials, in groups of ten. In the
first ten trials, the anterior end was bent toward the light at
the instant the light was flashed; in the second ten it was in a
neutral position, that is, directed forward; in the third ten, it
was bent away from the light. Each worm was rested for about
seven minutes in darkness after each group of ten trials. A
light of slightly greater intensity was used, namely, a 25 w.
Mazda lamp, 160 mm. distant, so screened that the ray falling
on the worm was about 8 mm. wide. In other respects, the
conditions were essentially the same as in the first series.

64 L. H. BITTNER, G. R. JOHNSON, AND H. B. TORREY

TABLE 1

No. of
trials

Direction of first
movement

Toward
light

Away from
light

Earthworm No. 1

100

100 .

100

100

100

100

100

100

100

100

100

100

100

100

100

100

18
22
18
28
16
26
34
14
24
28
12
32
20
21
43
34

82

2

78

3

82

4

72

5

84

" 6

74

7

66

8

9

10

86
76
72

11

12

13

88
68
80

" 14

79

" 15

57

16

66

Totals

1600

390

1210

Percentages

24.4%

75.6%

TABLE 2

No. of
trials

Position of anterior end with reference
to light

Toward

Neutral

Away

Sense of response

— +

+

— +

Earthworm No. 1

30
.. 30

9 1
8 2
8 2
10 0
10 0
10 0
10 0
10 0
10 0
10 0

8 2

9 1
9 1

10 1
9 1
8 2

8 2

9 1

8 2

9 1

9 1

2

9 1

3

4

5

30
32
30
30
30
30
30
30

7 3

8 3
7 3

6..

9 1

" 1 ...

8 2

8

9

9 1
10 0

" 10

9 1

Totals

302

95 5

87 14

85 16

Percentages of first movements
away from light

95%

86.13%

83.16%

THE EARTHWORM AND THE METHOD OF TRIAL 65

Assuming now, the observed tendency of the anterior end to
swing in fairly regular alternation from side to side in succes-
sive extensions; and assuming, further, the tendency brought
out by the figures just given, for the anterior end to swing directly
away from the light; one should expect to find the anterior end
swinging away from the light most frequently, in this second
series, when it was turned toward the light at the instant the
latter was flashed, and least frequently when it was turned away
from the light at the moment of flashing.

This expectation is, in fact, realized in the following figures.
The light was flashed on the right of the first seven individuals,
on the left of the others.

The third double column of figures is especially significant,
as it shows a very marked negative reaction of the worms ob-
served, under the conditions of the experiment, in spite of the
conflicting tendency manifested in diffused light to swing the
anterior end in the opposite direction.

Holmes has pointed out the danger of failing to notice certain
very inconspicuous movements that might be started toward the
light but not followed up. We have tried to guard against this
opportunity for error. At the same time, it may be worth while
to remark that a certain degree of extension of the anterior
segments appears to be necessary to expose the photoreceptors
to effective light intensities. Our figures seem to us to show
clearly that photic stimulation, far from inducing random move-
ments, immediately calls forth reactions in a definitely predict-
able direction. In the face of the facts, a view based upon
minute random movements that are not referable to photic
stimulation can hardly affect the conclusion that the earth-
worm must be placed, with Porcellio, in that group of organisms
whose orientation to light is determined essentially by move-
ments that are predictable as to direction and hence neither
random movements nor " trials."

ELIMINATION OF ERRORS IN THE MAZE*

HELEN B. HUBBERT

While engaged in a research problem on the learning ability
of white rats at different ages, my attention was directed to
the question of the elimination of useless movements in the
learning of the maze. I decided to test whether or not such
eliminations occur progressively, i.e., whether useless movements
most closely connected with satisfaction (food) are the first to
drop out, while the useless movements most remote from the
source of satisfaction (food) persist the longest.

The observations recorded in this paper were made on four
groups of rats of different ages during their learning of the
Watson maze which, with its camera lucida attachment, is
described at length in a previous number of this journal.2 The
process of training and the criteria of learning were the same
as those set forth in a previous paper.3

As has been pointed out by Watson,4 according to the pleas-
ure-pain hypothesis, the inference of progressive elimination is
plain.' Food (the "satisfier") is at the center of the maze.
Errors in the alley nearest the food should be the first eliminated ;
those in the alley next nearest, second, and so on until we reach
those in the first alley (the one farthest from the food). Errors
in this alley should be the ones last eliminated.

An examination of the plan of the maze will show that in
every alley except VI there are three possibilities of error, viz. :

1. Taking the wrong turn at the alley entrance.

2. Going too far in the alley, i.e., past the entrance to the

next alley.

3. Taking the correct turn, but returning ("doubling" on the

pathway) .
In VI the first error is impossible because there is no stop,
and either turn leads to the food box. The second error re-
solves itself into a circling of the food box, which, however,

1 From the Psychological Laboratory of The Johns Hopkins University.

2 Watson, J. B. Journal Animal Behavior, vol. IV, p. 56.
3Hubbert, H. B. Ibid, pp. 60-62.

4 Watson, John B. Behavior. Holt & Co., p. 268.

66

ELIMINATION OF ERRORS IN THE MAZE 67

rarely occurs.5 The third error is the most common one. Start-
ing to the right, the rat retraces its path and goes to the left,
or vice versa. Clearly then, the sixth alley is not strictly com-
parable with the others, and should not be considered. It is
therefore set off from the rest in the accompanying tables.

In the first alley the emotional disturbance of the animal is
very great. Whether he will turn to the right or to the left
is a matter of pure chance. Watson has shown that the learn-
ing of the maze is due largely to the kinaesthetic and organic
impulses which cannot begin to play their role very effectively
until some distance has been run in the maze.6 As stated
above, the start in the first alley is as likely to be in the wrong
as in the right direction. If the start is wrong increasing dis-
turbance ensues, and is often carried over into alley II.7 Aside
from this fact, there is the very strong tendency to back-track
to the point of entrance (E), which has a different stimulating
value from any other part of the maze. It is for these reasons
that the first alley as well as the sixth is judged incomparable
with the rest and hence is set off from them in the tables.

This leaves for consideration four alleys, II, III, IV and V.
Whether the process in question is spoken of as the elimination
of errors, the "stamping in" of useful movements and the
"stamping out" of useless ones, or simply as the elimination of
alleys matters little; the facts remain the same. The writer has
chosen for convenience to speak of the elimination of super-
fluous movements in an alley as the elimination of the alley
itself, and the results are so tabulated. For example, Rat 4
of Group A made its last error in alley II at the 11th trial,
running the alley perfectly in all succeeding trials. The alley
is therefore spoken of as eliminated at the 12th trial. Likewise
III was eliminated at the 8th trial, IV at the 3rd and V at the
7th trial, no errors being made in those alleys after the 7th,
2nd, and 6th trials respectively. The first column gives the
laboratory number of the animal, while column 2 gives the
total number of trials the animal required to learn the maze.

5 This error seldom occurs, because in passing the entrance to the food box the
smell and sight of the food become directive.

6 Watson, J. B. Kinaesthetic and Organic Sensations — Their Role in the Reac-
tion of the White Rat to the Maze. Psychological Monographs, Series No. 33.

7 It is not unlikely that the deviation of the results in alley II from those in III,
IV and V may be explained in this way.

68

HELEN B. HUBBERT

In the tables, cases which undoubtedly show uniform pro-
gressive elimination, i.e., a 5-4-3-2 order, are doubly starred (**).
Cases which might possibly be considered progressive are singly
starred (*). Cases clearly not progressive are unmarked.

TABLE I
Group A— 25 Days

Trials

Alleys

Rat

I

II

III IV

V

VI

4

18

10

12

8 3

7

3

5

14

7

6

9 9

8

5

6

45

40

32

29 10

37

10

7

66

60

35

43 49

15

1

8

32

25

26

25 17

11

1

9

38

33

22

27 31

24

1

10**

28

21

22

14 8

5

9

11

18

13

12

7 2

10

5

12

32

19

27

16 17

13

1

13

46

39

38

41 13

26

1

14

24

17

17

4 3

12

2

15

34

25

13

11 1

28

4

16

27

17

14

22 5

6

1

17

26

21

13

11 6

7

19

19

40

30

33

34 30

19

5

20**

34

28

28

15 10

9

1

21

36

31

18

25 13

14

2

22

32

27

23

23 18

23

7

23

34

15

19

29 22

23

1

24

24

11

18

9 6

19

10

25

36

19

29

19 19

30

3

Totals. . 21 rats

508

457

421 293

346

92

Averages

24

22

20 14

16

4

2 cases (**) uniformly progressive or 10%, vs. 90% not progressive.
9 cases where IV and V are eliminated before II and III, or 43%.

DISCUSSION OF THE TABLES
Group A— 21 Rats

These rats began the problem when twenty-five days old.

Two of the twenty-one showed uniform progressive elimina-
tion, i.e., alley V was eliminated first, alley IV second, alley
III third and alley II fourth and last. We find then two cases
of uniform progression and nineteen cases clearly not uniformly

ELIMINATION OF ERRORS IN THE MAZE

69

progressive, i.e., ten per cent progressive versus ninety per cent
not progressive.

If we now count the cases where IV and V are eliminated
before II and III but not in a 5-4-3-2 order, e.g., Rats 4 and 16,
we find them to be nine, or forty per cent of the group, which
is less than would be expected on a chance basis.

If, however, instead of considering individual cases, we look
at the averages, we still find no uniform progression. But
here again IV and V are eliminated before II and III.

TABLE II

Group B— 65 Days

Alleys

Rat

Trials

I

II III IV

V

VI

11

18

13

8 8 9

3

1

12

34

25

28 20 29

25

1

13**

22

9

17 10 3

1

7

14

22

16

15 15 3

7

1

15

28

19

12 22 9

9

3

16

36

30

17 9 31

16

8

17

36

30

25 16 2

26

7

18

66

61

47 24 54

33

5

19

32

26

18 4 2

8

3

20

36

31

20 9 12

9

4

21

46

41

36 37 8

8

6

22

21

15

13 6 6

8

2

23

38

31

22 33 29

26

1

24

38

33

30 15 24

28

1

25

14

9

4 5 9

3

1

27

40

35

29 12 9

25

3

28

20

15

9 10 5

4

1

Totals — 17 rats

439

350 255 244

239

55

Averages

26

21 15 14

14

3

1 case (**) uniformly progressive or 6%,
vs.
16 cases not uniformly progressive or 94%.
5 cases where IV and V were eliminated before II and III, or 29%.

Group B— 17 Rats

These animals began the problem when sixty-five days old.

Of the seventeen, one rat showed uniformly progressive elim-
ination while sixteen did not, i.e., six per cent progressive and
ninety-four per cent not progressive.

70

HELEN B. HUBBERT

TABLE III
Group C— 200 Days

Alleys

Rat

Trials

I

II

III IV

V

VI

6

18

12

9

4 7

9

3

7

54

48

46

40 42

35

16

8

44

39

36

33 38

24

21

9

26

13

19

5 21

5

5

10

20

15

5

4 3

4

1

11

20

13

14

4 13

11

11

15

32

27

23

23 7

20

4

17

56

50

35

22 45

19

11

18

79

71

66

30 74

29

12

19

49

44

44

18 9

15

11

20*

27

22

9

8 8

8

8

21

32

26

18

7 13

12

2

23

30

25

17

25 4

22

3

24

30

25

15

13 14

9

1

25

35

26

30

9 30

8

8

27

22

11

17

9 14

6

6

29

104

99

95

74 88

88

5

30*

108

101

98

87 87

38

22

31

64

58

45

55 23

12

1

33

32

27

15

27 24

19

5

34

22

13

15

5 13

17

17

35**

37

30

30

16 13

10

2

36

32

21

8

2 8

15

26

38

14

9

7

4 4

6

1

Totals. . 24 rats

825

716

524 602

441

202

Averages

34

29

22 25

18

1

8

1 case (**) or 4% uniformly progressive.

2 cases (*) or 8% doubtful.

21 cases or 88% not progressive.

3 cases or 13% in which IV and V were eliminated before II and III.

Here we find five rats eliminating IV and V before II and
III, or twenty-nine per cent.

The averages show possible uniform progression, although the
values for III, IV and V are too nearly identical to warrant
such an interpretation.

Group C— 24 Rats

These rats began the problem when two hundred days old.

Of them, one rat showed uniform progressive elimination, two
possible progressive elimination, while twenty-one did not show

ELIMINATION OF ERRORS IN THE MAZE

71

such progression. Stated in percentages, four per cent were

progressive, eight per cent possibly progressive and eighty-eight

per cent non-progressive.

Here we find only three cases or thirteen per cent where IV

and V were eliminated before II and III. The averages showed

no progression; IV and V were not even eliminated before II

and III.

TABLE IV

Group D— 300 Days

Alleys

Rat

Trials

I

II

III IV

V

VI

15

78

67

72

35 39

35

3

16

20

14

11

9 10

8

1

17

48

43

28

15 36

14

3

18

40

31

35

9 32

34

7

19

14

9

9

4 9

5

1

20**

58

45

52

35 28

27

5

21

30

25

12

6 9

9

13

22

82

77

67

47 64

66

66

24

42

37

33

26 25

28

34

25

54

49

27

37 49

49

37

26*

19

14

10

7 7

7

4

27*

70

65

61

24 24

22

24

28

38

33

24

20 6

24

5

30

27

22

16

15 8

13

6

31

84

78

32

53 72

69

69

33

16

11

8

5 2

11

3

34

66

60

60

25 26

48

27

35

38

32

20

19 20

17

9

36

26

15

15

5 15

11

21

37

44

39

29

17 13

30

5

38**

34

28

23

15 8

6

1

39**

35

5

29

23 21

11

4

Totals . . 22 rats

799

673

451 523

544

128

Averages

32

30

20 24

25

16

3 cases (**) or 14% uniformly progressive.

2 cases (*) or 9% doubtful.

17 cases or 77% not progressive.

3 cases or 14% where IV and V were eliminated before II and III.

Group D— 22 Rats

These rats began the problem when three hundred days old.
Three of the twenty showed uniformly progressive elimina-
tion, two showed possible progressive elimination, while seven-

72 HELEN B. HUBBERT

teen did not show uniform elimination, i.e., fourteen per cent
were progressive, nine per cent possibly progressive and seventy-
seven per cent not progressive.

There were three cases where IV and V were eliminated before
II and III or fourteen per cent.

The averages do not show progressive elimination nor were
IV and V eliminated before II and III.

We do find, however, in every group that alley II is nearly
always the last to be eliminated. A possible explanation of this
has already been offered on page 67. The results in alleys III,
IV and V are so nearly identical that the three may be con-
sidered as eliminated at practically the same time.

From these experiments it seems fairly probable that the rapid-
ity with which a given co-ordination in a complex habit is formed
is not proportional to the distance from the point at which
the co-ordination takes place to the point at which food is to
be obtained.

NOTES

NOTE ON THE REACTION OF THE HOUSE-FLY

TO AIR CURRENTS

F. ALEX. McDERMOTT
Mellon Institute, University of Pittsburgh, Pittsburgh, Pa.

While making some experiments on the drying of certain vege-
table materials in a current of air, the following observation was
made, which may be of interest.

The material had a strong attraction for flies, of which there
were several in the room, and as their presence did not interfere
with the work, no precautions were taken to screen them off.
The apparatus consisted of a flat bottomed aluminum dish,
20 cm. in diameter, with vertical sides 8 cm. high; into this dish
was blown a current of air having a volume of about one-fourth
to one-half cubic meter per minute, by means of an electric
hair-drier (speed equals about 100 meters per minute). The air
was slightly heated, showing 29 to 30° C, when the room tempera-
ture was 26 to 27° C. The air current struck the center of the
bottom of the dish at an angle of 60°, passing over two 5 cm.
aluminum dishes, in which the material being dried was contained.
Flies alighting on the material in these dishes soon turned toward
the direction from which the air was coming, walked down over
the edge of the dish, on to the bottom of the large dish, and toward
the point where the air current struck the bottom, usually stop-
ping two or three centimeters from the center; here they would
remain, with their axes parallel to the direction of the air current,
and their heads facing to windward for half an hour or longer,
if not disturbed. They appeared to be pressed down against
the bottom of the dish by the force of the air current, quivering
slightly with variations in the pressure, and they were observed
not to be feeding. New comers, alighting in any other than the
position above described, moved about in short jerks, until they
had assumed this position. Sometimes chains of two or three,
immediately back of one another, would be formed, with spaces

73

74 F. ALEX. McDERMOTT

of only a few millimeters between them, though more usually
they placed themselves so as to have the head in the direct
air current. Those in other portions of the dish assumed posi-
tions with the axis parallel to the stream lines, with the head to
windward, even though they happened to be in a slight eddy
current. A thermometer was placed in the dish, inclined toward
the fan; a few insects climbed up this toward the fan, but the
current appeared to be too strong for them. Increasing the tem-
perature of the air current to 40° C. caused scattering and finally
flight, though the flies seemed reluctant to go, rather attempting
to back away slowly, before taking to flight. Sudden stopping
of the current .of air caused immediate dispersal. While most
of the insects took to flight at once on being disturbed mechani-
cally, as with the bulb of the thermometer, a few of them would
allow themselves to be pushed about and even pressed down
tightly on the bottom of the dish, with the thermometer bulb,
without taking flight. The writer believes that the observation
has been made that flies lighting on moving vehicles usually turn
with the axis parallel to the direction of motion, and with the head
forward, but he is not aware of any observation of the kind here
recorded. Unfortunately, means were not at hand to try the
effect of wider and lower variations of the temperature of the air.

FINANCIAL STATEMENT

For the information of its subscribers, contributors, and bene-
factors, the Journal of Animal Behavior proposes hereafter to
publish, in the first number of each volume, a brief statement of
its financial condition.

Financial Statement for the Journal of Animal Behavior,
December 30, 1913 to December 1, 1914 (Volume 4)

receipts

Balance from 1913 $154.67

Receipts from sales of complete volumes and

odd numbers 786.30

Receipts from advertising 50.00

Gifts and contributions toward the cost of

illustrations and tabular material 222.13

Interest 27.26 $1,240.36

EXPENDITURES

Cost of manufacturing and distributing vol-
ume 4 (this does not include cost of paper,
paid in 1913) $868.48

Office expenses, including postal and express
items 180.00 1,048.48

Balance on hand $191.88

JOURNAL OF ANIMAL BEHAVIOR

Vol. 5 MARCH-APRIL 1915 No. 2

A STUDY OF THE BEHAVIOR OF THE CROW

CORVUS AMERICANUS AUD. BY THE

MULTIPLE CHOICE METHOD

CHARLES A. COBURN AND ROBERT M. YERKES1
The Harvard Psychological Laboratory and the Franklin Field-Station

We have previously reported in this Journal2 observations
on the behavior of crows in certain forms of visual discrim-
ination. The subjects of that investigation were transferred
from the Franklin Field-Station in September, 1913, to the
Laboratory of Animal Psychology in Cambridge, and were there
kept until June, 1914, in a cage approximately six feet in its
several dimensions. Despite their close confinement and the
lack of an out-of-door fly, the birds continued in excellent health
and proved themselves able to withstand wholly satisfactorily
the conditions of laboratory life. When returned to the Field-
Station, they were considerably less tame than during the previous
summer. For this reason they were not used further for exper-
imental purposes, but were kept for general observations. Young
crows were captured for the experiments which are reported
in this paper.

Instead of following up the study of visual discrimination,
we devoted our attention, during the summer of 1914, to an
attempt to analzye ideatiqnal and allied forms of behavior in
the crow by means of the Yerkes multiple choice method, and

1 The observations reported were made chiefly by Mr. Coburn and the paper
was written by Mr. Yerkes.

2 Coburn, C. A. The behavior of the crow Corvus Americanus, Aud. Journal
of Animal Behavior, 1914, 4, 185-201.

76 CHARLES A. COBURN AND ROBERT M. YERKES

to the accumulation of additional facts concerning the natural
history, instincts, and general habits of the birds.

On June 7th, 1914, three young crows were captured near
the Station. These birds were about ready to leave the nest.
One, indeed, was taken from a limb beside the nest. This indi-
vidual from the first exhibited fear and was so troublesome
that after two days it was discarded and the remaining two
birds wTere kept for observation. They were placed in a box
which was frequently passed by human beings, and were several
times a day fed by hand, being allowed to come out of the box
at will and become thoroughly accustomed to the experimenters.
From the time of capture they were perfectly tame, ate readily,
and the characteristic fear reactions never appeared. When
taken from the nest, they were probably at least six weeks old.

Throughout this report, these birds will be referred to as
number 3 and number 4. Number 3 was from the first the
larger of the two and the less timid. It, during the several
months of observation, always came to us, perching on arms,
shoulder, or head, as it had opportunity, and showing a friendly
interest which was apparently somewhat independent of its
desire foi food. It evidently liked to be petted. Our assumption
is that this bird is a male.3 Number 4, by contrast, was smaller,
shyer, more wary, and after a few weeks ceased to come to either
of us, except as drawn by hunger, and even then it often hesi-
tated to perch upon the hand or arm. In all probability, it is
a female. It has eaten less than number 3, and has been
considerably more difficult to experiment with. Usually, in the
course of an experiment, if the birds were in competition, number
4 would stand aside for number 3.

Our additional experience with crows during the present season
but emphasizes our conviction that they are among the most
interesting of birds, and that their behavior is in every respect
worthy of careful analytic study. With respect to what we
shall term "ideational behavior," they have fallen short of our
expectations, for in the light of their varied interests, ingenuity,
curiosity, ceaseless activity, and apparent insight into simple
situations, we had assumed that they possess an intelligence
equal to that of many of the more intelligent mammals. The

3 Since this was written, dissection has definitely established our surmise in the
case of both birds.

A STUDY OF THE BEHAVIOR OF THE CROW 77

experiments now to be reported were conducted for the special
purpose of obtaining definite and reliable information concerning
the nature and limitations of their ability to adjust themselves
to certain fairly simple, although novel, situations.

We sought to make our measurements of intelligence by a
method recently devised at the Psychopathic Hospital, Boston,
by R. M. Yerkes, for the comparative study of ideational and
allied forms of behavior in man and other animals. This method
has been named the soluble-problem multiple-choice method. It
was devised primarily for the purpose of enabling the comparative
psychologist to present to any human or infra-human subject,
no matter what the age, degree of intelligence, or condition of
normality or abnormality, a series of situations increasing in
complexity from an extremely simple one to one so intricate
that even the most intelligent human subject might spend hours
or days in adjusting himself to it. By means of this multiple
choice method, it is hoped and confidently expected that the
materials of comparative psychology may be rapidly increased
and the analyses of animal behavior be made invaluable to the
psy chopathologist .

A general description of the method should preface this account
of the special form in which it was applied to the crow, inasmuch
as only a very brief account of it has been published.4

In brief, the essentials of the method are these. A series of
reaction mechanisms, appropriate to the subject, are presented.
From this series one mechanism must be selected which, when
properly approached, will yield the subject the satisfaction of
success and, possibly, the reward of food. With each presenta-
tion of the reaction mechanisms, they are varied in number and
in position. The subject is therefore forced to select the proper
mechanism on the basis of some particular relationship of that
mechanism to its fellows, this relationship having been determined
upon in advance by the experimenter. It may be, for example,
such a simple relation as first at the left of the series as the
subject approaches, or first at the right of the series, or second
at the left, or alternately the first at the left and the first at
the right, or the middle of the series. Imagine, then a series
of piano keys which may be presented to a human subject. They

4 Yerkes, Robert M. The study of human behavior. Science, 1914, 39, 625-633.
In this paper the writer describes his method in contrast with the Hamilton quad-
ruple choice method.

78 CHARLES A. COBURN AND ROBERT M. YERKES

may vary in number from two to twelve (this was the original
form of apparatus). Some one key, in any group of keys pre-
sented, when pressed will cause a bell to ring, thus indicating,
success. Without other aid than his own observation, the subject
is expected, from repeated presentations of the keys, to discover
the essential relation and to acquire the ability to select the
right key with certainty.

This method has the advantage of enabling the experimenter
to present increasingly difficult problems to his subjects. It
has further the advantage of enabling him conveniently to record
the essential features of reaction, and later to analyze the reactions
at his leisure. But most important of all, it yields strictly
comparable results when applied to widely differing organisms.
Naturally, although the same problems may be presented to
diverse types of organism, the reaction mechanisms must be
suited to the subject in question.

Without further general comment or discussion of the multiple
choice method, we shall describe the form of apparatus and
procedure employed with the crow.

APPARATUS AND METHOD

In the accompanying plate, designated as figure 1, and in
the ground plan of the observation-room and apparatus, shown
in figure 2, the general experimental situation is represented.
Figure 1 shows in the background the building which was used
both as a shelter for the crows and as an observation place for
the experimenter. To this building is attached a fly which
appears in C, D, and E of Figure 1. In figure 2, the ground
plan of the building, are seen the experimenter's room, A, and
the crow room, B, the latter containing a perch, P. All coarsely
dotted lines in this figure indicate walls or partitions made of
poultry wire. The large fly was, for the purposes of our ex-
periment, divided into two parts by a wire partition. In the
smaller of these portions, shown at the right of figure 2, the
multiple choice apparatus was located. The crows could enter
this portion of the fly only at the will of the experimenter, where-
as they were allowed the freedom of the larger portion, which
we have labelled C. As figure 2 is drawn to scale (one inch to
forty-eight) it is unnecessary to give the measurements of the

*■■■*_

V

I

i'ii J

■HBH

Figure 1. Views of crows and apparatus for multiple choice experiments. A and
B, crows, number 3, d\ on shoulder of experimenter, and number 4, 9 , on
arm; C, the multiple choice box seen from the observer's room and from the
direction of approach by the crow, the compartments are numbered 1 to 9
and below each number is an entrance door. D, the same seen from the oppo-
site side or rear, with the nine exit doors closed. E, the box seen from the
observer's room, with entrance doors 1 to 6 and exit door 2 open. At the
extreme left, above the entrance door to the experiment compartment of the
fly, one of the crows is visible. F, the observer's table, showing curtain before
window (partially drawn aside to admit light for the camera) and the weighted
cords with pull buttons for opening and closing doors.

\ 't lii i I i i\ i ii if i /

I l\ \|\ i I i / 1 ;i j if 1 1

\\ i \ v win n~r~jn

H

i I mj i» i i/ i/ i rh-r

\ I \j > iUi ii i if r-tr

-<-t-H -H-H-f/l / (/ )

Figure 2. Ground plan of crow house, fly, and apparatus. Scale, TV- A, obser-
vation room; B, bird room; C, main portion of fly; D, passageway for experi-
menter; E, multiple choice box; F, entrance door between main fly, C, and
alley to reaction chamber, H; G, exit door between alley S and main fly; H,
reaction chamber, the floor boards of which are separated somewhat; I, L,
approaches to the doors F and G; J, observer's table and key-board; K, observ-
er's stool; N, doors for experimenter's use; P, perches; R, alley leading to
middle of reaction chamber H; S, alley leading from exits to main fly; W,
water tub for crows.

Numerals 1 to 9, compartments of multiple choice box; a, attachment of
cord to entrance door, t, of compartment 9; b, screw eye for cord; c, screw eye
at entrance to observer's room; d, wooden button on cord; under d is a small
brass pulley for cord; h, i, j, k, indicate course of cord from exit door of com-
partment 9 to key-board; x, metal cover for food receptacle of compartment
9; z, food receptacle of compartment 4.

80 CHARLES A. COBURN AND ROBERT M. YERKES

building and fly. We shall give a more detailed description of
the experimental device.

The latter is shown fairly well from different points of view
in the parts of figure 1. Figure 1 C is a view of the multiple
choice box from the front, that is, the side of approach by the
subject. All the entrance doors are closed. Figure 1 E shows
the apparatus from the same point of view, with the entrance
doors 1 to 6 and the exit door 2 open. Figure 1 D, instead,
shows the apparatus from the opposite side, with the several exit
doors closed.

By referring now to both figures 1 and 2, we should be able
to obtain a clear idea of the construction of the experimental
mechanism and its use.

The multiple choice box, as we shall call it, appears in ground
plan as E of figure 2. It is divided into nine like compartments,
each with a door at both ends, opening outward. The outside
measurements of the multiple choice box are 81 inches long by
20 inches wide by 15 inches high. The frame of the box is made
of 2 by 2 inch stock, and the floor, ends, partitions, and doors,
of half -inch stock. The top, which is hinged for convenience
of access, consists of wire netting, If inch mesh, on a wooden
frame. On the inside, each of the nine compartments is 19 inches
long by 8 inches wide by 13 inches high. The entrance and
exit doors are 9| inches high by 7f inches wide. All of the doors
are mounted with spring hinges which hold them shut. On the
lower inner edge of each exit door is a piece of tin (x) which,
when the door is closed, projects 2 inches into the compartment
and covers a hole (z) in the floor of the compartment 1^ inches
in diameter by f inches deep. These metal covers, as well as
the holes, are represented in the ground plan of the apparatus,
figure 1, x and z. The use of these holes is to contain food
which serves as a reward for the bird when the exit doors are
opened.

The system of entrance and exit doors, nine of each, and also
the main entrance door, labelled F in figure 2, and shown in the
extreme lower left corner of figure 1 E, and the main exit door,
labelled G in figure 2, and shown at the right end of the multiple
choice box in figure 1 D, are controlled from the experiment room
A by a system of cords passing through screw eyes and pulleys.

A STUDY OF THE BEHAVIOR OF THE CROW 81

These cords are indicated by dotted lines where they pass under
the floor of the multiple choice box or under the boards which
serve as an approach to the box : Elsewhere they appear as solid
lines. The arrangement of the cord-system within the experi-
ment room is rather unsatisfactorily shown in figure 1 F.

On a table, J, before which the observer sits on the stool,
K, are two groups of cords, each with a wooden button attached
in a convenient position. The group at the experimenter's left
consists of the cords connected with the ten entrance doors,
and the group at the right, similarly, of those connected with
the ten exit doors.

We may now trace the course of the cords from the doors of
compartment 9. A cord is fastened at a to the lower outer
corner of the entrance door t. It thence passes through the
screw eye b in the edge of the approach board. From this point
it extends, under the interrupted floor of the reaction chamber
H, to a screw eye, c, in a block across the aperture leading to
the experiment room. Thence the cord passes over a small
brass pulley at d and through a hole in the table J. (In figure
2 the pulley is hidden by the wooden button on cord.) It is
kept taut by a lead weight under J. Similarly, the cord for
the exit door of compartment 9 is attached to the lower outer
corner of the door at h, passes through the screw eyes, i and j,
to the pulley k, and is kept taut by a leaden weight. The cords
for the main entrance and exit doors, F and G, run to the extreme
left and right respectively of the experimenter's table.

The experimenter operates a door by grasping the wooden
button shown on each cord in figure 1 F and pulling it toward
him. When he has pulled as far as the button will come, the
door to which the cord is attached stands wide open, and the
leaden weight under the table serves to hold it in this position
as long as the experimenter desires. When he wishes it closed,
he simply pushes the button back to its former position, and
the strength of the spring hinges suffices to overcome the pull
of the weight.

In order that the bird should not see and be influenced by the
movements of the experimenter, a black curtain was hung before
the opening into the experiment room, and through small holes
cut in it, the experimenter was able to observe the movements

82 CHARLES A. COBURN AND ROBERT M. YERKES

of his subject. At no time during the investigation did the
crows give evidence of noticing the experimenter when they
were reacting.

The remaining features of the apparatus will be mentioned
in connection with the following brief description of the exper-
imental procedure. In preparation for a series of trials, the
experimenter opens each of the exit doors and places in each
food container a small bit of milk-soaked bread. He then closes
the exit doors, thus covering the food, and takes his place at K.
He next opens a group of entrance doors. Let us suppose, as
is shown in figure 1 E, that the doors numbered 1 to 6 are opened,
and, further, that the compartment which may be designated
as the correct one is the first at the subject's left, that is number
1. Having made these preparations, the experimenter, by means
of the proper cord, opens the main entrance door F, and the
bird, either by walking up the approach board I or by alighting
on the approach board L, on a level with the entrance door,
is immediately able to enter the reaction chamber H, by way
of the alley R. By two wire partitions which appear as dotted
lines in figure 2, it is forced to walk straight ahead until it reaches
the center of compartment H. It may then face and, if it so
chooses, directly approach the central compartment of the mul-
tiple choice box. But under the circumstances, with entrance
doors 1 to 6 open, it would naturally swerve toward the left.

In case it enters compartment 1, the experimenter quickly
and noiselessly closes the entrance door after it, by releasing
the appropriate cord, and immediately thereafter, opens the exit
door of the compartment by pulling on the appropriate cord. He,
thus, with one hand prevents the retreat of the bird from the
compartment and with the other uncovers the food, so that the
bird may obtain the reward for a correct reaction. As soon as
the food has been swallowed, the crow steps out of the compart-
ment, the exit door is closed by the experimenter, and the bird
either immediately, or at the experimenter's pleasure, is allowed
to return to the fly C by way of the main exit door G.

If, instead of choosing the right compartment, the crow enters
some other one, the procedure is different. Immediately upon
its entrance, the experimenter closes the entrance door. He
then, with a stop-watch, measures a definite period during which
the bird is confined in the compartment. This period was varied

A STUDY OF THE BEHAVIOR OF THE CROW 83

during our experiments from 15 to 60 seconds, in an attempt to
discover the most satisfactory length of confinement. At the
proper moment, the experimenter opens the entrance door and
the crow is allowed to retrace its steps. It may then immedi-
ately make another choice. But not until it enters the right
compartment, is it awarded with food and allowed to return
to the fly. Thus punishment for incorrect choices is combined
with reward for correct choices.

In further description of the apparatus, it should be said that
wire partitions at each side of the multiple choice box, and
extending from the lid of the same to the roof of the fly, prevented
the crow from walking or flying over the box, while boards both
in front of the box and behind it and on a level with its floor form
a floor which prevented the bird from getting under the box.
The only possible course for the subject from main entrance
to main exit door is by way of one of the compartments.

Experience shortly indicated that the crows could be used
most satisfactorily if given their trials alternately, and the method
finally settled upon was that of admitting one crow to the appar-
atus, allowing it to make its choice, and then holding it in the
passageway beyond the exit doors until the other crow had
passed through the main entrance door into the reaction chamber.
Thus, as one subject emerged from a compartment of the box E,
the other bird entered the reaction chamber. When, as some-
times happened, the one or the other bird failed to respond
immediately and appropriately and both were in the fly, it was
fairly easy for the experimenter to admit the proper bird by
carefully manipulating the entrance door.

PRELIMINARY TRAINING

The crows obtained almost all of their food in the multiple
choice box. In order that they should work steadily and indus-
triously, it was necessary to have the pieces of bread or mouse
meat, which was sometimes used instead of bread, very small.
It proved possible to obtain as many as twenty reactions per
day from each bird, in series usually of five each.

We shall now consider the course of experimentation and its
results. One June 21st, the crows having attained ability to
feed themselves, preliminary training was undertaken, and from
that time they were fed in the multiple choice box. They

84 CHARLES A. COBURN AND ROBERT M. YERKES

exhibited no fear, rapidly became familiar with the apparatus,
and acquired skill in making the trip from the main fly, through
the experiment compartment, back to the fly. For several
days, both the entrance and the exit doors of the compartments
were kept open. Then the situation was changed by the closing
of the exit doors, and the crows were trained to enter a compart-
ment and wait for their food.

On June 27th, the first series of trials worthy of special mention
was given. The apparatus was in perfect working condition.
Food was placed on the floors of the several compartments ; the
exit doors were closed and the entrance doors were open. The
main entrance door was opened, and both birds were allowed
to enter the reaction chamber and go to the compartments for
food. As they entered the compartments, the exit doors were
opened and the entrance doors closed. Thus, by a series of
trials they were habituated to the opening and closing of the
doors and were taught to make the circuit promptly from the
main fly back to the same by way of the multiple choice box.

On the following day, June 28th, the food was placed in the
food containers and the exit doors were closed. Number 3
entered the compartments rapidly and made the circuit usually
without delay, but number 4 at first refused to enter the compart-
ments. Within two days, it, however, was readily entering,
in its search for food.

On June 28th, only three or four of the entrance doors to the
compartments were opened at any one time. In the previous
preliminary training all of the doors had been opened. Neither
bird showed any marked preference for a particular compartment
in the multiple choice box.

On June 30th, the method was tried of confining one of the
crows in the crow room B, of figure 2, while the other was given
its trials. Later in the day, the birds were given another series
of trials alternately, the one being kept in the exit alley as
described on page 83, until the other had entered the reaction
chamber. This method proved satisfactory and was later
employed to the exclusion of the former.

Up to this point, the two subjects adapted themselves to the
different situations with almost equal rapidity. Number 4 was
somewhat less willing to try new things than number 3, and
seemed to be hampered by its shyness.

A STUDY OF THE BEHAVIOR OF THE CROW 85

A significant incident is the following. In one of the trials*
number 4 accidentally fell through a five inch space which had
been left before the entrance doors in order that the crow should
not too closely approach a compartment unless it intended to
enter it. The bird fell to the ground beneath the apparatus,
finding there some pieces of bread which had been dropped
earlier in the day. Naturally enough, it ate them before it
could be induced to return to the fly. Ever thereafter, until
this crack had been closed, this bird, as it approached the com-
partments, would look through the crack to the ground. Several
times it flew down in search of food.

RESULTS, PROBLEM 1

With the final series of trials given on June 30th, regular
experiments were initiated. The problem which the birds were
required to solve was that of learning to select the first open door
at the right.

Ten settings as we shall call them, were chosen by the exper-
imenters. These are given below, numbered 1 to 10. After
each number appears the series of open doors ; in the next column,
the total number of doors open; and finally in the last column,
the number of the right compartment in which the reward of
food might be obtained.

Problem 1. First door at the subject's right to be chosen
Settings Doors open No. of doors open No. of right door

1 7.8.9 3 9

2 2.3.4 3 4

3 3.4.5.6.7 5 7

4 1.2 2 2

5 2.3.4.5.6 5 6

6 6.7.8 3 8

7 3.4.5 3 5

8 2.3.4.5.6 5 6

9 1.2.3 3 3

10 7.8.9 3 9

In this series of ten settings, a total of thirty-five doors were
open, of which number, ten were of course "right doors." Con-
sequently, the chance of a selection of the right door, without
previous experience or trial, is one to two and one-half.

In general, it was the purpose of the experimenter, as far as
possible, to follow through this series of settings from 1 to 10,
and then to return to the beginning and repeat the series. No
matter how many trials in succession could be given, the exper-

86 CHARLES A. COBURN AND ROBERT M. YERKES

iments were resumed at the point of interruption of the regular
series of settings. Thus, if five trials were given, beginning with
setting 1 and extending through setting 5, the next series would
begin with setting 6 and continue through setting 10.

As a matter of convenience, it was also decided to have the
two crows work on different settings. For example, while crow
3 was presented with the settings 1 to 5, crow 4 would be presented
with settings 6 to 10. This enabled the experimenter to avoid
the necessity of refilling the food containers after . each trial,
and it also prevented the crows from developing the tendency
to follow one another by sensory cues.

After a very few days of experimentation, both birds reacted
with remarkable alacrity and facility. They were, as a rule,
prompt to enter the reaction area and almost as prompt to
leave the exit area.

In the initial regular experiments, thirty seconds confinement
in the wrong compartment was used as punishment for mistakes.
But it shortly appeared that this was too long an interval, for
the birds hesitated to enter any of the compartments after a
half minute confinement in one of them. It was therefore
decided to use the period of fifteen seconds as punishment for
incorrect choices. Especially during the early experiments, the
crows often exhibited considerable fear and excitement when
shut in the small compartments. This diminished toward the
end of our work, and it was then possible to confine them for
a half minute or even a minute without causing disturbing
excitement.

The experimenter kept, as a matter of routine, a record of the
time from admission to the reaction chamber to entrance into
the right compartment. There is no special reason to consider
these records significant, and we shall omit them from this report.

Careful record was also kept of the chief features of the behavior
of the bird during this interval. The simple system of symbols,
which appears below, was adopted for this purpose.

O, to center of the reaction area
r, to left hand far corner of the area
-|, to right hand far corner of the area
L, to left hand near corner of the area
_j, to right hand near corner of the area
U, to center of the near side of the area
C, to center of the left side of the area
3, to center of the right side of the area

A STUDY OF THE BEHAVIOR OF THE CROW 87

If the crow merely looked into one of the compartments with-
out entering, the number of the compartment was recorded.

If it, instead, entered a compartment, the number was under-
scored. In case the compartment entered happened to be a
"wrong one", the time of entrance was placed in parenthesis
immediately after the number of the compartment. When the
time exceeded a minute, the number indicating the minutes
was placed in a circle. For less frequent forms of behavior,
other provisions were found convenient, and by the use of symbols
and other abbreviations it was found easy to obtain a fairly
complete description of the subject's behavior.

To illustrate the use of the above symbols, the following record
of a trial (trial 32 of number 3 on July 23), setting 1.2, is presented.

4, 3, i_, J, l_> ®, L, o. L, 1, L, ©, (trying to get out of area),
L, _l, ®, J, L, J, (pkd. at hole in floor), ®, 1, o, L, 9, ©, ©,
©, O, n L, 2, ®, 1, 2, 8' 13".

In this trial, crow number 3 did not enter the wrong compartment
at all. The time between the fifth and the seventh minutes was
spent before compartment 9.

It was decided by the experimenters that when a crow had
made ten correct choices in succession, its training should be
considered complete, or in other words, it should be said to have
solved the problem.

In the case of the problem in question, crow number 3 at the
end of thirty-two trials had entered the right compartment
twelve times in succession, but in several of these trials it had
been aided by the experimenter, who moved the exit door slightly
in order to attract the attention of the bird after it had for
several minutes refused to enter any compartment.

In the accompanying table 1, a summary of the trials for
each of the birds in problem 1 appears. At the head of the
several columns are the settings numbered 1 to 10, with the
right number in bold faced type. In the first column -at the
left, under each of the several settings, appears the number of
the trial and the series of compartments entered. Thus, for
example, referring to the results for crow number 3, in trial
number 5, which was the first trial in the regular series, the bird
entered compartment 8 and then compartment 9. In trial 6,
it immediately entered compartment 4, the right one. The

88 CHARLES A. COBURN AND ROBERT M. YERKES

letter a, following a number, indicates that the bird was aided
in its choice by the experimenter.

It is possible by careful study of this and succeeding tables to
discover the reactive tendencies of the organism, and to note
both the appearance and the disappearance of the same.

Problem 1, the first door at the right, proved a very easy one
for both crows. It was mastered by number 3 after fifty-five
trials, and by number 4 after fifty-one trials.

Table 2 presents the results of the various series of trials,
ranging in number from three to five for each subject. The
number of successes and failures in each series and the ratio of
successes to failures for each day appear. The letter R in this
table indicates correct first choices, the letter W, incorrect first
choices. The table has to do only with first choices.

In contrast with the above results in problem 1, the first door
at the right, we present in table 3 a summary of the results for
problem la, the first door at the left, the trials for which were
given not immediately after those just described but at the end
of the season, and after the crows had for several weeks worked
on problem 2, the second door at the left. Naturally the influence
of their training to go to the second door retarded the formation
of the habit of choosing the first door at the left. For the satis-
factory solution of the problem, one hundred trials were required
by each bird. Doubtless a change of experimenters after trial
75 somewhat delayed progress. The results which appear in
tables 3 and 4 demand no further comment.

Recurring now to problem 1 , it is obvious that from the human
point of view this is a very simple problem. The crows solved
it readily, but in the course of their work they frequently exper-
ienced discouragement and were aided in a considerable number
of their early trials by the experimenter. Doubtless our results
would be more significant had this aid been withheld, but at
the outset of our work we hesitated to run the risk of spoiling
our subjects by over-discouraging them. In problem la, no aid
was needed.

Varied reactive tendencies do not appear in connection with
this problem. Very few wrong choices were made. Conse-
quently, all that can be gleaned from the results is a general
knowledge of the behavior of the crow in the face of a certain
fairly simple experimental situation.

A STUDY OF THE BEHAVIOR OF THE CROW

89

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90

CHARLES A. COBURN AND ROBERT M. YERKES

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A STUDY OF THE BEHAVIOR OF THE CROW

91

TABLE 2

Daily Series and Averages with Ratios of Correct to Incorrect

First Choices

Crow Number 3

Problem 1

Crow Number 4

No.

Ratio

No.

Ratio

Date

of

trials

R

W

R

W

of
R to W

Date

of

trials

R

W

R

W

of
R to W

June 30

4

2

2

2

2

1: 1

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4

3

1

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1:.33

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3

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92

CHARLES A. COBURN AND ROBERT M. YERKES

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A STUDY OF THE BEHAVIOR OF THE CROW

93

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94

CHARLES A. COBURN AND ROBERT M. YERKES

TABLE 4

Daily Series and Averages with Ratios of Correct to Incorrect

First Choices

Crow Number 3

Problem 1a

Crow Number 4

No.

Ratio

No.

Ratio

Date

of

R

W

R

W

of

Date

of

R

W

R

W

of

trials

R to W

trials

R to W

Aug.

8

5

1

4

Aug.

8

5

2

3

a

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5

2

3

it

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5

4

1

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RESULTS, PROBLEM 2

Our second problem, which we arranged as a more difficult
one than the first, proved for the crows much more difficult
than we had expected. It may be described as the problem of
the second door at the left. The series of ten settings for this
problem is as follows:

Problem 2. Second door at the subject's left to be chosen

Settings Doors open No. of doors open No. of right door

1 7.8.9 3 8

2 6.7.8.9 4 7

3 2.3.4.5.6.7 6 3

4 4.5.6.7 4 5

5 1.2.3.4.5.6 6 2

6 5.6.7.8.9 5 6

7 1.2.3.4.5.6.7.8.9 9 2

8 3.4.5.6.7.8 6 4

9 7.8.9 3 8

10 2.3.4.5 4 3

A STUDY OF THE BEHAVIOR OF THE CROW 95

For these ten settings the total number of doors open is fifty,
of which ten are "right doors." The chance of a correct first
choice, without previous experience or the prejudical influence
of training in problem 1, is one to four.

In this problem, the first fifty trials were given to the crows
in groups of two and three each. The birds made so many
mistakes at the beginning that they became discouraged, and
after two or three trials, would refuse to work. Later, as they
became accustomed to the situation and the experimenter
increased the degree of hunger, they could be induced to react
five times in succession. Consequently the number of trials
per series was increased to five.

Now, as in the case of problem 1 , the experimenter was forced,
in order to avoid the possibility of utterly discouraging his
subjects, to aid them after they had worked for several minutes
without success in locating the right door. This was always
done by slightly moving the exit door of the right compartment.

After sixty-one trials had been given, the period of punishment
was increased from fifteen seconds to thirty seconds. The
thirty-second interval was used up to the four hundred and
sixtieth trial. It was then increased to sixty seconds, but as
the crows refused to work, it was decreased after forty trials
to fifteen seconds.

After the fiftieth trial, the series regularly consisted of five
trials, and four series were, as a rule, given each day.

Table 5 presents for problem 2, as does table 1 for problem 1,
a summary of the choices for each of five hundred trials given
each crow. As in table 1, the settings are indicated at the top
of the various columns, and under each setting appear the results
of the various trials for that particular setting.

It appears from table 5 that number 3, in the case of setting
No. 1, 7-9, failed with few exceptions in its first choices until
the three hundred and forty- third trial, whereas thereafter it
usually succeeded. On the contrary, in the case of setting No.
6, 5-9, we observe that the bird almost never succeeded in selecting
the right compartment in the first trial. Moreover, there is
absolutely no evidence of improvement.

96

CHARLES A. COBURN AND ROBERT M. YERKES

TAB

Results for Crow Nu

S. 1

S. 2

S. 3

S. 4

S. 5

T.

7.8.9

T.

6.7.8.9

T.

2.3.4.5.6.7

T.

4.5.6.7

T.

1.2.3.4.5.6

1

9.8

2

9.7

3

/7.6.7.7
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4

6.7.5a

5

6.2a

11

8a

12

7a

13

3

14

5a

15

2

21

(9.9.9.7
\9.8

22

9.7a

23

2.6.7.3a

24

(4.7.4.4

25

1.2a

\4.5a

31

7.9.8

32

6.9.7

33

4.3a

34

4.4.7.5

35

4.4.3.2

41

8

42

6.6.7

43

3

44

4.4.5

45

3.2

51

7.9.8

52

f6.6.6.6

53

2.3

54

4.4.4.5

55

3.2

61

7.8

62

6.7

63

3 •

64

(4.4.4.4

\4.7.5

65

2

71

/7.9.7.7
\7.8

72

/6.8.6.6
\6.7

73

(2.2.2.7
\2.3

74

J4.4.6.7

75

2

\7.7.5

67

6.7

81

7.8

82

8.9.7

83

(4.5.6.7

84

14.4.7.7
\7.4.4.5

85

1.1.2

V7.7.7.3
(5.6.7.7.7.6

91

7.8

92

6.7

93

94

4.5

95

2

14.5.7.2.3

103

7.8

104

6.7

105

4.5.6.7.3

106

J6.7.7.7.6
[4.7.4.5

107

(3.4.5.1.1.1

13.1.1.5.3.2

113

8

114

6.7

115

7.7.7.3

116

7.5

117

2

123

7.8

124

6.7

125

3

126

4.5

127

2

133

7.8

134

6.7

135

3

136

5

137

3.4.5.1.2

143

7.8

144

6.7

145

(4.5.6.7.5
\6.2.2.3

146

4.5

147

1.2

153

7.8

154

6.7

155

2.3

156

4.5

157

2

163

7.8

164

6.7

165

2.3

166

4.5

167

1.2

173

7.8

174

6.7

175

2.3

176

4.5

177

1.2

183

7.8

184

6.7

185

2.3

186

4.5

187

1.2

193

7.8

194

6.7

195

2.3

196

6.7.4.5

197

2

204

6.7

205

3

206

4.5

207

(3.4.5.6
11.2

213

7.8

214

6.6.7

215

2.3

216

4.5

217

2

223

8

224

6.7

225

4.5.2.3

226

4.5

227

3.4.5.1.2

233

7.8

234

6.7

235

3

236

4.5

237

2

243

8

[7.7.7.7.7

244

7

245

2.3

246

7.5

247

1.2

253

\l .1.1 .1.1

254

6.6.7

255

3

256

[4.4.4.4
\4.7.5

257

3.4.2

(7.7.7.8a

263

8

264

8.7

265

3

266

4.6.7.5

267

2

273

7.7.8

274

9.6.8.7

275

(4.2.2.6
\5.3

276

4.4.4.7.5

277

3.2

283

7.7.8

284

8.7

285

3

286

5

287

3.2

A STUDY OF THE BEHAVIOR OF THE CROW

97

LE 5

mber 3 in Problem 2

S. 6

S. 7

S. 8

S. 9

S. 10

T.

5.6.7.8.9

T.

1.2.3.4.5
6.7.8.9

T.

3.4.5.6.7.8

T.

7.8.9

T.

2.3.4.5

6

8.9.9.6a

7

2a

8

3.4a

9

9.8a

10

3a

16

6a

17

2a

18

4a

19

8

20

3a

26

6a

27

2a

28

4a '

29

8

30

3

36

[5.8.7.5
\5.5.6a

37

3.2

38

[3.3.3.3
\3.3.3.4

39

7.8a

40

3

46

5.5.6a

47

2

48

4

49

[7.777.7
\77.97.8a

50

4.2.3

56

5.6

57

2

58

3.3.3.3.4

59

7.77.97
17.9.7.8

60

2.3

66

8.9.7.6

68

[3.3.6.8
15.6.4

69

8

70

3

76

8.5.6

77

2

78

3.4

79

7.8

80

3

86

6

87

1.2

88

4

89

7.8

90

2.3

96

6

97

2

98

5.6

99

2

100

3.3.6.4

101

7.8

102

3

108

17.8.9.5

\8.6

109

/3.4.5.1
12

110

3.3.3.3.4

111

7.8

112

2.2.3

118

5.5.6

119

3.4.2

120

3.4

121

7.8

122

2.3

128

7.8.9.6

129

3.4.5.2

130

3.4

131

7.8

132

2.4.5.2.3

138

7.8.5.8
\9.6

139

1.2

140

3.4

141

8

142

2.3

f3.4.5.6.7
•{8.9.5.5

148

6

149

150

3.4

151

7.7.7.8

152

2.3

[6.7.8.2

158

8.9.5.5.6

159

2

160

3.4

161

7.8

162

2.3

168

5.6

169

2

170

3.4

171

7.8

172

3

178

5.6

179

1.2

180

3.4

181

7.8

182

2.3

188

5.6

189

2

190

4

191

7.8

192

3

198

5.6

199

2

200

4

201

7.8

202

[4.5.5.5
\2.3

203

5.6

208

5.6a

209

1.2

210

/8.8.3.3

\3.4

211

8a

212

2.3

218

7.8.8.6a

219

2

220

4

221

8

222

4.5.4.2.3

228

8.9.6

229

2

230

4

231

7.8

232

4.5.2.3

238

8.9.7.6

239

/3.4.5.6

\7.2

240

3.3.3.3.4

241

8

242

3

248

5.6

249

2

250

3.3.3.6.5.4

251

7.7.8a

252

3

258

5.6

259

2

260

/3.3.37.8
17.5.3.3.4

261

7.7.8

262

3

268

7.6

269

1.2

270

7.3.8.6.8
\6.3.3.4

271

7.8

272

3

278

8.7.6

279

3.2

280

8.7.6.4

281

7.8

282

3

288

9.8.7.6

289

3.1.2

290

4

291

7.7.8

292

4.3

98

CHARLES A. COBURN AND ROBERT M. YERKES

TABLE 5—
Results for Crow Number

S. 1

S. 2

S. 3

S. 4

S. 5

T.

7.8.9

T.

6.7.8.9

T.

2.3.4.5.6.7

T.

4.5.6.7

T.

1.2.3.4.5.6

293

8

294

8.7

295

3

296

4.4.5

297

3.2

303

8

304

6.7

305

5.4.3

306

J4.4.7.6.4
16.4.6.7.5

307

3.1.2

313

7.7.8

314

7

315

3

316

4.4.4.6.5

317

3.2

323

8

324

8.7

325

3

326

4.5

327

4.3.1.2

333

7.8

334

8.7

335

4.3

336

6.7.4.5

337

1.2

343

8

344

6.7

345

2.2.3

346

7.5

347

2

353

8

354

8.7

355

3

361

8

362

8.7

363

2.2.3

364

6.5

365

3.2

371

8

372

7

373

4.3

374

7.6.5

375

3.2

381

7.8

382

7

383

4.2.2.3

384

4.4.4.5

385

2

391

8

392

8.7

393

3

394

6.5

395

2

401

8

402

8.7

403

3

404

^'.5

405

2

411

8

412

6.7

413

2.2.3

414

5

415

3.2

421

7.8

422

6.7

423

3

424

4.4.4.5

425

2

431

8

432

8.7

433

3

434

4.5

435

1.2

441

8

442

8.7

443

4.3

444

6.5

445

2

451

8

452

7

453

2.4.3

454

4.5

455

2

461

8

462

6.7

463

2.4.3

464

7.6.5

465

2

471

8

472

8.7

473

2.4.3

474

7.6.4.5

475

/5.4.5.6
\5.5.4.2

481

7.8

482

8.7

483

3

484

7.4.5

485

2

491

8

492

9.8.7a

493

2.3

494

6.4.5

495

4.3.2

6
16

26

36

46

56

66

76

86

Results for Crow Nu

9.9.8a
8a

7.8

8

7.9.8

8

9.8
7.7.8

8

7
17

27

37

47

57

67

77

87

9.7a
7a

6.7

8.9.7

7
7

7a

6.8.6.8
9.8.7a

6.8.7

8
18

28

38

48

58

68
78

88

4.3a
3

9
19

4.6.7.3

29

4.6.2.7

7.3a

4.6.5.7.2

7.7.2.2.3a

2.7.2.6.3a

39

49
59

2.3

69

2.7.2.6
2.3

79

2.7.7.3

89

5a
5

4.6.7.7

4.4.5a

7.5a

4.4.4.7.5

7.4.7.6.5a

4.7.5a

10
20

30

40

50

60

70
80

90

2a

5.6.6.6
2a
4.5.3.2a

2a

3.6.2

2

3.2
2a

6.1.4.6 2

A STUDY OF THE BEHAVIOR OF THE CROW

99

Continued

3 in Problem 2— Continued

S. 6

S. 7

S. 8

S. 9

S. 10

T.

5.6.7.8.9

T.

1.2.3.4.5.
6.7.8.9

T.

3.4.5.6.7.8.

T.

7.8.9

T.

2.3.4.5

298

8.7.6

299

2

300

4

301

7.7.8

302

4.3

308

5.6

309

8.7.5.3.2

310

7.6.4

311

8

312

5.3

318

7.6

319

2

320

8.7.6.5.4

321

7.8

322

4.3

328

7.6

329

4.3.1.2

3 0

3.4

331

8

332

5.5.3

338

8.6

339

1.2

340

3.3.3.4

341

7.7.7.8

342

4.3

348

7.6

349

J4.3.4.3
\1.1.2

350

3.3.3.4

351

7.8

352

5.4.3

356

7.8.7.6

357

2

358

8.7.5.4

359

8

360

3

366

7.6

367

4.3.2

368

5.4

369

8

370

5.4.3

376

8.7.6

377

3.2

378

6.5.4

379

8

380

2.3

386

8.7.6

387

2

388

7.6.5.4

389

9.8

390

5.4.3

396

8.7.6

397

2

398

5.4

399

7.7.8

400

2.2.2.3

406

7.6

407

2

408

8.7.6.5.4

409

7.7.8

410

3

416

7.6

417

4.3.2

418

3.3.4

419

8

420

4.3

426

5.5.6

427

3.2

428

3.4

429

8

430

3

436

8.6

437

3.2

438

3.4

439

7.8

440

2.4.4.3

446

6

447

2

448

6.5.4

449

8

450

2.2.4.3

456

8.7.6

457

1.2

458

6.7.5.4

459

7.8

460

2.2.3

466

7.6
[8.7.9.8

467

3.2

468

3.5.4

469

7.8

470

2.3

476

7.8.8.7
8.8.6
[8.7.8.5

477

2

478

4

479

8

480

5.4.3

486

^7.7.9.8
8.6a

487

2

488

3.4a

489

7.8

490

2.2.3

496

[9.8.8.8
\5.6

497

2

498

3.3.4

499

9.9.8

500

3

mber 4 in Problem 2

11
21

31

41

51

61
71
81

91

9.9.6a

6a
6

5.9.5.9.8

5.9.5.6a

9.9.6a

5.9.8.6

[9.5.7.9
7.9.8.7

[9.5.8.6a
9.8.6

/8.9.8.7
16

8.8.6

12
22

32

42
52

62
72
82

92

2a

3.2a
5.6.6.8.2

4.2

1.6.2a

3.2

[8.4.7.1
8.9.1.4
8.4.2a

13
23

33

43

53

63
73
83

93

4a

4

4a
4

14
24

3.3.3.4a

34

5.8.3.8
4a

44
54

3.8.4

64

3.8.8.4a

74

3.4

84

4

94

7.8

8a
7.8

8

7.9.7.8

8

8

7.9.8

8

7.7.8

15
25

35

45

55

65
75
85

95

5.5.2.2

5.5.3a

4.3a

4.5.5.2

2.3

5.5.2.5.2

5.5.2.3a

4.3

4.5.3

2.5.3a

2.5.2.4.3
2.2.3a

100

CHARLES A. COBURN AND ROBERT M. YERKES

TABLE 5—
Results for Crow Nu

S. 1

S. 2

S. 3

S. 4

S. 5

T.

7.8.9

T.

6.7.8.9

T.

2.3.4.5.6.7

T.

4.5.6.7

T.

1.2.3.4.5.6

96

9.8

97

J8.8.8.6
\8.7a

98

17.9.7.7

17.7.7.8

99

8.9.9.7

100

(7.4.2.6
\2.4.4.3a

101

(7.7.6.4

102

2

\4.5

108

'7.9.8

109

6.9.8.7

110

3

111

/4.7.4.4
\6.4.6.5

112

2

118

8

119

6.8.7

120

J2.6.4.6
\2.7.3

121

4.6.4.5a

122

1.1.4.2

128

7.8

129

7

130

3

131

(4.6.6.4
\6.7.4.5

132

/1.3.3.1
\5.2 ■

138

7.8

139

7

140

2.4.2.3

141

4.6.5

142

1.3.2

148

7.8

149

(8.6.8.6

\6.8.6.6.7

150

(5.2.7.2
15.2.4.2.3

151

4.5a

152

2

158

8

159

8.8 8.7

160

3

161

4.4.5

162

2

168

7.7.8

169

6.8.8.7

170

2.3

171

5

172

1.6.4.2

178

8

179

7

180

J5.2.2.6
\4.3

181

(6.4.4.7

182

2

14.6.6.5

188

8

189

7

190

4.2.3

191

5

192

1.3.2

198

7.8

199

6.7

200

4.2.3

201

6.5

202

3.1.4.2

208

8

209

7

210

5.3

211

J4.4.7.6
\4.5a

212

2

218

8

219

(8.6.6.9

220

4.3

221

7.5

222

2

228

7.8

229

6.7

230

2.4.3

231

(4.4.4.7.4
\4.6.4.4.5

232

1.3.2

238

7.8

239

7

240

3

241

7.7.4.5

242

2

248

8

249

7

250

2.3

251

4.5

252

1.2

258

7.8

259

6.7

260

2.4.5.6.3

261

5

262

2

268

8

269

6.7

270

2.3

271

4.5

272

1.2

278

7.8

279

6.7

280

2.3

281

4.5

282

1.3.1.2

288

7.9.7.8

289

6.7

290

2.3

291

5

292

1.2

298

7.8

299

6.7

300

301

4.5

302

(1.3.5.3

14.1.2

308

7.8

309

7

310

2.3

311

6.7.5

312

1.2

318

8

319

8.8.7

320

[6.7.4.2

321

4.5

322

1.3.4.2

2.3

328

8

329

7

330! 2.4.2.3

331

5

332

6.3.4.1.2

338

8

339

8.8.6.7

340 | 2.2.3

341

5

342

3.2

348

8

349

7

350

2.3

351

4.5

352

1.2

356

8

357

6.7

358

7.5.2.3

359

7.4.5

360

6.3.4.1.2

366

8

367

8.7

368

(2.4.6.7

U.5.3

369

5

370

3.4.5.2

376

7.8

377

5.7.8.6*

378

3

379

5

380

3.4.5.2

386

7.8

387

6.7

388

2.3

389

4.5

390

1.3.4.2

* I

Mistake, se

tting

5-9^

A STUDY OF THE BEHAVIOR OF THE CROW

101

Continued

mber 4 in Problem 2

S. 6

S. 7
1.2.3.4.5

S. 8

S. 9

S. 10

T.

5.6.7.8.9

T.

6.7.8.9

T.

3.4.5.6.7.8

T.

7.8.9

T.

2.3.4.5

103

6

104

8.2

105

4

106

9.8

107

3

113

f9.7.8.7
\9.86

114

(3.8.7.4
16.2

115

(3.6.3.3

116

8

117

2.3

\3,4

123

5.9.7.6

124

2

125

3.6.8.6.4

126

(7.7.7.7..
\7.8

127

3

133

5.8.8.6

134

(1.3.8.7

135

[3.5.3.7

13.6.4

136

J7.9.7.7

137

2.2.3a

\8.6.7.2

\7.8

143

9.5.8.6

144

(1.8.5.7
1 1.4.5.3.2

145

3.4

146

8

147

2.3

153

(8.7.8.7
16

154

2

155

3.4

156

7.8

157

3 .

163

'8.9.9.6

164

2

165

3.3.4

166

8

167

2.2.5.2.3

173

8.8.6

174

2

•175

4

176

8

177

3

183

8.6

184

2
(3.6.7.8

185

3.3.3.5.4

186

7.7.7.8

187

2.2.3

193

6

194

{5.4.6.3

[4.3.2

195

4

196

7.9.7.8

197

4.3

203

f7.9.7.7
\8.6

204

2

205

4

206

7.8

207

3

213

6

214

(3.4.9.5
\3.2

215

3.3.4

216

.78.

217

2.3

223

[9.7.5.8
\7.8.5.7.6

224

3.1.2

225

5.3.3.3.4

226

9.7.8

227

2.3

233

5.6

234

3.2

235

5.3.7.3.4

236

8

237

2.3

243

8.8.6

244

2

245

3.4a

246

8

247

2.3

253

6

254

3.4.3.2

255

4

256

8

257

3

263

(7.8.7.8.7
\7.5.8.7.6

264

2

265

4

266

8

267

2.2.2.3

273

5.6

274

3.4.2

275

(8.7.7.3

\5.7.4

276

7.8

277

2.3

283

5.6

284

3.4.2

285

5.6.4

286

7.8

287

4.2.3

293

5.6

294

2

295

3.4

296

7.8

297

2.4.2.3

303

8.6

304

1.2

305

5.7.6.4

306

7.8

307

3

313

5.7.8.6

314

/1.3.4.5
\6.7.5.2

315

(7.6.7.6

17.4

316

9.8

317

2.3

323

8.7.5.6

324

5.6.2

325

5.4

326

8

327

2.3

333

6

334 ' 1.2

335

8.6.3.4

336

7.8

337

2.3a

343

7.8.6

344

1.2

345

3.4

346

7.8

347

5.2.3

353

8.9.5.6

354

J7.8.6.4
\5.4.6.2

355

4

361

8.7.8.5.6

362

2

363

4

364

9.7.8

365

4.2.3

374

(5. 7.8.9
15.5.6

372

2

373

4

371

7.8

375

3

381

5.6

382

2

383

3.4

384

7.8

385

2.3

391

5.6

392

1.3.2

393

3.4

394

7.8

395

2.3

102

CHARLES A. CO-BURN AND ROBERT M. YERKES

TABLE 5—
Results for Crow Number

S. 1

S. 2

S. 3

S. 4

S. 5

T.

7.8.9

T.

6.7.8.9

T.

2.3.4.5.6.7

T.

4.5.6.7

T.

1.2.3.4.5.6

396

8

397

6.7

398

4.4.5.6.3

399

4.5

400

1.3.4.5.2

406

7.8

407

8.6.7

408

2.3

409

4.5

410

2

416

7.8

417

7

418

J2.4.5.2.4
\2.4.2.4.3

419

5

420

1.2

426

7.9.7.8

427

6.7

428

2.3

429

4.6.4.5

430

2

436 8

437

6.7

438

3

439

5

440

6.2

446

8

447

[6.8.8.6

448

J2.2.4.5
\6.2.4.2.3

449

4.5

450

2

\8.6.7

456

8

457

6.7

458

2.4.2.3

459

4.5

460

3.2

466

467

f8.6.8.8
\6.7

468

3

469

4.5

470

3.4.3.2

476

8

477

7

478

2.4.5.2.3

479

4.5

480

1.2

486

8

487

8.7

488

2.4.2.3

489

7.6.5a

490

1.2

496

7.8

497

7

498

2.3

499

4.6.7.5

500

2

A STUDY OF THE BEHAVIOR OF THE CROW

103

Concluded

4 in Problem 2 — Concluded

S. 6

S7
1.2.3.4.5

S. 8

S. 9

S. 10

T.

5 6.7.8.9

T.

6.7.8.9

T.

3.4.5.6.7.8

T.

7.8.9

T.

2.3.4.5

401

6

402

2

403

4

404

8

405

3

411

5.7.8.5.6

412

3.4.2

413

3.4

414

7.9.7.8

415

2.3

421

(5.7.5.7
\8.6

422

2

423

8.3.4

424

7.8

425

2.3

431

6

432

3.4.2

433

3.4

434

8

435

4.3

441

6

442

2

443

6.6.7.3.4

444

7.8

445

2.3

451

(5.8.8.5
\7.8.5.6a

452

2

453

3.4

454

8

455

2.3

461

5.6

462

3.1.2

463

3.4

464

7.7.8

465

2.3

471

5.7.5.6

472

2

473

3.4

474

8

475

2.4.2.3

481

8.6

482

2

483

3.4

484

7.8

485

3

491

5.6

492

2

493

3.4

494

7.8

495

2.3

104

CHARLES A. COBURN AND ROBERT M. YERKES

TABLE 6

Daily Series and Averages, with Ratios of Correct to Incorrect

First Choices

Problem 2
Crow Number 3 Crow Number 4

No.

Ratio

No.

Ratio

Date

of

R

W

R

W

of

Date

of

R

W

R

W

of

trials

R to W

trials

R to W

July

6

3

0

3

July

6

3

0

3

a

a

3

0

3

tt

tt

3

0

3

tt

tt

2

0

2

0

8

0:8.

a

ii

2

0

2

0

8

0:8.

tt

7

2

0

2

tt

7

2

0

2

a

it

2

0

2

ti

ii

2

0

2

a

ti

2

1

1

a

a

2

0

2

ti

a

2

1

1

2

6

1:3.

a

a

2

0

2

0

8

0:8.

u

8

1

0

1

u

8

1

0

1

a

ii

3

1

2

1

3

1:3.

tt

11

3

2

1

2

2

1:1.

a

10

3

0

3

ti

10

3

2

1

»

a

2

0

2

ti

u

2

0

2

a

»

3

0

3

a

u

3

0

3

u

tt

2

1

1

1

9

1:9.

tt

ii

2

0

2

2

8

1:4.

tt

11

3

0

3

tt

11

3

0

3

a

u

2

0

2

it

ii

2

1

1

it

u

3

0

3

a

u

3

1

2

a

a

2

1

1

1

9

1:9.

it

ii

2

0

2

2

8

1:4.

it

12

2

1

1

tt

12

2

0

2

a

a

3

1

2

it

u

3

0

3

a

a

3

2

1

tt

ii

3

1

2

tt

it

2

0

2

4

6

1:1.50

it

a

2

1

1

2

8

1:4.

a

13

5

0

5

ti

13

5

2

3

tt

a

5

1

4

it

a

5

3

2

tt

a

5

2

3

3

12

1:4.

it

a

5

1

4

6

9

1:1.5

a

14

5

1

4

it

14

5

0

5

u

u

3

0

3

it

ii

3

0

3

it

a

2

1

1

it

ii

2

0

2

It

tt

5

2

3

4

11

1:2.75

ti

ii

5

0

5

0

15

0:15

a

15

5

0

5

u

15

5

1

4

ti

a

5

2

3

a

it

5

1

4

a

a

5

1

4

tt

a

5

2

3

it

u

2

2

0

5

12

1:2.40

it

ii

2

0

2

4

13

1:3.25

11

16

5

2

3

tt

16

5

1

4

tt

a

5

0

5

u

u

5

3

2

tt

u

5

0

5

u

ii

5

2

3

11

a

5

2

3

4

16

1:4.

u

it

5

1

4

7

13

1:1.85

a

17

5

0

5

it

17

5

1

4

tt

a

5

2

3

ii

ii

5

2

3

it

a

5

0

5

ii

it

5

2

3

ti

a

5

2

3

4

16

1:4.

a

u

5

0

5

5

15

1:3.

i

18

5

1

4

ii

18

5

1

4

■i

a

5

0

5

ii

ii

5

1

4

it

tt

5

1

4

ii

ii

5

1

4

it

tt

5

1

4

3

17

1:5.66

u

ii

5

2

3

5

15

1:3.

tt

19

5

1

4

ii

19

5

3

2

it

ti

5

0

5

ii

u

5

2

3

tt

a

5

2

3

ii

ii

5

1

4

tt

it

5

0

5

3

17

1:5.66

it

a

5

4

1

10

10

1:1.

ti

20

5

0

5

it

20

5

3

2

A STUDY OF THE BEHAVIOR OF THE CROW

105

TABLE 6 — Continued

Daily Series and Averages, with Ratios of Correct to Incorrect

First Choices

Problem 2 — Continued
Crow Number 3 Crow Number 4

No.

Ratio

No.

Ratio

Date

of

R

W

R

W

of

Date

of

R

W

R

W

of

trials

R to W

trials

R to W

July 20

5

0

5

July 20

5

1

4

a

it

5

3

2

ii

ii

5

3

2

it

(i

5

1

4

4

16

1:4.

tt

tt

5

2

3

9

11

1:1.22

a

21

5

2

3

ti

21

5

0

5

u

a

5

1

4

it

it

5

3

2

tt

tt

5

0

5

it

ti -

5

3

2

u

it

5

1

4

4

16

1:4.

ti

a

5

1

4

7

13

1:1.85

a

22 ,

5

3

2

it

22

5

2

3

it

tt

5

1

4

it

it

5

0

5

«

It

5

2

3

it

tt

5

0

5

it

it

5

2

3

8

12

1:1.50

ii

it

5

1

4

3

17

1:5.66

a

23

5

2

3

2

3

1:1.05

tt

23

5

3

2

3

2

1: .66

u

24

5

2

3

ii

24

5

2

3

u

U

5

2

3

a

tt

5

2

3

ft

ii

5

1

4

it

tt

5

4

1

u

ii

5

2

3

7

13

1:1.85

ti

it

5

2

3

10

10

1:1.

u

25

5

3

2

tt

25

5

3

2

u

a

5

1

4

ti

a

5

1

4

It

tt

5

0

5

tt

it

5

0

5

It

ti

5

1

4

5

15

1:3.

ti

u

5

0

5

4

16

1:4.

It

26

5

2

3

ii

26

5

0

5

It

u

5

1

4

it

a

5

1

4

It

a

5

2

3

ti

u

5

1

4

11

a

5

2

3

7

13

1:1.85

tt

ii

5

0

5

2

18

1:9.

If

27

5

1

4

it

27

5

1

4

a

ii

5

1

4

it

ii

5

1

4

u

a

5

1

4

ti

a

5

0

5

a

it

5

1

4

4

16

1:4.

u

ti

5

1

4

3

17

1:5.66

it

28

5

2

3

u

28

5

1

4

tt

tt

5

1

4

ti

tt

5

3

2

it

u

5

0

5

3

12

1:4.

a

ti

5

1

4

5

10

1:2.

«

30

5

0

5

it

30

5

1

4

a

u

5

2

3

u

ti

5

0

5

tt

a

5

0

5

ii

tt

5

2

3

it

ii

3

1

2

3

15

1:5.

it

ti

3

1

2

4

16

1:4.

a

31

5

3

2

it

31

5

1

4

a

u

5

1

4

it

it

5

2

3

it

a

5

1

4

5

10

1:2.

tt

it

5

2

3

5

10

1:2.

Aug.

1

5

2

3

Aug.

1

5

3

2

it

it

5

1

4

tt

tt

5

2

3

tt

ii

5

2

3

ii

ti

5

1

4

tt

a

5

1

4

6

14

1:2.33

it

it

5

0

5

6

14

1:2.33

ti

2

5

3

2

tt

2

5

0

5

a

ti

5

1

4

it

it

5

1

4

it

ii

5

3

2

7

8

1:1.14

tt

tt

5

5

0

6

9

1:1.5

tt

3

5

2

3

tt

3

5

1

4

tt

ii

5

2

3

tt

ti

5

0

5

u

a

5

1

4

5

10

1:2.

ti

u

5

9

3

3

12

1:4.

tt

4

5

2

3

a

4

5

1

4

106

CHARLES A. COBURN AND ROBERT M. YERKES

TABLE 6— Continued

Daily Series and Averages, with Ratios of Correct to Incorrect

First Choices

Problem 2

Crow Number 3

Crow

' Number 4

No.

Ratio

No.

Ratio

Date

of

R

W

R

W

of

Date

of

R

W

R

W

of

trials

R to W

trials

1

R to W

Aug.

4

5

2

3

Aug.

4

5

4

a

a

5

2

3

u

a

5

2

3

a

u

5

0

5

6

14

1:2.33

It

a

5

3

9

7

13

1:1.85

it

5

5

2

3

it

5

5

2

3

it

a

5

3

2

It

it

5

2

3

a

a

5

3

2

8

7

1: .87

a

It

5

2

3

6

9

1:1.5

it

6

5

0

5

a

6

5

1

4

it

u

5

2

3

it

ii

5

0

5

tt

it

5

0

5

ti

ii

5

2

3

a

a

5

1

4

3

17

1:5.66

it

it

5

1

4

4

16

1:4.

tt

7

5

2

3

.

a

7

5

2

3

a

u

5

2

3

a

a

5

2

3

a

It

5

1

4

tt

tt

5

1

4

it

It

5

1

4

6

14

1:2.33

tt

a

5

1

4

6

14

1:2.33

it

8

5

2

3

2

3

1:1.5

tt

8

5

2

3

2

3

1:1.5

The summary of choices given in table 5 is 'chiefly valuable
as a means of detecting reactive tendencies. But it also indicates
that neither crow succeeded in solving the problem. We had
supposed, from our previous experience, that within two or
three weeks the crows would be choosing the second compartment
at the left with ease, but as a matter of fact, with the appearance
and disappearance of the more or less unsatisfactory reactive
tendencies apparent in table 5, they continued their work over
a period of several weeks without mastering the situation. It
seemed utterly useless to continue the experiment with this
problem beyond the five hundredth trial. Had there been any
consistent improvement, even although extremely slow, we
should have felt justified in continuing the training.

The presentation of results in table 6 is of interest primarily
because the reader can from it see the fluctuation in the measure
of success during the long continued period of training. We
have presented in this table for each bird the number of correct
and incorrect first choices by series of trials under each date.
Following the results appear the ratios of successes to failures
for each day.

A STUDY OF THE BEHAVIOR OF THE CROW

107

In table 7 the ratios of correct to incorrect first choices are
given for the trials by groups of twenty-five, in order that the
influence of "good" and "bad" days may be fairly distributed.

TABLE 7

f Correct

to Incorrect First Choices in Pf

Groups

OF TWENTY-

FIVE

Trials

Crow No. 3

Crow No.

1- 25

1

7.30

1

5.25

26- 50

1

3.16

1

5.25

51- 75

1

4.00

1

3.16

76-102

1

2.00

1

4.40

103-127

1

5.25

1

1.77

128-152

1

5.25

1

1.40

153-177

1

5.25

1

1.08

178-202

1

3.16

1

1.77

203-227

1

3.16

1

1.77

228-252

1

1.50

1

2.12

253-277

1

2.57

1

1.50

278-302

1

1.12

1

11.50

303-327

1

3.16

1

5.25

328-352

1

7.33

1

2.57

353-375

1

1.87

1

1.55

376-400

1

2.12

1

5.25

401-425

1

1.15

1

1.77

426-450

1

1.77

1

1.50

451-475

1

3.16

1

3.16

476-500

1

2.12

1

2.12

The probability of a correct choice in this experiment, supposing
that chance alone is involved5, is one to four. At the beginning
of the experiment, it is noted (table 7) that the ratio for number
3 was 1 to 7.30; that for number 4, 1 to 5.25. For neither bird
does the ratio fall as low as 1 to 1 at any time during the training.
The nearest approach to this measure of success was made by
crow number 4 in the trials 153 to 177, for which the ratio was
1 to 1.08.

Further, it is to be noted that neither crow shows a steady

increase in the number of correct choices. There is, instead,

for each, an increase up to a certain point, then a sudden decrease,

followed by a more or less rapid increase. Number 3 exhibits

three well marked improvement waves. Beginning with the

ratio 1 to 7.3, there is fairly constant improvement until the ratio

stands 1 to 2. Then a backsliding occurs which, for the next

twenty-five trials results in a ratio of 1 to 5.25. Slowly the bird

improves again, achieving, after about three hundred trials, a

5 Of course the previous work on Problem 1 influenced the birds very markedly
in their early trials.

108 CHARLES A. COBURN AND ROBERT M. YERKES

ratio of 1 to 1.12. But this, after fifty additional trials, is
replaced by a ratio of 1 to 7.33. Immediately thereafter, rapid
improvement sets in, and shortly a ratio of 1 to 1.15 results.

The same in general holds for number 4. At the end of fifty
trials, its ratio is 1 to 5.25. After one hundred and seventy-
seven trials, it is 1 to 1.08. Then the number of correct first
choices slowly decreases until finally, at about the three hundredth
trial, the ratio is 1 to 11.50. There follows, during the next
seventy-five trials, improvement which results in the ratio of

1 to 1.55, which, in turn, is immediately followed by the ratio
of 1 to 5.25.

These fluctuations in the ratio of right to wrong first choices
are indicative of the appearance, "trying out," and disappearance
of more or less satisfactory reactive tendencies. The fact that
neither bird achieved a ratio of 1 to 0 indicates that no reactive
tendency appeared which was wholly satisfactory, or in other
words, led to the complete solution of the problem. These
various reactive tendencies we should describe, in the case of a
human subject, as the "trying out" of ideas, but it is unnecessary
for us to have recourse to this mode of psychological description
in the case of the crows. They may or may not have had ideas
corresponding to those which would have existed in the ordinary
human subject. In any event, their behavior is strikingly
similar to that of the human subject of a low level of intelligence.

ANALYSIS OF THE REACTIONS OF CROW NUMBER 3, cT

An analysis of the data of table 5 renders these fluctuations
of the ratio of correct to incorrect first choices at once intelligible
and deeply significant. We shall attempt an analytical exam-
ination of the results for each subject in order to bring the several
reactive types and tendencies into prominence.

For crow number 3 the first thirty or forty trials in problem

2 in large measure destroyed the subject's well formed habit
of choosing first, as a result of previous training in problem 1,
the first compartment at the right. The bird then began to
choose very frequently the first compartment at the left and to
distribute the remainder of its choices among the other compart-
ments, until the right one happened to be chosen. From the
beginning of work on this problem, the persistency of number 3,

A STUDY OF THE BEHAVIOR OF THE CROW 109

as also of number 4, in reentering the same compartment was
surprising. Examples of this are trials three, twenty-one, twenty-
four, thirty-eight, forty-nine, fifty-nine, sixty-four, and so on,
for number 3.

By the time number 3 had been given one hundred trials, a
habit of always going to the first compartment at the left, and
after receiving the punishment of confinement in the compart-
ment, entering the one next in order, had become fairly well
fixed. For some of the settings, this habit developed earlier
than for others. For instance, in settings Nos. 1 and 9, 7-9,
this particular reactive tendency appeared first in the thirty-
ninth trial, again in the sixty-first, and in the seventy-ninth,
when it seems to have been accepted as the most satisfactory
method of reacting, and appears as a habit for almost two hundred
trials.

With setting No. 2, 6-9, this same reactive tendency appears
definitely at about the ninety-second trial; for setting No. 3,
2-7, at about the one hundred and fifty-fifth; for No. 4, 4-7, at
the one hundred and twenty-sixth; for No. 5, 1-6, at the one
hundred and twenty-sixth; for No. 6, 5-9, at the one hundred and
sixty-eighth; for No. 8, 3-8, at the one hundred and twentieth;
for No. 10, 2-5, at the one hundred and forty-second; but for
No. 7, 1-9, neither this tendency nor any other became well
established during the five hundred trials.

In the fifty trials, one hundred and fifty-one to two hundred
inclusive, the habit of entering the first compartment at the
left, and next the adjacent one, which of course was also the
correct one, appeared thirty-eight times. In ten of these fifty
trials, the right compartment was entered immediately, and in the
remaining two trials, the compartment first entered was the
second from the right instead of the second from the left end
of the group.

From trials two hundred and forty to two hundred and fifty,
a new reactive tendency began to appear. This shortly replaced
the one just described. Previously, number 3, when it came
out of the first compartment at the left, turned sharply to its
left and entered the second compartment, the right one, but
now instead of turning to its left, it began to turn to its right,
with the result that it faced the compartment which it had just
left. Formerly, it had always met with reward when, after

110 CHARLES A. COBURN AND ROBERT M. YERKES

coming out of the first compartment and turning sharply it
entered the one directly in front of it, but now it met, instead,
with punishment. Nevertheless, it persisted in reentering the
wrong compartment, and in trial two hundred and fifty-three it
was punished thirteen times for entering compartment 7. It
was then aided in finding the right compartment. In this
instance, even after the door of the wrong compartment which
had been so often reentered had been closed and the door of the
right compartment left open beside it, the bird stood for some
seconds before the wrong door, cawing and apparently eager
to enter.

Naturally the tendency to turn to its right instead of to its
left greatly diminished the number of correct first choices by
number 3, and completely obliterated the old reactive tendency.
Shortly, the number of reentrances diminished to two or three,
and the bird began to enter the second compartment from the
left, even although it were not facing it after it turned about.
This peculiar behavior continued for only a short time, and was
followed by a tendency to enter first a compartment near the
right end of the series. On escaping from this, it would turn
to its right and enter the compartment directly in front of it.
Repetition of this performance of course soon brought the bird
to the right compartment. In trial after trial, number 3 would
enter the first compartment at the right and then work back,
compartment by compartment, until it reached the second from
the left. Examples of this behavior are trials two hundred and
eighty, two hundred and eighty-eight, three hundred and nine,
three hundred and twenty, and so on.

After the thorough testing of the reactive tendency just
described, no additional habit became well established, but the
crow shifted from one method to another. The one most often
used was that of entering the third from the left, and on leaving
this, turning to the right and entering the compartment before
it, which was of course the right one. This method is exhibited
for setting No.. 2, 6-9, after the two hundred and eighty-fourth
trial; for setting No. 5, 1-6, after trial two hundred and seventy-
seven; for setting No. 6, 5-9, after trial three hundred and
eighteen; and for setting No. 10, 2-5, after trial two hundred
and ninety-two. For the other settings, it appeared less
frequently.

A STUDY OF THE BEHAVIOR OF THE CROW 111

To complete our comments on the behavior of number 3,
we may say that beginning with trial four hundred and sixty-
one, the period of punishment was increased from thirty seconds
to sixty seconds, since it seemed possible that the crow might im-
prove under this condition. But the punishment was over-severe,
and after only a few trials, number 3, as also number 4, began to
work very badly indeed, It would move about constantly and
excitedly while confined in a compartment, and when the door
was opened would rush out and immediately enter another
compartment without pause. This random and excited choosing
naturally yielded few successes, and by the time forty trials
had been given, number 3 was very hesitant about entering any
of the compartments and had returned to an earlier habit of
wandering about the reaction chamber. When the time of
punishment was reduced to fifteen seconds, he very quickly
resumed his former method of reacting, and worked quite as
assiduously as ever, and with as small a measure of success.

ANALYSIS OF THE REACTIONS OF CROW NUMBER 4,9

The behavior of number 4 in problem 2 differs in some respects
from that of number 3 and is worthy of brief description. The
first fifty trials served to break up the habit of choosing the
first compartment at the right. Thereupon, her attention
shifted to the opposite end of the series. But this was not so
definite as in the case of number 3. Number 4 often went to the
first compartment at the left and then to the one next to it,
thus requiring but two choices in order to get the right com-
partment. This tendency became fixed only after two hundred
and fifty trials, and even then it was not so definite as for
number 3.

It is indicative of the temperamental differences in the two
subjects that number 4 should have required assistance in almost
twice as many of the first two hundred trials as did number 3.
Significant also is the fact that until very late in her training
she was not nearly as systematic in her choices as was he. She
tended rather more frequently to the compartments near the
middle instead of those at the ends, and chose in no definite
or predictable way. This . naturally resulted in a much larger
number of choices before the right compartment was reached,
than in the case of number 3. Discouragement was proportional

112 CHARLES A. COBURN AND ROBERT M. YERKES

to the number of mistakes. But at the same time, number 4,
just because of the lack of a definite inadequate reactive tendency,
happened upon the right compartment more frequently than
did number 3. For her, therefore, the ratio of correct to in-
correct choices is more favorable than for him. This is true
up to about the three hundredth trial, when it appears that
number 4 for some reason became more systematic in her work,
going most frequently to the first compartment at the left and
then to the second. This habit, which had appeared also in
the behavior of number 3, had by this time been replaced, and
as a result he was more often choosing correctly than she. Num-
ber 4 continued to exhibit this reactive tendency rather insis-
tently throughout the remaining trials.

We must conclude from this analysis of the data of table 5
that both crows, in the five hundred trials with problem 2
which were given them, tried and found inadequate all of the
reactive tendencies which were immediately available. Toward
the end of the experiment, it was evident, especially in the case
of number 3, that the bird's only resource was to return to some
one of the methods previously employed. Strange as it may
seem to the human subject, and especially to those human
beings who have a high estimate of the intelligence and origi-
nality of the crow, these individuals proved entirely incapable
of learning to enter directly the second compartment from the
left in a series of compartments.

Doubtless, many readers will object that longer training
would almost certainly have enabled our subjects to solve this
problem. We cannot deny this possibility, but we must insist
that all of the indications of our results are against it, for ordi-
narily the adequate solution of such a problem as this by an
animal of intelligence far lower than the human is achieved by
slow improvement. We are of the opinion that the crow is
incapable of perceiving and properly reacting to the relation
of second from the left, and we do not hesitate to admit that
we were very much surprised by this outcome of our experiments,
as we had fully expected our subjects, and especially crow number
3, to deal successfully with much more difficult problems than
this one.

This opinion rests not solely upon the fact that no steady
and consistent improvement occurred as the result of five hundred

A STUDY OF THE BEHAVIOR OF THE CROW 113

trials distributed over a period of thirty-two days, but also
upon the observation that in the case of the setting 7-9, which
appeared twice in the series, as Nos. 1 and 9, and was therefore
presented to each crow one hundred times instead of fifty times,
the successes were surprisingly few. In the first presentation
of this setting, number 1 in the series, for both of the crows
there is marked increase in the number of correct first choices
between the beginning and the end of the training. But for
the second presentation, number 9 in the series, this is not the
case. Crow number 3, in the first ten presentations of this
setting, as number 9 in the series, chose correctly only twice,
and in the last ten, only four times, while crow number 4 chose
correctly in the first ten, four times, and in the last ten, four
times. Even without experience they should have chosen
correctly twice in ten trials.

This is an easy setting and it is surprising indeed that the
crows should not have succeeded in reacting correctly in the
latter part of the training. Doubtless their failure is due to
the confusing effect of the diverse settings.

We feel that our analysis and discussion of results is inadequate,
but the report is already overlong because of the necessarily
lengthy description of apparatus and experimental procedure,
and we may add only a brief summary.

SUMMARY

1 . Two crows, No. 3, a male, and No. 4, a female, about
three months old, were presented with two of the simplest types
of standard problem in the Yerkes multiple choice apparatus.
These problems were: (1) selection of the compartment first
at the right in a series; (2) selection of the compartment second
at the left; and (3) the other form of problem 1, the selection,
namely, of the compartment first at the left.

2 . Of these three problems both birds succeeded in solving
perfectly, in from fifty to one hundred trials, the first and the
last. The second problem they failed to solve in five hundred
trials.

3 . Various types of reaction and reactive tendencies appeared
during the work on problem 2. Examples of these are: (1) to
go to the first compartment at the right because of training
in problem 1 ; (2) to go to the first at the left, and then to the

114 CHARLES A. COBURN AND ROBERT M. YERKES

next in order ;(3) to reenter the compartment first chosen and
then to choose the second from the left of the series; (4) to enter
a compartment at or near the right end of the series and on
emerging to turn to the right and enter the one directly in front,
and so on until the right compartment is entered.

4. Since no one of these types of reaction is satisfactory,
the birds shifted from one to another, trying them for varying
periods.

5 . The male was more tame, bold, and aggressive than the
female. Consequently, he made the better showing in the
experiments.

The multiple choice method, with four standardized problems,
has been employed with pigs, rats, and ring-doves, as well as
with crows; and, among human subjects, with normal and
defective children and adults and with dementia praecox patients.
The results will appear in a series of papers of which this is
the first.

COLOR BLINDNESS OF CATS
J. C. DeVOSS and rose ganson

From the Psychological Laboratory of the University of Colorado

FOUR FIGURES

INTRODUCTION

The term "color-blindness" is used in the title of this paper,
not because color-vision should be denied of an animal as a result
of a single investigation, no matter how carefully it may have
been conducted, but because the results of our experiments
certainly make the term "color-blindness" a less presumptuous
one than "color-vision" when applied to these animals.

The experiments were carried on in diffuse daylight and during
the same hours each day, so that the results apply to the light-
adapted eye of the cat. The fact that every discrimination
and confusion made by one cat were also made by another,
"the follower," would indicate that the conditions were not
variable enough to cause a difference between the responses
of the two animals. This agreement would indicate further
that our results represent general characters of feline vision
rather than individual peculiarities.

The investigation was begun in February 1911 and continued
until June 1913. Thus it required twenty-eight months to test
the animals with the large number of colors and grays which we
employed.

We are indebted to Professor Lawrence W. Cole, under whose
supervision the work was done, for invaluable advice and en-
couragement as well as for the suggestion of the problem. We
also wish to acknowledge our obligation to Miss Mary E. Lakenan,
who did some preliminary work toward devising a method
suited to the animals to be tested.

Among the mammals, the vision of mice, rats, rabbits, squirrels,
dogs, cats, raccoons, and monkeys has been investigated. Only
one cat was included but Colvin and Burford1 found it equal in

1Colvin, S. S. and Burford, C. C. The color-perception of three dogs, a cat,
and a squirrel. Psych. Rev. Monog. Supp., vol. 11, Nov., 1909, pp. 1-49.

115

116 J. C. DeVOSS and rose ganson

color-vision to the dogs and the squirrel which they tested.
They concluded that 'The tests seem to show a surprising
fineness of color-discrimination among the animals tested".

The chief results of recent experiments on mammalian color-
vision have been the refinements in methods achieved through
comparison and keen criticism. We cannot here deal with the
technique of experiments other than our own, but the following
generalizations will indicate the direction which the improvement
in methods has taken.

1 . So great a difference exists between the results obtained
from the light-adapted and the dark-adapted eye that those
secured under the one condition give us almost no clue to those
which may result from the other.

2 . All secondary criteria must be rigidly excluded. Differ-
ences of form, depth, size, texture, and especially differences
of brightness between the lights or test papers used are especially
to be guarded against.2

3. Much stress has been placed on the need of "natural
conditions" in testing an animal's vision. It is reasonable to
suppose that artificial conditions, like testing the animals in a
dark room, or by artificial light, might lead to false views of
his visual powers.

4. The stimulus color may be (a) reflected light from colored
objects, usually papers, or (b) transmitted light which may be
filtered through colored glasses or colored fluids, or isolated
from certain spectra. The first method is used to test the light-
adapted eye, or daylight vision, while the second is used chiefly
to test the dark-adapted eye, or twilight vision.

The second class of methods strives to secure different hues
of pure or homogeneous light. Both plans seek to find pairs
of colors, or colors and grays which will be confused by the
animal, assuming that the intensities of the colors for the animal
and for human vision may not be the same.

Many criticisms of the use of colored papers for testing vision
have been made. Their surfaces are said to differ greatly owing
to accidents of manufacture. It is said to be difficult to bend
them around glasses. They do not reflect homogeneous light
but overlapping bands, etc. etc. None of these criticisms,
however, applies very clearly to pairs of colors which are confused
2 See Yerkes, The Dancing Mouse, pp. 91-92, and 151.

COLOR BLINDNESS OF CATS 117

by the animal. Rather they are meant to point out all of the
"secondary criteria" by which the animal may discriminate the
colored papers. When an animal has confused a color and a
gray for some six hundred trials, though quite accustomed to
making discriminations, it seems fair evidence that he is unable
to discriminate them by secondary criteria, nor even by the
primary one, and that they appear the same to him.

After a confusion had been made between two colors (or a
color and a gray) it seemed desirable to define it accurately for
the sake of reproducing it at will. This we have done by stating
its "flicker equivalent," a term used by Polimanti3 to avoid any
theoretical implication. A comparison of the equivalents we
obtained with those of Cole and Long4 shows that the flicker
test reveals any fading of a colored paper and that the Bradley
papers, except the violet hues, remain constant for a long time,
if kept in darkness when not in use. In determining the flicker
equivalents of the colored papers the decision was invariably
based on inspection by two observers, and each color was tested
with the gray just darker and just lighter than that with which
it gave the minimum of flicker, a process which Ives5 aptly calls
"stepping off in various directions." Hence the decision in
each case was the result of the comparison of at least three
amounts of flicker. The method of determination was that
described by Cole and Long (pp. 660-664). When a color gives
a slight amount of flicker with each of two consecutive grays
it is designated as between the two by giving the numbers of
both. Thus Gray 1-2 means a gray which gives a slight amount of
flicker when rotated with Hering Gray 1 or Hering Gray 2, a
large amount when rotated with Gray 3, but which gives no
flicker with those papers which in turn give very slight amounts
with Grays both 1 and 2. These intermediate flicker equivalents
occur because there are but fifty gray papers with which to
test ninety or more colored papers. Cole and Long met this
condition by establishing three amounts of flicker between each
pair of grays, (p. 662). As we cannot adapt that device to the

3 Polimanti, O. Ueber die sogennante Flimmer-Photometrie. Zeitschrijt fuer
Psychologic vol. 19, 1899, S. 263ff.

4 Cole, L. W. and Long, F. M. Visual discrimination of Raccoons. Jour, of
Comp. Neur. and Psych., vol. 19, 1909, p. 657ff. •

5 Ives, H. E. Photometry of lights of different colors. Phil. Mag., 1912, p. 858.

118 J. C. DeVOSS and rose ganson

tables to be given in this paper, we shall designate a few of the
colors by the numbers of both of the adjacent grays.

In our search for grays which would be confused with the
stimulus color we were finally driven to make tests with a number
of gray cambrics. These also can be accurately defined by their
flicker equivalents, and by no other method which we can dis-
cover. Of course the cambrics were used in both double and
triple thicknesses, to prevent their transmitting light, both in
experiments with the cats and in ascertaining their flicker values.

Quite aside from disputes as to the cause of the phenomena of
flicker or what it measures, it makes colored and gray surfaces
comparable, accurately definable and hence reproducible. It
permits any series of colors or grays to be interpolated with
any other since rotation obliterates differences of texture. It
is accurate because very slight amounts of flicker are readily
perceptible. Consequently we regard it as necessary to define
our colors by their flicker equivalents, though our work is explor-
atory and qualitative.

While we have used flicker values merely for the sake of
definition, Ives (p. 852) says of flicker photometry:

1. "It surpasses all other photometric methods in sensibility
and reproducibility in the presence of color difference."

2. "It agrees at high illuminations with the equality of
brightness method, when the latter is freed from the psychol-
ogical uncertainties inherent in its use."

3 . It measures at high illuminations what may fairly be termed
the true brightness."

4. Brightnesses measuring equal to the same measure equal
to each other and the sum of the measurements of the parts
is equal to the measurement of the whole."

While these conclusions are drawn for the conditions of Ives's
experiments they at least do not diminish the probability that
our own flicker equivalents are at least rough approximations
to measurements of brightness, though we have used them for
the purpose of defining our papers.

In the following tables and description we shall use the initials
F. E. for flicker equivalent and except where otherwise stated
we shall not regard it as a measure of any property of the colored
or gray papers but merely as the most accurate method of identi-
fying any one of them.

COLOR BLINDNESS OF CATS 119

We began this investigation with the intention of studying
the vision of the cat under both daylight and twilight illumination,
thus planning to use both reflected and transmitted light. Some
work was done on the dark-adapted eye with filtered light,
and we hope to carry the investigation further. At present
we can report only the results obtained under light adaptation
and by the use of colored papers. The enormous variation
in the size of the cats' pupils suggested the possibility that
this is a device which keeps the retina always in twilight. But
as yellow, apparently, is the brightest of the colors for the cat
as well as for the human eye, under light adaptation, the possi-
bility of the animal's possessing twilight vision alone is very
doubtful.

Three female and six male cats were tested. There is abundant
evidence that these cats represented entirely non-related strains.
Each cat was given from thirty to one hundred twenty trials
a day according to his degree of hunger. One cat was given
fifteen thousand trials and the trials of all the cats number over
one hundred thousand.

By taking care not to over-feed the animals they were kept
(with one exception) in excellent health throughout the progress
of the experiments. The cats often purred during the experi-
ments, which perhaps indicates that the conditions were not
sen ously ' ' artificial ' ' .

The colors were presented in pairs and each cat was given
preliminary training with easily discriminable pairs until his
selection of the "food color" or stimulus color was rapid and
accurate. Since most of the pairs were readily discriminated
no cat reached a "confusion area" until he had been thoroughly
trained in the experiment. With one animal we would begin
at the red end of the Bradley series. With the other, which
was to confirm or refute the results gained with the first, we
began at the violet end, and so on. Since red is known to
have a low stimulating power in the case of mice, rabbits, etc.,
we began our experiments with yellow and blue as stimulus
colors.

From the beginning our object was to search systematically
for confusions between a gray and a color, or between two colors,
without any preconceived theory as to where, in the series,
such a confusion might occur, or even whether it might occur

120 J. C. DeVOSS and rose ganson

at all. During hundreds of our first trials no confusions did
occur, for we used Hering grays paired with Bradley colors.
Discrimination was prompt and apparently this was due to the
difference in texture between the two types of paper, for we
later found numerous confusions. As shown by the cats' re-
sponses, pieces of ordinary cambric may be found which are so
near the texture of the Bradley papers (when both are placed
behind clear glass) that they are not discriminable by the animals.
This is not true of Hering grays with Bradley papers. In such
pairs we think that the Hering papers are not suitable for the
study of any but the most defective eyes, because of their granular
texture. This opinion is based on tests of the whole series of
Hering grays with three cats. Miss Washburn6 obtained admir-
able results with Hering grays and Bradley colors in investigating
the vision of the rabbit. But as the rabbit has medullated
nerve fibres passing in front of the retina7 we should imagine
that that defect would make the rabbit's eye very poor for the
discrimination of textures.

In order to avoid awkward circumlocutions we have used
such subjective terms as "confusion," "discrimination" (both
"easy" and "difficult") etc. The reader will observe, however,
that in every case these terms signify a definite objective con-
dition, measured by the responses of the animals.

APPARATUS AND METHOD
The apparatus was that used by Cole and Long (p. 667). It
was painted dead black and had black partitions between the
glass holders. These partitions were necessary because in our
experiments the colored papers were placed within the glasses.
This permitted the possibility of a certain amount of reflection
from a glass to the one beside it in case no black partitions were
interposed. Since one cat seemed to make the choice of a glass
by the position of the thumb-buttons, which fasten the levers,
the buttons were concealed by shields of black cardboard cut
for the purpose. The glasses mentioned were the feeding vessels
and were ordinary jelly glasses, selected from a large assortment
for clearness, freedom from flaws, and uniformity of size and
shape. By means of the levers these glasses were clamped with

6 Washburn, M. F. and Abbot, Edwina. Experiments on the brightness value of
the red for the light-adapted eye of the rabbit. Jour. Animal Behavior, vol. 2, 1912.

7 Howell, W. H. Physiology, 1908, p. 319.

COLOR BLINDNESS OF CATS

121

their tops pressed closely against the under surface of the top-
board, so that the animal must select the glass at which he
pulled by its outside appearance only and without being able
either to reach into it or look into it until he had pulled it down.

Figure 1. A. Apparatus for displaying the glasses which were tinted with col-
ored papers. B. Cat depressing lever to release food-glass. C. Cat looking
over the top of the apparatus in order to discriminate by the positions of the
thumb-buttons.

By means of the thumb-buttons at the rear of the apparatus
every glass except one was locked against the topboard. A pull
at the glass which was on the free lever depressed its short arm

122 J. C. DeVOSS AND ROSE GANSON

and exposed the top of the glass so that the cat could reach into
it or tip it over and secure the food which it contained. This
glass will be referred to as the "food-glass" or the stimulus
glass. The others will be called "confusion glasses," or confusion
colors. The latter term will often include a gray where the
context or the heading of the table has already specified a gray.
From the front of the apparatus the colored papers, which lined
the glasses made the only visible difference between them.

As already stated, the Bradley colored papers were used, and
one blue cambric. After failing to find any confusions of the
stimulus color with Hering grays we tried the cats with any
gray we could obtain. The justification for this procedure is
that we finally found a gray which two cats confused with each
of the food-colors during at least six hundred trials. Only after
this had been done was its flicker equivalent determined for the
purpose of describing it.

At the beginning of the tests of each cat each day several
glasses were cleaned and fitted with the necessary papers. The
experimenter then took a position at one side and in front of the
apparatus. Two glasses were displayed on adjacent levers and
the cat was allowed to approach the apparatus from in front.
If he went directly to the food-glass and drew it down, the choice
was recorded as correct. But if he touched the confusion-glass
ever so lightly, either with paws or head, the choice was called
incorrect. After making his choice, the cat was allowed to
discover the food-glass and secure food, but no record was made
of this act. The cat was then placed where he could not see
the levers while the glasses were being changed about. After
this precaution, he was started again from his former position.

Thirty consecutive choices were considered a "series" and
twenty-four or more right choices were required in a series before
it was recorded as discrimination. If a cat consistently failed to
discriminate two colors for twenty such series (six hundred trials),
the result was recorded as complete confusion. In some instances
an animal failed to make a discrimination for eight or more
series, but showed by the low percentage of errors in each series
that it might learn to discriminate and eventually did choose
correctly twenty-four times in each of two consecutive series,
thus making a discrimination. These were called "difficult
discriminations." They doubtless indicate that the cats had to

COLOR BLINDNESS OF CATS 123

learn to discriminate what was for them close to a match. It was
not difficult to identify a complete confusion, for the number
of errors in each series almost invariably was twelve or more,
while for six hundred tests the errors were not far from fifty per
cent. On the other hand, the series in a difficult discrimination
would contain a smaller proportion of errors, but it was here
that greatest care was required.

Let us summarize the precautions taken to guard against
discrimination by criteria other than the hue or intensity of the
paper. The glasses were kept scrupulously clean so as to show
no marks of any kind on their outer surface. They were all of
clear glass without flaws. All of the papers were cut by a single
pattern and placed in the glasses so that the overlapping edges
were on the opposite side from the cat and hence invisible to him.
Finally, circular disks of pasteboard were forced down within the
cylinders of paper so that they held the paper closely pressed
against the inner surface of the tumblers, and thus did away with
wrinkles or apparent differences of depth. Several observers
reported that the tumblers when thus prepared appeared to be
made of colored glass. The apparatus prevented looking into
the glasses before making a choice, and the experimenter put
the glasses in position and made all changes while the cats were
where they could not see the apparatus.

To prevent choice by position, the glasses were presented in
random order, (one on the right, then on the left, then on the left
again and so on) , and they were changed in their positions along
the apparatus. Whenever a cat formed the habit of choosing
the glass on the left (or the right), the food-glass was placed no
the other side until the habit was broken up.

To eliminate odor as a factor in discrimination, equal amounts
of food were placed in the food-glass and the confusion glass;
clean glasses and clean papers promptly replaced any that had
become soiled, and the papers were exchanged within the two
glasses so that the confusion-paper replaced the food-paper, and
vice versa. Aside from the odor thus taken into account, the
odor of the pigments of the two papers might presumably aid
discrimination, hence within the paper in the food-glass, we
placed a cylinder or lining of the confusion-paper and likewise
within the paper in the confusion-glass was placed a cylinder of
the food-paper. Moreover, the various papers were kept in one

124 J. C. DeVOSS AND ROSE GANSON

drawer and thus any odor peculiar to a certain pigment must
have been pretty well diffused through them all.

There seems to be an almost irrefutable proof that our pre-
cautions were successful in at least a large number of cases.
This proof rests in the fact that we obtained many complete
confusions and, as already stated, each confusion was controlled
by second cat or follower, which made it certain that the con-
fusion was not due to accidental circumstances nor to some
individual peculiarity of the first cat.

In working through the series of Bradley colors we came
gradually to those among which confusion was difficult (required
at least two hundred forty trials to attain twenty-four correct
choices in a series of thirty trials). Then we came to colors
which were confused with the food-color. We shall call these
groups of colors, respectively, areas of "difficult-discrimination"
and "confusion-areas," though in some cases these "areas"
overlapped, i. e., one color was confused with the stimulus color,
the next was discriminated from it with difficulty, the next was
confused with it etc.

Tables I, II, and III show typical cases of discrimination,
difficult discrimination, and confusion.

TABLE I (A)

Typical Discrimination by Series

Cat 2

Stimulus Color — Yellow

Yellow with

Errors

Correct Choices

No. of trials

B

0

30

30

BT1

0

30

30

BT2

5

25

30

GBS2

0

30

30

GBS1

0

30

• 30

GB

0

30

30

GBT1

0

30

30

GBT2

11

49

60

BGS2

0

30

30 .

BGS1

0

30

30

COLOR BLINDNESS OF CATS

125

TABLE I (B)
Typical Discrimination by Series with Approach to a Confusion Area

Cat 4*
Stimulus Color — Yellow
Yellow with Errors Correct Choices No. of Trials

YGS2

0

YGS1

0

YG

6

YGT1

5

YGT2

14

GYS2

1

GYS1

4

GY

38

GYT1

207

GYT2

207

30
30
24
25
46
29
26
82
393
393

30

30

30

30

60

30

30

120

600

600

F. E.

Verdict

10

Discrimination

7

a

3

a

3

u

7

u

8-9

«

5

a

3

u

2

Confusion

1-2

«

TABLE II
A Typical Case of "Difficult Discrimination"

Cat No. 3
Stimulus Color, Blue. Confusion Color, VBT1

Series

Errors

1

11

2

10

3

14

4

14

5

9

6

15

7

13

8

8

9

10

10

5

11

11

12

8

13

14

14

9

15

10

16

12

17

8

18

5

19

12

20

5

21

7

22

12

23

14

24

3

25

4

26

5

Total

248

Grand Total

.780

Correct Choices
19
20
16
16
21
15
17
22
20
25
19
22
16
21
20
18
22
25
18
25
23
18
16
27
26
25

532

Per Cent of Error

46f

46f

30

50

43|

26f

33|

16f

33!

46|

30

33|

40

26|

16f

40

16f

23|

40

46f

10

13!

161

Average 3liz%

*This cat had discriminated the yellow from the Bradley colored papers, begin-
ning with the Red Violets through to the place where this table begins, i.e., he had
discriminated it from forty Bradley colors.

126 J. C. DeVOSS AND ROSE GANSON

TABLE III

A Typical Confusion

Cat No. 4

Stimulus Color, Yellow. Confusion Color,

Gray 1-2*

Series

Errors Correct Choices

Per Cent of Error

1

15 15

50

2

14 16

46f

3

18 12

60

4

13 17

43|

5

12 18

40

6

19 11

63i

7

15 15

50

8

15 15

50

9

14 16

46f

10

16 14

53^

11

15 15

50

12

17 13

56|

13

14 16

46f

14

13 17

43J

15

. 15 15

50

16

16 14

53J

17

17 13

56f

18

13 17

m

19

14 16

46|

20

15 15

50

Total.. .20

300 300 Av. No. Errs.

.50%

Grand Total

600

CONFUSIONS OF COLORS WITH GRAYS

In a recent report on the vision of the rabbit Miss Washburn8
says, "In order to eliminate the brightness error in experiments
on color vision in animals, it is not sufficient to show that the
animal tested can distinguish a color from the gray that a color
blind human being would see in place of the colors, but the animal
must be proved capable of discriminating this color from all
grays." For a year before Miss Washburn published her report,
we had been searching for a gray which the cats would confuse
with orange-yellow, yellow, or blue. In their turns, cats num-
bered one, two, and three discriminated these colored papers
from each of the fifty Hering grays.

Meanwhile some of our experiments had revealed the fact that
the cat could not discriminate the yellow from some other colors
of the same flicker equivalent. It was consequently suspected
that the texture of the Hering papers was furnishing the clue
to discrimination. But Hering grays numbered one and two

*Throughout the paper grays will be referred to as "colors" in this way.
8 Washburn, M. F. Psych. Bull., vol. 9, 1912, p. 54.

COLOR BLINDNESS OF CATS 127

had been discriminated from yellow by one cat only with con-
siderable difficulty and after a long period of training. We then
sought to find a gray, of a texture similar to that of the yellow
paper and of an intensity near to that of the grays mentioned
above. We found a gray, an ordinary writing paper of rather
dull finish, which fulfilled these conditions. We shall refer to
it as Gray 1-2, since its flicker equivalent was mid-way between
grays 1 and 2. This gray was confused with the yellow, as the
following tables show.

Though very extensive tests were made, we could find no
gray paper which was not very promptly discriminated from
blue. It occured to us that a very considerable range of gray
cambrics is supplied by the dry goods stores. As a last resort
we turned to trying these. Most of them were promptly dis-
criminated from the blue, but finally a dark gray shade (F. E.
—44-45) was found which neither Cat 3 nor Cat 5 could dis-
criminate from the Bradley blue. Meanwhile, we had found a
blue cambric which these cats confused with Bradley blue. For
the sake of still further evidence we paired this blue cambric
with the gray cambric. The two were, in turn, confused.

Again, in using violet as a stimulus color it was found to be
confused only with a gray cambric of F. E. — 48.

The following tables record the confusions of yellow, blue,
red, green, and violet with grays.

Confusion of Yellow with Gray 1-2

Correct

No. of

Per Cent

Errors

Choices

Trials

of Error

Cat 2

275

325

600

46.8

Cat 4

300

300

600

50.0

TABLE V (A)
Confusion of Blue Paper with Gray Cambric

Correct

No. of

Per Cent

Errors

Choices

Trials

of Error

Cat 3

283

317

600

47.1

Cat 5

280

320

600

46.6

TABLE V (B)
Confusion of Blue Paper with Blue Cambric

Correct

No. of

Per Cent

Errors

Choices

Trials

of Error

Cat 3

287

313

600

47.8

Cat 5

280

320

600

46.6

128 J. C. DeVOSS and rose ganson

TABLE V (C)

Confusion of Blue Cambric with Gray Cambric

Correct No. of Per Cent

Errors Choices Trials of Error

Cat 3 285 315 600 47.5

Cat 5 274 326 600 45.6

TABLE VI
Confusion of Bradley Red with Bradley Black

Correct

No. of

Per Cent

Errors

Choices

Trials

of Error

Cat 8

273

327

600

45.1

Cat 3

271

329

600

45.1

TABLE VII
Confusion of Bradley Green with Dark Cool Gray*

Correct

No. of

Per Cent

Errors

Choices

Trials

of Error

Cat 4

272

328

600

45.3

Cat 9

301

299

600

50.11

TABLE VIII
Confusion of Bradley Violet and Gray Cambric. F.E. — 48

Correct

No. of

Per Cent

Errors

Choices

Trials

of Error

Cat 8

278

322

600

46.3

Cat 9

292

308

600

48.6

TABLE IX
Summary of Confusions of Colors with Grays

Gray Confused

F.E. of the

Color

with the Color

Color

Yellow

1- 2

1- 2

Green

9-10

6

Violet

48

16-17

Blue

44^5

21

Red

50

25

The following curves show graphically the flicker-equivalents
of the colors and the numbers of the grays with which they were
confused. If Ives's results could be generalized to cover our
nicker tests, these curves would represent the relative brightnesses
of the colors for the cat and for the human eye.

*This gray was somewhat faded. F.E. — 9-10.

COLOR BLINDNESS OF CATS 129

Thus far we have shown that, the colors, yellow, green, violet,
blue, and red have each been confused with a colorless paper
(or cambric) by the cats.

Each confusion was found to be identical for two cats.

In each case inability to discriminate was shown by six hundred
trials, during which there was no increase in the proportion of
right choices. (This is not shown in the above tables but it is
shown clearly in our records by series of trials).

F.E..

T&A.oJiyS,

The confusions were made in each case after the cat had
discriminated its food-color from a number of other grays.

The colors, blue, red, violet, and green were each confused
with a gray which is much darker than the gray which represents
the brightness value of that color for the human eye.

The yellow was confused with a gray of identical flicker
equivalent.

Conclusions: It seems probable that cats cannot distinguish
any one color from all the shades of gray, under light adaptation.
It is possible that the animal may be totally color-blind by
daylight.

Our results in the case of red seem to agree with those of other

130

J. C. DeVOSS and rose ganson

investigators, namely that red is of low stimulating value for
the animals studied. But we may go further and say that blue,
and violet are also of low stimulating power for the cat. This
suggests the possibility of a much shortened spectrum (i. e. gray
band). Yet blue is not confused with black by the cat.

CONFUSION OF COLORS WITH COLORS

Since our animals have confused colored papers with grays,
even when the textures were as different as those of paper and
cambric, they ought presumably to confuse many pairs of colors,
all chosen from the same series of papers. To ascertain whether
they would do so we tested each cat by presenting for its choice
the stimulus color paired in turn with each of the eighty-nine
remaining Bradley colors. In each case the behavior of one cat
was confirmed by giving the same tests to a second one. As in
the work with grays we began with yellow and blue as stimulus
colors.

In the following tables we have included only cases of confusion
and of difficult discrimination. The stimulus color was dis-
criminated from all of the Bradley papers not named in the
tables, and such discriminations were prompt, with but few
exceptions. Examples are given in TABLE I (A). The con-
fusions in each table are recorded in the order of their occurrence
in the experiments, but it must be remembered that discrimina-
tions, both easy and difficult, intervened between the confusions
in many cases.

TABLE X (A)

Confusions Made by Cat 2

Stimulus Color Yellow. F.E. — 1-2

Yellow

Correct

No. of

Per Cent

with

Errors

Choices

Trials

F.E.

of Error

GYT1

374

436

810

2

46.8

GYT2

274

326

600

1-2

45.6

YT1

286

314

600

1-2

47.6

YT2

267

333

600

1-2

44.5

OY

264

336

600

2

44.0

OYT1

276

324

600

2

46.0

OYT2

294

306

600

1-2

49.0

YO

236

364

600

4

39.3

YOT1

266

334

600

2

44.3

YOT2

293

307

600

1-2

46.8

OT1

230

280

510

3

45

OT2

298

182

480

2

60.2

COLOR BLINDNESS OF CATS

131

TABLE

X (B)

Confusions Made by Cat 4

Stimulus Color, Yellow. F.E. — 1-2

Yellow

•

Correct

No. of

Per Cent

with

Errors

Choices

Trials

F.E.

of Error

GYT1

207

393

600

2

34.5

GYT2

207

393

600

1-2

34.5

YT1

197

193

390

1-2

50.5

YT2

157

233

390

1-2

40.2

OY

172

128

300

2

54.4

OYT1

193

197

390

2

49.4

OYT2

293

427

720

1-2

40.7

YO

236

364

600

4

39.3

YOT1

266

334

600

2

44.5

YOT2

293

307

600

1-2

48.8

OT1

230

280

510

3

45

OT2

298

182
TABLE

480
XI (A)

2

62.0

Confusions Made by Cat 3

Stimulus Color, '.

Blue. F.E.— 21

Blue

Correct

No. of

Per Cent

with

Errors

Choices

Trials

F.E.

of Error

BT1

257

343

600

8

42.8

VB

238

362

600

21

39.6

BV

250

350

600

13

41.6

BVT1

209

391

600

7

34.8

Blue

with

Errors

BT1

260

VB

158

BV

232

BVT1

199

TABLE XI (B)

Confusions Made by Cat 5

Stimulus Color, Blue. F.E.— 21

Correct No. of

Choices Trials

340 600

442 600

368 600

401 600

TABLE XII (A)

Confusions Made by Cat 3
Stimulus Color, Red. F.E.— 25

Per Cent

F.E.

of Error

8

43.3

21

26.3*

13

38.6

7

33.1

Red

Correct

No. of

Per Cent

with

Errors

Choices

Trials

F.E.

of Error

RVS2

283

317

600

23

47.1

RVS1

210

390

600

20

35.0

ORS1

260

340

600

30

43.3

RS2

240

360.

600

31

40.0

RSI

243

357

600

25-26

40.5

RT1

240

360

600

10

40.0

VRS2

260

340

600

30

43.3

VRS1

230

370

600

23

38.3

VR

257

343

600

17

42.8

*It will be seen from this record of VB that an animal may make as high as 73%
of correct choices and yet fail to discriminate twenty-four times out of thirty trials,
and this failure is confirmed by the record of Cat 3 on the same color.

132

J. C. DeVOSS and rose ganson

TABLE XII (B)

Confusions Made by Cat 8

Stimulus Color,

Red. F.E.— 25

Red

Correct

No. of

Per Cent

with

Errors

Choices

Trials

F.E.

or Error

RVS2

277

323

600

23

46.1

RVS1

219

381

600

20

36.5

ORS2

258

342

600

30

43.0

RS2

247

353

600

31

41.1

RSI

240

360

600

25-26

40.0

RT1

238

362

600

10

39.6

VRS2

257

343

600

30

42.8

VRS1

238

362

600

23

39.6

VR

241

359

600

17

40.1

TABLE XIII (A)

Confusions Made by Cat 9
Stimulus Color, Green. F.E. — 6

Green

Correct

No. of

Per Cent

with

Errors

Choices

Trials

F.E.

of Error

YGS1

230

370

600

7

38.3

YG

241

359

600

3

40.1

YGT1

239

361

600

3

39.8

GS2

290

310

600

8

48.3

GS1

257

343

600

7

42.8

GT1

237

363

600

3

39.5

BG

288

312

600

7

44.6

BGT1

240

370

600

3

40.0

GBT1

261

339

600

6

43.5

TABLE XIII (B)

Confusions Made by Cat 4
Stimulus Color, Green. F,E. — 6

Green

Correct

No. of

Per Cent

with

Errors

Choices

Trials

F.E.

of Error

YGS1

260

340

600

7

43.3

YG

239

361

600

3

39.6

YGT1

257

343

600

3

42.8

GS2

257

343

600

8

42.8

GS1

230

370

600 •

7

38.3

GT1

240

360

600

3

40.0

BG

238

372

600

7

39.3

BGT1

290

310

600

3

48.3

GBT1

253

347

600

6

42.1

In all, these tables show a total of thirty-four confusions of a
color with a color. This strengthens the probability suggested
by the experiments with grays, that wave length may not be a
stimulus for the cat. It is further strengthened by the close
agreement of the flicker values of the yellow, that of the gray
confused with that color, and that of the colors confused with
yellow. The gray, the yellow itself and five of the colors confused

COLOR BLINDNESS OF CATS 133

with it have the same flicker-equivalent, namely 1-2, while the
six remaining confusion colors differ very slightly from that
number. Other groups of colors differ widely from the flicker
values of the stimuli, which agrees once more with the experi-
ments with grays.

The relations of the flicker values of the colors to those of the
stimulus colors are shown in Figure 3.

The cats have been found to confuse each stimulus color with
a certain gray on the one hand, and with a group of colors on
the other. If we should assume that in each pair of these papers
the cat has merely seen that gray once more, we may assign to

*» >F.E

to
AT
io

*r

3e

ar
v°

Figure 3

the group the brightness value of the gray with which the stimulus
color was confused. The gray values are then represented,
Figure 4, by the straight horizontal lines, whose positions prob-
ably indicate the "brightness equivalents" of the several colors
for the cats, in the sense in which Miss Washburn uses that term
(pp. 145 and 146).

The deviations of the curves from the horizontal then indicate
how much the several colors may vary, for the human eye, from
that gray and yet be indistinguishable from it for the animals.
These deviations are large for red and blue, slight for green, and

*ff °£ ~R.

134

J. C. DeVOSS and rose ganson

very slight for yellow, as if there the animals approximated the
brightness-difference-threshold of the human eye.

The deviations probably show much more the defects of colored
papers. They are complex colors and while one factor, say the
tint, may presumably brighten the paper, another, say the red
or violet, darkens by at least an equal amount. Thus RT1 is
very much brighter than R for the human eye, yet the influence
of the tint is slight in comparison with the influence of the red

W naJUtxJ

%**£*

jo

sr

Figure 4

for the animal. Hence it is still confused with red. RT2, how-
ever, is discriminated from R after many trials, but darkened
orange-red is confused. The relations are shown in the following
tabulation.

Red

Correct

No. of

Verdict*

with

Errors

Choices

Trials

F.E.

RT1

238

342

600

10

Confusion

RT2

156

444

600

7

Diff. Dis.

ORS2

258

342

600

30

Confusion

ORS1

240

360

600

30

Diff. Dis.

OR

6

24

30

15

Discrimination

* Based on our standard of twenty-four correct choices out of thirty-trials, as
the test for discrimination.

COLOR BLINDNESS OF CATS 135

This low stimulating effect of red has been shown for the
dancing mouse, the rabbit, and "possibly"9 for the monkey.
Apparently the cat is no exception to the rule. Yet even in the
case of red the cat appears to need no such enormous differences
in brightness as does the dancing mouse, in order to discriminate
promptly. Nevertheless it would be quite unfair to base an
opinion of the cat's discriminating ability on his reactions to
red.

DISCRIMINATIONS

Our account of the confusions made by the cats is complete.
Only matters of minor importance are shown by the discrim-
inations. To our surprise no trace of individual variations ap-
peared in the confusions. This is more apparent because of our
determination to employ so many trials that the results would
not be vitiated by improvement due to training.10

Individual differences did come to light in what we have called
difficult discriminations, i. e., those which required at least two
hundred forty trials for the animal to learn to discriminate.
The greatest difference between any two animals appears in
certain colors presented with yellow as the stimulus color. It
is indicated by the number of trials required for discrimination
by each animal and is shown in the following table.

TABLE XIV

Yellow

No. of Trials

No. of Trials

with

for Cat 2

for Cat 4

G

240

30

GT1

330

30

GT2

360

60

YG

330

30

OYS1

60

330

0

630

630

ROS1

240

240

RO

480

480

VRT2

210

150

There are four prompt discriminations by one cat, only one
by the other. The great difficulty of discriminating orange from
yellow shown by both animals indicates that it must appear
to them very much like the yellow. In this case stopping after
five hundred seventy trials would have resulted in a decision

9 Watson, J. B. Some experiments bearing on the color vision of monkeys*
Jour. Comp. Neur. and Psych., vol. 19, 1909, p. 19.

10 See Yerkes, The Dancing Mouse, pp. 127 and 128.

136 J. C. DeVOSS AND ROSE GANSON

that orange is confused with yellow. The per cent of right
choices of orange was but 66.2, of VRT2 by Cat 4, only 60.7.

There were six cases of difficult discrimination with blue, four
with red none with green.

It remains to present the colors which, in experiments with
yellow as a stimulus color, were promptly discriminated from it
and yet were of nearly the same flicker value as the yellow. It
will be interesting to set down in parallel series the colors confused
with yellow, those discriminated from it with difficulty, and those
easily discriminated from it but of similar flicker value, and
underneath each color the number denoting its flicker equivalent.

Stimulus Color, Yellow. F.E.— 1-2

1. Confused

GYT1, GYT2, YT1, YT2, OY, OYT1, OYT2, YO, YOT1, YOT2, OT1, OT2
2 1-2 1-2 1-2 2 2 1-2421-23 2

2. Discriminated with Difficulty

G, GT1, GT2, YG, OYS1, O, ROS1, RO, VRT2
6 3 1-2 3 5 6 15 9 5

3. Discriminated Easily

RVT2, VT2, BT2, GBT2, BGT1, BGT2, YGT1, YGT2, GY, ROT2, ORT2,
2 332 3 2 3 1-2 32 3

The first two series of flicker-equivalents show that flicker
values were a factor in producing confusions and in causing
difficulty of discrimination. In the second series the presence of
orange, which we have already seen to be almost as bright as
yellow for the cat, is a factor which produces difficulty in four
cases. In the case of GT2 the extreme brightness of the tint is
overcome by the darkening effect of the green, though they come
near balancing each other.

In the third series of flicker values the effect of red, violet,
blue, green, and orange in darkening the tints for the cat is very
evident. This would indicate that those colors have great dark-
ening effect and that fact confirms to a great degree the brightness
position we have given them in Figure 2, which is drawn from the
results of grays.

If further evidence of 'the opposite effects of antagonistic
factors is needed, we may take the case of GY. Though the

COLOR BLINDNESS OF CATS 137

flicker value differs slightly from yellow the presence of green
enables discrimination. Add a "tint" and confusion takes place.
Brighten the color to the next brighter tint and the result is
still confusion. Thus,

Color

F.E.

Result

GY

3

Discrimination

GYT1

2

Confusion

GYT2

1-2

Confusion

Here the effect of the tints overbalances the effect of the
green and produces confusion. Elsewhere the darkening effect
of the colors is so enormous that the tints and shades have
relatively slight effect on the cat. This was to be expected, of
course, if the curve derived ' from experiments with grays is
approximately correct. Altogether the results derived from
experiments with grays and with colors are surprisingly consistent.

USEFULNESS OF FLICKER EQUIVALENTS

The great drawback of our experiments was the time they
consumed in trying so long a list of colors. Could this, by any
means have been shortened ? In our work with colors had we
tested for yellow only those of its flicker equivalent, we should
have discovered five of the twelve confusions. Had we explored
one-half of a flicker unit on each side the yellow, we should have
discovered five more confusions, and had we explored for two
and one-half units on either side, we should have found them all.
To have done the same thing with blue we should have had to
explore a range of fourteen units, but using only the exact flicker
equivalent would have found for us one of the four confusions
with blue.

Exploring a range of three flicker units on either side the green
would have discovered all the confusions. Using the exact flicker
value of the green would have revealed one confusion. Using
the exact flicker-equivalent of red would not have yielded any
one of the confusions, (It is true only of red.) but using one half
of a flicker unit on either side of the red would have brought
out one confusion. Two flicker units would have shown three
of the nine confusions, five units would have shown six, fifteen
flicker units would have shown them all.

Even exploring a range of fifteen flicker units on each side of

138 J. C. DeVOSS and rose ganson

every stimulus color would be a very different affair from pairing
each stimulus color with each of the eighty-nine other Bradley
colors. Such procedure in the experiments with these cats would
probably have reduced the time required from twenty-eight
months to eight. An animal which discriminates the stimulus
colors from all those of the same and nearly the same flicker
values has a very different type of vision from that of the cat.

Though the colors have vastly different brightness values for
the cat and for the human eye, the brightness equivalents and
the flicker-equivalents have intersected many times. A claim
that the use of flicker values would not save time must assume
that four broad bands of flicker-equivalents on either side of
yellow, blue, red, and green respectively might none of them
meet, at any point, the brightness values of the animals. Such
an assumption is so improbable that in work with colors the
neighborhood of the flicker-values of the stimulus colors should
be explored first, provided the animal has already made a number
of discriminations to become accustomed to the experiment.

In the experiments with grays, yellow was confused with a
gray of the same flicker value. To find the confusion gray for
green, we should have had to use a range of four flicker units.
With red, blue, and violet flicker values would have been useless
for discovering the grays, and "systematic groping" such as we
have used in our experiments would be necessary in finding the
gray values of those colors for the cats.

GENERAL REMARKS

We frequently tried the cats with two glasses lined with the
same colored paper, e. g., two yellows, two blues, etc. They
failed, so that the assumption that they distinguished by wrinkles
or spots on the paper is gratuitous.

Our records show practically a dead level of uniformity in
the responses of each pair of cats. It seems hardly necessary
to confirm the work of one cat by giving the same tests to another.
It adds a trifle of reliability, but it has added but one new fact
to our results, and that of slight importance.

This uniformity of behavior suggests also a dead level of
stupidity. A glimmer of intelligence was observed, for, as already
stated, one cat gave good evidence of selecting the food-glass by
the position of the thumb-button at the rear of the apparatus,

COLOR BLINDNESS OF CATS 139

and as good evidence of failing to do so when the buttons were
concealed by shields.

Our experiments show that the cat has very defective day-
light vision as compared with that of human beings. Is it
possible that this defective vision accounts for the behavior of
Thorndike's cats which clawed at the place where the loop had
been when the loop was no longer there ? For such vision as
the cat possesses, a mad scramble would conceivably be a much
quicker way to lay hold of a loop than an attempt to see it. An
accident of similarity of brightness between the loop and the
background might render it well nigh invisible to the animal. Is
it possible that the poorer the vision an animal possesses the
more he becomes dependent on kinaesthetic sensations, which
Watson has shown to play a fundamental role in the life of some
animals.

Our records show that an animal may make more than fifty
per cent of right choices throughout a large number of trials
and yet not learn to discriminate between the two objects.

Our experience shows that the possibility of the texture error
should be guarded against, as well as the error due to improvement
by training. In some cases discrimination occurred only after
eight hundred trials.

So many criticisms have been made of the use of colored papers
that one advantage in using them, no matter how trifling it be,
should be welcome. All the confusions made by these cats can
be exhibited to the eye by pasting the papers on gray cardboard.
The result of viewing the papers will be a better conception of
the nature of the cats' vision than can be got from reading pages
of description of their behavior in the experiments.

Finally we asked two persons of dichromatic vision to sort
these colored papers as Holmgren worsteds are sorted. Each of
the dichromates made five confusions which had been made by
the cats. Both of the dichromates and the cats agreed in the
matches (confusions) of two pairs of colors, and for each of
these pairs the flicker-equivalents were identical.

Our account of our exploratory tests of the cats' vision is
finished. We hope that feline vision may now be studied quanti-
tatively, by means of apparatus which permits of accurate
measurement of the wave-lengths and intensities of the lights,
as they reach the eye of the animal.

THE WHITE RAT AND THE MAZE PROBLEM

II. THE INTRODUCTION OF AN
OLFACTORY CONTROL*

STELLA B. VINCENT

Chicago Normal College

What part has olfaction in the life of a rat ? The answer to
this query would have to be based upon what we know of brain
structure and from our casual observation of rat behavior, since,
there has been very little direct experimentation published
that has as its main concern this form of sensitivity.

The rat has well defined olfactory lobes and tracts. But
these parts are relatively smaller than those of some other rodents
and decidedly smaller than those of some other mammals. The
olfactory paths in the brain of the rat have not had much study
and we are thrown back, therefore, upon what we know of the
life and habits of the animal for the answer to our question.

It might be thought, from watching the reactions of the rats
in the maze, that smell was a very important sense. The frequent
sight of a rat lifting itself on its hind feet and sniffing vigorously,
the constant use which it makes of its nose on the floor and
sides of the maze, would lend credence to such a supposition.
Yet it has been shown that anosmic animals are under no serious
disadvantage in learning the maze and that much of this sniffing
and apparent smelling has an important tactual function. What
the world of odor is to a rat we have little power of conceiving
but how it affects the behavior we may somewhat discover.

The odors which are vital in the animal world are, presumably,
food odors, sex odors and body odors. By the term body odor
is meant those olfactory qualities which perhaps are peculiar to
individual animals but which certainly characterize the animals
of a single cage or group. By differentiation from this familiar

1 This work was done in the Psychological Laboratory of the University of Chicago.
I am greatly indebted to the department for the opportunity to do it and to pro-
fessor Carr for suggestive help and criticism of both experimentation and paper.

140

THE WHITE RAT AND THE MAZE PROBLEM 141

odor it serves to mark off a strange animal or give warning
of an enemy.

Rats are omnivorous and hence there can be slight necessity
for any fine discrimination in the way of foods. A generalized
response to food odor will be all sufficient. I have, indeed,
never seen in white rats any clear discrimination of foods which
might be said to depend upon smell and have failed to find any
mention of such power by others. If food be introduced into a
cage unobtrusively, a rat usually stumbles over it before dis-
covering it. It might be supposed that blind and normal rats
would show different behavior in food seeking, yet in some
preliminary experiments covering several weeks, the food in
every instance, by both normal and blind rats, was apparently
found accidentally. The animals were very tame and were very
hungry. The food used was nuts, cheese and milk soaked bread.
The experiments, although significant, were too brief to be
conclusive. The instances which Small2 cites of the reactions of
very young animals to different odors may clearly depend upon
the chemical sensitivity of the mucus membrane of the nostrils
and must be sharply distinguished from olfaction proper. Pro-
fessor Watson,3 however, found that blind animals, otherwise
normal, were affected by odors to which anosmic animals failed
to respond. To repeat, smell is more closely associated with
food getting than is any other sense; yet it may be safely assumed,
and we should expect to find, that the sense is less refined in
animals which do not pick and choose their food than in those
which do.

If a rat from another group is introduced into a cage containing
other rats they "nose" the whole body of the stranger. The
rats do not appear to get the odor across the cage for the excite-
ment and characteristic actions begin only with contact. Rats
also respond by different behavior to strange handling. No
doubt a large part of the excitement is due to different methods
of lifting, etc. ; but after the emotional disturbance is allayed
the "nosing" of the hand seems to indicate an odor stimulation
also. The power to follow a trail is usually supposed to depend
upon slight traces of body odor which remain upon the path which

2 Small, W. S. Notes on the psychic development of the young white rat. Am.
Jour, of Psych., 11,89.

3 Watson, J. B. Kinaesthetic and organic sensations, etc. Psych. Rev. Mon.
Sup., 8, no. 2, p. 65.

142 STELLA B. VINCENT

an animal has taken. Animals which do not prey upon others
for food have little need for tracking. Experimentation has
failed to show such ability in these animals.

Sex odor calls forth specific behavior. This odor, however,
does not seem to carry from cage to cage even though the cages
are placed side by side. Efforts to establish the tracking of one
sex by the other have been made4. Watson said he found no
good evidence of tracking but that adult rats showed preferences
for entrances that contained the odor of the opposite sex.5 Small
insists that he had no evidence to show that the males followed
their own tracks or those of other males or that females followed
the tracks of the males.6 Possibly these attempts have not been
made at the right periods; at least the results are inconclusive.

How well rats or other animals can localize odors is still an
open experimental field as is also the possibility of olfaction
functioning in giving distance values.

The object of this work was to see whether an olfactory control
could be introduced into the learning of the maze, and, if it
could be, to discover how it would affect the learning process as
compared with other forms of control.

The modified Hampton Court maze was used, the same one
which served for the experiments with vision.7 Before beginning
the work, the inside of the maze was heavily coated with white
enamel paint to cover and to destroy any previous odors, and
upon the floor of all of the runways were laid long strips of heavy
white paper. The paper was cut 4 in. in width and where the
strips overlapped they were fastened with gummed paper. Upon
this papered floor was rubbed in, down the center of the runways,
a narrow trail of alternating beef extract and cream cheese. It
was thought better to use two substances in order to guard
against a possible olfactory fatigue. The trail was laid upon
paper because of the ease with which such a covering could be
removed in varying the experiment and because of a desire to
avoid a permanent odor in the maze.

The rats used in this work were young, untrained rats about

4 Watson, J. B. Animal Education, p. 51.
Small, W. S. Experimental study of the mental processes of the rat. Am.
Jour, of Psych., 12, 232.
6 Op. cit., p. 53.

6 Op. cit., p. 213.

7 Vincent, S. B. Vision in the maze. Jour. Animal Behav., 5, t.

THE WHITE RAT AND THE MAZE PROBLEM 143

90 days old. They were fed in the -maze and handled for a week
preceding the beginning of the real work. During the experi-
mentation they ran the maze three times a day under the stimulus
of hunger and were amply fed at the conclusion of each day's
work. The first experiment was one in which the trail was laid
in the true path in the maze and not in the cul de sacs.

EXPERIMENT I. Olfactory Trail in True Path
1. Behavior

The behavior in this experiment will be described somewhat in
detail since it is significant. There was none of the wild running
seen in the usual maze reaction. When put in the box the rats
were at once attracted by the odor. Their little noses went
down to the trail and they began to follow it immediately. They
moved along in a jerky fashion stopping occasionally to smell
and to lap the trail with their tongues. This manner of running
made their progress an exceedingly slow one. Both the cheese
and the beef extract which were used were diluted with water
so that there was but a very slight trace of the food on the paper.
Still the animals may have obtained some satisfaction in lapping,
but such gratification must have been very limited. In general
the rats lingered longer over the cheese than over the beef extract
trail. The odor was probably stronger. They often hesitated
at the places where the trail changed from one substance to
another and sometimes struck the "back" or "home trail" here.
These returns only now and then resulted in an entrance into a
blind alley. They usually ended where the trail changed again.
The maze is so constructed that the food box is in the center.
When in use, there is always food in this box which the animals
are encouraged to smell before the beginning of the experiment
and which furnishes their reward when they reach the box at
the end of their run. The true path passes directly by the side
of this box. (See "Vision in the Maze," Fig. 1.) In the normal
maze the early runs are always broken at the food box which
the animals have to pass in the center of the maze. The food
odor is stronger here and they bite and claw and scratch in a
futile endeavor to end the quest at this spot. But notwith-
standing the marked early influence of the odor of the food box
this behavior, in the normal maze, is very quickly abandoned.

144 STELLA B. VINCENT

Long before the rats cease to enter the cut de sacs, before any of
these errors are entirely cut out, the loitering at the food box
is no longer to be seen. It only thereafter occurs in exceptional
cases where an animal is entirely lost and as a consequence is
in a disturbed and emotional condition in which all the old errors
reappear. The behavior of the animals following the odor trail,
on the contrary, although similar at the food box was more
persistent than any "off trail," blind alley error. The odor,
it will be remembered, was that of the food with which they
were accustomed to be fed. Perhaps the previous stimulation
of the olfactory trail had made the animals more susceptible to
this influence. But whether, as a result of following a food odor
trail, all food odors attracted the attention more, or whether
this stronger food odor represented the natural instinctive ending
of a food trail and thus called a halt, these are questions for
thought. Either or both positions are plausible.

Whatever the cause of this behavior, as a result of it, the
speed in all of the early trials was slower than that in the normal
maze; but by following the trail the animals were kept in the
true path so that the errors were greatly decreased in both the
initial and in the succeeding trials.

2. The Tables

Table 1 shows, side by side, the records for the first twenty-
five trials in the normal and the olfactory mazes. Figs. 1, 2,
and 3, show the curves plotted from these records. These curves
are not made like those shown in "Vision in the Maze" because
in the olfactory maze the learning period covered less than ten
trials and was practically uniform. The units used in plotting
were one trial, one minute and one error. Since it was the
following of the trail in which we were interested, the error
consisted in leaving the track. Returns were not counted and
this fact makes these curves comparable with those made for
the black- white maze where the returns could not be counted.

The results of this experiment show an increase in accuracy,
both initial and total, over the normal maze and an increased
final speed. We will consider first the facts which bear out
these assertions as to accuracy.

Jo

<0

5

THE WHITE RAT AND THE MAZE PROBLEM 145

3. Comparative Accuracy

As the table shows, in the first trial, these animals in the
olfactory maze averaged only 4.5 errors as compared with 14.7
made in the normal maze. Thus the initial accuracy was three
times as great. The final accuracy was greater also. The
olfactory maze shows .04 average errors per trial for the last
five trials while the normal maze has an average error of .1 per
trial for the same five runs. The total number of errors per
animal in the olfactory maze is only one-third that of the animals

5" (0 iS 30 3,5 io

Figure 1. Time and error curves for Experiment I. Olfactory trail in the true
path. Full line time, dotted line errors.

in the normal maze. The error curve, seen in Fig. 1, bears out
all of the above statements. Its chief features are the low begin-
ning height, and hence slight fall, and the almost complete low
level which it maintains after the twelfth trial. A comparison
of the error curve of the normal maze with this will emphasize
these facts better than words.

4. Speed

The time per run for the early trials was less than in the normal

maze as may be seen from the table but this was entirely owing

to the fact that there were so few errors. The actual speed was

much slower. In the first trial they averaged only 4.5 errors per

146 STELLA B. VINCENT

animal yet the time average is 13.5 minutes. The record for
the second trial is practically the same. Almost the same average
number of errors, 4.1, was made by the normal animals in the
fifth trial in an astonishingly shorter time. For the first trip
without error these rats had an average time of 160 sec. The
time record for fifteen rats in the normal maze for the first perfect
trip is less than one-fifth of this — 30 sec. In final speed, however,
these animals excel. This maze has an average record of .28
min. for the last five trials as against .31 min. for the normal
maze. This is a difference of nearly two seconds — an appreciable
difference when one remembers that the maze can be run in
ten seconds.

The time curve (Fig. 1) is very unlike the usual time curve.
Compare it with Fig. 3. It is not the beginning height which is
remarkable but the persistence with which it maintains this
level — the slow rate of elimination of the surplus time. Forty-
seven per cent of the surplus time was eliminated in the normal
maze in the second trial, in the olfactory maze only 2.5% was
eliminated at this time; 80% was eliminated in the first four
trials in the normal maze, but it took the rats in the olfactory
maze nine trials to reach this point. By the tenth trial the
animals in the normal maze had only 2% surplus time left to
eliminate, but the rats in the olfactory maze did not fall per-
manently below this 2% point until the twenty-fifth run.

It must be clearly evident that this olfactory trail was affecting
the learning process but before any definite conclusions were
drawn it was necessary to put the trail in the cut de sacs, instead
of the true path and to see what would happen then.

EXPERIMENT II. TRAIL IN CUL DE SACS
1. Behavior

This experiment was conducted exactly like Experiment 1,
with animals of the same age, etc. The only difference was in
the trail which was laid from the entrance of each cut de sac to
its extreme end. There was a noticeable difference in the numer-
ical results as well as in the behavior under these conditions.

The animals in this maze also made fewer errors from the
beginning than the animals in the normal maze and the speed
was greater also. When put in the maze the rat ran, as in the
usual maze, headlong down the runways. Soon he blundered

THE WHITE RAT AND THE MAZE PROBLEM

147

TABLE I

Records of the First 25 Trials, Time and Errors, of Rats in
Normal and Olfactory Mazes

Average Time in Seconds per Trial

Average Errors per Trial

Trial

Olfactory

Olfactory

Olfactory

Olfactory

Normal

trail in

trail in

Normal

trail in

trail in

true path

errors

true path

errors

1

1804

820

991

14.7

4.5

9.6

2

966

800

463

11.9

4.

5.6

3

1043

224

598

10.4

1.1

7.3

4

847

609

331

7.4

1.6

5.3

5

231

175

49

4.1

2.

2.

6

192

165

54

3.5

1.5

1.8

7

64

376

30

1.6

.6

1.1

8

49

295

27

1.4

.8

.5

9

37

178

37

1.5

.3

.5

10

32

52

22

1.1

.3

.1

11

26

155

30

.7

.6

.1

12

25

29

36

.4

.3

.3

13

31

35

32

1.

.1

.1

14

20

52

21

.3

.8

0.

15

32

27

45

.6

.3

0.

16

46

26

83

.7

.1

1.1

17

44

24

97

.5

0.

.3

18

51

25

173

.6

0.

2.1

19

40

23

150

.1

0.

.8

20

32

39

177

.2

.1

1.1

21

31

29

94

.2

.1

.7

22

26

32

262

0.

.3

1.7

23

17

32

117

0.

.3

.8

24

19

37

107

.1

0.

.8

25

22

76

147

0.

0.

.7

TABLE II

Tabulated Statement of the Results in the Three Mazes

Normal Maze

Average time of learning. . 12.1 ±3.6 trials
Average time of the first

five trials J16.3 ±6.7 min.

Average speed of the last

five trials I .31 ± .05 min.

Total surplus time 93.9 min.

Average errors first trial. . . 14.7 ±7.7
Average errors in the last'

five trials | .1 ± .14

Total average errors per

animal 66.6 ± 16

First run without error. ... 8.3 ±3.1

Olfactory

trail in
true path

8.1 ±2.4 trials

8.7 ±3.9 min.

.28 ± .08 min.
64.98 min.
4.5 ±3

.04 ± .04

20.5 ±5.6
6.3 ±2.8

Olfactory

trail in

errors

7.3 ±3.8 trials

8.1 ±5.2 min.

.47 ±.08 min.
66.45 min.
9.6 ±6.8

.44 ± .21

52.1 ±12
7.5 ±1.8

148

STELLA B. VINCENT

THE WHITE RAT AND THE MAZE PROBLEM 149

into a cul de sac and down went his nose to the trail which he
followed for its entire course, to the end of the alley. He moved
along by jerks, as described before, and when he reached the
end, he turned and in the same irregular, slow, halting way
returned to the entrance of the alley. Between the cul de sacs,
he ran; but when in them, slow movements were the rule. As
a result more time was spent in a single cul de sac than had been
the case in any of the other experiments. Still, from the first,
these excursions from the true path were lessened in number
as compared with the normal maze. The blind alleys seemed
to be marked for the animal in some way. He began to go less
and less deeply into them and finally, as he was running more
and more confidently in the true path, I have seen him, time
and again, actually thrown back on his haunches if chance
running flung him into the entrance of a cul de sac. Or, he
might be running quickly, swerve into an entrance, and there
would be seen an instant decisive turning the minute he struck
the trail. It looked like a real discrimination. Surprisingly
enough, however, after the problem was learned, and the animal
was making 90% correct trials, these errors began to reappear
and it took almost as long to get rid of them the second time as
it did the first. The meaning of this will be discussed later.
There were many more returns in this experiment than there
were in the one where the trail was laid in the true path — five
times as many in the first trial, It was a long time before the
rats learned to pass the food-box without lingering. The numer-
ical results for accuracy confirmed the conclusions drawn from
the observed behavior.

2. Comparative Accuracy

Under the conditions of this experiment, the accuracy was
decidedly greater than in the normal maze in the first fifteen
trials. If we now make a comparison with the other olfactory
experiment, we find that more errors were made in the first
nine trials than were made by the animals which followed the
trail in the true path but that the next six trials were more perfect.
From the fifteenth trial on, the accuracy was far less than in
Experiment 1, or in the normal maze, and it was only toward
the end of the experiment, that it again approached their standard.
The curve (Fig. 2) shows this variation exactly. The total

150

STELLA B. VINCENT

average number of errors per animal was 20% less than in the
normal maze but the animals made two and one-half times as
many errors as their brothers in the experiment where the trail
was in the true path. The learning time was actually shorter
than in Experiment 1. There is so little difference, however,
that it may be a matter of chance. The conditions, as a whole,
were very favorable for learning as compared with the normal

Figure 3. Time and error curves for normal maze. Full line time, dotted line

errors.

maze and scarcely less so than those in Experiment 1, where
the trail was in the true path. It seems fair to conclude, there-
fore, that these conditions did affect the accuracy, and in general
favorably, but that there was a variableness in the final reactions
which will require explanation.

3. Comparative Speed
The speed in this maze was quite comparable with that in the
normal maze except when the rats were in the cul de sacs and,

THE WHITE RAT AND THE MAZE PROBLEM 151

because the errors were so few, the slowness in these places
placed the animals under only a slight disadvantage. The
running was much more rapid than that reported in Experiment
1. The figures in Table 1, giving the time per trial, do not show
this since the data for the total distance is lacking. In the first
trial in Experiment 1, there was an average of 4.5 errors and 1
return. The animals did not go to the end of each cul de sac
and the returns were only partial. In this experiment, with
trail in cul de sacs in the first trial, there was an average of 9.6
errors and 5 returns per animal. The larger proportion of these
returns were home returns and the cul de sacs were explored to
their farthest limits. According to these figures the time should
have been three times as long in the latter case had the speed
been comparable, instead of which it is practically the same
(See Table 1). From this we should conclude that the speed
was three times as great in the first trial in Experiment II as it
was in the same trial in Experiment 1 where the trail was in the
true path. There was a variability of speed in the middle part
of the experiment which clearly depends upon the increase in
errors. (See the curves Fig. 2). The average speed of the first
trial without error may be taken as a point of comparison as we
do not possess the figures for the total distance. The normal
maze gives us an average of 30 sec. for this trial, the maze with
the trail in the true path 160 sec, and this one 28 sec. At this
point, then, in this experiment, we have a speed which is quite
as fast as that in the normal maze. The final speed, however,
within the limits of the experiment, was less — .47 min. (See
Table 2 ) . Whether longer experimentation would have developed
a speed equal to that in the normal maze, or whether the condi-
tions would always have mediated against it is a question for
discussion.

EXPERIMENT III. TRANSFER OF TRAINING

This experiment was the crucial one. The conduct of the rats
had been affected by the olfactory trail in the maze, the learning
had been aided, but had the animals really gained anything
which they could carry over to another problem ? Was an
olfactory control so well established that it could be utilized in
another situation ? It was determined to take the animals, at
the conclusion of Experiment 1 on the maze, over to a problem

152 STELLA B. VINCENT

box. This box had three runways, leading from a common
entrance, and they terminated in a food-box. The paper trail,
some of the original paper from the runways, could be laid along
these runways, changed in irregular order, and the rats tested
here. Before taking them to the box, however, after the con-
clusion of Experiment 1, the paper was entirely removed from
the maze and the rats given one trial each on the maze itself.
They made perfect runs showing no hesitation whatever. They
did not seem to miss the paper at all and even incorporated
in the runs a slight "slowing up," as had always been the case
at the places where the trail changed from beef extract to cheese.
Evidently the control had become kinaesthetic. The question
we had to face now was this: Had the olfactory experience
persisted notwithstanding the change of control.

The rats were now taken over to the box. The first trials
here gave entirely negative evidence. The olfactory trail might
as well have been absent for all the attention which the rats
gave to it. The path with the trail was only taken on an average
of six times out of twenty trials. The next morning the animals
were tried again and then it was seen what they were doing.
No matter where the trail was laid, they were always making
a straight run to the left and down the runway on the left side.
Now this was just their first run in the maze. Clearly kinaesthesis
was at the helm and olfaction had retired from the engagement.
It was necessary, therefore, to arrange conditions such that
the opportunity to make this run to the right or to the left
should be done away with — a condition in which position so far
as possible should be eliminated.

A long rose box, about three feet in length was procured from
a florist and in its end were inserted long, heavy, pasteboard
mailing tubes. These tubes just filled one end of the box. They
were lined with paper taken from the maze and one tube contained
paper on which was the trail. In the experiment the tubes
were alternated according to an irregular schedule. For the
next few days the rats were tried out in this box. When they
were put in at the end farthest from the tubes they immediately
ran down to these exits. The two openings were side by side,
there was no chance to turn, and in fifty trials they made 90%
correct choices: i. e., they followed the trail nine-tenths of the
time. While sitting in front of the tubes the rats could smell

THE WHITE RAT AND THE MAZE PROBLEM 153

either one indifferently so there was usually a momentary hesi-
tation at the entrances and then a dash into one or the other.
Sometimes the head was put in tentatively and then came the
sudden run through or the withdrawal. The experiment showed,
conclusively, that the olfactory experience had been retained
and that it could be utilized again. It also showed that the
reaction to the original problem had become a matter of habit
and that so strong and powerful was kinaesthesis that the removal
of the sensory factors which helped to establish it had no effect
upon its control. When later the animals were confronted with
a problem where turning to the right or to the left was possible
the response was in kinaesthetic, or tactual-motor terms. But
when the possibility of runs and turns were cut out the effects
of the olfactory learning and experience were asserted in a per-
fectly effectual way. That this was not due to any attractiveness
of the trail in itself is shown by Experiment IV.

EXPERIMENT IV. ANOTHER TRANSFER
This was the discrimination test for Experiment II. The same
box and the same method was used as in Experiment III. Under
these conditions the animals had to choose the path where
there was no trail. They did this just as consistently as the others
making just as good a record and confirmed in all points the
conclusions drawn from Experiment III. The details are not
needed here.

DISCUSSION AND CONCLUSIONS

Whatever may be true of rats in their native environment,
we agree with Small,8 that these animals do not usually follow
a path in the maze by means of scent; yet, as these results show,
they can do so. The evidence here is also against Professor
Watson's statement that. "Olfactory sensations have no role
in the selection of the proper turns in the maze.9" This assertion
may be quite true of work on the maze as he used it, but certainly
olfaction, in the experiments reported in this paper, helped to
cut out the errors. Although we have seen no signs of instinctive
tracking, these animals will follow an odor trail on first trial
and can learn to follow an olfactory trail or to avoid such a trail.
If a maze problem presents such a trail the result is an initial

8 Op. cit., p. 232.

9 Kinaesthetic and organic sensations, etc., p. 91.

154 STELLA B. VINCENT

and total accuracy which is greater than normal although the
final accuracy, when the trail is in the cul de sacs, is less. The
learning time is also shortened. We should therefore say that
such an olfactory control distinctly favors accuracy.

How shall we explain this increased accuracy ? Was it a
result of real sensory discrimination ? It can be explained, as
the results in the black-white maze were explained, as being
due to the dominance of some particular stimulus. A path,
out upon which an animal first runs in a maze, if not alarming,
becomes a familiar place — a home place. There may afterward
be other such places in the maze, but this is the first one. He
runs out from here, returns, goes a little farther, etc., but always
with the possibility of the home return. In Experiment 1, the
path was associated with a strong odor trail. Departure from
this was to go into the unfamiliar and strange. Thus from the
first the animal had more of this stimulus and it became in-
creasingly familiar and increasingly dominant. Dominance, as
a term here, may be explained in one way as the power of the
familiar. It may have other explanations. Rats are seemingly
possessed with an instinctive curiosity or tendency to explore;
but fighting against this is an innate tendency to keep in familiar
or known situations. The familiar or known situation in Exper-
iment 1, was near the odor trail; in Experiment II, it was away
from it. If we accept this view the odor stimulus would be
powerful enough to keep an animal in the true path if it arose
from this path or to keep it from the blind alleys if it lay there.
It would work both ways. It wrould do so by holding the atten-
tion to the true path or by catching the attention and so serving
as a warning when the animal strayed from the path. The
errors would be lessened in either case.

There were actions, however, which seemed to show that
this behavior was more than a mere passive affair. I take it
that an instant response to a stimulus, wThen not instinctive, —
a response which can be learned and which can be varied, now
positively and now negatively — involves discrimination. There
was none of this seen in the black-white maze. There was
such behavior here. If this be the case, while the first explanation
may be a true and a reasonable one, the increased accuracy
here was partly, at least, a result of discriminative ability.

There was an increase of errors in the middle of the learning

THE WHITE RAT AND THE MAZE PROBLEM 155

period in Experiment II, and some slight evidence of the same
thing in Experiment I. (See curves Fig. 1 and 2).

The only interpretation 1 can offer is this: It was the result
of the changing sensory control. The initial control was dom-
inantly olfactory: but with repeated trials the kinaesthetic
experience grew and strengthened and finally began to come
into its own. The running became easy and rapid and the
accuracy was becoming habitual. Attention, now being released
from the control of the movement, was free to be attracted by
the olfactory trail in the cut de sacs and errors became more
frequent. The final elimination may have been, and probably
was, a relearning with kinaesthesis more firmly established. But
besides accuracy there is also speed to consider.

The conditions of the two experiments give results which
differ radically here. As compared with the normal maze,
Experiment 1 showed slow initial speed and quick final. Ex-
periment II showed quick initial speed and slow final. Let us
first discuss Experiment II.

There is no need to take much time here to discuss the speed
in Experiment II. The true path resembled that of the normal
maze and the beginning speed was comparable. The slower
final speed was a result of the increase of errors. The variable
curve seen in Fig. 3 has the same explanation. But let us turn
to Experiment 1, where the facts are better seen.

Olfaction has two uses. First it functions as a distance sense.
The reaction in this case is always running — toward food, away
from danger. The second function is associated with food-
taking. Olfaction is so intimately associated with food-taking
that, in man, taste and smell are difficult to disassociate. The
point which is here to be emphasized is that when the second
of these functions is set up in animals in connection with food it
inhibits the first. It seems probable that olfaction furnishes
animals with a more accurate criterion of distance than it fur-
nishes man and that the nearness of food, with the consequent
increased intensity, is the stimulus for the food-taking reaction
and the running ceases or slows up. The one response is antici-
patory, as Sherrington says,10 the other consummatory. The one
is a somatic reaction, involving the whole body, the other is
visceral and confined to certain organs and segments.

10Sherrington, C. S. Integrative action of the nervous system.

156 STELLA B. VINCENT

If we now attempt to explain the slowness of the reactions
of the rats in the maze in Experiment 1 , there are several possible
interpretations: First, the slowness may be due to the fact
that the odor of the food box which served to initiate the reaction
is swamped, overpowered, by the nearer, more potent odor of
the trail; or, second, that attention is divided between the two
and hence we have the characteristic behavior; third, it may
be that the pleasurable feeling set up by the odor of the trail
is in itself a deterrent and results in loitering; or fourth, it may
be that the nearness and strength of this stimulus does initiate
the preliminary instinctive food-taking reactions which of them-
selves end or modify the distance reactions of running.

As one observed the behavior in the initial trial, there did not
seem to be any emotional excitement which would suggest the
inhibition of running through conflicting motor tendencies and
hence the second explanation is discredited. That the trail odor
was the predominating one in the first trial seems probable
and that it was also pleasurable. The satisfaction of hunger
at the end of this trial, however, must, in all succeeding trials,
have played a large part and made the original trail a different
more intense, more stimulating trail, a somewhat else, viz., a
trail which ended with this satisfaction. Yet still there was
the loitering and slow movement through all of the early trials
which would lead us to think that the fourth supposition may
be a reasonable one. Why, then, did this behavior alter in the
later trials ? Because of the organization of the whole response
into an habitual motor series which only required the odor for
the initiation and possible reinforcement of the act. The more
rapid final speed, which exceeded the normal, may have been
caused by the reinforcement of the kinaesthetic control, now
established, by the olfaction of the trail.

Miss Richardson says,11 "Olfaction may accelerate or retard
the learning process; accelerate when the odor is a part of the
stimulus connected with the problem — otherwise be disadvan-
tageous." It is easy to conceive that it may have the same
effect upon the actual rate of running — that it may result here
in a genuine acceleration of speed.

While the main purpose of this work was to establish and to

11 Richardson, F. R. A study of sensory control in the rat. Psych. Rev. Mon.
Sup., 12, no. 1, p. 68.

THE WHITE RAT AND THE MAZE PROBLEM 157

study the effects of an olfactory control in the maze, one of the
most interesting features of the results was the proof of a transfer
of training. So far as the writer knows there has not been
shown before in the animal world, at least in such a graphic
way, this change of sensory control from one form to another
within a single learning process.

THE CHICAGO EXPERIMENTS WITH RACCOONS

L. W. COLE

University of Colorado

At the University of Chicago, three of Professor Carr's gradu-
ate students, Dr. W. S. Hunter,1 and Messrs. F. M. Gregg and
C. A. McPheeters2 have been engaged in repeating experiments
similar to mine on raccoons, with results which are most grati-
fying to me.

Hunter (p. 46 and beyond) found the behavior of the raccoons
as different from that of his dogs and rats as I found it different
from the behavior of cats. He was compelled, as a result of
his experiments, to give up the mere sensori-motor explanation
of the behavior of these animals, nor could he attribute it to the
association of motor impulses with a whole situation. Motor
attitudes could, he thought, account for the behavior of the rats
and dogs. It would not serve for an explanation of the reactions
of the raccoons. At the close of my experiments, I, too, was
compelled to regard those explanations as inadequate. He
found that children and raccoons could respond successfully
to a stimulus after a much longer delay than could the rats and
dogs. He found for the raccoons a maximum delay of twenty-
five seconds. The longest delay that I used was at least six
seconds, or possibly nine seconds, if we consider only positive
reactions of the animals. He compares the behavior of the
raccoon favorably with that of a two-and-a-half -year-old child.
Moreover, he admits an idea as a "possible cue" used by the
raccoons and the children, as against purely motor or sensory
cues, used by the other animals tested, though he prefers to
attribute the reactions of the raccoons and those of, at least,
the youngest child to "imageless thought."

Now that my experiments have been confirmed so fully I must

1 Hunter, Walter. S The delayed reaction in animals and children. Behavior
Monographs, vol. 1, no. 1, 1913.

2 Gregg, F. M. and McPheeters, C. A. Behavior of raccoons to a temporal
series of stimuli. Jour. Animal Behavior, 1913, 3, 241-259.

158

THE CHICAGO EXPERIMENTS WITH RACCOONS 159

regard them as established. This seems to me to be an item of
progress. The psychology of mammals must now cease to be
a mere generalization of the psychology of cats. And two of
my former students, Professor DeVoss and Miss Rose Ganson,
have recently shown what I believe to be an excellent reason
why cats may not be expected to behave the same as animals
with less defective vision.

We have, then, been driven from the cover Of accounting for
all mammalian behavior by the sensori-motor hypothesis alone,
and psychologists are free at last to try to learn how animals
differ in their behavior, instead of denying all differences. This
will help enormously, for it may enable us finally to discover a
psychology of the higher animals which can explain as well as
deny, which can be taken out of the laboratory and yet bear the
light of day and the scrutiny of intelligent persons who observe
animals. This we have not had. When you meet an observer
of horses, who thinks his horse remembers its home, you do not
convince him by denying his statements and the evidence he
gives, or by calling him "naively anthropomorphic," or by telling
him that he did not record the date of the occurrence, or by
hurling at him the anathema of "anecdotal psychologist" with
opinions "too trivial for serious analysis or notice". A science
which can only deny everything and explain nothing is no
science and will never receive nor deserve confidence. It
certainly was legitimate in 1898 to start by denying the worth
of anecdotes of animals for comparative psychology, but only
if by denying them we should eventually find a way to explain
them, or at least to explain observations of animal behavior
which are made almost every day. Experimental animal
psychology is now sixteen years old. Consequently it must
soon cease to be a generalization of the behavior of cats and
take some step which promises eventually to explain animal
behavior. Otherwise it must confess bankruptcy and its inferi-
ority to common sense, and remain a sort of science which
cannot emerge from the laboratory and which cannot be believed
by the psychologist himself the moment he emerges from it.

I am in no hurry for this science to make progress but I should
like to see it take a direction which promises something. I do
not think that a devoted effort to adhere to an objective nomen-
clature, or to hang the fate of progress on some word, as behavior,

160 L. W. COLE

or behaviorism, or forever to deny what many observers affirm.
is taking a promising direction. It is true that the professors
at the University of Pisa saw Galileo drop the weights, and saw
them reach the ground at the same moment, and yet refused
to believe the evidence of their senses. Animal psychology
which merely denies has had an influence in university circles
similar to the influence of Aristotle on the professors at Pisa,
but it has gained no such influence upon intelligent observers
elsewhere. Instead of denying all psychic traits to animals
would it not be better to deny our competence to explain more
than the merest trifle of animal behavior ? I believe that
Hunter's confirmation of my results should give a new stimulus
to investigators to devise ingenious new experiments suited to
find new facts. That avenue seems more hopeful than a denial
that there are new facts to be found, and affirming that animal
psychology must become a sort of "organic physics."

It is of interest to observe also that while current mammalian
psychology cannot come out of the laboratory, common sense
observations continually find their way into it. In this paper
of Hunter's, for example, one animal is a "stranger" to another
and so pays close "attention" to the latter's movements. Pre-
liminary experiments make his animals "acquainted" with the
place and apparatus. The raccoons display a directness and
"sureness" in their behavior which defies the mathematics of
chance. Their "attention" was "distracted" by "yelling at
them at the top of my voice" (P. 71). (A procedure likely to
make them fierce beyond recall, and which, perhaps, explains
the last statement of Dr. Hunter's paper. It is gratifying to
learn that this method of distraction was used only infrequently.)
Attention and association are everywhere ascribed to the animals
and not the association so accurately described by Thorndike,
but association pure and undefined. Surely these are greater
and more gratuitous assumptions to make than that a horse
remembers his stable, even when distant from it, or that a raccoon
remembers the box from which it is difficult for him to escape.

I realize that these remarks will expose me to the charge of
being as completely deceived as was Herr von Osten, but his
is not my position. My view is that "imageless thought," if
Hunter's hypothesis is deemed correct, or, at least sporadic,
images if my own explanation is accepted as the simpler one,

THE CHICAGO EXPERIMENTS WITH RACCOONS 161

are perhaps so rare in animal experience that the most refined
experiments will be required to discover and identify them;
experiments beside which Hunter's experiments, and mine, will
pale into insignificance, because of their simplicity.

There is still another reason for hoping that the study of
animal intelligence may sometime get beyond the stage of dispute
and denial. Dispute and denial are poor material to occupy
the time of college students. Long ago I had to give up that
kind of teaching ,and occupy myself with the more solid infor-
mation which we possess, of animal sense organs, because dialectic
should be taught in philosophy and not in science. Note the
extensive work of Kafka3, the first volume of which has just
appeared.

Dr. Hunter's agreement with me does not end with the facts
noted above. He is almost persuaded to credit my experiments
in putting the animals through the act to be learned, because
he has observed the same sort of behavior in rats. At least
he admits my apparent credibility relative to my four raccoons.
It would be unfair to him, however, not to state his qualifications.
On page fourteen he says: "Now with reference to that type
of experiment in which the problem learned is that of working
latches rather than climbing into boxes, I believe the data
presented by Cole are conclusive, as far as the facts are concerned.
Some raccoons at least appear to learn by being "put through."
Whether all raccoons would do so is, of course, quite another
matter/' (Italics mine.)

The reader may reply, "You can surely get but cold comfort
from this admission." It gives you the merest semblance or
'appearance' of credibility with regard to your report on your
four animals alone. I at least have not charged you with having
invented your records." True enough, but the admission means
that Hunter's rats, if they have not made a breach, have at
least made a weak place in the blank wall of opposition and denial.
The latter is definitely given up. How wonderful is the rat at
undermining !

The cold comfort comes from the facts that those experiments

of mine have not been repeated at Chicago University. I fear,

because their raccoons would not permit it (Hunter p. 86).

Now should the Chicago laboratory secure a toothless raccoon

3 Kafka, Gustav. Einfuhrung in die Tierpsychologie. Leipzig, 1914.

162 L. W. COLE

what may not become of the credibility, temporarily and with
qualifications, accorded me ? But what disposition, pray, will
then be made of the behavior of Hunter's rats ? With many
misgivings, therefore, I await the report of experiments which
may even now be in progress.

In instinctive behavior the Chicago raccoons confirmed my
observations rather than those of Davis. Yet I am sure Davis's
report is correct, despite the authorities quoted against him,
for I saw occasional cases of what he observed regularly. We
must not be too cocksure in these matters. Remember that
Audubon never saw his pet raccoon wash its food in the water
beside it (Davis p. 45 1 ) . 4 Yet that behavior gives to the raccoon
both the name "lotor," and the name "Waschbar".5

Interpretations: The reader who is familiar with Dr. Hunter's
thesis will recognize the agreements I have mentioned between
the behavior of my raccoons and those of the Chicago laboratory.
Our interpretations of this behavior are entirely different, of
course, except that we were both forced to give up the sensori-
motor explanation. Forced from that position, I thought the
animal might have memory, or at least a few memory images
carried in visual terms, hence a visual image. I still believe
that this is the simplest, or as some prefer to say, the most
"parsimonious hypothesis." Hunter prefers the assumption of
"imageless thought" or "sensory thought" to account for the
raccoons behavior, and for that of at least the youngest child.
This "imageless thought" must be, at least partly, visual, for
he says (p. 74), "In the present case there seems to be no room
for doubt that the object reacted to was the light." The reader
must remember that this light had been turned off for twenty-
five seconds before the animal was permitted to react to it, in
the maximal delays with raccoons, hence the "representative
functions," next mentioned. For he continues thus: "Now if
a representative function were involved in the behavior of the
reagents, as seems to have been the case with the raccoons and
children, it must in part at least, have been representative of the
lighted box, because all else — including the three possibilities

4 Davis, H. B. The raccoon : a study in animal intelligence. Amer. Jour, of
Psychology, 1907, 18,

5 1 have to thank Mrs. R. M. Yerkes for calling my attention to this splendidly
appropriate German name for the raccoon, and its superiority to the American
name, whose source is not certain.

THE CHICAGO EXPERIMENTS WITH RACCOONS 163

of movement — was constant from trial to trial, whereas a selective
response must needs have an alternating cue". (Italics mine).

I know of no way in which light can stimulate these animals
except visually. And when the animals were permitted to react,
it was by means of a function representative (at least partly)
of the lighted box. One would think that the simplest escape
from this dilemma would be by means of a visual image. But
no, it is visual in source or cause, yet imageless in content. We
have often been led to believe that sensation gives a rather
fundamental content to thought. Perhaps we may now teach
that Helen Keller, for example, has both the content of visual
experience as well as a knowledge of its relations. Loeb6 has
recently given evidence to show that a retinal image produces
a brain image, which corresponds with the former point for
point. "Diese Tatsachen enthalten aber, wie mir scheint, auch
den Nachweiss, dass in Gehirn ein Bild der gesehenen Gegen-
staende entsehen muss" (p. 1016). By Hunter's hypothesis
all of this image forming apparatus is rather useless, for no mental
image arises in the raccoon, nor perhaps in the youngest child,
under the conditions of the experiment.

Doubtless it will occur to the reader of Hunter's paper that
this explanation of the raccoons' behavior, by means of imageless
thought, was in no way suggested to him by his experiments
and seems to be a rather foreign addition to his thesis, forced
upon him by the milieu or suggested by current discussions
of the topic in human psychology. In order to use the concept
to account for the results of his experiments he must make the
claim (p. 77) that imageless thought is genetically prior to
thoughts with images, and he must dismiss the opposite teaching
as having "no factual basis" but seeming to be "the result of
prejudice or of temperamental leaning." Then the point of
origin of imageless thought is placed "at least as low as the
raccoon" (p. 77). All this seems a trifle complex to me but the
actual advance made is, now that the old explanation has been
given up, that the reader may choose what hypothesis he will
under the law of parsimony.

Doubtless psychologists will be more interested in Hunter's
immediate explanation than in his final one, which I have already

6 Loeb, J. Die Bedeutung der Anpassung der Fische an den Untergrund fuer
die Auffassung des Mechanismus des Sehens. Zeit.f. Physiol., 1911, 25, 1015-1017.

164 L. W. COLE

outlined. When the conditions of his experiment demanded that
the animals go to an electric bulb, whose light had been extin-
guished some seconds before, in order to execute a successful
reaction, the rats and the dogs oriented toward the light, either
with the whole body, or at least faced in its direction. They
kept this orientation during the period of delay in so many of
their correct responses that this "motor attitude" evidently
served to bridge the time gap between the disappearance of the
light and the release of the animal. Consequently their "motor-
attitude" accounts for the success of the rats and dogs. The
raccoons and the children did not even face the light in so great
a proportion of their successful responses that the "motor-
attitudes" hypothesis breaks down completely, as an explanation
of their behavior.

As a result of this outcome of the experiments, Hunter (p. 80)
decides that, "Some intra-organic (non-orientation) factor not
visible to the experimenter must be assumed in order to explain
a significant number of the correct reactions of the raccoons
and all of the successful reactions of the children. These cues
fulfilled an ideational function." (Italics mine.) And again
(p. 72), "As we have indicated, such a mechanism would apply
only to the non-orientation cues used by the raccoons and children.
The type of function here involved is ideational in character.
By applying the term "ideas" to these cues, I mean that they
are similar to the memory idea of human experience so far as
function and mechanism are concerned. They are the residual
effects of sensory stimuli which are retained and which may be
subsequently reexcited. The revival, moreover, is selective and
adaptive to the solution of a definite problem, and when aroused,
they function successfully as a necessary substitute for a definite
component of the objective stimulus aspect of the problem."
He has already said that the effective component of the stimulus
was the light. Unless he denies, then, a visual content to this
"factor," it is a visual, imageless thought. But since he does
deny it a representative content, though it has a representative
function, he terms it "sensory thought," though the stimulus
has been absent twenty-five seconds in the longest delays of
the raccoons. This "sensory thought" then becomes the image-
less thought of current discussion, by the genetic reversal of
current opinion on that subject that I have mentioned above.

THE CHICAGO EXPERIMENTS WITH RACCOONS 165

It is interesting to observe how very "similar to the memory
idea" is this "intra-organic factor." It is a residual effect of
a sensory stimulus. It may be retained and revived, is selective,
etc. Elsewhere (p. 69), he describes this factor as "Some
unknown intra-organic cue non-observable by the experimenter.
Our data prove conclusively that some such cue was utilized

by the raccoons and the children, the nature of such a

factor must necessarily be defined at present in negative terms."
When this statement was written it evidently had not occurred
to Hunter to place this negative thing in the positive category
of imageless thought. His experiments were completely described
before reaching this point. Hence, it seems to me that imageless
thought was an afterthought, as an explanation.

On the second page of the paper we find this significant state-
ment. "In the interpretative discussion at the close of the
present monograph, we shall be confronted with the possibility
that images or ideas may have guided the reactions of the subjects.
In discussion, we shall assume that there is no necessity that
psychology postulate such a representative factor save where
successful reactions occur in the absence of the stimulus (object)
or movement represented." So images may have been present.
Yet throughout his references to my paper Hunter complains
that I did not reach a proof of the presence of images. When
his experiments were completed, he seems to be in much the same
position. Just how an experimenter can give proof that animals
remember or think, even in imageless thought, I am quite unable
to guess. I thought that my animals gave evidence of possessing
visual memory. Hunter's experiments strengthen this opinion
of mine very much.

Like Brehm and all subsequent observers of the raccoon,
Hunter has noted the fly-catching activities of this animal. He
consequently accords to the "Waschbar" the possession of acute
vision. In this he agrees with my report.7

Errors: On page eighteen, in re-describing some of my
experiments, Hunter says, "a block with a steeple was placed
in a hole," etc. With absolute confidence I must assure the
psychological public that I used no "steeple" in my apparatus.

7 Cole, Lawrence W. Observations of the senses and instincts of the raccoon.
Jour, of Animal Behavior, 1912, 2, 302.

166 L. W. COLE

I have, very rarely, heard the word "steeple" used for "staple,"
but never before have I seen it so used in a scientific monograph.

Again, I am regarded as having been "misleading" (p. 86)
in my statement that "the year-old raccoons apparently are
not quite full grown," for Dr. Hornaday and Mr. DeVry say
"that raccoons reach maturity at three years of age." But do
Dr. Hornaday and Mr. DeVry mean, therefore, that the raccoon
accomplishes but one third of his growth each year, as Hunter
seems to interpret them ? I cannot believe it. I kept my
animals three years and I wish now to re-affirm the statement
above. They grew but little after the first year. Work and
confinement may have stunted them, though they were fed
each day to satiety. In parks I have now seen many raccoons of
about the same size which mine attained. They had been in
confinement for a long time so they must have been full grown.
I have also seen a number of much larger specimens.

Criticisms of my Work: The introduction to Dr. Hunter's
thesis takes the form of a fearful arraignment of both my experi-
ments and my arguments. To use his own phrase, most of
the latter "can be dismissed summarily" (p. 16). They are in
turn dismissed summarily in favor of the sensori-motor explan-
ation, so his theory of raccoon behavior at the beginning of his
paper differs entirely from that at its close. I suppose that I
ought to make some reply to these criticisms, but I shall be as
brief as possible and at that I shall select only the most important
ones. It seems better to omit any answer at all to such remarks
as, "To some it may seem too trivial either for serious analysis
or notice" (p. 10), a criticism which I seem to share with Lloyd
Morgan and others, save that I have persisted in their trivialities.

Criticism 1. "Hence assuming the facts that Thorndike and
Cole assume to be unquestionable, it need only follow that the
raccoon exhibits more complex sensori-motor behavior than the
dog and the cat, and not that it shows a new type of behavior,
i. e., a type of behavior involving the functional presence of a
representative factor." (P. 15.)

Reply. Yet he later found just such a factor functionally
present in raccoons.

Criticism 2 . 'To argue that this means image of apple is
certainly naive at least. Could the raccoon not sense the apple
when his nose was within a foot of it ?" (P. 18.)

THE CHICAGO EXPERIMENTS WITH RACCOONS 167

Reply. Hardly probable, since the floor between him and
the piece was carefully rubbed with another piece of the same
apple, and his forepaws were still moist with the pieces of apple
he had already eaten. But note Hunter's argument (p. 27)
that smell was eliminated in his experiments because the rat
was given only a bite, "so almost no food fell on the floor."
Food was used with the raccoons in the same way.

Criticism 3 . Varying means to the same end. My data
under this head are just as inconclusive as that presented above.
(P. 17.)

Reply. Curious then that Professor James thought this "the
mark and criterion of the presence of mentality in a phenomenon."
"We all use this test," says James, "to discriminate between an
intelligent and a mechanical performance."

Criticism 4 "The criticisms on Cole's entire work reduce
to these: (1) The facts are either inconclusive or irrelevant.
And (2) there is no evidence of adequate controls." (P. 20.)

Reply (a) Why then are the same facts, namely, responses
to an absent stimulus, so satisfyingly conclusive of imageless
thought ? This recalls the remark of Hodgson, "What you
know least about, assert to be the explanation of everything
else." (I quote from memory.) (b) "No controls." This is
the repeated cry in these papers. It seems probable from the
statements of the papers that their authors did not read my
account and that they misunderstood the few pages they did
read. I shall show this in detail in showing that Gregg and
McPheeters (and their experiment was planned by Hunter) have
entirely misunderstood what I did.

In concluding the discussion of Hunter's report alone the
points of similarity between his experiments and mine may be
enumerated. He extinguished lamps which were used as stimuli,
while I put a series of objects in view of the animal, then out of
view again, and he must discriminate, under these conditions,
between absent stimuli. Hunter secured delay by caging the
animal, while I secured it by not feeding the animal until every
member of the series had been put in view and (except the last
member) out of view again. Sometimes six objects were used
by me (i. e., each of three cards was shown twice). Hunter
found it inapplicable to use the third light in many cases.

168 L. W. COLE

The second paper, that of Gregg and McPheeters, had no
other object than "to demonstrate the inadequacy of Cole's
experiment." (P. 258.)

They reconstructed my " card-display er," except that the
levers were not screened from the view or touch of the animal
and a system of strings and pulleys was added which the animal
could also see.

Then they gave the two raccoons two days training on the
levers alone without any cards attached to them. (P. 245.) One
of the two animals, Jack, failed utterly to discriminate. "Further
training might have developed discriminative reactions in his
case but time did not permit a continuance of the tests." (P.
246.) Jill discriminated between the two series on some basis,
but Jill also "soon acquired the habit of standing close to the
levers and touching her nose to them as they appeared." (P.
247.) Here, the reader will doubtless say that all analogy with
my experiment ends. I should agree to this so far as the method
and apparatus are concerned but it seems easier to change those
than to change the nature of the raccoon, for there is a startling
agreement between the behavior of their one successful animal
and my four.

Let us find this agreement. In the training series Gregg and
McPheeters kept two constant factors. (1) A "normal" order
of lever positions used, according to their respective distances
from the animal. (2) They always presented the levers in
series of three. Jill reacted to the order of lever positions chiefly,
perhaps (p. 249), but she responded partly to the threes, for
they say (p. 252), "Positive reactions of food getting may be
stimulated successfully by any of the following groups, 1-2-3,
1-3-3, 1-2-2, 2-2-2, or 1-1-1. Likewise, inhibition, or negative
responses may be stimulated by either group 3-3-3, or 2-2-2.
The nature of the stimulus is relative to the character of the group
with which it is alternated." One cannot help asking, why
continue to alternate by threes only, unless they meant to teach
the animal to respond to alternate threes ? Why not alternate
by sixes as I did ? This was one of my "controls," which they
have overlooked.

Jill reacted to the two constant factors. In my experiments
only the color (and brightness) of the cards was kept constant.
My four animals responded to that. In both the Chicago

THE CHICAGO EXPERIMENTS WITH RACCOONS 169

experiments and my own the raccoons responded to the constant
factor. What more could they do, pray ? This seems to me
to be an excellent example of the method of agreement.

But this was the behavior of Jill, the single raccoon which
succeeded in discriminating in their experiments. One would
suppose that no very weighty conclusions would be drawn from
the behavior of the animal which failed. But he is said to have
responded to the sounds of the levers. Their "usual sound."
(P. 248.) (Why not make the levers noiseless ?). This animal
then responded to sound, perhaps partly to lever order and,
I have no doubt, to any other element of the situation which was
left constant, and which also enabled him to get food. "He
seemed to watch the peep hole, although possibly he was merely
listening for some sound upon which to base his reactions"
(P. 246), so they set a metronome going to drown the noises
made by movements of the experimenter!

I confess I can see nothing in these experiments except a
rather determined effort to divert the animal's attention from
the cards and to get him to respond to the levers. The following
items seem to show this:

1. Two days preliminary training on levers alone.

2. The board screen was reduced to "about five inches" in
width (p. 244), thus showing apparently two thirds of the
length of the levers, if Figures 2 and 4 (pp. 243 and 247) correctly
represent the apparatus.

3. Putting the cards above the raccoon's line of vision, if
Figure 4 is correct.

4. Converting my visual experiment into a tactual one by
letting the raccoon touch the levers.

5. Adding the cue of noises in operating the levers, as well
as noises due to the experimenter's movements.

6. Each of the three strings attached to the levers (Figure
4, p. 247) must have changed from slack to taut before the lever
appeared, thus further directing the animal's attention to the
levers' positions. I am unable to find "controls" against the
animals having reacted to the strings.

7. Feeding the raccoon for having reacted to the levers. .

8. The colored cards were much smaller than mine.

9. Finally only one of their animals succeeded in discriminating
as compared with four of mine.

170 L. W. COLE

'The essentials of Cole's apparatus and method were duplicated
in our experiment." (P. 244.) Truly, with all these carefully
arranged differences, I am quite unable to find that the "essen-
tials" of the experiment were even similar to mine, but the
reader may judge for himself. Any one who is familiar with
my paper will remember that only a small part of the upper
portion of the lever projected above the screen board. To be
specific, my notes of Dec. 6, 1905, state that the lever "when
upright" extended "one inch above the upper edge of the front
piece."

"Controls1'1 By the charge that I did not employ "adequate
controls" is meant chiefly that I did not guard against discrimin-
ation by position of cards and levers nor against discrimination
by cues given by the experimenter. Let me call attention to
two items which my critics have overlooked relative to the first
precautions, and quote from notes of the experiments. On
page 228, I say, "During one test red would be on the forward
lever, one inch in front of the other, during the next test on the
rear lever. The animal could not, therefore, react to the position
of the cards." I did not re-state this precaution in the portion
of my account on which the Chicago laboratory based its experi-
ments, but one presumes that a critic reads completely the paper
he criticises. To show that this precaution was kept up during*
the three-color work I will quote my "daily plan" for one animal
for three consecutive days.

"April 23. Jack. Same as preceding. Blue middle, orange
back, white front."

"April 24. Jack. Three colors. Orange front, white middle,
blue back."

"Jack. April 25. Three colors. Blue front, orange middle,
white back."

It is evident that each card occupied every possible position
in each three consecutive tests, and that no card occupied the
same position for any two tests. Does this look as if I took no
precautions against the animals reacting to the positions of the
cards ? I find no such precautions as this, to leave only the
colors constant, in the work of Gregg and McPheeters, so it
seems that the animal was fed for depending on another cue.

But the uninformed reader may ask, "But what of level
position ?" At the beginning of each days work the levers

THE CHICAGO EXPERIMENTS WITH RACCOONS 171

were "strung" on their supporting pivot in any order in which
they were picked up. We did not remove them from the room
in which the raccoons were kept and we generally found them
scattered about the room. The levers were all alike so far as
we could detect, until having split one, we replaced it with one
having a "new" appearance. This should have brought a new
type of result if the animals were responding to the appearance
of the levers.

It is true that this change of card position is mentioned briefly
at the outset of the experiments instead of within the portion
on which the Chicago experiments were based. But was no
further precaution taken which was described on the final pages
of report ? On page 259, Table 11,1 record that for two hundred
trials the threes were "shown twice." Since this has been un-
noticed or misunderstood let me explain it. It means that I
would show red, red, red, red, red, red, and the animal must stay
down through it all. Then came white, orange, red, and only
then would the animal climb up on the high step to be fed.
Thus nine movements were made, and all the levers were used.
Then followed white, orange, red, and the animal reacted posi-
tively and was fed. Thus he could hardly have been responding
to alternate threes, or to lever position. Note also that there
was an abrupt transition from showing the cards by threes to
showing them by sixes. Yet the animal gradually learned to
discriminate in this complicated experiment in which all factors
were different, except the colors of the absent cards. I describe
this showing the cards by sixes at the bottom of page 258, and
refer to it as "while you raise three or even six colors, again on
page 261." Perhaps tiiis detailed account of the precautions
taken to guard against discrimination by threes, and against
discrimination by position will serve to convince the reader that
the experiments were not so careless or hasty as my critics
have supposed.

But it is further assumed that I mixed the experiments in
which the experimenter manipulated the levers with those in
which the animal was permitted to claw at them. The two types
of experiment were separated by months. My paper states
(p. 233) that no tendency to claw at the levers appeared for
six weeks of the first type of experiment. After it did appear,
clawing at the levers was not permitted until we had learned

172 L. W. COLE

what we could by the experimenter's operating them. Nor did
the raccoons attempt to claw at the levers, if the experimenter
manipulated them rapidly. In fact we developed the habit by
moving the levers slowly. This confusion on the part of Hunter,
Gregg and McPheeters appears to be due to my giving a logical,
instead of a chronological account of my experiments.

The behavior of my raccoons was not, therefore due to touch.
Consequently Hunter's experiments with lights is more similar
to mine than that of Gregg and McPheeters, whose "card-
displayer" had some points in common with mine.

As to cues from the experimenter, I always extended my hand
as if to feed the animal, at the negative as well as at the positive
series. My notes contain many instances, at first, of this re-
sponse to the hand. These were of course counted against the
animal, and finally he ceased to be influenced by the movement.
Different experimenters operated the levers and, in one case, it
was found that the animals were responding to unconscious
movements of the operator. This is mentioned in describing
the vision of the raccoon.8 This experience shows that if the
mere presence of the experimenter, or his breathing, had been
the cue to which the animals were responding the raccoons
would have made far better records than they did, and the work
of months would have been reduced to days. I should still
prefer to have the experimenter present rather than to use the
system of strings, which caused the noise, the peep hole, the
opening for food, and to permit the noise of the experimenter's
movements, which had to be overcome by a metronome, all of
which were used by my critics.

Conclusions: It is noticeable that, so far as Gregg and Mc-
Pheeters draw a conclusion, they ascribe the raccoon's behavior
to "motor attitudes," "sensory attitudes" and, if images were
present in our animal, they must have been kinaesthetic, i.e.,
imaginal attitudes." (P. 258.) Thus they give the explanation
of the raccoon's behavior which Hunter found was entirely
inadequate to account for it, but which, he believes, does account
for the behavior of the dogs and rats. Perhaps, at the time
their experiments were made, Hunter's results were still in-
complete and it was assumed that the raccoon's behavior would

8 Cole, Lawrence W. Observations of the senses and instincts of the raccoon.
Jour, of Animal Behavior, 1912, 2, 302.

THE CHICAGO EXPERIMENTS WITH RACCOONS 173

be found in nowise different from that of the dogs and rats.
At any rate, we now have three different hypotheses to account
for the behavior of raccoons.

1. Attitudes, motor, sensory or imaginal. Gregg and Mc-
Pheeters.

2. Not attitudes, but imageless thought. Hunter.

3. Visual memory, at least sporadic. Cole.

Truly, "Homines perfacile credunt id quod volunt."

JOURNAL OF ANIMAL BEHAVIOR

Vol. 5 MAY-JUNE 1915 No. 3

THE WHITE RAT AND THE MAZE PROBLEM:
III. THE INTRODUCTION OF A TACTUAL CONTROL

STELLA B. VINCENT

Chicago Normal College

In two papers, appearing in preceding numbers of this Jour-
nal, I have attempted to show that vision and olfaction can
be introduced as controls into the maze problem and to demon-
strate some of the effects of such an introduction upon the
learning process of the white rat. In this article I wish to re-
view, briefly, in the light of the previous discussions, some
work on the maze problem where the conditions for tactual
and cutaneous control were emphasized and to add some experi-
mentation not previously reported. For the full details of the
earlier work see my monograph, : The Function of the Vibris-
sae in the Behavior of the White Rat."1

While this paper, the third of a series, attempts to show
how tactual elements enter into and modify the maze reactions,
it must be understood that the sensory experience is always a
complex. Yerkes has sounded the warning clearly when he
says: "An animal responds to a situation, not to any one inde-
pendent and isolated stimulus. Every situation, to be sure,
may be analyzed into its component simple stimuli, but the
influence of each is conditioned by the situation."2 The diffi-
culty of isolating the tactual element is the chief reason why
there has been so little work done with it in studies of labyrinth

1 Vincent, S. B. The Function of the Vibrissae in the Behavior of the White
Rat. Behavior Mon., vol. 1, no. 5.

2 Yerkes, R. M. Relations of Stimuli in the Frog. Harvard Studies, vol. 2,
p. 546.

176 STELLA B. VINCENT

learning: The experimentation which has been undertaken up
to this time has consisted mainly in moving the labyrinth to a
different base, covering the floor path with different substances,
interposing hurdles, and the use of anesthetics on the feet of
the animals.

Opinions as to the value of the sense in such problems have
been based upon observation and voiced in general statements
like this: " The longer one observes the behavior of the dancing
mouse the more he comes to believe in the importance of touch
and motor tendencies."3 Or the assumption was perhaps a
specific one and yet unsupported by any evidence, as: ' Tac-
tual-motor sensations furnish the essential data for the recog-
nition and discrimination involved in forming the special asso-
ciations at critical points."4 One investigator has made appar-
ently contradictory statements, as : ; The indications point to
the fact that the rat in no way uses his cutaneous sensations
as a basis for 'sensing' the correct turns in the maze as distin-
guished from the incorrect."5 In this case the feet of the animal
were anaesthetized with ethyl chloride. Reporting some experi-
ments with blind animals he said: ' Runs squarely down the
middle of the galleries, makes his turns into the various entries
as boldly and with as much sureness as do the normal rats.
The vibrissae undoubtedly play a large part (though not an
indispensable one) in the early reactions of these rats to the
maze."6 Of normal animals he remarks: ' In all probability
the rat does not discriminate his turns by means of any data
contributed by the vibrissae." ' Vibrissae undoubtedly warn
him of the presence of solid objects. . . . The function of the
vibrissae to some extent at least may be dispensed with once
the path is learned."7 These seeming contradictions, however,
are due to the confusion in the report of those activities involved
in the formation of the habit and those essential to its control
when established. The conclusions are those drawn from one
type of maze and one form of motor habit and while possibly
valid in this particular problem cannot be carried over to all
such co-ordinations.

3 Ibid, Dancing Mouse, p. 178.

4 Small, W. S. Mental Processes of the Rat. Amer. Jour. Psy., vol. 12, p. 237.
0 Watson, J. B. Kinaesthetic and Organic Sensations. Psy. Rev. Mon. Sup.,

vol. 8, no. 2, p. 78.

6 Ibid, p. 58.

7 Ibid, p. 69.

THE WHITE RAT AND THE MAZE PROBLEM 177

Miss Richardson makes some definite statements though not
in connection with labyrinth problems: " Slight contact (with
plane) seemed to give her immediate orientation."8 " The
basis seemed to be that afforded by touch. Contact with the
plane was doubtless evidence of its presence." . . . " It was
only when they came in contact with the plane that some sen-
sory impulse connected with its fall set off the old association
and they would dash to the door of the box."9 " There was no
indication that any of the rats located the door by means of
vision for each rat passed the door while 'searching' for it with-
out reaching to it. Yet when the door was touched there fol-
lowed the examination of the latch and the requisite movements
to open the door." . . . Locating the door as before prob-
ably with the snout."10 " The normal rats like the blind rats
seemed to discover the latch by contact."11

A layman would scarcely question the importance of the
tactual experience in the life of animals, yet in experimental
work its function had been called in question even in such prob-
lems as Miss Richardson mentions and kinaesthesis had barred
all rival contestants in labyrinth learning. It was in order to
test the control in the maze that this work was undertaken.

DESCRIPTION OF MAZE

The method used in testing this tactual control was not quite
the same as that employed in the work with vision and olfac-
tion. In those experiments the stimulating values of the true
path and the blind alleys were made to differ in as pronounced
a manner as possible. In this case there was no attempt made
either to accentuate the contact values of the floor or walls
of the maze or to offer contrasting standards in the true path
and the false. Another maze was built on a new plan where
the conditions, it was hoped, were such that not only could the
tactual functioning of feet and vibrissae be seen but also that
such functioning would be a necessary part of the learning
process. (Figure 1.)

8 Richardson, Florence. A Study of Sensory Control in the Rat. Psy. Rev.
Mon. Sup., vol. 12, no. 1, p. 39.

9 Ibid, p. 40.

10 Ibid, p. 55.

11 Ibid, p. 56.

178

STELLA B. VINCENT

The runways to this maze had sides which could be detached.
When this was done there was left a maze pattern of open,
elevated paths but these paths had sufficient space between
them so that the animals did not try to jump from one to the
other. It was found that on this open maze, wrhere the whole
pattern was exposed, the visual control was not sufficient to
prevent there being just as real a problem as was seen in mazes
with enclosed sides. The situation forced the use of the feet
and the vibrissae in a way that the other mazes did not and
this fact accounts for the title at the head of this paper. Other
sensory elements contributed to the learning, without doubt,

Fig. 1 — The maze as used with sides down

but the tactual-cutaneous factors were the prominent ones and
the ones which we wished to throw into relief. As it is desired
to compare the results obtained in this w7ork with those secured
where vision and olfaction were emphasized in the Hampton
Court maze, let us compare the two labyrinths.

COMPARISON OF HAMPTON COURT AND X MAZES

The length of the true path in the Hampton Court maze is
40 feet, in this 17 feet. There is one more blind alley in the
H.C. maze than in this. The cut de sacs have a total length

THE WHITE RAT AND THE MAZE PROBLEM 179

of 30 feet in the one and 9 feet in the other. The paths, both
true and false, of the H.C. maze are more complex in nature.
The results obtained from the H.C. maze and those given by
the smaller maze, which we will call the X maze, when the sides
are on are very similar. In table 1 they are given in tabular
form together with the dimensions of each maze.

To make these results comparable it is necessary to multiply
the errors of the X maze by 7/6, since the H.C. maze has 7 errors
while the X maze has only 6. The time taken to run the maze
should be directly proportional to the length of the path. In
the first trial in any maze the cul de sacs are explored rather
thoroughly; therefore the time of the first trial in the X maze
should be multiplied by 40/17 x 30/9, the ratios between the
lengths of the true paths and the cul de sacs in the two mazes.
In the final trials, however, the errors are cut out and to get
the comparative speed we multiply the figures for the X maze
by 40/17 to correct the speed for the true path. By comparing
the corrected results of the X maze with those of the H.C. maze
we can see that the statement of similarity is substantiated.

The X maze took an average of four more trials to learn than
the H.C. maze. The slower learning time for the X maze is
doubtless a result of the character of the cul de sacs. There are
three pairs of blind alleys in this maze. One and three are exactly
of the same length and character and so are two and six and
likewise four and five. The two latter pairs differ only four
inches in length while after the turns the distances in 1, 2, 3
and 5 are identical. (See figure 1.) The distances on the true
path between the turns are also comparable. If, after the habit
is formed, the running under these conditions is . carried on
largely in kinaesthetic terms, as we believe, then differences
between the kinaesthetic elements in the series should favor
such an accomplishment. Such differences in kinaesthetic
elements are differences in complexity, differences in the dis-
tances between the turns as well as in the direction of the turns,
and differences in the lengths of the cul de sacs, etc. Too great
a similarity between such kinaesthetic units would hinder the
learning. The plan of the H.C. maze, according to this con-
ception, is more favorable for learning and hence the slower
learning time of the X maze. The corrected figures for the
X maze show a greater average number of errors in the first

180 STELLA B. VINCENT

trial and in the last five trials but looking at the average number
of errors for the first five trials and the total errors per animal
we see that the balance is in favor of X maze.

Thus the error balance in the figures of the two mazes now
leans to one side and now to the other. These differences, also,
probably spring from the form and character of the cut de sacs.

The lower final speed in the X maze is caused by one slow
animal. If we take the time for all of the runs in which there
were no errors in both series and from these records compute
the speed per foot for each maze we find it to be exactly the
same, 2.5 feet per second. This is not the final speed, however.

The object here is not to go over these details item by item
but merely to show that, in general, these mazes are alike in
type and the reactions made in them are therefore approximate.

COMPARISON OF EXPERIMENTS ON X AND Y MAZES

We will now turn to a consideration of the experimentation
on the X maze, where the sides to the runways were on, and
the same maze, which we will call the Y maze, the open maze,
where the runways had no sides.

The behavior in the X maze needs no description but that
in the Y maze showed essential differences. When the sides
were taken from the runways and the rats put on the maze
they showed a marked tendency to follow the edges of the
paths. They did this either by turning their vibrissae down
against the sides or by curling their toes over the edges of the
board. That this was a real control was shown by using rats
whose vibrissae had been cut on one or both sides of the head,
by using blind rats with and without vibrissae and rats in which
the branch of the fifth nerve which innervates the upper lip
and snout had been cut. The learning in all of these cases was
made more difficult except in one instance. In this case the
vibrissae were cut on one side only. As a result, the animals
were forced to keep to one side of the maze and by following this
side they made their way around the labyrinth almost imme-
diately. It is impossible here to go into all of the evidence and
readers are referred to the original monograph.12 The work
conclusively showed that the tactual-cutaneous experience had

12 Op. cit.

THE WHITE RAT AND THE MAZE PROBLEM 181

a vital part in the solution of the problem. In the end the rats
ran this maze with as much boldness and confidence as the
other, with heads up, almost leaping corners, etc. The one
exception was the group of blind rats without vibrissae.

Let us compare the results of the two mazes as to accuracy
and speed. We find that the time of learning was the same but
in the Y maze the errors were less by one-half in the first trial
and one-third in the first five trials, and the total number of
errors was decreased about one-third although the final accuracy
of the two mazes was practically the same. The beginning
time was shorter because of the fewer errors but the average
time of the first five trials was about the same in both. The
final speed in the Y maze was slightly better. The most notice-
able difference, then, was the decrease in errors. The open maze,
from the beginning, favored accuracy and it should be noted
that this accuracy was not attained at the expense of speed.

In a maze, where the paths are enclosed by restraining walls,
there is little need of fine bodily adjustments. The turns in the
H.C. maze and in this maze are always 90 degrees but the place
of the turn in the H.C. maze is always marked by some corner
or projecting wall against which the body of the rat brushes
or his vibrissae drag as he runs. A railway engineer does not
have to keep his train on a straight course by the fraction of
an inch, he has only to develop speed, his track is laid for
him. The analogy is not perfect but in the enclosed maze the
rat is comparatively ' safe." He does not have to control,
as on the open maze, the finer postural and positional adjust-
ments and as a result of this looseness of running he makes
more errors. On the open maze the control of these finer adjust-
ments is necessary in order to avoid slips and falls and hence
there is greater initial and final accuracy.

The nose, feet and vibrissae were constantly used at the
different places of turning. The direction of the turn seemed
a much easier thing to conquer than the exact place. The
operated animals were at a great disadvantage. Vision aided
these finer adjustments but the nose and feet and vibrissae
seemed to be of greater help to the rat than sight. However,
either sight or the touch of nose or vibrissae seemed to be a
vital necessity to the learning. The animals could not well
dispense with both in such a problem as was here presented.

182 STELLA B. VINCENT

THE X MAZE RE-LEARNED AS THE Y MAZE

That the habits set up in the two mazes were inherently of
different type was shown by the following experiment: After
the group of animals whose records are given for the X maze
in table 1 had learned the maze the sides were removed and the
rats were tried again. Kinaesthesis had apparently been firmly
established during the first experiment and while some dis-
turbance was to be expected, it was thought that it might affect
the runs of but one day. The outcome shows the danger of
supposing anything about animals. These rats had to relearn
the maze almost as if it were a new problem. The old habits
did not meet the situation. The animals went out upon the
maze with flattened, crawling bodies; they clung to the edges
with their toes, they followed these edges with their vibrissae;
they used apparently every tactual-cutaneous help possible.
While the fewer initial and total errors seem rather good evi-
dence that something was carried over from one maze to the
other, the fact that it took over eleven trials on an average for
the relearning, as well as the evidence of the observed behavior,
indicates that the habit had to be re-established through new
sensory aids. A summary of the numerical data may be seen
in the last column of table 1.

The maze pattern was the same. The kinaesthetic series was
the same: the distances, turns, all that goes to form what Pro-
fessor Watson calls a kinaesthetic element, but the other sensory
elements, always present in the kinaesthetic complex, light,
possibly odor and sound but chiefly touch had greatly changed.
Always, as the rat ran in the X maze, his sides and vibrissae
brushed the walls, the projecting partitions and the angles of
the box. All at once this part of the sensory experience was
gone. It could be and it was replaced but with a tactual ex-
perience of another sort requiring very different adjustments.
In addition there was the necessity for the finer adjustments
previously mentioned. Thus the problem became a new one.
The position which I desire to maintain here and upon which
I desire to lay emphasis is that, while in a fully formed habit
kinaesthesis probably predominates as a control, the sensory
experience is never purely kinaesthesis but always a complex and
the finer are the adjustments which need to be made the more
necessary the associated sense qualities of vision and touch become.

THE WHITE RAT AND THE MAZE PROBLEM

183

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184 STELLA B. VINCENT

CONCLUSIONS

The conclusions from this study are that, given conditions
which favor or necessitate the use of vibrissae or the tactual
use of nose or feet, the maze habit is not more quickly established
but that during the setting up of the habit fewer errors are made
and because of this the time per trial is lessened and time is
gained. The conclusion is also drawn that these conditions
make, within the limits of the experiments, for greater final
speed as well as for greater final accuracy.

A STUDY OF THE BEHAVIOR OF THE PIG SUS
SCROFA BY THE MULTIPLE CHOICE

METHOD

ROBERT M. YERKES AND CHARLES A. COBURN

The Harvard Psychological Laboratory and the Franklin Field-Station

INTRODUCTION

The multiple choice method of studying ideational and allied
forms of behavior was first briefly described in a lecture on the
study of human behavior delivered at Cold Spring Harbor in
1913. x It has recently been more fully described in a paper
which presents the results of its application in the study of the
crow.2 We shall, in the present report, assume knowledge of
the previous descriptions and state only the essential features of
the method and its adaptation to the organism observed.

It was devised in the Psychopathic Hospital, Boston, as a
means of obtaining comparable records of the ideational behavior
of mentally deficient and deranged individuals. But it was also
hoped that it might prove widely serviceable as a comparative
method for the study of various types of organism.

In many of its essential features, the Yerkes multiple choice
method is similar to the Hamilton quadruple choice method,3
but whereas in the latter four reaction-mechanisms are employed
and only problems which, strictly speaking, are insoluble are
presented to the subject, the present method involves the use
of a variable number of reaction-mechanisms and the presenta-
tion of soluble problems of a wide range of dimcultness.

The experimenter seeks, in using the multiple choice method,
to present to his subject, no matter what its type, age, or condi-
tion, a problem which may be solved by the perception of a

Yerkes, Robert M. The study of human behavior. Science, 1914, 39, pp.
625-633.

2Coburn, Charles A. and Yerkes, Robert M. A study of the behavior of the
crow Corvus Americanus Aud. by the multiple choice method. Journal of Animal
Behavior, 1915, 5, pp. 75-114.

3 Hamilton, G. V. A study of trial and error reactions in mammals. Journal
of Animal Behavior, 1911, 1, pp. 33-66.

185

186 ROBERT M. YERKES AND CHARLES A. COBURN

certain constant relation or group of relations within the reac-
tion-mechanisms. For example, the mechanism to be operated
may, in the case of one problem, be the middle one of the group,
and the total number of mechanisms presented may vary from
three to nine. Only by perceiving and appropriately responding
to the relation which the experimenter designates as middleness,
can the subject solve the problem.

It is necessary only, in the presentation of a varied series of
multiple choice problems to a given subject, for the experimenter
to devise a type of reaction-mechanism which is appropriate to
the action-system of the organism to be observed. We have
thus far made use of a simple keyboard for human subjects,
while for crows, ring-doves, and rats, we have employed a series
of similar boxes, each with entrance and exit doors which can
be operated at a distance by the experimenter. The form of
device which has proved suitable for the study of pigs will be
described in this report.

It has proved very easy to develop suitable mechanisms and
we have every reason to suppose that this new method has great
advantages over most others for the comparative study of be-
havior in that essentially the same problems may be presented
to extremely different types of subject.

The method has been employed in experiments with normal
and defective children, normal and insane adults, pigs, rats,
crows, and ring-doves.4 To all of these subjects,. four problems
have been presented. They may be described briefly, by defini-
tion of the correct reaction-mechanism, as Problem 1, the first
mechanism at the subject's right; problem 2, the second mechan-
ism at the subject's left (that is, from the end of the series at
the subject's left) ; problem 3, alternately the first mechanism
at the subject's right and the first at its left; problem 4, the
middle mechanism of the series.

It has become increasingly clear, as our investigations pro-
gressed, that the perfect solution of a problem by a given subject
is of much less importance as a matter of record than is detailed
information concerning the types of reaction and the appearance
and disappearance of reactive tendencies during the course of
experimentation. For the solution of a problem means simply

4 The results of our experiments, except in the case of the crow, have not been
published.

A STUDY OF THE BEHAVIOR OF THE PIG 187

the termination of a series of observations. It is essential,
therefore, that the experimenter fix his attention rather on the
immediate response of his subject than on the attainment of the
solution of problems. We especially call attention to this matter
because many experimenters seem to feel dissatisfied with other
than speedy and completely positive results. It seems fair to
insist that by the multiple choice method positive results are
obtained even if a subject cannot solve any of the problems
which are presented to it.

Since it is our intention to more fully discuss the essential
features and the technique of the multiple choice method else-
where, we shall here content ourselves with these brief intro-
ductory statements and references. It should perhaps be added
that only by reading the earlier article on the behavior of the
crow can the reader hope to fully understand the present report.

SUBJECTS

The subjects of the experiments which constitute the obser-
vational basis for this paper were two Chester white pigs. They
were born April 1st, 1914, and they were therefore two months
old when, on June 2nd, they were taken to the Field Station
from an adjoining farm and placed in the experimental situa-
tion. We shall refer to these individuals as the male and the
female, since both sexes were represented. The male, however,
had been castrated before we obtained the animals.

From the first, individual differences were conspicuous. The
male was considerably smaller and less active and energetic
than the female; he ate less and showed less initiative. Through-
out the period of observation, both animals were in perfect
health and at no time was there reason to suppose that either
environmental or physiological conditions were unfavorable to
our experiments.

From birth these pigs lived practically out of doors, having
a yard to run in and a rather open shelter from storm.

Although the experimenters had expected much of the pigs
because of the indications from casual observation of their
behavior, it may be said at once that they proved far more
satisfactory subjects than we had dared to hope. Indeed, they
worked so steadily and uniformly through the investigation that
there was practically no loss of time. It is chiefly because of

188 ROBERT M. YERKES AND CHARLES A. COBURN

this unexpectedly favorable relation of subject to method that
we were enabled to obtain, during the summer of 1914, the
numerous results reported below.

APPARATUS

Fortunately, it was possible at the Franklin Field- Station to
locate our apparatus in an orchard convenient to the buildings.
A rough shelter was built for the pigs under a large apple tree,
and convenient yards were arranged by the appropriate use of
wire fencing.

The accompanying figures give a fairly good idea of the ex-
perimental situation. In figure 1 A, the multiple ^choice appa-
ratus appears in the foreground, behind a fence which com-
pletely surrounds the enclosure. Immediately in front of the
apparatus is a bench for the observer. Systems of weighted
cords, conspicuous in 1 A, enable the experimenter to operate
the slide doors of the multiple choice boxes.

The arrangement of the yards is made clear by figure IB
and figure 2. It was necessary to be able to isolate the pigs
for observation as we 1 as to have the apparatus so arranged
that an individual could readily be admitted for a trial and on
the completion of its reaction, be returned to its appropriate
yard.

The multiple choice apparatus proper consists of nine similar
boxes, shown in ground plan in figure 2. They were built of
rough boards and numbered conspicuously 1 to 9. Each box
is sixty inches long, by twenty inches wide, by forty-eight inches
deep, with a slide door at each end. The distance between these
doors on the inside of the box is forty-eight inches.

From each of the entrance and exit doors a woven window-
weight cord extends upward, through a pulley, then horizontally
forward through another pulley, and downward, ending in a
weight nearly over the observer's bench. To all of the cords
from the entrance doors, white weights were attached; to all
from exit doors, black weights. Each weight was sufficient to
hold its door in position after the latter had been raised. It
was found that this required about ten pounds, and iron window
weights served our purpose.

In front of the exit door of each box is a v-shaped food trough
which is divided into nine like parts by the partitions between

Figure 1. Multiple Choice Apparatus for Use with Pigs

A. The reaction-mechanisms from the experimenter's position,
cords for operating doors. Entrance doors 2 to 6 are raised.

B. The same from the pig's point of view, showing one pig w
trial. Entrance doors 2 to 6 raised as in figure A.

C. The same view as that of figure B except that the pig has
the reaction-space and is about to enter the middle box (no. 4) of
are open.

D. Here the pig is shown, after appropriate reaction, feeding
box no. 4. The experimenter appears in the position necessary
of cords and observation of response.

E. The reaction-mechanisms seen from one end.

showing weighted

aiting in yard for

been admitted to
those whose doors

in the trough of
for manipulation

B-

,

■ m

0 .

m

V

A

1

2

3

4

5

6

7

8

9

■

!

[ "

f

P

1

•

■

T

D

Figure 2. Ground Plan of Multiple Choice Apparatus Used for Pigs. Scale

A, reaction mechanisms, nine similar boxes or stalls; V, stall number 4; 0, en-
trance door of box; P, exit door of box; T, food trough of box; G, observer's stand
and H, writing table; D, runway between trough, T, and stand, G; S, S, yards;
B, reaction space; R, E, alleys or runways connecting D with S; I, observer's en-
trance door to apparatus; J, observer's entrance door to reaction space B; L, M,
slide doors between* yards and reaction space; K, N, slide doors between yards
and alleys.

The weighted cord systems for operating the entrance and exit doors (twenty
in all) are not shown in this figure. They may be seen in figure 1, A, B, and C.

190 ROBERT M. YERKES AND CHARLES A. COBURN

boxes. When the exit doors are down, the various parts of the
food trough are covered by a horizontally placed sheet of metal
which fits closely over them and thus prevents the subjects from
obtaining food from the outside of the apparatus.

The large enclosure is divided into four principal parts: (1) the
part which contains the reaction-mechanisms with space for the
observer's bench, G, and writing table, H, and a passageway
for the subject from the exit doors of the apparatus to the yard,
S; (2) second, the reaction space which is labelled B in figure 2,
in which the subject responded to the multiple choice situation;
(3) and finally, the two yards, S, S, from which the subjects
started in the case of each trial and to which they returned on
the completion of their reaction. K, L, M, and N, designate slide
doors between the several portions of the large enclosure, while
J and I represent doors which were used by the experimenter.

The entire apparatus was constructed in sections, so that at
the end of the season it might readily be taken down and stored.

This brief and very incomplete description will be supple-
mented somewhat in the section on experimental procedure.

PROBLEMS AND GENERAL METHOD

The four problems enumerated on page 186 were presented to
each subject in the order named. For each of these problems,
a series of ten settings of the doors was determined upon. These
settings differ somewmat from those employed in our study of
the crow. It is our intention, so far as possible, to use them
with all types of subjects until our observations indicate desirable
changes.

We present below for each of the four problems (1) the num-
bers of the settings, (2) the numbers of the doors open, (3) the
total. number of doors open in each setting and for the series of
ten settings, and (4) the number of the right door.

It was our plan to give each subject an opportunity to respond
to each of the ten settings for a given problem in order and to
return then to setting 1 and repeat the series. It was found
impossible, however, to give ten trials in succession in our early
experiments, and in the case of both problems 1 and 2, as a rule
a subject was given five trials in succession. For problems 3
and 4 it was found possible to give ten trials in succession.

*

A STUDY OF THE BEHAVIOR OF THE PIG

191

Problem 1. First Mechanism at the Subject's Right

Settings Doors open No. of doors open No. of right door

1 1.2.3 3 1

2 8.9 2 8

3 3.4.5.6.7 5 3

4 7.8.9 3 7

5 2.3.4.5.6 5 2

6 6.7.8 3 6

7 5.6.7 3 5

8 4.5.6.7.8... 5 4 .

9 7.8.9 3 7

10 1.2.3 3 1

Total 35

Problem 2. Second Mechanism at the Subject's Left

Settings Doors open No. of doors open No. of right door

1 7.8.9 3 8

2 1.2.3.4 4 3

3 2.3.4.5.6.7* 5 6

4 1.2.3.4.5.6 6 5

5 4.5.6.7.8 5 7

6 1.2.3 3 2

7 2 3 4.5 4 4

8." .'.'.'.'.'.'.'.'.'.'.'.'.' '. '. .1.2.3*. 4.5.6. 7.8.9! '.'.'. .9. '.'.'.'.'.'.'.'. '.'.'.'.'.'.'. '.'.8

9 1.2.3.4 4 3

10 3.4.5.6.7.8 6 7

Total 50
Changed from 3.4.5.6.7 to 2.3.4.5.6.7 after about one hundred trials.

Problem 3.

Setting

8

9

10

Alternately the First Mechanism at Subject's Right and the
First at Its Left

Doors open No. of doors open No. of right door

5.6 7

3

5 6 7..

. .3 .

1.2.3.4.5.6

1.2.3.4.5.6

. .4.5.6.7.8. ..

6

6

5

4.5.6.7.8

. .2.3.4 5.

5

. .4

. .2.3.4.5...

. .4. .

3.4.5.6.7.8.9

7

3.4.5.6.7.8.9....

7

Total 50

192 ROBERT M. YERKES AND CHARLES A. COBURN

Problem 4. Middle Mechanism of the Series

Setting Doors open No. of doors open No. of right door

1 2.3.4 3 3

2 5.6.7.8.9 5 7

3 1.2.3.4.5.6.7 7 4

4 7.8.9 3 8

5 4.5.6.7.8 5 6

6 1.2.3.4.5.6.7.8.9 9 5

7 1.2.3 3 2

8 2.3.4.5.6 5 4

9 3.4.5.6.7.8.9 7 6

10 6.7.8 3 7

Total 50

Both punishment and reward were used in these experiments.
The punishment consisted of confinement for a definite interval,
usually one minute, in each wrong box entered, while the reward
consisted of food which could be obtained in the trough of the
right box.

EXPERIMENTAL PROCEDURE

We shall now briefly enumerate, in order to supplement the
descriptions of apparatus and methods which have been given,
the steps in a regular series of observations.

The experimenter having entered the enclosure with a supply
of food, record-book, stop-watch, etc., first raises each of the
nine exit doors and places in each section of the trough a quantity
of food (sour milk, shelled corn, vegetables). He then lowers
the exit doors, thus covering the food, and takes his position
on the observation bench. In case both pigs are in the shelter
yard, it is next necessary for him to drive one of them into the
other yard. This having been done, he may proceed to set
the entrance doors for the first trial. Let us suppose that the
problem to be presented is problem -1 and that setting 1 is first
to be used. In this case the experimenter raises entrance doors
1, 2, and 3. He is now ready to admit one of the pigs to the
reaction space B of figure 2. This he does by raising momentarily
the appropriate slide door between B and S.

The instant the pig enters the reaction space, the experimenter
starts his stop-watch and begins to record the important features
of the behavior of the animal, noting especially its approach
to the several doors, its tendency to enter boxes and the actual
entrance and time of entrance into any one of the three acces-

A STUDY OF THE BEHAVIOR OF THE PIG 193

sible boxes. Let us suppose that the animal enters directly
box 3. Immediately the experimenter lowers the entrance door
and thus confines the animal in the small compartment as
punishment for an incorrect choice. At the expiration of one
minute, the entrance door is raised and the pig is allowed to
retreat from the box and make another choice. We may now
suppose that the animal, after passing in front of boxes 2 and 1,
returns to 1 and enters it. The experimenter immediately stops
his stop-watch, lowers the entrance door, and, since this box is
by definition the right one, he immediately raises the exit door
and rewards the animal for correct choice by allowing it to eat
for a few seconds. He then, either by speaking to the pig or by
touching it with a whip, induces it to pass from the box by way
of the passage, D, and the alley, R or E, back to the appro-
priate yard, S.

Having reset the apparatus, the experimenter now gives the
other pig a trial with the same problem and either with the same
or with a different setting of the doors.

As a rule, the animals were fed only in the trough of the
apparatus. They were almost always hungry, and although
sufficiently well fed to keep them growing and in excellent
health, they usually seemed fairly hungry at the end of a day's
work. In no case was it necessary, in order to induce them to
work steadily, to have them extremely hungry.

The influence of visual and olfactory factors was to be ex-
pected, and at various points in the investigation, precautions
had to be taken against following.

PRELIMINARY TRAINING

On June 2nd the pigs were brought to the Field Station and
placed in the shelter yard, and in the afternoon of the same
day, they were fed in the trough of the apparatus, all of the
doors of the boxes and the yards being raised.

During the next six days they became thoroughly accustomed
to the apparatus and learned both to feed in the trough and to
make the trip readily from the yards, through the apparatus,
and back to the starting point. They very quickly and satis-
factorily adapted themselves to the situation, while at the same
time becoming thoroughly tame and indifferent to the presence
of the experimenter.

194 ROBERT M. YERKES AND CHARLES A. COBURN

On June 9th it seemed fitting to attempt a series of prelim-
inary trials. Each animal was given, in turn, opportunity to
secure food in each of the nine boxes. When the subject entered
the reaction space, B, the entrance door of a certain box stood
open, and as soon as the animal had entered that box, the ex-
perimenter closed the door behind it and opened the exit door
in front of it, thus enabling it to obtain food. During these
preliminary trials, the pigs were in separate yards and were
given their trials alternately.

We shall now' report the results of our regular experiments.

RESULTS OF EXPERIMENTS

As it is essential to present the data for each trial in the series
of experiments, tables 1, 3, 4, 6, 7, 9, and 10 have been con-
structed after the following manner. At the head of each table
stand the several settings, the letter S serving as an abbreviation
for setting and the number following it designating the place of
the setting in the series. Immediately under the number of the
setting appear the numbers of the doors open with the one to
be chosen (correct one) printed in bold face type. Below this
preliminary information concerning the particular problem in
question, appear the results for each of the trials of each subject.
The column headed T gives the number of a trial in the total
series of trials for a given subject, in a given problem. Follow-
ing the number of the trial are the numbers of the boxes entered,
in the order of entrance. Referring to table 1, we discover that
the female in her first trial under problem 1 selected, of the
three boxes whose doors were open, first, number 3 She was,
of course, punished by being confined in this box for one minute,
and on release entered box 1, which was the correct box, and re-
ceived the reward of food. Or again, in table 3 it may be noted
that in trial 146, under problem 2, the female entered, in order,
boxes 7, 9, 7, and 8, the group of open doors including 7, 8, and
9, and the box to be entered being number 8.

These tables will enable the reader to obtain quickly definite
information concerning the forms of response and the changes
therein during the course of experimentation. We shall present
the several tables under the problem numbers and reserve further
comment for the section on the discussion of results.

A STUDY OF THE BEHAVIOR OF THE PIG 195

DISCUSSION OF RESULTS

The results will now be discussed under the headings of the

four problems, and in connection with each a condensed tabular

summary of the experiments will be offered, together with such

comments as are necessary on the experimental procedure, the

behavior of the subjects, and the significance of the various

forms of response.

PROBLEM 1

This problem, for which the definition of the correct mechan-
ism is the first at the subject's right, proved extremely easy for
the pigs. Incorrect choices were surprisingly few, and the
number of trials necessary for the perfect solution of the prob-
lem was also surprisingly few for both subjects, the female having
chosen correctly throughout a series of ten settings at the end
of forty trials and the male having similarly succeeded at the
end of forty-five trials.

As is indicated by tables 1 and 2, which contain all of the
data for this problem, the experiments were not discontinued at
this point, but each individual was given additional opportunity
to work out the problem. In the light of our later experience,
this was a mistake, but at the time we were unconvinced that
the animals were depending upon the relation of the correct
mechanism to the other members of the group, and we proceeded
further with our observations in. order to settle certain points
which were in doubt.

From the first it was evident in connection with this problem
that the female was more intelligent than the male, and that he
tended to be markedly influenced by her. After observations
were discontinued with her on June 14th, he reacted very poorly
for a number of series, and then again improved and reacted
perfectly in the last three series given on June 15th.

In this problem the total number of doors open in the ten
settings was, as may be seen by reference to the data presented
on page 191, thirty-five. Of these, ten were of course correct.
Hence the probability of a correct first choice apart from ex-
perience would be 1 to 2.5. In table 2, it appears from the data
of the last column for each individual that the ratio of correct
to incorrect first choices was on the first day of training 1 to 1
for the female and 1 to 2.33 for the male. It should here be
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196

ROBERT M. YERKES AND CHARLES A. COBURN

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A STUDY OF THE BEHAVIOR OF THE PIG

197

TABLE 2

Daily Series and Averages with Ratios of Correct to Incorrect

First Choices
Problem 1
Female Male

No.

Ratio

No.

Ratio

Date

of

trials

R

W

R

W

of
R toW

Date

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R

W

R

W

of
R toW

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6

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1?

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1

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a

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1

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problems, the data refer only to first choices in each trial, the
column headed R containing the number of correct first choices
and that headed W the number of incorrect first choices for
each series of trials or for the day. It further appears from this
table that five trials constituted the regular series in problem 1,
and it should here be stated that the experimenter always re-
sumed experimentation at the point in the regular series of
settings at which work had been interrupted. He therefore pro-
ceeded in regular order from setting 1 to setting 10 and then
returned to setting 1 and repeated the trials.

Further comment on the behavior of the animals in problem
1 is needless, for the task is but slightly more difficult than the
acquisition of a simple position habit, and it has already been
satisfactorily demonstrated that many of the vertebrates acquire
such habits with ease.

198 ROBERT. M. YERKES AND CHARLES A. COBURN

PROBLEM 2

For this problem, which is definable as the second mechanism
from the subject's left, all of the data for discussion will be
found in tables 3, 4, and 5. Again, as in the case of problem 1,
the regular series consisted, throughout the training, of five
trials, but as many as six such series were given on a single
day. Bracketed series appearing, for example, in table 5, under
the dates June 23, 24, 25, and 28 and July 1, 2, 3 and 4, were
continuous, that is, ten trials were given in succession instead
of only five.

For the ten settings of problem 2, the total number of open
doors is fifty, and the expectation therefore is that prior to
experience an animal will choose correctly once in five times,
thus giving a ratio of right to wrong choices of 1 to 4. That
this expected ratio does not appear on the first day of experimen-
tation is due to the effect of the previous training in problem 1.
The tendency to enter the first box at the left was persistent
in both subjects and often that box was re-entered a number of
times in spite of punishment. In tables 3 and 4 the data for
these statements are presented, and in table 5 it may be noted
that on the first day of work on problem 2 neither subject made
a single correct first choice.

The ratio of correct to incorrect first choices for the female
rapidly, although somewhat irregularly, decreased with experi-
ence until on July 4th it stood 1 to .19. On this date she suc-
ceeded in choosing correctly in ten successive trials, and was
therefore considered to have solved the problem perfectly.

Similarly, the ratio for the male changed fairly rapidly until
on July 11th it stood 1 to .11. At this time, although he had
not succeeded in choosing correctly in each of the ten settings
consecutively, his training was discontinued, for he had already
delayed experimentation with the female for a week, and it
was perfectly clear that although he made an occasional error,
he was capable of perfectly solving the problem.

Whereas the female finished this problem as a result of 390
trials, the male had made only nine out of ten correct choices
at the end of 520 trials, when his training was discontinued.
We are inclined to think that this is a reliable indication of the
difference in docility between these two individuals.

A STUDY OF THE BEHAVIOR OF THE PIG 199

We shall now turn to tables 3 and 4 for a further brief analysis
of the reactions.

For about 50 trials in problem 2, both pigs showed the effect
of their experience in problem 1. Then the number of correct
first choices rapidly increased for each of the ten settings. There
were in the case of setting 1 few mistakes on the part of the
female after 150 trials, whereas on the part of the male there
were more than twice as many incorrect first choices. The
same holds in general of each of the other settings, she proving
herself much more steady and predictable in response than he.
This was doubtless due in a measure to hunger, for it was much
more difficult to keep him in the proper condition of eagerness
for food than her.

The data of these tables indicate no definite and persistent
reactive tendencies during the course of experimentation other
than the original acquired tendency to enter the first box at
the right in the group and the subsequently acquired tendency
to select the second box from the left in the group. Certain
of the settings proved very much more difficult than others.
Contrary to expectation, difncultness is not directly variable
with the number of doors open. Setting 1, for example, as
contrasted with setting 6, is much the easier, yet three doors
are open in each case. In general, however, it is evidently true
that the larger the group of open doors the more difficult it is
for the animal to choose correctly and the larger the number
of mistakes in a given trial, if the first choice is not correct.

From the behavior of the two pigs in this problem, as con-
trasted with the first, it is safe to conclude that they are per-
fectly capable of selecting the proper reaction, mechanism by
its relation in a group of similar mechanisms when the number
in the group is as large as nine and when the constant relation
of the correct mechanism is second from one end. It is further
clear that this problem is a much more difficult one for the pigs
than problem 1. But it is also certain that the difference in
difncultness is not indicated by the difference in the number
of experiences necessary for the solution of the problems, since
the early days of work on problem 2 served merely to overcome
the tendency acquired in connection with problem 1. It seems
probable that should we subtract 100 trials from the totals
under problem 2 we should have a fair basis of comparison

200

ROBERT M. YERKES AND CHARLES A. COBUltX

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A STUDY OF THE BEHAVIOR OF THE PIG

203

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204

ROBERT M. YERKES AND CHARLES A. COBURN

TABLE 5

Daily Series and Averages with Ratios of Correct to Incorrect

First Choices

Female

Problem 2

Male

No.

Ratio

No.

Ratio

Date

of

trials

R

W

R

W

of
R to W

Date

of
trials

R

W

R

W

of
R to W

June

June

16

1- 5

0

5

16

1- 5

0

5

«

6-10

0

5

0

10

0:1

u

6-10

0

5

0

10

0:1

17

11-15

2

3

17

11-15

2

3

ii

16-20

0

5

ti

16-20

1

4

a

21-25

0

5

2

13

1:6.50

it

21-25

1

4

4

11

1:2.75

18

26-30

2

3

18

26-30

1

4

u

31-35

1

4

it

31-35

2

3

a

36-40

0

5

u

36-40

1

4

it

41-45

1

4

4

16

1:4.00

«

41-45

1

4

5

15

1:3.00

19

46-50

1

4

19

46-50

1

4

it

51-55

4

1

it

51-55

2

3

ii

56-60

2

3

it

56-60

1

4

a

61-65

1

4

8

12

1:1.50

tt

61-65

3

2

6

9

1:1.50

20

66-70

1

4

20

66-70

2

3

«

71-75

2

3

it

71-75

2

3

u

76-80

0

5

it

76-80

0

5

«

81-85

2

3

5

15

1:3.00

tt

81-85

2

3

6

14

1:2.33

21

86-90

0

5

21

86-90

3

2

»

91-95

0

5

it

91-95

3

2

u

96-100

2

3

tt

96-100

1

4

it

101-

1

4

3

17

1:5.67

it

101-

2

3

9

11

1:1.22

22

106-

0

5

22

106-

0

5

a

111-

2

3

tt

111-

2

3

ti

116-

0

5

a

116-

4

1

«

121-

1

4

3

17

1:5.67

it

121-

1

4

7

13

1:1.86

2.?{

126-

1

4

23

126-

2

3

131-

1

4

tt

131-

3

2

it

136-

2

3

ii

136-

2

3

a

141-

1

4

it

141-

3

2

a

146-

2

3

7

18

1:2.57

tt

146-

5

0

15

10

1: .67

24

151-

1

4

24

151-

2

3

'•{

156-

1

4

tt

156-

4

1

161-

3

2

tt

161-

2

3

u

166-

3

2

tt

166-

5

0

ii

171-

4

1

12

13

1:1.08

tt

171-

2

3

15

10

1: .67

25 f

176-

2

3

25 f

176-

2

3

" \

181-

3

2

* \

181-

4

1

it

186-

3

2

it

186-

1

4

it

191-

3

2

11

9

1: .82

tt

191-

3

2

10

10

1:1

26

196-

1

4

26

196-

1

4

it

201-

3

2

tt

201-

3

2

it

206-

2

3

6

9

1:1.50

it

206-

3

2

7

8

1:1.14

27

211-

3

2

27

211-

2

3

ti

216-

2

3

tt

216-

2

3

it

221-

2

3

7

8

1:1.14

it

221-

3

2

7

8

1:1.14

?{

226-

2

3

28 /

226-

2

3

231-

3

2

" I

231-

3

2

tt

236-

2

3

ti

236-

4

1

ti

241-

5

0

ii

241-

2

3

it

246-

4

1

it

246-

4

1

it

251-

5

0

21

9

1: .43

u

251-

2

3

17

13

1: .76

29 I

256-

2

3

29

256-

3

2

A STUDY OF THE BEHAVIOR OF THE PIG

205

TABLE 5 — Continued

Daily Series and Averages with Ratios of Correct to Incorrect

First Choices

Problem 2
Female Male

No.

Ratio

No.

Ratio

Date

of

trials

R

W

R

W

of
R to W

Date

of
trials

R

W

R

W

of
R to W

June

June

29

261-

3

2

29

261-

4

1

«

266-

4

1

u

266-

4

1

«

271-

3

2

a

271-

2

3

u

276-

2

3

a

276-

2

3

a

281-

4

1

18

12

1: .67

u

281-

4

1

19

11

1: .58

30

286-

4

1

30

286-

1

4

u

291-

2

3

u

291-

2

3

a

296-

5

0

a

296-

4

1

a

301-

2

3

13

7

1: .54

«

301-

3

2

10

10

1:1

July

July

1 /

306-

3

2

M

306-

3

2

" I

311-

4

1

311-

3

2

1

u

316-

5

0

a

316-

3

2

u

321-

2

3

14

6

1: .43

a

321-

2

3

11

9

1: .82

M

326-

5

0

2 /

326-

4

1

331-

4

1

" I

331-

3

2

u

336-

4

1

a

336-

4

1

a

341-

4

1

17

3

1: .18

u

341-

2

2

13

7

1: .54

M

346-

5

0

M

346-

2

3

351-

2

3

351-

3

2

a

356-

4

1

a

356-

2

3

a

361-

3

2

14

6

1: .43

a

361-

3

2

10

10

1:1

4 /

366-

4

1

4 f

366-

4

1

" 1

371-

3

2

:

371-

3

2

" /

376-

4

1

376-

3

2

" \

381-

5

0

" \

381-

3

2

a

386-

5

0

21

4

1: .19

u

5

u

386-
391-
396-

3
5
2

2
0
3

16

9

1: .56

11

391

4

1

a

396

5

0

9

1

1: .11

a
a

401-
406-
411-

3

1
3

2
4
2

it

14

11

1: .79

6

416-

0

5

u

421-

4

1

4

6

1:1.50

7

426-

2

o
O

a

431-

1

4

a

436-

3

2

<f

441-

2

3

8

12

1:1.50

8 1

446-

4

1

" \

451-

3

2

a

456-

5

0

a

461-

2

3

u

466-

4

1

18

7

1: .39

9 /

471-

5

0

" \

476-

1

4

u

481-

2

3

a

486-

1

4

9

11

1:1.22

10 f

491-

3

2

" \

496-

3

2

u

501-

4

1

a

506-

2

3

12

8

1: .67

11

511-

5

0

a

516-

4

1

9

1

1: .11

206 ROBERT M. YERKES AND CHARLES A. COBURN

with problem 1. It would then appear to be from four to eight
times as difficult as the latter.

One important aspect of the experiment should be here con-
sidered. According to our procedure, one of the pigs led and
the other followed in a series of trials. It was therefore possible
that the follower might be aided in its choice either by watching
its companion or by the odor of the box in which the animal
fed. There can be no doubt of the tendency of the pigs both to
watch one another and to be influenced by the odor of the
boxes, but that the solution of the problems did not depend
upon either of these factors, although the number of trials
necessary to solution may have been modified thereby, is proved
by the fact that both subjects made ninety per cent of correct
choices when leading.

PROBLEM 3

All of the data in connection with this problem are to be
found in tables 6, 7, and 8. The problem is definable as alter-
nately the first mechanism at the right and the first at the left.
At the beginning of work on this problem, the animals were
given their trials alternately as in the preceding problems, but a
strong tendency to follow manifested itself, and on the second
day the trials were given by pairs. That is, each individual
was allowed to choose in succession the first door at its right
and the first door at its left, and was then required to wait while
its companion responded to the same pair of settings. Thus,
following was rendered impossible.

The tendency to choose the second door from the left natur-
ally manifested itself in .the early work on this problem, but it
was soon destroyed by training, and the course of experimen-
tation proceeded smoothly to the perfect solution of the problem.

It is to be noted that from the first, ten trials constituted a
series. Because of the familiarity with the general experimental
situation which the animals had acquired and the experience of
the experimenters in the control of hunger and punishment,
it was easier to obtain reactions to ten successive trials at this
time in the investigation than to five early in the work, with
problems 1 or 2.

The female succeeded in solving problem 3 as the result of
420 trials; the male, as the result of 470.

A STUDY OF THE BEHAVIOR OF THE PIG 207

For this problem as for problem 2, the expectation prior to
experience is one correct first choice to four incorrect first choices.
The male in his first series exhibited exactly this ratio, whereas
the female gave a ratio of 1 to 1. Her success, however, was
undoubtedly due to following, for in immediately subsequent
trials when following was rendered impossible by the giving of
the trials by pairs, she did very poorly. The daily ratios for each
individual, as presented in table 8, are of interest, but they are by
no means as important as are the detailed data of tables 6 and 7.

As might have been expected, after the previously acquired
tendency to select the first mechanism at the left had been
overcome, the pigs shortly exhibited the tendency to select the
end boxes, and they then had to overcome the difficulty of
selecting the right end. It is quite possible that this task was
rendered easier by the rhythm which resulted from the giving
of trials by pairs, but it was perfectly evident from control
experiments that the animals could choose correctly even if
given their trials in rapid succession, without the irregularity
due to alternate experimenting with the two individuals.

Since it seemed possible that the animals might have learned
the proper settings and be responding to definite situations
rather than to the relation of the right box to the other members
of the group, a control experiment was made by the presentation
of a new series of settings. At the bottoms of tables 6 and 7
appear the results of these control observations.

The female had solved problem 3 on the completion of trial
420 (see tables 6 and 8), and the male on the completion of
trial 470 (see tables 7 and 8). The next series of ten trials for
each was preliminary to the control experiments and served
also as a demonstration series to certain other observers. Fol-
lowing this demonstration in which both pigs reacted fairly
well, the series of settings indicated in tables 6 and 7 was pre-
sented. Both individuals were somewhat disturbed by the
change, her record being seven correct choices out of ten, and
his nine out of ten. Later in the day another series of ten trials,
according to the original settings, was given with the result
that the female made three incorrect first choices in ten and
the male two. Still later, the control settings were again pre-
sented. This time she chose correctly eight times in ten and he
only five times.

208

ROBERT M. YERKES AND CHARLES A. COBURN

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212

ROBERT M. YERKES AND CHARLES A. COBURN

TABLE 8

Daily Series and Averages with Ratios of Correct to Incorrect

First Choices

Problem 3

Female

Male

No.

Ratio

No.

Ratio

Date

of
trials

R

W

R

W

of
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Date

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R

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R

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1-

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1-

2

8

2

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1:4.00

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0

10

12

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6

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7

3

17

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15

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13

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8

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7

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16

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5

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14

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4

6

14

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7

7

13

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18

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15

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4

6

15

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8

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8

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14

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4

6

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6

6

14

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6

8

12

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17

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7

17

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7

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14

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18

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5

5

18

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5

5

a

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6

4

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6

4

a

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5

5

16

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3

7

14

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19

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4

6

19

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4

6

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6

4

10

10

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6

4

10

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20

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4

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6

4

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a

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6

4

12

8

1: .67

21

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6

4

21

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6

4

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5

5

11

9

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5

5

11

9

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22

221-

8

2

22

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5

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7

3

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1: .33

ii

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5

10

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9

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2

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4

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24

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1

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6

4

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1

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3

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1: .25

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A STUDY OF THE BEHAVIOR OF THE PIG 213

Although these figures are far from conclusive, we are con-
vinced from the behavior of the animals that neither was choos-
ing by familiarity with the particular settings. She, as has
been pointed out, did as well with the control series as with the
regular series, and he did even better in the first control series
than in the regular series, while showing extreme confusion in
the second control series. This was doubtless due to insufficient
hunger and the distracting influence of a mistake in the first
trial of the series. His carelessness throughout the last control
series was conspicuous.

Comparison of the results for problems 2 and 3 indicate that
for the female problem 3 was somewhat the more difficult,
whereas for the male, problem 2 required a larger number of
trials. We are by no means convinced by this comparison that
the problems have not been used in the order of increasing diffi-
cultness, for we consider the female subject a much more reliable
individual than the male, and we suspect that his greater facility
in the solution of the third problem was due in part, at least,
to the experience of the experimenters in dealing with his tem-
peramental and other peculiarities.

PROBLEM 4

The data to be considered in this connection appear in tables
9, 10 and 11. The correct mechanism is definable simply as
the middle one, and the expectation prior to experience is one
correct to four incorrect first choices, since the total number of
doors open in the series of ten settings is fifty. As is shown in
table 11, precisely this ratio resulted from the first day's experi-
mentation in the case of each individual.

Ten trials per series were given regularly throughout the
work on this problem.

Unlike the preceding problems, this one proved insoluble.
Consequently, the detailed results as they appear in tables
9 and 10 are especially important, since from them may be
read the reactive tendencies and their relations to one another.
It is, of course, easy to understand why the ratio of correct to
incorrect first choices should change steadily in the direction
of the solution of the problem, for each subject gradually learned
to react appropriately to certain of the settings while failing
to acquire the ability to react to the relation middleness.

214

ROBERT M. YERKES AM) CHARLES A. COBURN

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218

ROBERT M. YERKES AND CHARLES A. COBURN

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A STUDY OF THE BEHAVIOR OF THE PIG

219

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220

ROBERT M. YERKES AND CHARLES A. COBURN

TABLE 11

Daily Series and Averages with Ratios of Correct to Incorrect

First Choices

Female

Problem 4

Male

No.

Ratio

No.

Ratio

Date

of
trials

R

W

R

W

of
R to W

Date

of
trials

R

W

R

W

of
R to W

Aug.

Aug.

4

1-

0

5

4

1

0

5

a

6-

0

5

a

6-

1

4

ti

11-

4

6

4

16

1:4.00

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11-

3

7

4

16

1:4.00

5

21-

2

8

5

21-

2

8

u

31-

3

7

5

15

1:3.00

a

31-

2

8

4

16

1:4.00

6

41-

3

7

6

41-

4

6

ti

51-

4

6

7

13

1:1.86

n

51-

4

6

8

12

1:1.50

7

61-

2

8

7

61-

2

8

a

71-

4

6

6

14

1:2.33

«

71-

3

7

5

15

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8

81-

4

6

8

81-

4

6

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91-

2

8

a

91-

5

5

ti

101-

2

8

8

22

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a

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5

5

14

16

1:1.14

9

111-

3

7

9

111-

3

7

«

121-

4

6

u

121-

3

7

«

131-

8

2

15

15

1:1

ti

131-

4

6

10

20

1:2.00

10

141-

3

7

10

141-

4

6

a

151-

4

6

a

151-

3

7

it

161-

6

4

13

17

1:1.31

a

161-

3

7

10

20

1:2.00

11

171-

5

5

11

171-

5

5

«

181-

3

7

a

181-

4

6

ti

191-

4

6

12

18

1:1.50

u

191-

6

4

15

15

1:1

12

201-

5

5

12

201-

5

5

ti

211-

3

7

a

211-

3

7

«

221-

5

5

13

17

1:1.31

a

221-

4

6

12

18

1:1.50

13

231-

8

2

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231-

4

6

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241-

3

7

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5

5

a

251-

4

6

15

15

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5

14

16

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261-

8

2

14

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5

5

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271-

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6

a

271-

3

7

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281-

6

4

18

12

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6

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15

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7

13

17

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16

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7

16

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4

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6

13

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8

11

19

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351-

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6

17

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6

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361-

5

5

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371-

4

6

12

18

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3

15

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381-

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5

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13

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7

12

18

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19

411-

6

4

19

411-

6 1

4

A STUDY OF THE BEHAVIOR OF THE PIG

221

TABLE 11 — Continued

Daily Series and Averages with Ratios of Correct to Incorrect

First Choices

Female

Problem 4

Male

No.

Ratio

No.

Ratio

Date

of

trials

R

W

R

W

of
R to W

Date

of
trials

R

W

R

W

of
R to W

Aug.

Aug.

H

421-

7

3

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421-

6

4

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431-

4

6

17

13

1: .76

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431-

5

5

17

13

1: .76

20

441-

6

4

20

441-

4

6

a

451-

2

8

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4

6

a

461-

7

3

15

15

1:1

(i

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7

3

15

15

1:1

21

471-

6

4

21

471-

5

5

a

481-

6

4

12

8

1: .67

ft

481-

7

3

12

8

1: .67

22

491-

7

3

22

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5

5

a

501-

4

6

ft

501-

4

6

((

511-

4

6

15

15

1:1

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7

3

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1: .25

222 ROBERT. M. YERKES AND CHARLES A. COBURN

After six hundred trials had been given to each individual
by use of the series of settings presented on page 192, under
problem 4, it was apparent that the animals could succeed
in solving the problem only by acquiring a definite habit for
each particular setting, and it was further evident that the
settings including seven and nine open doors were extremely
difficult for the animals. For these reasons it was decided to
present a modified series of settings in which the groups should
consist of either three or five open doors. Two hundred trials
were given with the new series of settings, and the settings
themselves, as well as the results obtained, appear at the bottom
of tables 9 and 10.

Two important conclusions are justified by these results.
First, that the pigs, in so far as they had succeeded in responding
correctly to the middle door, had reacted to particular settings.
And second, that with sufficiently prolonged training they could
perfectly solve the problem of the middle member of a series,
if the total number in a group of open doors did not exceed five.
As a matter of fact, no series of ten correct choices was obtained
with either individual because of the surprisingly strong and
persistent influence of the original settings.

Let us consider, for example, setting 3. This originally con-
sisted of the group 1.2.3.4.5.6.7, in which no. 4 was the box to be
entered. In the modified settings, this group was changed to
3.4.5.6.7, consequently, the box to be entered was 5 instead
of 4. Now, whereas in the case of setting 1 which remained
unchanged, the female made only one mistake in twenty-one
trials subsequent to the modification of the settings, in the
case of setting 3 she chose wrongly in all except three of the
twenty-one trials, and this in spite of the fact that in the case
of settings 2 and 5, both of which involved five open doors, she
chose correctly sixteen times out of twenty-one. Similarly in
the case of setting 6, in which originally all nine of the doors
were open, whereas in the modification only doors 1, 2, 3, 4
and 5 were used, both the female and the male chose correctly
only once in twenty-one trials.

Although the above conclusions are of primary importance,
further examination of the data of tables 9 and 10 should throw
additional light on the reactive capacity of our subjects.

We shall consider the materials according to the number of

A STUDY OF THE BEHAVIOR OF THE PIG 223

mechanisms used in the settings. Settings 1, 4, 7 and 10 involve
three members, setting 2, 5 and 8, five members; settings 3
and 9, seven members; and setting 6, nine members. Below
are presented the number of correct first choices made by each
individual in connection with each setting, the total number of
choices being sixty.

Correct First Choices in Sixty for Each Setting in Problem 4

S.l

S.2

S.3

S.4

S.5

S.6

S.7

S.8

S.9 S.10

Female

35

22

16

45

22

10

49

11

22 38

Male

41

21

4

48

. 27

J2

52

11

19 34

These figures prove that to select the middle member of a
group of three is fairly easy for the pig. This, to be sure, might
be gathered from the fact that the animal can solve the problem
of the second from the left. It further appears that attempts
to locate the proper box when it was the middle of a series of
five resulted in a gradual reduction in the number of incorrect
choices, but never yielded success. The selection of the middle
member of a group of seven or of nine is clearly still more diffi-
cult, and there is no reason to suppose that with less than thou-
sands of trials the subjects in question would have learned to
enter it directly.

It is practically certain that the series of settings rather than
the number of members in a group is responsible for the animal's
confusion. Doubtless by training a pig to react correctly to
each setting and by then presenting the several settings in a
certain definite order, a habit could be built up which would
apparently yield a perfect solution of problem 4. It is, however,
needless to point out that this would not be the kind of solution
that has been obtained for problems 1, 2 and 3, or in other words,
would not be dependent upon response to the general relation
middleness.

Analysis of the records for the sixty trials under setting 6 are
of special interest, since this setting proved the most baffling
of all to the subjects.

To begin with, they naturally tried the end members of the
series. This proving unsatisfactory, they next tended to choose
rather at random, and then there gradually appeared a tendency
to enter, first, box 2 and to proceed thence either directly or

224 ROBERT M. YERKES AND CHARLES A. COBURN

by way of 3, 4 and sometimes also 6, to the middle box, number
5. This tendency to select, when in doubt, a box second from
the right end of the series may possibly be due in part to the
fact that the box to be chosen in setting 7 was number 2. At
any rate, the frequency with which the female throughout her
training chose box 2 first of all under setting 6 is surprisingly
high, whereas for the male, this frequency while rather high
early in the course of the training, tended to diminish and to
give place to the decidedly profitable tendency to choose a box
near the middle of the series, 6, 7 and 5 frequently being entered.
Similarly, wTe might, if space permitted, analyse in detail the
results for the other settings. We have chosen to use our space
in this report for the presentation of data in tabular form rather
than for their description, because we are convinced that the
facts are more important than early attempts at interpretation.

SUMMARY

1. The pig has proved itself an ideal subject for studies in
adaptive behavior.

2. The new multiple choice method, by means of which
standardized problems ranging in difficultness from the very
easy to the very difficult may be presented to widely differing
types of organism, has in our opinion fully justified our expec-
tations, for it has proved admirably suited to the discovery and
analysis of increasingly complex types of behavior.

3. For the purpose of discovering the extent to which idea-
tional and closely allied types of behavior exist in the pig, four
problems were presented. They may be defined simply in terms
of the constant relation of the right mechanism, as (1) the first
at the right end of the series; (2) the second from the left end
of the series; (3) alternately, the first at the left and the first
at the right; (4) the middle member of the series.

The purpose of the experiments was to discover the pig's
reactive tendencies and especially its degree of ability to disso-
ciate the essential and constant relation of the right mechanism
from its accidental and variable accompaniments.

4. The two subjects solved perfectly the first problem with
less than fifty experiences. The indications are that visual and
kinaesthetic guidance sufficed.

The second problem was solved more slowly, partly because
the influence of the earlier training had to be overcome, but

A STUDY OF THE BEHAVIOR OF THE PIG 225

also because this is a much more difficult problem than the first
one. In this also, visual and kinaesthetic guidance seems to
account for success, but the extent to which the animals learned
to respond to the relation of secondness from the left, no matter
what the other relations of the mechanism, was a surprise to
the experimenters and is important in connection with the
problem of ideation in animals.

The third problem also was solved with reasonable ease, and
the animals demonstrated their ability to acquire the habit of
alternation without respect to particular groups of reaction-
mechanisms.

Problem 4 proved too difficult for the pigs. They learned
to select the middle mechanism of the series when the groups
were small, but when seven or nine mechanisms were in use,
they were confused. The indications are that with long train-
ing they would learn to react to the particular settings cor-
rectly, although incapable of reacting to the constant relation
of middleness.

5. Our results indicate for the pig an approach to free ideas
which we had not anticipated. There seems no reason to doubt
that visual and kinaesthetic factors in the main determine their
responses, but it is evident that they are not so dependent upon
the particular situation as are many other mammals. While
hesitating to claim that we have demonstrated the presence of
ideas, we are convinced that the pig closely approaches, if he
does not actually attain, to simple ideational behavior.

6. The multiple choice method has revealed a number of
interesting reactive tendencies, their relations to one another,
and the varied ways in which they are manifested in connec-
tion with situations which are rather difficult to meet.

7. Finally, we would again call attention to the fact that
this method of studying behavior should enable us, when it
has been reasonably perfected and its problems standardized,
to determine the level of mental development in different indi-
viduals, species, stages of growth, and conditions of normality,
and to compare the reactive tendencies, whether or not idea-
tional, of other organisms with those of the human subject.
Our results thus far fully convince us that the method may be
made to yield more valuable psychological and behavioristic
information than has any previous approach to ideational
problems.

HABIT FORMATION IN THE FIDDLER CRAB

BY BENJAMIN SCHWARTZ AND S. R. SAFIR

From The Biological Laboratory, Cold Spring Harbor

Albrecht Bethe (1898) was the first one to investigate asso-
ciative memory in Crustacea. After analyzing the normal be-
havior of the green crab, Carcinus moenas, on the basis of the
structure of the nervous system, Bethe endeavored to discover
whether the animal could modify its behavior and thus profit
by experience. He liberated a crab in an aquarium containing
a cephalopod, Eledone, in the darkest corner. The crab, fol-
lowing its instinct to hide, ran to that corner and was imme-
diately seized by the squid. At this point the experimenter
interfered, and quickly freeing the animal from its captor,
placed it again in the lighted portion of the aquarium. The
animal ran back to the dark corner and was again seized by
the squid. This experiment was repeated five times with one
individual and six times with another, without any evidence
that the animal learned to avoid the dangerous corner. Bethe
then tried another experiment. He baited a crab with a piece
of meat and maltreated it every time that it snapped at the
bait. This was repeated a number of times, and as in the^pre-
vious experiment, he found no modification in the animal's
reaction to the stimulus. He, therefore, concluded that the
activities of Carcinus are limited to reflexes and instincts, the
animal being incapable of exercising any higher mental faculties.

Yerkes (1902) objects to Bethe's conclusion on two grounds:
(1) He maintains that the data is altogether insufficient to
warrant any generalization, and (2) that the experiments are
of such nature that negative results based on more sufficient
data would still be inconclusive proof of the animal's inability
to profit by experience. It is evident that Bethe endeavored
to suppress two fundamental instincts, namely, fear and hunger.
To expect an animal to modify these after five or six experiences
is almost preposterous. Yerkes therefore tested the American

226

HABIT FORMATION IN THE FIDDLER CRAB 227

form, Carcinus granulatus, for habit formation. He constructed
a simple labyrinth containing two blind alleys and one opening.
In this labyrinth a number of crabs were liberated daily for a
period of two weeks, and were given on an average of four trials
per day. It was found that the animals gradually learned to
avoid the blind alleys, although even fifty experiences in the
case of most did not result in a perfect habit. He also found
that if the aquarium was divided into two compartments by
means of a wire screen, which contained an opening in its center,
the animals learned with increasing rapidity to find the opening,
in order to get to the food at the opposite side. From these
results Yerkes concluded that Carcinus possesses associative
memory.

Yerkes and Huggins (1903) studied habit formation in the
crawfish, Cambarus affinis. They constructed a labyrinth con-
taining a triangular chamber at one end, while the opposite
end contained one closed and one open corner, the latter leading
into an aquarium. The animal was placed in the triangular
chamber, and could go to either corner in seeking to escape.
For one month, each of three animals was given on an average
two trials per day. The records of the movements to the closed
and open corners showed an increase from fifty to ninety per
cent in the direction which led to escape. A test of habit reten-
tion after a rest of two weeks, showed that the association
persisted. Their general conclusions are: (1) Crawfish are able
to learn a simple labyrinth habit, (2) they profit slowly, fifty
to a hundred experiences being necessary for perfect association,
(3) the chief factors in the habit forming process are smell,
touch, sight, and muscular activity, (4) if the possibility of
scent is excluded by washing the box after each trial, the animals
are still capable of learning.

Other investigators working with different forms have con-
firmed Yerkes' conclusions. Spaulding (1904) found that the
hermit crab, Eupagurus longicarpus, which is positively photo-
tactic, could learn to go to a shaded portion of an aquarium
for food. The association became so perfect, that the mere
introduction of the screen, in order to divide the aquarium
into two compartments, caused the animals to run to the shaded
half. Drzewina (1908) observed that Pachygraspus marmoratus,
which is negatively phototactic during the day, reacts positively

228 BENJAMIN SCHWARTZ AND S. R. SAFIR

to light at night. Taking advantage of this tropism, she suc-
ceeded in making the crabs come from the shaded side of the
box to the side which was artificially illuminated, although in
doing this, the animals had to find an opening in the partition
which divided the box. The rapidity with which the opening
was found increased with successive trials. The same writer*
(1910) studied habit formation in the hermit crab, Clibanarius
misanthropus. She placed tightly corked gastropod shells near
naked crabs. The latter immediately fastened themselves upon
the shells, trying to pull out the corks. Since all their efforts
to enter the shells were in vain, the animals were observed to
relax, and at the end of from six to eight days, they became
entirely indifferent to their presence. If at this point of the
experiment, shells, similarly sealed but of different shape, were
introduced, the crabs began to attack them immediately. These
results indicate that Clibanarius not only possesses associative
memory but that it is also able to discriminate form. Cowles
(1908) found that Ocypoda arenaria could learn to escape from a
labyrinth, although it did not learn the position of the exit very
accurately. He also found that if he buried a dish of salt water
in the sand of their trap, so that the rim of the dish was on a
level with the surface of the sand, the crabs learned to climb
into the vessel to moisten their gills.

The experiments described hereafter were performed with the
fiddler crabs which inhabit the sand spit at Cold Spring Harbor,
Long Island. They live on sandy beaches as well as on mud
flats, where they construct burrows about one foot in depth.
They are diurnal in their habits, and on bright, sunny days
they may be seen in large numbers, running hither and thither,
feeding and burrowing. The males are particularly striking
because of the large cheliped with which they perform curious
antics, and which they use as a weapon for combat. When
the tide comes in the crabs retreat to their burrows, where they
remain until the area above them is again exposed by the reced-
ing waters. Their general activities are therefore interrupted
at regular intervals, during which they remain perfectly quiet.
Their behavior appears to be regular and unchanging, almost
stereotyped.

There are two species of fiddler crabs on the sand spit, Uca

*This paper was not available to us. We read an abstract of it in The Jour, of
An. Beh., Vol- I, No. 6, pp 450-451, 1911.

HABIT FORMATION IN THE FIDDLER CRAB 229

pugnax and Uca pugilator, the most distinguishing characteristic
of the latter being a ridge across the palm of the large cheliped.
In the experiments the pugilators were utilized almost exclu-
sively, because of their greater vigor and resistance. The pugnax
forms did not thrive in captivity, and became very sluggish.
The work with them could not progress very rapidly.

The aim of the experiments was to determine (1) whether
the fiddler crabs can form a simple labyrinth habit, (2) whether
the habit is retained for a few days, and (3) whether the habit
can be broken up.

When the crabs are placed in a wooden box which is about
one-half full of moist sand or mud, they immediately begin to
seek a means of escape. They usually run to the side opposite
which the experimenter is standing, and climb up the sides,
near the corners, by inserting the sharply pointed ends of their
ambulatory feet into the rough surfaces of the wood. They
climb gradually and do not seem to become discouraged by
failures. As soon as they reach the top of the box, they escape.
It was observed that the animals showed a decided tendency
to go to a particular corner, even though escape was rendered
impossible by inserting glass plates against the sides. Table 1
gives the records of twelve individuals, showing the corner to
which they went, as well as the average interval between two
successive trials.

No.

T.

ABU

E 1

Corner

of

Average

Individual

trials

Time

interval

1

2

3

4

1

25

30:

min.

1

min

. 12 sec.

1

21

0

3

2

25

44

a

1

a

47

«

3

19

1

2

3

20

27

a

1

a

22

a

4

15

0

1

4

20

30

a

1

a

30

u

0

9

0

11

5

20

28

a

1

u

24

a

14

6

0

0

6

20

37

tt

1

it

49

u

15

1

4

0

7

20

54

it

2

a

42

u

11

8

0

1

8

20

24

it

1

a

12

tt

2

18

0

0

9

20

53

tt

2

tt

40

u

4

12

3

1

10

30

30

a

1

tt

0

a

3

4

22

1

11

18

31

a

1

it

43

u

0

5

13

0

12 35 45 " 1 " 17 " 30 10 3 2

An examination of the above table shows (1) that the interval
between two successive trials varies from about one and a half
to two minutes, (2) that the animal's desire to liberate itself
from the trap persists even when thirty-five trials are given,

230

BENJAMIN SCHWARTZ AND S. R. SAFIR

(3) that each animal chooses one particular corner from which
to escape. The last fact is of the utmost importance, because
the labyrinth habit with the fiddler crab involves not only a
process of learning, but also the overcoming of a strong incli-
nation. By closing the corner to which the animal is inclined
to go, the experimenter is in a position to determine whether
the animal can modify its behavior.

i

TABLE 2

Right Handed

Left Handed

Males

Males

Females

No.

Right

Left

No.

Right

Left

No.

Right

Left

Center

1

7

3

1

1

9

1

3

3

4

2

5

5

2

1

9

2

4

5

1

3

7

3

3

2

8

3

4

2

4

4

10

0

4

10

0

4

1

3

6

5

0

10

5

0

10

5

2

1

7

6

7

3

6

0

10

6

2

3

5

7

7

3

7

6

4

7

3

2

5

8

0

10

8

7

3

8

3

3

4

9

1

9

9

3

7

9

2

3

5

10

0

10

10

6

4

10

4

0

6

11

7

3

11

8

2

11

5

2

3

12

7

3

12

2

8

12

1

6

3

13

6

4

13

5

5

13

7

1

2

14

7

3

14

5

5

14

5

3

2

15

9

1

15

5

5

15

1

8

1

16

5

5

16

5

5

16

1

7

2

17

7

3

17

3

7

17

3

5

2

18

5

5

18

2

8

18

4

3

3

19

6

4

19

2

8

19

3

3

4

20

6

4

20

2

8

20

2

2

6

21

7

3

21

0

10

21

4

0

6

22

7

3

22

2

8

22

1

2

7

23

8

2

23

0

10

23

5

2

3

24

5

5

24

2

8

24

6

2

2

25

4

6

25

2

8

25

5

3

2

26

9

1

26

3

7

26

2

5

3

27

9

1

27

8

2

27

1

8

1

28

7

3

28

7

3

28

6

1

3

29

10

0

29

2

8

29

4

2

4

30

9

1

30

4

6

30

5

2

3

31

9

1

31

1

9

31

1

7

2

32

10

0

32

2

8

32

3

3

4

33

8

2

33

8

2

33

3

5

2

34

7

3

34

4

6

34

5

2

3

35

' 8

2

35

2

8

35

3

4

3

226

124

122

228

114

113

123

The reasons for the individual preferences were by no means
evident. Since the animals exhibit a positive phototaxis it was
at first supposed that this peculiar reaction was -caused by

HABIT FORMATION IN THE FIDDLER CRAB

231

light, but it was found that when the latter was eliminated, the
preference was not changed. Hence some other explanation had
to be sought. An examination of the male crab shows it to be
unsymmetrical, owing to the possession of the large cheliped,
which may be either on the right or the left side of the body.
This suggested the hypothesis that the right handed males are
inclined to go to the right side, and the left handed males to
the left side. Since the females possess no large cheliped, they
were expected to be neutral in this respect. That these expec-
tations were fairly borne out maybe seen in table 2.

Fig. 1. Showing labyrinth and adjoining box. Dotted lines represent glass
plates, and circles represent burrows.

An examination of the data presented above shows that 70%
of the males made a majority of their movements to the corner
corresponding to the position of their cheliped. About 10%
showed no preference for either side, while the remainder, about
20%, went to the side directly opposite to the expectation. But
the fact remains that about 90% are inclined to go to a par-
ticular side. The number of trials for the right handed males
is 226 to the right and 124 to the left, giving a ratio of about
2:1, that of the left handed males is 228 to the left and 122 to
the right, giving a similar ratio. The females made 114 attempts
to the right, 113 to the left, and 123 to the center, "giving a ratio
of 1:1:1. By an attempt to the center is meant a direct move-
ment from one end of the box to the center of the opposite end,

232 BENJAMIN SCHWARTZ AND S. R. SAFIR

where the animal pauses for about five seconds before going to
either corner.

With these facts before us, we subjected ten animals, seven
males and three females, picked up at random, to a simple
labyrinth test. Our labyrinth was modelled after the one de-
scribed by Yerkes and Huggins, with modifications adapted to
the needs of the fiddler crabs. We selected a box 50 cm. long,
30 cm. wide, and 30 cm. deep. It was filled to a depth of 12
cm. with moist sand, in order to give the animals a natural
substratum. By means of glass plates, 12 cm. square, we made
a triangular space at the center of one of the narrower ends,
with an opening sufficiently large to enable the crabs to pass
through. At the corners of the opposite end we cut out open-
ings, 8 cm. wide and 5 cm. high, which could be closed by means
of glass plates. To prevent the animals from going to the cor-
ners of that end of the box which contained the triangular
chamber, we placed glass plates extending at right angles from
each side of the opening of the chamber to the long side of the
box. Adjoining the labyrinth there was another box, 60 cm.
long, 25 cm. wide and 25 cm. deep. It was filled with moist
sand to a depth of 12 cm, several artificial burrows being made
in the sand. By means of an opening at each end of the longer
side, the box could be made to commuuicate with the labyrinth
on either side.

At first both corners of the labyrinth were closed by means
of glass plates and each of the animals to be tested was given
a series of preliminary trials to determine to which side of the
box it was inclined to go. As soon as this was determined, the
favorite corner was left closed, while the one opposite was
opened. The crab was then placed in the chamber by the
experimenter, who took up his position three feet behind the
box, remaining perfectly quiet. His position afforded him a
good view of the animal's movements, which were carefully
noted. As soon as the crab was liberated it made a number
of efforts to climb up the sides of the glass chamber. In doing
this it fell after each attempt, the shock evidently frightening
it. It then abandoned climbing, and either ran out of the en-
closure very rapidly, or moved out rather cautiously, going
to its favorite corner. Here, too, it made attempts to climb,
but making no headway against the smooth surface of the

HABIT FORMATION IN THE FIDDLER CRAB 233

glass, it began to move to the opposite corner. In the begin-
ning the animal would go half way and turn back, trying to
climb again. Finally it would venture all the way across, run
out through the opening into the adjoining box, and enter one
of the burrows. If an individual showed too much stubborness,
by remaining at the closed corner even after it had given up
its climbing, the experimenter gently drove it in the direction
of the open corner. The crab was allowed to remain in this
burrow for about a minute, after which it was taken out and
again placed in the triangular chamber, the experimenter taking
up the same position as before. It usually took the animal
about one minute to recover its composure before making a
second trial. With successive trials it seemed to learn that
there was one corner which afforded an exit, for no sooner than
it reached the closed side, it reversed its direction, and liberated
itself from the trap. Sometimes a crab would start off in the
direction of the closed corner, but before reaching it, would
turn and go to the open. Occasionally an animal ran directly
to the center and remained there for a few seconds, often running
first in one direction and then in another, before making its
final choice. Gradually movements to the open corner became
more frequent, attaining almost perfection at the end of ten
days, with an average of twenty trials per day.

Following, in table 3, are the records of ten* individuals:

TABLE 3

No. 1. U. pugilator, female

No. 2.

U. pugi

lator, male, left handed

%

%

0/

/o

/o

Day Closed

Open

Closed

Open

Day

Closed

Open

Closed

Open

1 18

2

90

10

1

18

2

90

10

2 15

5

75

25

2

16

4

80

20

3 12

8

60

40

3

15

5

75

25

4 10

10

50

50

4

18

2

90

10

5 10

10

50

50

5

14

6

70

30

6 8

12

40

60

6

10

10

50

50

7 9

11

45

55

7

3

17

15

85

8 7

13

35

65

8

10

10

50

50

9 6

14

30

70

9

3

17

15

85

10 1

19

5

95

10

3

17

15

85

* Nos 1, 2, 3, 4 and 10 were experimented with at Cold Spring Harbor. The
remaining five were tried at Hunter's Island, New York City.

234

BENJAMIN SCHWARTZ AND S. R. SAFIR

No. 3. U. pugilator, male, right handed

No. 4. U. pugnax, right handed

i t

Day Closed Open Closed Open

1 14 6 70 30

2 5 15 25 75

3 4 16 20 80

4 3 17 15 85

5 4 16 20 80

6 1 19 5 95

7 1 19 5 95

8 0 20 0 100

9 1 19 5 95
10 0 20 0 100

Day Closed Open Closed Open

1 13 7 65 35

2 8 12 40 60

3 9 11 45 55

4 2 18 10 90

5 4 16 20 80

6 3 17 15 85

7 4 16 20 80

8 4 16 20 80

9 2 18 10 90
10 3 17 15 85

No. 5. U. pugilator, left handed

No. 6.* U. pugilator, left handed

Day Closed Open Closed Open

1 18 2 90 10

2 15 5 75 25

3 10 10 50 50

4 7 13 35 65

5 9 11 45 55

6 10 10 50 50

7 5 15 25 75

8 4 16 20 80

9 1 19 5 95
10 4 16 20 80

No. 7.* U. pugilator, left handed

/o

( ■
/o

Dav Closed Open Closed Open

1 15 5 75 25

2 8 12 40 60

3 12 8 60 40

4 10 10 50 50

5 10 10 50 50

6 11 9 55 45

7 9 11 45 55

* This animal died at the end of
seven days.

No. 8. * U. pugilator, female

/c

/c

Day Closed Open Closed Open

1 15 5 75 25

2 9 11 45 55

3 8 12 40 60

4 7 13 35 65

5 5 15 25 75

6 4 16 20 80

7 3 17 15 85

8 3 17 15 85

9 2 18 10 90
* Died.

< ■■■

/o

Day Closed Open Closed Open

1 12 8 60 40

2 9 11 45 55

3 6 14 30 70

4 6 14 30 70

5 7 13 35 65

6 7 13 35 65

7 5 15 25 75

* Died.

No. 9. U. pugilator, female

/c /o

Day Closed Open Closed Open

1 12 8 60 40

2 5 15 25 75

3 8 12 40 60

4 3 17 15 85

5 5 15 25 75

6 4 16 20 80

7 6 14 30 70

8 4 16 20 80

9 2 18 10 90
10 5 15 25 75

No. 10.* U. pugilator, right handed

%

/c

Day Closed Open Closed Open

1 14 6 70 30

2 13 7 65 35
4 13 7 65 35
6 11 9 55 45
9 14 6 70 30

10 11 9 55 45

12 10 10 50 50

14 10 10 50 50

16 9 11 45 55

18 10 10 50 50
* This crab was tested at irregular
intervals.

HABIT FORMATION IN THE FIDDLER CRAB 235

The individual records presented above are summarized in
table 4.

TABLE <

Open

Open

att.

att.

c

%

No.

1st

last

1st

last

cr
/o

Min.

Max.

Min.

Max.

/o

of

No.

day

day

day

dav

gain

open

open

%

%

gain

days

1

2

19

10

95

85

2

19

10

95

85

10

2

2

17

10

85

75

'2

17

10

85

75

10

3

6

20

30

100

70

6

20

30

100

70

10

4

7

17

35

85

40

7

18

35

85

50

10

5

2

16

10

80

70

2

19

10

95

85

10

6

5

11

25

55

30

5

12

25

60

35

7

7

5

18

25

90

65

5

18

25

90

65

9

8

8

15

40

75

35

8

15

40

75

35

7

9

8

15

40

75

35

8

18

40

90

50

10

10

6

10

30

50

20

6

11

30

55

25

10

Table 4 shows (1) that none of the individuals experimented
with ever made fewer open attempts than it made on the first
day, (2) that the maximum number of open attempts approx-
imates those of the last day, (3) that the greater the number
of days an animal was tried, the greater the gain. Number 10,
which was tried at irregular intervals, lasting for a period of
eighteen days, gained less than any other individual. To be
sure, considerable variation in the rapidity of habit formation
is exhibited, some of the crabs made their maximum number of
open trials about the sixth day, while others did not succeed
in learning the direction of the open corner accurately until
the last day. Habit formation, like any other character, is
subject to the law of variation, being stronger in some individ-
uals than in others.

It is evident, however, that the fiddler crab can overcome his
proclivity for one direction, and learn to go in the opposite one,
if the latter enables him to escape from a trap. The mere fact
that after encountering the glass obstruction, the animal goes
to the open side, is in itself significant. The experimenter was
obliged to drive the animal away from the closed end in the
very beginning of the experiment. After the first ten. attempts,
it learned to find the opening by itself. But the ability to over-
come its inclination almost entirely, making 90% of its move-
ments in the direct;on which leads to escape, is unmistakable
evidence that the fiddler crab possesses associative memory.
To be sure, it learns slowly, perhaps more so than the crawfish,
but it should be remembered that the crawfish showed no

236

BENJAMIN SCHWARTZ AND S. R. SAFIR

preference for any side, whereas the fiddler crab had to over-
come a strong inclination. Viewed in this light the gains which
the animals made during the 10 days during which they were
tried are enormous.

It should be mentioned that the possibility of establishing
pathways was obviated by either scraping off the top layer of
the substratum, or by adding a fresh one. Sight and touch
seemed to be the chief factors in the habit forming process,
the former predominating. It was observed that an animal
would often begin to go in the direction of the closed end, but
before approaching it, would turn and go in the opposite direc-

FlG. 2. Showing labyrinth with alley. Dotted line represents glass
plates, and circles represent burrows.

tion. This seemed to point to sight as the basic factor in the
habit forming process.

. In order to test this hypothesis, another type of labyrinth
was devised. By means of glass plates, an alley, 10 cm. wide,
leading directly to the closed end, was made on one side of the
box. The glass plates which formed one side of the alley ex-
tended to within a distance of 8 cm. of the end of the box in
order that the crab might turn and avoid the blind corner.

Five crabs which had given the best results with the laby-
rinth test, were made the subjects of the experiment. They
were tried for two successive days, being given ten trials per
day. Upon being liberated at the end of the alley nearest the
experimenter, the crab began to seek a means of escape. If

HABIT FORMATION IN THE FIDDLER CRAB 237

it did not turn before reaching the end of the alley, it was
charged with a closed trial. If it did turn, however, and lib-
erated itself from the alley by going to the open corner, the
attempt was recorded open. The results are given in the fol-
lowing table, 5 :

TABLE 5

No.

Days

Closed

Open

% Closed

% Open

1

1

2

8

20

80

2

1

9

10

90

3

1

1

9

10

90

2

0

10

0

100

4

1

3

7

30

70

2

1

9

10

90

5

1

2

8

20

80

2

2

8

20

80

9

1

2

8

20

80

2

2

8

20

80

From the above data it is evident that the animal was guided
by its sense of sight in liberating itself from the alley. It should
be borne in mind that the fiddler crab is positively thigmo-
tactic, and under ordinary circumstances it has a strong tendency
to follow the sides of the box. The animals which were subjected
to this test had already learned to free themselves from the
trap, and therefore knew the direction of escape. They were,
therefore, able to avoid the side which led to the blind end of
the alley.

The crabs were given a rest of ten days, at the end of which
they were tested for habit retention. Unfortunately, five of
the animals died during the interval, and two of the remaining
ones were too sluggish to give results. Those which were
tested gave the following records, table 6 :

TABLE 6

No. Closed Open % Closed % Open

13 7 30 70

3 1 9 10 90

4 2 8 20 80

These three crabs were now tried for unlearning. The corner
which had been closed was opened, and the open one closed.
Each animal was tried for five days, being given twenty trials

238

BENJAMIN SCHWARTZ AND S. R. SAFIR

per day. The reversal of the open corner was at first very con-
fusing to the creature. Upon being liberated in the chamber,
it ran to the closed corner, and remained there with greater stub-
bornness and persistence than had ever been witnessed before.
It was almost impossible to drive the animal in any other direc-
tion. Sometimes it would venture to the open corner but would
abandon it for the closed one. Gradually, however, it learned
to escape, although the effect of previous experience had no
influence on the rapidity of unlearning. The records are given
below :

Day

Closed

No. 1
Open

0

Closed

TABLE
Open

7
Day

Closed

No.
Open

3

%
Closed

/o
Open

1
2
3
4
5

17
7
4
4
4

3
13
16
16
16

85
35
20
20
20

15
65
80
80
80

No.

4

1
2
3
4
5

19
13
15
10
5

1

7

5

10

15

95
65
75
50
25

05
35
25
50
75

/o

<7
/O

Day Closed Open Closed Open

1 9 1 95 5

2 17 3 85 15

3 10 10 50 50

4 11 9 55 45

5 7 13 35 65

SUMMARY AND CONCLUSIONS

1. The fiddler crab shows a strong desire to liberate itself
from a trap, making on an average of thirty-five attempts an
hour.

2. It goes persistently to a certain corner, even though escape
is rendered impossible by placing glass obstructions to prevent
it from climbing out.

3. The hypothesis that dextrous males are inclined to go to
the right side, the sinistrous males to the left side, and females
equally to the center and both sides, is fairly well borne out by
experimental evidence.

4. Taking advantage of the foregoing tendencies, the fiddler
crab may be made to reverse its proclivity, and escape from
a labyrinth through an opening at the opposite side.

HABIT FORMATION IN THE FIDDLER CRAB 239

5. It learns slowly, increasing its movements to the open
corner with successive trials.

6. The rapidity of habit formation varies directly with the
frequency of the trials.

7. Sight and touch are the most important factors in the
habit forming process, the former predominating.

8. An animal which formed the habit can avoid a blind corner
by turning before reaching the end of an alley.

9. The habit persists after a lapse of ten days.

10. The crab can unlearn the habit, although previous ex-
perience seems to have no influence on the rapidity of unlearn-
ing.

In concluding, we wish to express our indebtedness to Dr.
H. E. Walter for his reading of the manuscript.

LITERATURE

Bethe, Albrecht. Das Centralnervensystem von Carcinus moenas. II Theil.

1898. Arch, fur Mik. Anal., Bd. 51, S. 447.
Drzewina, A. Les Reactions Adaptives des Crabes. Bull. Inst. Gen. Psvch.,

1908. 235, 8.

1910. Creations d 'associations sensorielles chez les Crustaces. C. r. Soc.
Biol. LXVIII, 573.
Cowles, P. R. Habits, Reactions, and Associations in Ocypoda arenaria. Papers

1908. from the Tortugas Laboratory, of the Carnegie Institution of Wash-
ington.
Holmes, S. J. The Evolution of Animal Intelligence. Henry Holt and Company.

1911.
Spaulding, E. S. An Establishment of Association in Hermit Crabs, Eupagurus

1904. longicarpus. Journal of Comparative Neurology and Psychology, vol.
14, p. 49.
Yerkes, R. M. Habit Formation in the Green Crab, Carcinus granulatus. Bio-

1902. logical Bulletin, vol. 3, pp. 241-244.

Yerkes, R. M. and Huggins, G. E. Habit Formation in the Crawfish, Cambarus

1903. affinis. Harvard Psychological Studies, vol. 1, 565.

THE ABILITY OF THE MUD-DAUBER TO RECOGNIZE
HER OWN PREY (HYMEN.)

PHIL RAU

St. Louis, Missouri

INTRODUCTION

During the summer months two species of mud-dauber are
often seen at the edges of streams, filling their mandibles with
the soft mud, carrying load after load to some sheltered spot
and fashioning it into a many-celled nest. As each cell is com-
pleted the wasp provisions it with spiders, usually paralyzed by
her sting, cements her egg to one, almost always the last one
brought in, and then seals the cell. The egg hatches and the
larva spends its time in devouring the spiders while the mother
wasp goes on adding cell to cell until the nest grows to great
proportions, sometimes as many as thirty-six cells.

Of these two species so commonly seen the steel-blue wasp
is Chalybion caeruleum and the yellow-legged one Sceliphron
(Pelopoeus) caementarium. Our observations are almost entirely
upon the latter species. The experiments are for the purpose
of ascertaining the wasp's ability to distinguish her own prey
or to recognize another's spiders, and her attitude toward such.

In 1912 * we were watching a Pelopoeus mother industriously
filling her cell with spiders. While she was out foraging we
borrowed four fine fresh spiders from another new nest near
by and with the forceps carefully inserted them into her cell.
Upon her return she was at once aware of the intrusion and
set about to carry out the foreign spiders with much indignant
buzzing. Nor did she stop at this, but carried out and threw
away three of her own hard-earned prey as well, before her
indignation had cooled sufficiently to permit her to continue
her work. It was quite apparent that she recognized the spiders
not of her own capture, but why should she reject them because
a sister wasp had caught them, and why should she discard a

1 Ent. News, vol. XXIV, pp. 392-396.

240

ABILITY OF MUD-DAUBER TO RECOGNIZE OWN PREY 241

part of her own unless she meant to clear them all out as though
they were contaminated ? Would other mother wasps act in
the same way under similar circumstances ? These questions
led us on to further experiments the following summer, with
many varied and surprising results. The observations were
made during a week's vacation, on wasps building in an old
barn at Lake View, Kansas. Only the details of each experi-
ment can give the reader a fair idea of their varied behavior.

EXPERIMENTS

Exp. 1. A new Pelopoeus cell was found already one-fourth
filled with spiders. When an opportunity occurred, I slyly
filled it high with spiders from another nest. The mother wasp
returned with a large spider, and spent some time in laboriously
cramming it in. Quite satisfied now with her store, she brought
balls of mud and duly closed up the cell. But while she was
gone for another load I picked open the seal and extracted part
of the contents. Arriving at the nest with the next pellet she
saw the injury and was alarmed, hurried out and threw the mud
away, returned and indignantly carried out the remaining spiders
one by one, her own as well as mine, until the nest was quite
empty.

Exp. 2. While Pelopoeus was gone I stirred up the spiders
which she had placed in her cell and added one from another
nest. When she returned she promptly carried it out, and made
four more trips, each time carrying out one of her own capture,
until all were gone. Then, after a brief, unexplained absence
she came back and inspected the empty cell, fretted and ex-
amined and stood guard over it for an hour and a half all because
a few spiders had been disturbed.

Upon returning three hours later I found the cell sealed.
I opened it and found just two medium-sized spiders, with an
egg attached to one. Thus this mother was so anxious about
her progeny that she carried out and rejected all of the spiders
which had been touched by human hand or forceps, and now
she sealed up the egg with only sufficient food to carry it half
through its larval life.

Exp. 3. One day while collecting nests I removed a large
one from a shelf against the barn-wall. No sooner done than a

242 PHIL RAU

blue wasp, Chalybion caeruleum, returned to it. She examined
the spot very carefully for about thirty minutes. When she
flew out I replaced the nest, but before doing so I removed five
spiders from the new cell which she was engaged in filling. She
returned, still with the green spider which she carried when
first she missed her nest. She hovered about on the nest very
nervously for some minutes and entered the cell five or six times
and seemed greatly excited and puzzled; she re-examined the
whole nest again and again and re-entered the cell many times,
and finally after thus hesitating for about forty minutes she
soared away with an indignant buzz, without even depositing
her new prey.

While she was gone I removed six spiders from another cell
of her own nest (this cell was at the back of the nest, against
the wall, so one side was open, but when the nest was returned
to its position against the wall no mutilation was apparent to
confuse the owner), and placed them in the new cell. She soon
returned and set about promptly to remove these six spiders
one by one and either dropped them after a flight of a few inches
from the nest or carried them quite outside the barn.

Apparently she had had enough of this cell, for after a few
minutes she flew in with a pellet of mud and began to seal it
up, empty.

Exp. 4. A Pelopoeus mother was busily engaged in stocking
her new cell. I plundered the nest of a blue wasp near by and
placed six spiders from it in the new cell. The owner returned
with a spider of her own, placed it in the cell on top of the stolen
booty, pushed the whole in with her head and rammed it down
about six times as though it were all her own, then flew out,
returning almost at once with a pellet of mud with which she
sealed the cell, and reinforced it with four or five more such
balls. All this she did with an air of peace and satisfaction in
work well done.

If some females can by some sense detect the spiders which
have been caught and paralyzed by another of her kind, and
express such resentment toward their presence, how much more
strange it is that this one does not seem to be aware that part
of her prey had been handled by a foreign species entirely,
besides myself, or if she does know it, she cares not a whit.

ABILITY OF MUD-DAUBER TO RECOGNIZE OWN PREY 243

Exp. 5. Next I tried a new form of interference, placing three
spiders in a Pelopoeus cell which was only in course of construc-
tion, being but one-fourth completed. So it was not at all sur-
prising that the wasp, after a little commotion, promptly emptied
this and proceeded with her masonry.

Exp. 6. A blue wasp had completed her cell and placed her
first spider there. I removed it, filled the entire cell with spiders
from other nests and replaced her own spider in the front of
the cell so that she would see her own prey when she returned.
However, in handling the contents, I broke out a small piece
of the wall at the opening. When I returned in a half hour
I found that the cell had been emptied and deserted by the
mother. Why did she go to the trouble of emptying it if she
meant only to desert it?

Exp. 7. A new Pelopoeus cell appeared complete, but was
still empty. The insect brought a load of mud, but used it to
reinforce the nest, then she went all the way into the empty
cell, and remained there for four minutes, only her tarsi pro-
truding. What may have been her business during this per-
formance we could not determine. When she had gone, thirteen
spiders (one with a small egg attached) from another nest were
placed in the cell. Upon the second and third trips she also
walked over her nest and deposited the mud on the outside to
reinforce it; she did not enter the cell, and I did not see her
even look inside, but when she again came she used the load of
mud to close the cell, then another and another until the seal
was firm, just as though all were normal. Whether she detected
the ample supply of spiders and closed the cell on that account,
or whether she would have sealed it empty, had we not filled
it for her, we could not determine.

Exp. 8. A Pelopoeus cell was finished and quite ready for
use, but the larder was not yet stocked, so I filled it with spiders
from another nest. The mother wasp returned with a fresh
spider, started to enter the nest but retreated and flew out of
the window, taking her burden with her. She returned empty-
handed and carried out the intruders one by one. After the
cell had been empty for a half hour, I again placed eleven spiders
in it. The next morning when I arrived to examine this cell I
found it had again been emptied.

244 PHIL RAU

Exp. 9. A Pelopoeus mother was carrying in spiders to fill
the twelfth cell of a handsome nest, but had not gone far with
the work when I added fourteen from the nest of another of the
same species. The wasp returned and at once emptied the cell
of my spiders and her own as well, and quietly stood guard
over the cell for fifteen minutes with an air of indecision, and
then flew away and was not seen again.

Exp. 10. A one-celled Pelopoeus nest was built under a piece
of bark on a log beam in the old barn. I carefully removed this
bark, -filled the cell with borrowed spiders and replaced it. When
the wasp returned she had great difficulty in finding the nest.
After finally locating it she paused only a moment and dashed
away, and returning removed the spiders one by one. Since the
position of the nest was disturbed in gaining access to it, I should
have been surprised if she had not resented the intrusion, although
I cannot understand what caused her great confusion in locating
the nest when the alterations in the locality were imperceptible
to me.

Exp. 11. A solitary cell contained five spiders when I added
six more from another nest. The wasp returned empty, put her
head into the cell and worked energetically for three minures,
either inspecting or packing them together or laying her egg.
Out she came at last and dashed away, but without a spider;
almost immediately she returned with her plaster and sealed
up the cell.

When she had gone, I broke the seal and removed part of
the spiders which she and I had together supplied. She soon
returned with another pellet of mud for the seal, but when she
found it broken she alertly poked her head in, hastily withdrew
and flew away with the mud. After that she made four trips
from the nest, each time carrying out a spider which I had failed
to remove, but these four were of those which she personally
had put in. Then for ten minutes she thoroughly examined
the inside and outside of the cell, going in and out many times,
apparently in an earnest attempt to discover the cause of the
mysterious trouble. When I returned at four p. m. I found her
again filling this cell with spiders.

During her absence I again meddled, inserting twelve spiders
from another nest. Returning she brought a spider which she

ABILITY OF MUD-DAUBER TO RECOGNIZE OWN PREY 245

crammed into the cell with the others and departed. After ten
minutes, however, she came buzzing back as if possessed of a
new idea, and commenced to empty the cell. First she took
out her own fine new one and threw it away, and returned re-
peatedly until the cell was again empty. She then remained on
the nest, holding watch for thirty minutes, as if resolutely wait-
ing to catch the hoodoo. When she left I expected her to refill
the nest with spiders of her own capture, but instead she brought
a load of mud and, to my amazement, spread it in a thin
layer on the inside of the cell, as though the very walls were
polluted, or else all of the trouble were due to its inadequacy.
So, for the first time, I saw a wasp adding mud to the inside
walls of a cell after she had once deemed it finished. .

The next day, August 17, at three p. m., she was still occa-
sionally coming to the cell with an air of angry suspicion and
uncertainty, but otherwise it was in the same empty condition
that I had left it. Unfortunately I was obliged to leave on the
evening train, so I never knew what she finally decided to do.

£#£.12 . At six o'clock one August evening I filled a new
one-celled Pelopoeus nest with spiders from another nest during
the absence of its owner. I was called away and could observe
it no further until the next day, August 17, when I found the
cell sealed. I opened it and found that my intruders were gone
and in their stead were two other spiders. The mother had
evidently begun to fill the cell after having thrown out my
spiders but had stopped with only two and sealed the cell with-
out having even deposited her egg.

Exp. 13. A certain nest of a Pelopoeus was almost com-
pleted when I filled it with spiders from another nest. The
proprietress returned with another load of mud to add another
ring. When she saw the spiders she withdrew her head with
a start, as though greatly shocked. Again she inquiringly put
in her head, with a like result. She then went away in bewilder-
ment and returned six times, but each time sought the nest at
a spot two feet distant. Sometimes she would walk toward the
nest, but always with the manner of one seeking for something
lost.

After three days the cell was still in the same condition as I
had left it; the wasp never finished it. I think that she firmly

246 PHIL RAU

believed that her nest was lost, and that the one to which she
came again and again was the nest of another which had been
filled with spiders.

Exp. 14. At 10:20 a new cell, the fifth on this nest, was
commenced, and in just one hour and a half the new compart-
ment was completed and ready to be filled and sealed. At
this point I came forward with unasked aid and placed therein
fourteen spiders from another nest. The wasp returned with
a load of mud, no doubt to put on the finishing ring, but when
she saw the spiders she showed not the least surprise or con-
cern, but proceeded to seal the cell with the pellet she had
brought. Then she brought another and another and added
it to the closing in the normal manner, showing almost human
standards of conduct in being satisfied in doing the thing most
convenient at hand which gives the appearance of work well
done, and glad of the opportunity easily to forget that she had
quite overlooked the principal duty of her life. She seemed
to give no serious thought to the presence of the spiders, nor
did she make an effort to compress them nor show any concern
for depositing her egg. The sight or scent of the spiders seemed
to afford sufficient stimulus to cause her to seal the cell. Per-
haps the presence of the mud already in her mandibles lent
strength to the stimulus for this particular action.

At four o'clock that afternoon I found that this industrious
mother had made another cell and was finishing off what I
thought must be the last ring. When she flew out I placed six
spiders in the cell and had not time to insert more when she
returned with another load of mud. She got a glimpse of the
spiders, which in this case only half filled the cell, and almost
immediately flew out with the pellet. She threw away her
mud and came hurrying back, peered into the cell and then
bustled out again. She came back to the cell bent on her course
of action, got a spider and carried it out. I then hurried to com-
pletely fill the cell by adding ten more spiders. But her zeal
for righting wrongs was now aroused, and even this was no in-
ducement to seal it up, for she carried them all out one by one.

Exp. 15. The new cell on this nest was just completed but
as yet contained no food supplies, so I placed in it eight fresh
spiders taken from another nest. The mother wasp returned
with a load of mud and alighted on the nest, but from her be-

ABILITY OF MUD-DAUBER TO RECOGNIZE OWN PREY 247

havior I judge that she suspected that it was not hers, for she
arose on the wing and flew in wide circles and returned. This
she did three times, the last time making a good many smaller
circles. Through all of this confused search she carried her
pellet. By this time she seemed fully convinced that this was
her home, but that something was wrong. So she dropped her
ball of mud out at the window, returned in a direct line to the
nest, and began with a very positive air to carry out the spiders
one by one, throwing them away until all were gone.

Exp. 16. A wasp was discovered putting the first layer on
the closure of her cell. I removed this and also part of the
spiders, all of her own capture. The wasp came in with more
mud; hummed a little in anxious concern and flew out with
her load. She returned shortly, however, and again sealed the
cell. Again I opened it and inserted other spiders from another
nest. She came back and saw the opening, poked her head into
it enquiringly and proceeded to plaster it up. For the third
time I broke the cell, but she seemed inclined to repair it as
long as I would continue to damage it.

Exp. 17. A wasp had packed her cell nicely and already
sealed it with two layers of clay. I carefully removed the cover-
ing and part of the spiders. The wasp returned with the next
load of mud, hesitated only a little and spread it in its proper
place and was off again. Again I opened it and this time in-
serted four foreign spiders. In due time the mother returned
and again plastered the opening as if nothing had happened and
departed. Bent on commanding her attention I broke the seal
for the third time and placed a larva of Pelopoeus in the door-
way, half protruding, so she could not seal the compartment
without removing it. By the time she arrived with a pellet
this larva had worked itself out of the cell, so she spread the
mud as usual over the cell. When she had again gone I
tried another very large larva in the same way. The mother
wasp returned, made no attempt to remove the larva, or in
fact displayed no concern for its presence, but spread the
mud around it as it lay half protruding from the cell, often
severely jarring it as she worked, plastering her mud to the
sides of the larva as though it were a part of her wall, and thus
again sealing in this silly fashion her cell.

Exp. 18. To a Pelopoeus cell containing a few spiders I

248 PHIL RAU

added five from another nest. The wasp returned, carrying
another spider which she crammed into the cell, while with her
head she condensed the whole mass. In so doing she somehow
dislodged one and it fell into the spiderweb below; she alertly
recovered it, crammed it into the cell with precision and con-
tinued to pack the mass together for about five minutes, then
flew out and brought one more spider which she deposited,
almost filling the compartment.

When she had gone again I forced five additional spiders
into the cell ; after a half hour she returned with another capture
which she also forced in with great effort. It seemed that she
had a fairly definite idea how many spiders were required, and
bring them she must and would, regardless of unsolicited aid.
In this she differed from other individuals of her species, in whom
the sight alone of few or many spiders in the cell was sufficient
stimulus to induce the sealing process.

But upon her next return she brought a load of mud and
closed the cell. When she was gone I opened it and removed
one-third of the spiders. The next load of mud was used in
precisely the same way; absolutely no attention was paid to
the broken cell or the missing spiders. Again I removed the
seal and all of the spiders in order more forcibly to impress
upon her the seriousness of the injury. I accidentally broke a
small piece out of the wall of the cell at the opening. The wasp
returned, spread her mud over the opening, leaving the broken
part untouched and quite ignoring the emptiness of the nest
or the traces of vandalism. She discharged her duty always
with a mechanical faithfulness; she seemed, nevertheless, exact —
three loads of mud are usually required to seal a cell, and three
loads she brought and applied properly before finally leaving
the nest.

Exp. 19. When I arrived upon the scene the fourth cell of a
Pelopoeus nest was half filled with spiders. Not having other
spiders at hand, I placed a pupal case containing a pupa of the
same species in her cell so that no part protruded. When I
returned two hours later the cell was sealed and a fifth cell of
the nest half completed. I had to break open the cell to see
if the pupa had been removed. The cell was quite empty, but
the new item of interest was that at six the next morning I

ABILITY OF MUD-DAUBER TO RECOGNIZE OWN PREY 249

found this damaged cell repaired and the fifth cell still in its
half finished condition. This was the first case in my experience
of a wasp going back and giving attention to a previously finished
cell after a subsequent one had been begun.

CONCLUSIONS

When we attempt, finally, to formulate any generalizations
concerning the behavior or psychology of these insects, there
seems to be only one principle which can be relied upon to hold
good in all cases, viz. : that the madam will do as she pleases.
Cases of similar conduct under homologous circumstances
can hardly be found. Yet we cannot regard the behavior of
the wasp as indifferent or accidental when we see her very
positive air in taking action, and her usual determination and
persistence in pursuing it when she has decided upon her course
of action. It may seem to some readers that these observations
are too artificial or experimental in nature and too limited in
number to justify a conclusion so vague. To be sure all these
experiments threw the insects under abnormal and unnatural
conditions, so we need not marvel, perhaps, that no two behaved
alike under provocation. But the detailed examination of
many hundreds of completed nests2 shows that in normal, free
life these wasps commit blunders or follow disastrous whims
in a large proportion of their cells; sealing them stark empty
or with only a fraction of the food necessary for the young
one, or providing abundant supplies and omitting the egg, or
other blunders which would defeat the whole purpose of the
wonderful instinct of nest-building.

In answer to the question suggested in the title we can only
say that in most of the cases where the spiders were disturbed
the owner was quick to detect it and frequently resented it.
But since in her anger she often threw away part or all of her
own prey we cannot determine whether or not she recognized
her own, or merely regarded with alarm any meddling about
her home. Likewise in those cases wherein she accepted our
proffered aid she did so with such outward indifference, taking
it all as a matter-of-course after the manner of those accus-
tomed to welcoming charity, that we could not discern whether
or not she was the wiser.

2The data are in course of preparation for publication later.

OBSERVATIONS ON THE BEHAVIOR OF BUTTERFLIES

CHARLES W. HARGITT

The following observations have been made at various times
during several years as opportunity has afforded, and with little
thought that they might ever be offered for publication. Look-
ing them over recently it has seemed that there might be a
few sidelights which would have some interest to students of
behavior, and with this in mind they have been written out
quite briefly as an incidental contribution to a subject of vast
interest and importance.

The lepidoptera have been for many years a favorite group
among students of tropisms. The familiar phenomenon of the
moth fluttering in the candle flame at night has long ago passed
into a proverb. It is only within recent times that observations
upon butterflies, and also upon many larvae of these forms, have
come in for critical study and attempted explanation. It is no
part of the present purpose to attempt any review of the subject,
though a few references can not be avoided in discussing the
facts to be reported. While the earlier observations and deduc-
tions of Loeb, Davenport, Graber, Radl and others have been
of value, and have stimulated greatly the interest in the sub-
ject, it remained for later students to undertake to study with
accuracy and critical control the factors involved in the be-
havior. To the writer it has seemed that the work of Radl
and Parker have been noteworthy in this respect. It was the
graphic account by the latter on ' The Phototropism of the
Mourning-cloak Butterfly, Vanessa Antiopa Linn.," which
prompted the observations herein submitted. In most respects
they will be seen to confirm the facts cited by Parker, and but
for a few features which apparently differ in certain fundamen-
tals, there would have been small occasion for giving them
publicity.

Let me say at the outset that my observations were made
wholly in the open, that is, in the natural habitats of the organ-
isms, no attempt being made to put specimens under artificial

250

OBSERVATIONS ON THE BEHAVIOR OF BUTTERFLIES 251

control. In earlier papers I have expressed the conviction that
much of such artificial work has been far from convincing,
and some of it actually mischievous. It may be probable that
some of this failure attaches to study of lepidopteran behavior !

My observations began with the study of Vanessa antiopa,
and were chiefly directed to that species, but several other
species also came in for a share of attention. The following
points will be emphasized: (1) Marked individual differences
of behavior under apparently identical conditions; (2) differences
at various times of day, and various days; (3) marked sense of
locality and adherence thereto; (4) lack of evidence of any sex
adaptation in the color markings as related to behavior.

My observations confirm those of Parker, (1) as to the domi-
nance of ' chemotropic response to food;" (2) the general
negative phototropism in strong sunlight; (3) general indiffer-
ence of butterfly to shadow stimuli except in the head region.

My first notes on the behavior of Vanessa were made on a
bright, warm day, the 25th of March. The first two specimens
found were very wary and difficult to approach, but two other
specimens proved less wild, and allowed easy approach and
close observation and experiment. Several others were found
later which also allowed approach and similar observation. One
of these specimens alighted on an exposed snow-bank, oriented
in the usual manner, seemingly not at all disturbed by the
icy substratum on which it rested. In all some twenty careful
observations were made in relation to the particular orienting
behavior, and in general conformed fairly constantly to the
results obtained by Parker. As a basis on which to estimate
the degree of exactness of the orientation I regarded any reac-
tion which did not vary more than ten degrees from the precise
line of the sun's rays as conforming to the law, while anything
beyond this was regarded as a departure, or failure to conform
to the law. This is, of course, a purely arbitrary way of esti-
mating the reaction, but unless one insists on mechanical pre-
cision in every case (a method which might be demanded), it
seems as good as one might propose. In the first series, just
given, the majority clearly behaved in conformity with expecta-
tion, but a number as clearly fell outside such expectation. In
this connection were noted facts which clearly illustrate the indi-
vidual difference of behavior, e.g., the differing susceptibility

252 CHARLES W. HARGITT

to alarm. Shall one use the term alarm in referring to such
behavior ? If the organism is pure mechanism the use of such
terms is of course inadmissible. But if we are dealing with
an organism in the true sense, then no other term is more per-
tinent and significant. That this is the real state of the case
one is forced to believe in that the same specimen will exhibit
the same differences of behavior at different times, acquiring
keener sense of alarm from experience. Again, the behavior
varies on different days. On some days they seem to seek the
ground predominantly, while on others they " come to earth '
seldom and for brief periods. This was noted so often as to
leave no doubt as to the fact. That it may not be due to differ-
ence of light intensity is evident in that the same differences
will be observable in different specimens at the same time and
therefore under identical light intensity. For example, it was
found to be true in the behavior shown at ten o'clock and that
at two o'clock the same day, and under indistinguishable con-
ditions of light, though appreciable differences of temperature
were evident, and it is not impossible that this may be a factor
in the matter. Exactly these facts were illustrated by my next
field trip four days later, on March 29th. In the forenoon
specimens were extremely wary and difficult of approach, and
the behavior was erratic and uncertain. During the afternoon
of the same day, accompanied by an assistant, it was like en-
countering a different species. Specimens were " tame," obser-
vation was easy, and any number of tests could be made with
precision.

My next observations were made just a month later, with
a clear, warm day. At least seventy-five observations were
made during the afternoon, including numerous shadow tests.
While in the majority of cases there was a more or less evident
orienting response, as before a considerable number varied
greatly as to the precision of reaction. It was not unusual to
have a specimen alight at an angle of 90 degrees from the parallel
of the rays of the sun, and occasionally a specimen would come
to rest directly facing the sun and remain thus. A single speci-
men was found which proved very approachable and responded
very readily to tests, and on it were made about forty direct
tests, of which thirty showed orienting reactions more or less
precise. The other ten reactions showed considerable more

OBSERVATIONS ON THE BEHAVIOR OF BUTTERFLIES 253

*

deviation, sometimes as much as 45 degrees. In course of these
observations it was found that the position of the support upon
which the specimen came to rest often had a modifying effect
as to its final position. That is, if the specimen alighted upon
a twig which was slightly out of the line of the rays of sunlight
it conformed to the axis of support instead of that of the rays.
In one case the specimen alighted upon a dry leaf stem with
the head upward, and about 30 degrees from the parallel of
the sun's rays. This effect of the influence of the supporting
basis was frequently observed in later cases and I think affords
an important factor to be taken into account in such cases.
Evidently here was a stimulus which served to modify in a
very appreciable degree the character of the behavior., On this
specimen a number of experiments were made by means of
shadows cast upon the body. In some cases these were pro-
duced by means of the hand, sometimes by using one's hat,
and in some cases by a cane which might be made to cast a
definite and localized shadow. Under total shadow the speci-
men usually showed reaction in from 5-10 seconds, and within
15 seconds would fly into the light (occasionally the movement
would be by crawling). Under partial shadows, i.e., a part
of the body in shadow, the reaction was less prompt, from
15-20 seconds. As in the total shadows, the reaction might
involve flight, or a mere creeping forward or sidewise, as the
case required. The response was in general more prompt with
the shadow on the anterior of the body and head and slowest
when the posterior part was under shadow, which would seem
to imply the relation of sight in the reaction, though not wholly.
On May 27th a series of observations were made under very
favorable conditions, the specimens being easily approachable
and seldom taking fright or leaving the place. The records of
the day included fifty observations, and of these hardly more
than half of the photic reactions came within the 10 degrees
arbitrarily set as a sort of limit for precise orientation. Varia-
tions from 10-30 degrees were very common and in a few
cases the variation was definitely 90 degrees from the line of
the rays. Experiments with shadows showed some interesting
features not noted before. In a few cases total shadow
produced no reaction at all ; but in most cases there was response
within about the limits already noted. In some cases a specimen

254 CHARLES W. HARGITT

would give signs of reaction by becoming restless, edging side-
wise, forward, and finally in flight, alighting in open sun. One
of the unusual phases intimated above was noted upon two
specimens, namely, while resting and oriented in about normal
manner, with wings spread wide and flat, they would slowly
close them over the dorsum. While in this pose, if a shadow
were cast upon the specimen, its reaction would be an imme-
diate spreading of the wings. Upon removing the shadow the
wings would again close over the back; and repeating the shadow
the same reaction would occur. This experiment was repeated
upon one specimen seven times at intervals of from 15-20 seconds.

To test whether this particular form of reaction was due to
sudden visual reflex the interposition of the shadows was made
so gradually as to render any such reaction rather improbable,
or again by sudden thrusting of the shadow upon the body to
induce such reflex. But it was not evident that the reaction
was wholly visual.

Another feature of the observations today was the fact that
no selection was apparent upon the part of specimens as to the
place of coming to rest. For example, they frequently came to
rest on the open, spreading leaves of the mandrake, leaflets of
cohosh, grass blades, etc., and in some cases nestling down
among grasses, utterly indifferent to the hazy shadows of such
positions. In other cases they would alight on dead stumps,
naked limbs, flat stones, etc., and almost invariably with the
head directed upward, sometimes at an angle of 20-30 degrees
from level of the ground. In only one case in all the observa-
tions was a specimen seen to alight upon a tree trunk.

Sense of locality. It was frequently noted that a given speci-
men showed some sense of particular locality. For example,
it was often observed that a specimen at rest and oriented in
a given place would arise in chase of a passing specimen and
after a buffeting flight together for some distance the first speci-
men would return and alight in the same spot from which it
had taken flight. This was seen so many times that there hardly
seems doubt of the fact that it reveals a sense of locality almost
as marked as by such insects as bees. Reference will be made
to this matter in a later section in connection with the question
of sex attraction.

My next observations of importance took place at Woods

OBSERVATIONS ON THE BEHAVIOR OF BUTTERFLIES 255

Hole in July and early August and had to do with another
butterfly, namely, Argynnis idalia, a species rather common
in the locality. The specimens are of the field habit rather
distinctly and seek the open sunshine. Like Vanessa this butter-
fly orients itself in almost exactly the same manner. But their
reaction is much less exact than that of Vanessa. And when
tested as to the effect of shadows to my surprise they showed
hardly any reaction. In a number of cases the shadow of a hat
interposed and withdrawn as many as a dozen times at intervals
• of from a few seconds to as much as a minute produced no re-
sponse. These experiments were repeated on other specimens
and with the same results. When put to flight a specimen soon
comes to rest in the same general attitude as before. The color
of this insect is much more striking than is that of Vanessa,
and if this were a means of attracting mates, as Parker has
suggested, then it might be expected to be much more effective.
But I have never, in either case, seen the slightest evidence
that this is in any sense such a device, nor that the special pose
and orientation has anything to do with such ends. As with
Vanessa specimens of Argynnis show great variation as to ease of
approach, some being exceedingly wary and wild, others tame
and easily studied. Such is the case with almost all the species
studied. Whether this may be due to greater or less visual
sensibility or simply to more or less alarm in the presence of
strange objects may be matter of doubt.

My next observations which add anything essential to the
facts concerned were made in September of the following year
in the fields adjacent to Syracuse. I had at this time oppor-
tunity to observe several species in addition to Vanessa antiopa,
among them a species of Papilio, probably asterias, and another
which I was not able to identify. As compared with Vanessa
the behavior of Papilio showed several rather marked differ-
ences. In the first place there was no indication of phototropism
of any sort. On coming to rest upon the ground there was not
the slightest disposition to orient itself with reference to the sun's
rays. On the other hand there was orientation with respect
to direction of wind, the creature seeking to face the wind thus
probably taking the position of least resistance to the wind
which was rather strong at times in the exposed field. Con-
tinued observation showed that this behavior was not merely

256 CHARLES W. HARGITT

incidental, but definite and purposeful. In flight there was no
apparent reaction of the sort, the specimen flying as much directly
against, as with the wind currents. In repose the specimen
showed the same pose of wings as Vanessa, a fact which was
rather unusual fona Papilio, whose attitude is usually quite the
opposite, namely, to rest with closed wings. The response to
shadows was essentially the same as Vanessa, though less marked
At times a specimen would remain at rest indefinitely under a
shadow, but the opposite reaction was predominant.

The other species behaved in much the same manner as '
Vanessa, but its photic reactions were much less marked. Its
behavior in relation to other species in flight was exactly as in
\Tanessa and other species already mentioned. This chasing
and buffeting behavior appears to be related to the mating
instinct, but it was not possible to distinguish that it ever
resulted in actual copulation. Further reference to this will
be made in another section.

Numerous other observations were made, all giving about
the same results, and all revealing more or less clearly the indi-
viduality to which attention was directed in the introductory
section. It was quite evident that in this behavior one has to
recognize that reactions are not simple, nor are they definite
and stereotyped as might be expected on the assumption of the
so-called laws of phototropism. As Parker has well said, " this
problem, at least so far as butterflies are concerned, is much
more complex than was suspected by either Loeb or Davenport.
The reactions of Vanessa antiopa to light cannot be satisfac-
torily considered without dealing with the influence of heat,
food, and gravity." I think it may also be added, without
recognizing the influence of an individuality characteristic of all
higher organisms.

Sex as a Factor in Behavior. Parker has emphasized the
probable relation of certain phases of the behavior, especially
that of the peculiar pose of the wings and photic orientation,
to the problem of ' bringing the sexes together during the
breeding season." This view has received no confirmation in
my observations. At no time have I ever observed a specimen
in flight hover about one in repose as if attracted toward it.
Invariably the first sign of recognition has been by the resting
specimen, which often appeared to be on watch for the passing

OBSERVATIONS ON THE BEHAVIOR OF BUTTERFLIES 257

of one of its kind. This was true of all the species observed.
I have often noted the fact that any passing object in flight
over one of these "watching" specimens, such as a bird, or a
bumble bee, would have the effect of stimulating the same sort
of chase as would be the case with a similar passage of one of
its own species. I have seen a Vanessa chase a Papilio, or a
Pieris, or, indeed, almost any similar object.

That there is a sex factor involved in this peculiar behavior
I think altogether probable. But that the color pattern, or
the wing pose of the specimen has any such function seems
extremely improbable. A further fact which tends to support
this view is that the behavior in question does not seem to be
limited at all to the breeding season. It is quite as marked in
July as in April or May. Indeed, so far as my observations go,
there is nothing to show that this behavior differs materially
at any time during the active life of the butterfly.

Still a further point may be noted as bearing on the ques-
tion, namely, it does not seem to me that the color pat-
tern of the wings of Vanessa serve to make it a specially con-
spicuous object when in this orienting pose. If a perfectly
bare, white or grayish position were always sought this might
be the case to some extent, but the habit of Vanessa rather
dominantly in or about wood lots, where many and varied
lights and shadows mingle, would tend to render these markings
rather protective than otherwise. I have personally demon-
strated this on many occasions when following up a specimen
for closer study. Even when marking down a specimen as it
came to rest and hastening forward with the eye upon the spot,
it often was impossible to see the thing until it took flight, so
intimately had its markings been blended with its surroundings.

These facts and the further fact that the behavior is not
peculiar to Vanessa, but is shared by a considerable number
of species, some of which are very brilliantly colored, afford
a strong evidence in disproof of the view proposed by Parker
touching its function as a sex factor.

NOTES

THE ROLE OF THE EXPERIMENTER IN COMPARATIVE

PSYCHOLOGY

ROBERT M. YERKES
Harvard Psychological Laboratory

In Comparative Psychology attention has recently been concentrated upon the
control of the experimental situation to the neglect of two other aspects of our
task which are equally worthy of study, — namely, the management of the subject
and the reliable recording of responses. Every psychological problem presents,
if attacked experimentally, these three technical demands: first, such control of
the objective situation as shall render it not only suitable for the solution of the
particular problem, but at the same time, highly controllable and describable;
second, such knowledge of the subject, human or infra-human, as shall enable the
experimenter to avoid unnaturalness, or otherwise unnecessary ill-adjustment of
subject to objective situation; and third, such provision for the recording of response
as shall provide wholly reliable and sufficiently detailed descriptions of the sub-
ject's behavior.

By experience in working with various animals and with pathological human
subjects, I am convinced of the urgent need of attention to our methods of record-
ing reactions. We, at present, allow the experimenter too great range and place
upon him over-great responsibility. As observer, he is liable both to influence the
subject in his attempts to get data of reaction and, in turn, to be influenced, in his
descriptions of what he sees, by his unescapable tendencies to interpret. Quite
evidently, the ideal experiment is one in which the subject provides us a detailed
photographic record (or other form of graphic record) of its response. It is the
writer's belief that we should make systematic and persistent attempts to develop
recording devices which shall free us from the observational imprefections of the
experimenter.

This means that our apparatus for use in Comparative Psychology must be
largely automatic or self-controlling over considerable periods of time, not only
with respect to the objective situation or setting in which the subject reacts, but
also with respect to the recording of the several important aspects of response.
We should devise types of recording mechanism which shall either operate auto-
matically or be operated by the subject rather than by the experimenter. This
would mean not the elimination of the observer but the freeing of his attention
f or those aspects of the total experiment which most urgently demand control.

As an example of a practical recording device, I may mention that of the Hamil-
ton Quadruple Choice Apparatus which, in its latest improved form (thus far un-
described) permits the experimenter to confront his subject with a certain situation
and then leave that subject to work out a series of problems, its behavior in con-
nection with which is the while accurately recorded by a system of markers, elec-
trically actuated.

258

JOURNAL OF ANIMAL BEHAVIOR

Vol. 5 JULY-AUGUST 1915 No. 4

THE INFLUENCE OF DIVERTING STIMULI
DURING DELAYED REACTION IN DOGS

ARTHUR C. WALTON

From the Zoological Laboratory oj Northwestern University

INTRODUCTION

The experiments recorded below were undertaken to deter-
mine the effect of various diverting stimuli applied during
' Delayed Reaction " in Dogs. The diverting conditions were
either employed in connection with the primary stimulus, or
were interposed during the delay period. While the diverting
conditions disturbed the " Orientation Clues " to which Hunter
(13) has attached much importance, at the same time they may
be used to determine the power of the dog to retain the original
stimulus under complex conditions, resembling those which pre-
vail in natural behavior.

The observations were carried on during the year 1913-14,
at the Zoological Laboratory of Northwestern University under
the direction of Dr. E. H. Harper, to whom the writer expresses
his thanks for assistance, suggestion and criticism of the
manuscript.

DESCRIPTION OF THE DOGS: THEIR TRAITS AND
NATURAL CAPACITIES

The dogs were brother and sister of a litter of four, the re-
sults of mating an English bulldog and a Scotch Collie mother.
Both had the brown coats and white vests of shaggy hair that
is characteristic of the Collie, and the male was a collie in build,
while the female had the short bowed legs of the bulldog. The
female was fawning and easily diverted. Her attention was
mainly towards the experimenters, and rarely towards the pro-

260 ARTHUR C. WALTON

blem, unless the experimenter was entirely concealed. This
disposition was not conducive to the giving of good attention,
and, as her seemingly dainty appetite caused the ' hunger
stimulus ' to lose its potency, her attention was so poor that
results from only the simplest associations could be obtained.
The male was affectionate, but never fawning and, as the "hun-
ger stimulus" was very strong in his case, his attention was very
good in the more complex problems as well as in the simpler
ones. For these reasons the results set forth in this paper
are based almost entirely on the records obtained from the male.

The native disposition of the dogs was to shrink from the
electric light bulbs employed in the experiments, and only long
training would lead them to overcome this aversion to any
place thus indicated. The artificiality of the light stimulus is
unquestioned, and to react to it, the native fear of the dog must
be overcome. For this reason reaction to light stimuli cannot,
as some experimenters have claimed, be taken as indicating
the true native capacity of the dog. It seems more logical to
conclude that only the reactions to stimuli that are naturally
attractive to the dog can be taken as true indices of its native
capacity.

The health of the dogs during the whole period of the exper-
iments was good. Occasionally slight indispositions were shown.
The dogs were kept out of doors, and were allowed to run with
other dogs and play with the children of their owner. This
life prevented the acquisition of any characteristics peculiar to
housed animals.

DESCRIPTION OF APPARATUS AND METHODS OF •
THE EXPERIMENTS

The experiments were given in a room that was kept partially
darkened in order to have the light stimuli in a strong contrast
to the general lighting of the room.

The apparatus is illustrated in Fig. 1.

The release box (" B ") was thirty inches wide and forty
inches high with a glass top measuring fourteen by fourteen
inches. The door, made of wire screening, occupied the whole
of one side, hinged at the top and provided with a counter-
poise which enabled it to swing easily. The box could be rotated
very easily on its " domes of silence." This release box stood

STIMULI DURING DELAYED REACTION IN DOGS

261

^^

' w. — r

w.

D.

=o<>. *-

/?'

*

IBJ

14.

fc— -

vy

A- Control switch B-Reltase. box. C-SKmulus bulbs
D-Door W- Windows

Figure 1

twelve feet from the mouths of the food compartments, arranged
so that the mouth of each was an equal distance from the release
box. The compartments were five feet deep and two feet wide
and contained the food bowls. These bowls, during the latter
portion of the experiments, were kept filled with water, so that
the dog never suffered from thirst. The compartments were
at first of wire screening (two inch mesh), but in the four light
experiments the walls were made of muslin. In the two and
three light experiments the lights were placed at the rear end
of the compartments, but in the four light experiments they
were placed over the entrances. This gave an equal stimulus
from each compartment, keeping them all on a level. The fourth
compartment had the approach to the food bowl of a fourteen
inch board with cleats nailed to it, set up at a 30 degrees angle,
and leading to the food bowl on a platform thirty inches from
the floor.

The method of the experiments was at first to put the food
in the bowl, switch on the light for five seconds and then off
again and release the dog at the end of the delay period. Later
the method omitted the placing of the food in the bowls. At
first two observers were always in the room standing behind
the release box so as not to be visible to the dog during his trip
to the food compartment. While one handled the apparatus,
the other gave the reward and kept the records. In the early
tests, the food was placed .in a covered bowl in one compartment,
the bowls in the other compartments having been smeared with
the food to avoid a special olfactory cue to the correct compart-

262 ARTHUR C. WALTON

ment. Later this method was dropped to avoid giving visual
or olfactory cues as to the position of the reward. The food
was now thrown to the dog after the completion of the correct
reaction, but the dog developed a lax habit of only partially
completing a reaction. He would approach only to the en-
trance of the food compartment and then await the reward.
To avoid this result a new method of giving the food reward
was introduced. One experimenter stood outside of the door
(D — Fig. 1) watching the dog's actions through a peephole and
entered the room with the reward only after the animal had
traversed the entire length of the correct food compartment.

The experiments were given under varying conditions and
the results are recorded separately for each type under the
following heads:

Condition "A" — Light Stimulus — Operator in view of dog.
Release box faced compartments all the time. Used in the
training experiments with Two and Three Lights.

"Al" — Food placed in the compartment at the beginning
of the trial.

"A2" — Food thrown to compartment after a correct reaction.

Condition "B" — Operators out of sight of dog until after re-
action was complete. Release box faced the compartments
during stimulus and delay periods. Used in delay experiments
with Two and Three Lights.

"Bl" — Food placed in compartment at outset of trial.

"B2" — Food thrown to compartment after a correct reaction.

Condition "C" — Light Stimulus — Operator out of sight of dog
until after reaction was complete. Release box turned 90
degrees during delay period. Used in "Two, Three and Four
Light Experiments."

"CI" — Food placed in compartment at outset of trial.

"C2" — Food thrown to compartment after correct reaction.

"C3" — Operator out of room until reaction is complete..
Food given after correct reaction.

Condition "AD" — Used in 'Two Light" experiments. Dis-
turbing stimuli (Olfactory, Auditory and Visual) given during
delay period. Release box faced compartments during entire
reaction. Food given after correct reaction.

Condition "CD" — Used in 'Two Light" experiments. Dis-
turbing stimuli (Olfactory, Auditory and Visual) given during

STIMULI DURING DELAYED REACTION IN DOGS 263

delay period. Release box turned 90 degrees during delay
period. Food given after correct reaction.

In the early experiments the order of trials was prearranged,
and followed strictly during the trials. However, in the later
trials a given experiment was repeated as many times as necessary
to secure a successful reaction. Otherwise the prearranged order
was followed out. Care was taken that the order of trials
should not be such that a possible rhythm could be followed.
Record of attention to the stimulus was noted by means of
watching the dog through the glass top of the release box.

Any particular orientation during the delay period was watched
for and noted. The path to the food compartment was re-
corded and hesitations or wide turns were especially noted.

The designation " Two Light," " Three Light "and " Four
Light " experiments refer to those experiments in which the
stimulus was given in one of the possible two, three or four
compartments and the dogs were forced to discriminate the
correct one of these several possibilities.

In the early experiments the trials were given in series of
five and ten, and no advance was allowed until 50% of a series
were correct reactions. Beginning with the ' Two Light "
experiments, and continuing through the rest of the work, no
advance was made until at least five successive correct reactions
were obtained.

At first the dog was called back to the release box after a
trial, if he did not return at once of his own accord. It was
noticed, however, that after a number of unsuccessful trials,
the dog would refuse to leave the release box on the opening
of the door. The dog at the beginning of the ( ' Two Light '
experiments returned so regularly that it was decided not to
call him back anymore. After this change the dog would lie
down for a minute or two, if discouraged by several unsuccessful
trials, and then would return to the box with renewed energy
and with his attention to the problem as keen as ever. He did
not refuse to leave the release box any more after this change in
the method was made.

The time of the day when the trials were made varied from
8 to 11:30 A. M. As an interesting sidelight it may be noted
that the time from 10 to 11:30 A. M. was the period in which
the dog was the most attentive and eager, hence giving the

264 ARTHUR C. WALTON

best results. In considering the records, the difference in the
time of day has not been considered of enough importance to
be mentioned in each series of trials.

The system of retaining the stimuli at one compartment
until the dog reacted towards it correctly, begun in the " Two
Light " experiments, was continued in the new trials, with the

Three Lights," thus the compartment with the poorest associ-
ation received the greatest number of trials. While this savored
of the trial and error method, yet it was the most successful
method that could be found. It was in fundamental accord
with the noticed behavior of the animal in learning the associ-
ation to any one bowl or food compartment. He had to learn
to react to each compartment separately, and thus set up the
habit of going to that one when he received the proper stimulus.
This method gave immediate results as compared with the
method used at first of a prearranged schedule of compartments,
and no repeating on a failure. There, in the case when the
cue to "number two" had been lost, it took a series of eighty-
one trials, twenty-seven of which were on ' number two," to
regain the lost cue and respond to it ten times in succession.
By this latter method the association is generally set up again
within two or three trials.

The question of ' ' Punishment and Reward ' ' has been a very
important one to observers of animal behavior in the higher
forms of life. After the preliminary experiments it was decided
that a punishment, after an unsuccessful reaction, other than
that of losing the food was out of the question.- The dog lost
interest and became afraid to try for fear of punishment. That
the loss of food was in itself a severely felt punishment was
already shown by the sheepish action after a failure. His tail
dropped between his legs and he sneaked back to the release
box with his head down. It took several successful trials to
entirely lose his sheepish manner.

RECORD OF EXPERIMENTS

The dogs experimented with were not entirely unfamiliar with
associating the required reactions with the stimuli, for Dr.
Harper had trained them somewhat along such lines in working
on another problem. Thus the writer was able at once to begin
with light association experiments. Dr. Harper had found that

STIMULI DURING DELAYED REACTION IN DOGS 265

by the use of very attractive stimuli, such as (1), the smell of
meat, (2), waving a handkerchief, and (3), a whistle call, the
dogs gave very close attention and could bridge delay periods
of five seconds duration.

The work of the writer falls into two main heads, (1), the
" Training Experiments," to establish the Light Association and
(2), the trials of " Delayed Reaction."
1. Training Experiments.

These experiments were given to familiarize the dogs with
the electric light as a stimulus to reaction, in addition to the ones
they had already learned. This was done by combining the
light stimulus with a familiar one and gradually dropping out
the familiar one and leaving only the lights as a stimulus. When
the dogs came to react correctly to the stimulus when it re-
mained during the entire trial, the delay periods were introduced
in which the dog was forced to make the reaction when the
stimulus was absent. These trials were recorded separately
from the delay trials only in the "Three Light" experiments.
While some such trials were given during the ' Two ' and
" Four Light " experiments, they were too few to be discussed
under this separate head, but are mentioned at the beginning
of the corresponding " Delay Experiments."

"A" Al — The series of trials of this type extended over the
period between October 4th, and November 19th, 1913. The
curve representing the learning period for the discrimination of
the three compartments was very short and steep. By October
25th, perfect mastery was gained. The results of the series
up to October 25th are as follows: 50%, 25%, 25%, 73%, 80%,
90%, 80%, 100%, 100%. Every succeeding series, totaling
eighty trials, gave 100% results. As stated before, the choice
of the order of the compartment to be used was determined
in advance of the series and care was taken to avoid any possible
simple rhythmic succession of choices.

A2 — To avoid the possibility that the dog was gaining cues
to the proper reaction from the olfactory stimulus of the food
in the bowl, the problem was again taken up on January 12th,
1914, almost two months after the former experiments had been
stopped. In these trials, the food was not given until after
the reaction had correctly taken place. Four series (twenty
trials) from January 12th, to February 9th, 1914, were given

266 ARTHUR C. WALTON

and all showed 100% results, proving that the olfactory stimulus
was not necessarily a factoring one. During the 'same time,
check series were held to test the possible rhythm of the dog's
choice of compartments. A series of twenty-five trials was
given on No. 2 compartment, and one of ten trials on No. 1.
The first series gave 80% of the results correct, and the second
showed all the trials correct. These trials show that rhythm
was not a factor in the dog's choice and that the errors were
due to other causes. The habit of going to a different compart-
ment for each choice was so strong that it forced the dog at
first to another compartment in spite of the stimulus call ng
to the same compartment again. However, but five of the
thirty trials were mistaken in that way. That this rhythm
of going to one compartment did not form a habit was shown
by the fact that a return to the discrimination of the three
compartments showed no errors or even hesitations. These
results show that the dog can gain perfect mastery of a problem
involving the discrimination of three compartments when the
light stimulus is present at the time of reaction. The fact that
rhythmic and olfactory cues are not strong factors in successful
reactions is also shown.

"B" — Condition "B" means the release box faced the food
compartments only for the stimulus, so that the dog could not
gain any possible cue from seeing the operators go to the com-
partment. Only trials of the "B2" type were given, the food
reward being given after the reaction was completed. Seventy-
one trials of this type were given preliminary to the undertaking
of the "Three Light" experiments in condition " B." Thirty-
nine, or 55 %, of the trials were correct reactions, and indicated
enough of mastery to favor the adoption cf the delay periods
of the " B " type.

II. Delay Experiments,

" Three Light Experiments."

Condition "A" — Light out at release. This condition meant
that the light stimulus of five seconds' duration was present up
to the moment of the release. Thus the entire reaction. was
performed after the stimulus had been removed, but the associ-
ation was forced to bridge the gap between the instant of release
and the time of the choice of the compartment. As before,

STIMULI DURING DELAYED REACTION IN DOGS 267

the two phases, Al and A2, depending on the manner of giving
the food, were recorded separately.

Al — Ninety trials of this type, i. e. having the food placed
in the compartment before reaction, were given and seventy-
one were correct. These trials extended from October 18th,
1913 to November 19th, 1913, and show that practical mastery
had been gained. Perfect mastery could never be attained
because the factor of attention in the ■ dog was variable and,
hence, if he did not see the stimulus, at release, he was without
a cue and depended on chance. In the former tests, perfect
mastery was shown because the stimulus was always there and
could not be missed when leaving the release box. Several
series of five trials were all correct, but longer series showed
at best, only 80% of the reactions as correct.

A2 — In order to test the memory of. the association formed,
and also to avoid the possibility of olfactory stimuli from
food in the compartments, trials in which the food was given
after correct reactions were taken up on February 9th, 1914,
and extended over to February 16th, 1914. A series of ten
trials gave 80% correct reactions and showed that the associ-
ation was not based on olfactory cues in any appreciable extent.
The question of rhythm kept coming up as a possibility, so
check trials were given on each of the three compartments to
see if this change of rhythm would cause a falling off of results,
and if such a falling off should come, to see if changing the
rhythm "was the cause. Forty tsials were given on No. 1 com-
partment with only 50% of correct results on February 12th,
1914. This falling off in results cannot, however, be laid to
the changing of the rhythm. Just previous to the trials, the
dog had run into No. 1 when the light was on and had touched
the hot electric bulb with his nose and received a slight burn.
As a result he avoided No. 1 constantly for the first ten trials,
and for five of the next ten. The last twenty trials showed
fifteen correct reactions of which the last five were successive.
The later mistakes were due rather to the habit of changing,
than to the following of any rhythm. A check of ten trials
on No. 3 compartment followed on February 14th, 1914 and
60% were successful, the last five being in succession. The
four mistakes did not follow any rhythm for the dog went to
No. 2 three times in succession and the fourth time to No. 1 .

268 ARTHUR C. WALTON

The order of -his choices on No. 3 compartment were 1, 3, 2, 2,
2, 3, 3, 3, 3, 3. The habit of changing from one compartment
to another had to be broken up before the dog would go to any-
one successively on the proper stimulus. A check of fifteen
trials on No. 2 compartment gave 73%, or eleven of the trials
as correct reactions, the last five being in succession. All of the
four mistakes were on No. 2, which was the compartment on
which the previous check had been held. These results show
that habit rather than rhythm was the factor that governed the
successes of the check trials. The total results of A2 were lower
than those of Al, i. e. 60%, and 71%, but this difference was
due largely to the falling off for a while on No. 1 compartment.

Two Seconds Delay. — The trials in which there were two
seconds delay between turning off of the light stimulus and the
release, were all of the Al type and were not continued long
because the results showed that so short a delay had no effect
on the correct reactions of the dog. Thirty-three of these trials
were given between October 25th and November 19th, 1913,
with twenty correct, or a percentage of sixty-one. A slight
improvement was noted toward the end of the series, the last
ten trials giving an average of 70% of correct reactions. These
results were so nearly identical with those obtained with "Light
Out at Release" that it was decided to make five seconds the
minimum delay length in later experiments.

Five Seconds Delay. Al — One hundred and thirty-eight trials
of the type Al were given between October 22nd and December
1st, 1913. Of these ninety- two, or a percentage of sixty-six
and two thirds, resulted in correct reactions. The factor of
attention cut into the number of correct reactions, but the
results show that the dog could discriminate the three compart-
ments with practical certainty after a delay period of five seconds.
The best series were those on October 27th, 1913, when twenty
trials showed seventeen correct reactions, the last ten being
perfect, and on November 10th, 1913, when fifteen trials showed
82% successes. Here also the last ten trials were correct.

A2 — To obviate olfactory stimulus, two series of ten trials
each, were given January 7th and 12th, 1914, in which the food
was given to the dog after successfully completing the reaction.
The first ten trials gave eight correct results and the second
ten, five correct reactions. The average of 65% was so near

STIMULI DURING DELAYED REACTION IN DOGS 269

that of the average of experiments of the Al type that the
indications of the use of olfactory cues were negative. The
question of rhythm could be applied here, but no special checks
were given. However, checks on the simpler type of ' Light
Out at Release" coming immediately after the close of these
series showed no evidence of rhythmic choice. There was no
reason to think that the dog adopted a rhythmic choice for
a five second delay, when he did not for a shorter delay period
that was being used in experiments carried on at the same time.

Ten Seconds Delay. Al — On October 27th, 1913, the series
of trials with ten seconds delays under the type Al were begun
and extended to November 19th, 1913. The results of fifty
trials showed only twenty-five successful reactions. This was
evidently owing to the breaking down of the cues to the middle
compartment, and a return to a similar type of problem was
suggested. Accordingly the ; Two Light ' experiments were
employed again to determine what length of delay might be
obtained, with a view of applying the resulting training when
a return of the " Three Light " experiment should be made.

A2 — On January 7th, 1914, the ten second delay was again
tried under the type A2, and the benefit of training on the "Two
Light" tests became apparent. The first fifteen trials showed
ten correct reactions, of which the first five were successful.
In the next series of ten trials on January 10th, 1914, all were
successful. The 80% average showed that the dog had attained
practical mastery of the problem. The likelihood of rhythmic
choice of compartments was prevented by choosing beforehand
a certain order and following it closely. No simple rhythm
could follow the picked succession, viz., 1, 2, 1, 3, 2, 2, 3, 1, 1,
3, 2, 3, 3, 2, 1.

Longer Delays. — Scattered series of trials of fifteen seconds
delay, or longer, were made on days when the dogs' attention
was very keen. On November 15th, 1913, five trials, Condition
Al, with a fifteen second delay were all successful. On January
9th, 1914, ten trials with twenty seconds delay, Condition A2,
were all successful. As the interest of the experimenters was
along the line of further reducing the possible cues by which
the association might be made, no further trials were given
to demonstrate the mastery of longer periods of delay with
such complexity of cues as Condition Al and A2. However,

270 ARTHUR C. WALTON

from the ease with which the dog made the reactions, the experi-
menters were satisfied that with the same degree of attention
as then displayed, further trials would only definitely show that
the dog could retain his cues to reaction over a delay period
of at least twenty seconds. As later trials will show, this assump-
tion was not unfounded.

Condition "J3." — Condition "B" means that the results here
were made under conditions in which the release box faced
the food compartments only during the stimulus and delay
periods. The dog could not see the operator adjust the lights
and so could not gain any possible position cue to the right
compartment from his movements. Also the possibility of
smelling the food was removed, for in all the "B" trials, the
food was thrown to the animal after the successful completion
of the reaction.

B2 — The results here embraced the following series:

Light out at release .... 92 trials 44 correct 48%

Five seconds delay 80 trials 48 correct . 60%

Ten seconds delay 25 trials 1 1 correct 44%

Fifteen seconds delay. . 14 trials 6 correct 45%

These results are not high but nearly all well above a chance
percentage of successful reactions. The averages obtained were
about the same as those of the same length of delay in the "A"
types and the differences are too slight to be explained on any
ground, but that of the attention of the dog, which varied with
his physical and pyschical state. It was noticed that the mid-
dle compartment seemed to be discriminated more correctly
than the other two, so check experiments were given in the
"Out at Release" to see if this was really so. On No. 1 com-
partment, seventeen trials gave six correct reactions, or a per-
centage of 35. Compartment No. 2 gave seven out of ten,
or an average of 70%, while No. 3 compartment showed
only thirteen out of forty-five trials correct. This last result
confirmed the conclusion that the cues to No. 3 were weak and
that more training was necessary before correct discrimination
could be shown.

Close observation of the behavior of the dog showed that he
avoided the right side of the room on which No. 3 compartment
was situated because of the intensity of the light. Finally he

STIMULI DURING DELAYED REACTION IN DOGS 271

refused to g# there entirely. Of forty-five trials he reacted
correctly in only thirteen, or a percentage of twenty-nine. In
the last third of the trials he even refused to leave the release
box, refusing twelve of the last fifteen chances. A dimmer
light was put in No. 3 compartment and the next day the dog,
working up from a "Light Constant" position gave 44%, or
twelve correct out of twenty-seven trials. This was as good an
average as he had before reached. With ten seconds delay he
gave 44%, or eleven correct out of twenty-five trials. In both
series the dog still avoided No. 3 compartment so another check
of ten trials was given on it, with none of them successful. In
the last three trials the dog refused to leave the box. When
a trial on No. 1 was given, however, he left the box and reacted
correctly. Further trials, with only compartments No. 1 and
No. 3 in use, overcame the aversion to No. 3 and when the three
compartments were again used, the reactions were as good
towards it as towards either of the other two, viz.

Five seconds delay 67 trials 46 correct 68-3/5%

No. 1 16 trials 12 correct 75%

No. 2 27 trials 18 correct 66-2/3%

No. 3 24 trials 16 correct 66-2/3%

Condition "C." The experiments listed under condition "C"
were those in which the release box was turned away from the
food compartments during the delay period and in which the
dog did not see the operator until after the entire reaction had
been completed. The release box was turned facing the com-
partments just soon enough to release the dog at the end of the
delay period and not allow him any time to see the compart-
ments before he was forced to make his choice. This change of
conditions was an attempt to forstall the probable chance that
the dog was guided by orientation cues to a great extent and
was not using memory cues. If so, and this orientation should
be changed during the delay period, then he would not be able
to react correctly. A minor point in regard to the effect of
keeping the problem always before the dog during the delay
period was also involved in the change. If this had had any
effect of affording a cue to reaction, the turning of the box
destroyed its function. The introducing of a new field of view
during the delay that was entirely foreign to the problem was

272 ARTHUR C. WALTON

apt to have a distracting effect on the dog's attention and thus
tend to drive away the memory of the proper association. The
records from these experiments were taken as satisfactory proof
of the question as to whether the belief in such a probability
was well founded. The release box had to be turned rather
quickly in order to disturb the orientation of the dog within the
box, as well as to disturb the entire orientation toward the
food compartments. The preceding observations had borne
out the statement of Hunter (13), that the dog showed orien-
tation only by the movement of the head, and that causing
the head to change its position would effectively destroy the
dog's orientation. The sharp turn of the release box affected
this disturbance of orientation, for the dog was forced to move
the whole body in order to maintain his equilibrium. Under
these new conditions, no evidence was seen of the tense, eager
waiting that the dog had formerly displayed during the delay
period, and the dog even used the time for scratching at fleas,
and during the longer delays would close his eyes and apparently
take little cat-naps while waiting. As soon, however, as he felt
the release box return to the normal position, he was wide awake and
eager, and hurried out of the door before it was fairly opened.

The experiments are recorded under the two heads "CI"
and "C2" differing as before, in the manner of placing the food
reward. The records began with the minimal delay of five
seconds after a five seconds light stimulus.

Five Seconds Delay. CI — Only fifteen trials of this type were
given, as evidence of a breakdown on No. 3 compartment ap-
peared and a return to an "A" type of experiment was necessi-
tated. The results of the fifteen trials was nine correct reactions.
Of the five trials on No. 3 compartment, all were wrong.
Only one of the five trials on No. 2 compartment was a wrong
reaction. At this time, November 4th-8th, 1913, the aversion
or loss of cues to No. 3 was noticed in all the sets of experiments
then going on, and so the series of check trials described under
condition "A" was given. After this series the dog regained
his cues to No. 3 and went there as readily as to any other
compartment.

Ten Seconds Delay. C2 — On January 22nd, 1914, the "C2':
experiments were taken up again after the dog had had a month
and a half's training in all the conditions including "AD" and

STIMULI DURING DELAYED REACTION IN DOGS 273

"CD" on two compartments. Resumption of the "A" and
"B" types with the three compartments had been so successful
that a ten second delay was used at once on beginning the "C"
trials. Here the food was thrown to the dog after completion
of the correct reaction. The records obtained here show per-
haps better than any others the learning curve, beginning very
low and rising gradually to a practical mastery of the problem.
The first twenty-five trials were very poor, only seven being
correct. Of the errors, eight were because the dog refused to
leave the box at the release. The dog gave no attention at
all to the stimulus and when he left the box on release it was
more a result of training than a reaction to a formed associ-
ation. The inattention was due to the lack of hunger.

On January 24th, 1914, the dog was more alert, and tried to
solve the problem but was not very successful. Out of sixty
trials only twenty-seven or 45% of them were correct. This
low result was due to the dog's inability to retain the associa-
tions for the discrimination of the three compartments over a
delay period of ten seconds, and was not due to inattention
to the stimulus.

On January 27th, 1914, twenty-five trials were given and
the benefit of the previous training began to be evident, for
seventeen or 68% of the trials were successful. The last nine
trials were all successful.

The record of the twenty-one trials given on January 28th,
1914, were not so successful as those of the preceding day,
having only eleven or 52%, of the trials as correct reactions.
The falling off was due to the indifference of the dog to the
stimulus in the last ten trials. The average for the first eleven
trials was 73% and for the last ten only 30%.

February 16th, 1914 was the next day on which the "ten
second delay" trials were given, and of eighteen trials sixteen
or 88% of them were correct. The last twelve trials showed
perfect reactions. The records made on this date were the
best obtained on the ten second delay problem, for fifteen trials
on February 10th, 1914 showed eleven, or S3% of them correct.

The learning curve obtained in these trials with the ten second
delay shows the growth of the power of carrying the associ-
ations over the delay period the most perfectly of any of the
delay series. All show the same general results, but none show

274

ARTHUR C. WALTON

such a smooth curve. A short summary of the data may make
this growth more apparent.

"Five Seconds Light — Ten Seconds

1/22/14 25 trials 8 correct 27%

1/24/14' 60 trials 57 correct 45%

1/27/14 25 trials 17 correct 68%

1/28/14 21 trials 11 correct 52%

2/ 6/14
2/10/14

18 trials
15 trials

16 correct 88%
11 correct 73%

Delay."

Falling off on
Falling off on No. 3
Last nine correct, t.
Refused to act seven of

last eight trials.
Last twelve correct.
Trials five to eleven correct.

That the low records at the beginning of the experiment were
not due to the breaking down of orientation cues, is seen by
comparison of the records for trials of "Ten Seconds Delay"
condition "A2" given at the same time.

On January 17th, 1914 a series of thirty "A2" trials showed
only 33-1/3% or "Chance" percentage of trials correctly com-
pleted. Of the "C" trials, a series of twenty-five on January
22nd, 1914 showed only six or 27% of them as correct factions.
This shows that the lack of attention to the stimulus -vas th
cause of the failures and that attention and training .ost be
gained before higher results could be obtained, as the- results
show there was a parallel rise of the learning curve in the problem
given in both the "A" and "C" conditions. The added train-
ing and the better attention given to the stimulus ga> * d a
practical mastery of the problem at the same relative time, l. e.
February 5th, 1914 for trials of Condition "A2" and Febrr'Ary
6th, 1914 for trial of Condition "C2." The daily recorV of
January 27th, 1914 showed very nicely the typical day's work
with an advancement coming at the end of the series of trials.
Many of the daily records showed a higher average of results
for a single series, but this example is given because it shows
the growth from a very low beginning to a high ending.

Stimulus
at Com-
partment 3332111233213333321322123 25 Trials

Response
at Com-
partment 1232021223312002321322123

Correct

x x

X X

X X X X

XXXXXXXXX

Failures mostly
on No. 3 Com-
partment

17 Correct —
68%

STIMULI DURING DELAYED REACTION IN DOGS

275

The rhythm for these trials was very irregular, being selected

"■forehand and only varied by keeping the dog at a compartment

he had gone to it correctly. Then the regular schedule

,,cts resumed. This method seemed preferable to that of keeping

to the fixed schedule strictly, as it gave the dog extra practise on

the compartments to which his cues seemed to be weakened.

Fifteen Seconds Delay. C2 — The fifteen seconds delay type
of the experiments given under condition "C2" extended over
the j^riod between January 17th, 1914 and February 12th,
1914. In all there were sixty-seven trials, and of these forty-
four, or 66-2/3%, were successful reactions. The last twenty -
tWjO trials showed much improvement and gave 85% of them
as correct reactions. The highest record reached on any indi-
vidual day were those on February 6th and February 12th,
1914, when nine out of ten and twelve out of fourteen trials
were correct. The results of the earlier series were lower and
showed a decreased learning power instead of an increased one
as a result of training. This decrease was due to the apparent
failing, or the cues to No. 3 compartment. This failing was
noted in. til the types of experiments going on at this time, and
a specjUl check series of twenty trials on No. 3 compartment
was $i sn to restore these cues. After regaining the cues, the
records given above as the highest obtained, were the results.
The reactions to the other two compartments became more
aca1' :*;e, due to the training, as the records show, for while at
first ne errors on No. 3 were only 40% of the total number of
errors, they were 71% at the end, just before the check experi-
ments were given, and the total number of errors increased
onl) 7%. As the increase of errors on No. 3 was 74%, the
differ, ace can only mean that there was a strong decrease in
the ~ors on the other two compartments. The summarized
resm'ts for "Fifteen Seconds Delay"— "C2," are as follows:

d-/17/14 17 trials 10 correct 57% Errors equal on No. 1,

No. 2, and No. 3.

Falling off on No. 3.

6 of the errors on No. 3.

Last five correct — Error
on No. 3.

Last five correct — Errors
on No. 3.

l/icR/14

14 trials

8 correct

57%

1/20/ Af^

14 trials

8 correct

57%

y 6. i i

10 trials

9 correct

90%

2/12/14

14 trials

12 correct

83%

27G ARTHUR C. WALTON

The usual methods of avoiding possibilities of rhythm were
used, with the modification of keeping up the trials on one
compartment until a successful reaction to it was obtained.
The method of the experiment eliminated all possible olfactory
orientation or position cues.

Delays Longer Than Fifteen Seconds. The records quoted
above were the highest and best results obtained, for problems
of the "C" types that are complete enough to be the basis of
claims of mastery. However, shorter series of the longer delay
periods were given, with the view of discovering as to whether
the cues used could bridge delay periods of longer duration
than ten seconds. On February 10th, 1914, a series of ten
trials of "Twenty Seconds Delay" "C3" were given, with 90%
of the reactions correct. In the case of the error, an interesting
sidelight was noticed : The dog did not 'see the stimulus, to the
knowledge of the observer who had watched the animal carefully,
but seemed intent on rubbing his nose with his paw. On re-
lease he automatically hurried out until in front of the com-
partment toward which he had faced at release. Just at the
entrance he seemed to realize that a choice was to be made and
paused suddenly, then he slowly walked to each entrance in
turn and looked up at the light bulb as if seeking for a cue.
Then he gave up and returned to the release box without making
an attempt to enter any of the compartments. What the mental
attitude of the dog may have been, the writer leaves to some
experienced animal psychologist to explain. On the same day,
the dog gave four out of five reactions correctly on "Five Seconds
Light and Thirty Seconds Delay," which on February 12th,
1914 he reacted correctly in nine out of eleven trials of the same
length of delay for a percentage of eighty-three. Five trials
on the fourteenth were all correct and of the whole number
of thirty-one trials, twenty-seven, or 87% were successful re-
actions. These trials, though rather few in number showed
such a constancy in the per cent of successes that the experi-
menters believed that strong evidence of mastery of the problem
was presented.

Two series of trials of "Forty-five Seconds Delay" were given
on February 14th and 16th, 1914. Ten trials on the first day
showed only five correct responses and ten trials on the second
showed but six correct. Of the nine errors, five were for No. 2

STIMULI DURING DELAYED REACTION IN DOGS 277

compartment. Only three of the light trials on No. 2 obtained
correct reactions. This seemed to indicate that the cues to
No. 2 were almost lost. In the "Two Light" experiments
(discussed in the next section) No. 1 and No. 3 compartments
had been discriminated after a delay period of much longer
duration, but here the cues to each of the three compartments
did not seem to be localized well enough to be differentiated
after they had had the chance to become indistinct during the
delay period of forty-five seconds. The cues to No. 2 had so
lost their individuality during this long delay that the dog
could not differentiate them from those of No. 1 and No. 3 in
even a "chance" number of attempts. As a desire was felt to
increase the number of discriminated objects, and not to increase
the delay period on the three compartments, no more trials
were given on this type of experiment.

"Two Light Experiments."

By November 19th, 1913, the experimenters sawT that the
dog had not received proper training to do well at the three
light problems, and that success there would mean spending
much longer periods of training on each phase than was at
their command, so it was decided that a thorough training on
the two lights would gain time and also give a test for com-
parison with the results of Hunter (13) on the length of delay
possible to obtain with two lights. Another cause for the adop-
tion of the two light method was the fact that the trials so far,
had shown that the cues to No. 2 compartment were very weak
and could easily be dropped out. The method used in the
"Two Light" trials were slightly different from those in the
"Three Light" types. From the beginning, the stimulus was
retained at each bowl after a mistake until the dog made the
correct response. He was also kept at each type until each
series showed five successive correct reactions, before the diffi-
culty of the problem was increased. These methods, it was
hoped, would bring the association between stimulus and re-
action to the correct compartment, much more strongly into
mind. Previous training had failed to strongly set up this
association. After the two light association was thoroughly

278 ARTHUR C. WALTON

learned, the addition of a third compartment would be much
simpler than trying to teach association to all three compart-
ments at once.

The results were extremely successful from the very first,
and showed practical mastery of all the phases of the "A,"
"B" and "C" types immediately.

" Two Light ' trials were given in condition "A" of the
following types, ' Light Constant," ' Light Out at Release,"
" Two Seconds Delay," ' Five Seconds Delay," ' Ten Seconds
Delay," ' Fifteen Seconds Delay" and " Sixty Seconds Delay"
with the following results. All these results showed a high per-
centage except those on "Five Seconds Light, Fifteen Seconds
Delay" when the dog was very fatigued and gave but poor
attention at the beginning of the trials. In all cases each
series was continued until at least five successive correct
trials were made.

A short summary of the trials is as follows:

Light constant

8 trials

8 correct

100%

Light out at release

5 trials

5 correct

100%

2" delay

10 trials

9 correct

90%

2" delay

34 trials

32 correct

97%

10" delay

12 trials

11 correct

92%

15" delay

16 trials

11 correct

69%

60" delay

10 trials

8 correct

80%

The results for condition "B" which follows in summary, were
not so favorable, yet results beyond that of 50% of chance
were obtained in all but three series of ten each on 11/17/13,
11/19/13 and 12/16/13. On each of these three days the dog
showed symptoms of indigestion. These poor days pulled down
the general averages for the types in which they occur, but the
other records of each corresponding type were high enough to
balance up and give a safe margin over the 50% of " Chance."

5" delay

26 trials

18 correct

69%

10" delay

22 trials

14 correct

64%

15" delay

18 trials

11 correct

61%

30" delay

15 trials

10 correct

66-2/3%

60" delay

27 trials

18 correct

66-2/3%

20" delay

11 trials

8 correct

72%

STIMULI DURING DELAYED REACTION IN DOGS 279

The results for condition "C" were better than those of either
condition "A" or " B," as a much better practical mastery of
each type was shown

5" delay

35 trials

30 correct

86%

10" delay

30 trials

28 correct

93-1/3%

15" delay

15 trials

15 correct

100%

20" delay

10 trials

10 correct

100%

30" delay

38 trials

27 correct

70%

60" delay

13 trials

7 correct

54%

The results on "Sixty Seconds Delay" were but little better
than chance, because of an aversion to No. 3 compartment,
due primarily to a too brilliant light. When this was replaced
by a dimmer light on shorter delay trials No. 3 compartment
was chosen as well as No. 1.

The success of these series of trials led the experimenters to
attempt various types of diversion during the delay period,
first in condition "A" and then in "C." These experiments
were recorded under the heads of condition "AD" and "CD"
respectively.

Condition "AD "

In condition "AD," meat was held in sight of the dog during
the delay and the experimenters talked and whistled to him
in order to keep his attention away from the problem before
him. For the first five of the seventeen trials given, the dog
did not do very well, and seemed to have lost his cues, but soon
regained them and the diversion seemed to have no effect on
correctness of reactions, for the last nine reactions were all
correctly and unhesitatingly made.

The exact record will show the effects, the best of any way.

Stimulus at Compartment 13111133331313313 17 Trials
Reaction at Compartment 13333130331313313 4 Errors
Correct xx xx xxxxxxxxx 13 Correct

Condition " CD."

In this condition diverting stimuli were given during the
delay period of condition " C." These stimuli consisted (1)

280 ARTHUR C. WALTON

of the sight of operator walking in front of release box, (2) the
sound of the operator's voice calling the dog, and (3) a whistle
call with a piece of meat hung before the door. The object
was to find out if such stimuli could or would cause the dog to
forget his cues to the food compartments. The dog answered
each of these diversions by giving his whole attention to them,
often by snapping at the meat through the screen or by getting
up and turning around when called and not released.

These series of trials of this condition "CD" were given on
December 8th, 1913 and December 15th, 1913 and concluded
the trials on the 'Two Bowl" problems. The first series on
December 8th, 1913 was of Ten Seconds Delay with 100%
results. Five trials of One Hundred and Twenty Seconds Delay
also showed perfect reaction with no evidence of the effect of
the diverting stimuli. A series of light trials on Sixty Seconds
Delay followed and showed 75% of the reactions correct, the
last five being perfect. As there seemed to be no sign of the
dog losing his cue to either of the compartments, a sudden
jump was made to a delay of five minutes, and a series of five
trials showed all as perfect reactions. There was no hesitation
displayed in the dog's choice of compartments, nor did there
seem to be any sign of an hindering influence, due to the divert-
ing stimuli introduced during the delay. In order to ascertain
whether these results were chance, or whether they showed
the power of retaining a cue powerful enough to bridge the
five minute gap, and then discriminate perfectly between the
two bowls, another series of trials on these long delays was
held on December 15th, 1913. As usual the dog was kept at
a compartment until he succeeded, and no set of trials was
given up until five in succession had been correct. Beginning
with a two minute delay seven trials resulted in the last six
being correct (or a percentage of eighty-six.) With a three
minute delay, five trials were all correct. Then a five minute
delay showed seven successive correct trials. Then the next
trial was unsuccessful for the dog seemed to show fatigue and
during the delay period dozed in his box and did not pay atten-
tion to the attempts of the operators to attract his attention.
On release he went out slowly and wandered around and finally
reached the food compartments and entered the wrong one.
Because of the loss of attention, no more trials were given.

STIMULI DURING DELAYED REACTION IN DOGS 281

No attempts at longer delays were made as no further object
seemed to justify their continuance. During all these trials
of the "Two Light" type, the usual method of avoiding rhythmic
succession of trials was used, as well as the system of throwing
the food to the dog after a correct reaction had been made.
This latter method avoided the possibility of the use of the
olfactory stimulus as a cue to reaction. The time gaps already
bridged were too long for any sensory after image to have been
retained and hence diversion stimuli would have no lasting
effects on the cues by which the dog retained the association.
No attempt was made to find out definitely what those cues
were. The above results show that the power of discrimination
of two objects, fairly well separated (six feet), was within the
untrained capacity of the dog, and that the responses given
after the delay periods were the result of training. This training
enabled the retention of these powers of discrimination, necessa-
rily through some process, presumably memory. The negative
results gained by diverting stimuli during the delay period,
show that mere physical clues or sensory after images could
not suffice as cue retainers, but that there must be a definite
mental process involved, that may be called "Memory Associ-
ation." Since an association of stimulus and food compartment
was necessary, and since correct reaction demanded that such
an association be retained by some mental process, the "C"
type of problems having shown the absence of the physical
cues, therefore, as psychologists agree that sensory after images
could not bridge a gap nearly as wide as the five minute one
that this dog has done, the process must be one that involves
the memory.

" Four Light Experiments."

In the middle of February, 1914, it was suggested that the
problem be made more difficult by increasing the number of
compartments, the cues to which must be remembered, rather
than by the continued increasing of the length of delay periods
over which the association cues must bridge. So to increase
the number of compartments, No. 4 was added, but not on the
same ground level as the other three. The food was obtained
only by going up to the compartment on a board, eight feet
long and having a 30 degree pitch. The light stimulus was however

282 ARTHUR C. WALTON

at the same height from the floor as in the other three com-
partments. In order to quickly teach the dog the habit of
going to No. 4 compartment, and to climb the inclined board
without fear, the operators "put" the dog through the reaction.
That is, one held a piece of meat at the top of the incline and
called the dog. The other experimenter led and pushed the
dog up the incline. After four trials, in which he was helped,
the dog ran freely up the incline when called, without showing
any signs of fear. Then three trials were given in which both
light and voice were used as stimuli and the dog released
immediately from the release box. Each one of these trials
was successful. Next, three trials wrere given in which the
light alone was the stimulus, it being removed as the dog was
released. These three trials were all correct. From this point
the regular procedure of the experiments was taken up again.
Five trials of "Five Seconds Delay," position "C3" were given
on February 6th, 1914 and all were correctly reacted to. On
the same day series in "Ten Seconds," "Fifteen Seconds" and
"Thirty Seconds Delay" were given, all in condition "C3."
Of the ten seconds delay, five trials were all correct, as also
were five trials of fifteen seconds delay. On February 17th,
1914 a series of nine trials of twenty seconds delay was given,
of which seven or 76-2/3% were correct. The last five trials
were correct. On four different days, series of trials of "Thirty
Seconds Delay" were given and the record for the last day
showed very great improvement, over those of the preceding
ones. In the last three series, five successive correct reactions
were obtained before any longer delay was attempted. The first
day the dog broke down entirely on No. 3 compartment and a
shorter delay had to be used. The records for the four days
are as follows:

2/16/14 9 trials 4 correct 45%

2/17/14 14 trials 9 correct 64% Last 5 trials 100%

2/19/14 6 trials 5 correct 83% Last 5 trials 100%

2/21/14 9 trials 8 correct 89% Last 5 trials 100%

Encouraged by these results, on February 17th, 19th and 21st,
series of trials on "Forty-five Seconds Delay" were given. On
February 17th, five trials were all correct. On February 19th,
the last five of seven trials were correct, giving a percentage

STIMULI DURING DELAYED REACTION IN DOGS 283

of seventy-one. On February 21st, twelve trials were given
and of these trials 2, 4, 5, 6, 7, 8, 9, 11 and 12 were correct re-
actions giving a percentage of seventy-five. This series gave
six successive correct reactions in trials four to nine. On the
19th, nine trials on a one minute delay were given and 66-2/3%
of them were correct reactions. The last five were 100% correct.
These experiments showed that the dog was able to accurately
discriminate the stimulus from four compartments, that were
only two feet apart, and that he was able to retain the cues
to this discrimination over a delay period of at least one minute,
without showing signs of a break-down in the cues to any one
of the compartments.

RESUME OF RESULTS

The first conclusion drawn from the records was that perfect
mastery could not be gained because of the vacillating factor
of attention. This factor was high enough to give practical
mastery of the problems, but failed to give perfect mastery.
Sheepish behavior was apparent whenever the dog did not feel
exactly right, or when he made several unsuccessful trials in
succession. After such a period of failure the dog would hesitate
for fear of more mistakes, and in doing so would fail to get the
stimulus and make the association. This sheepish action was
the cause of a large percentage of the failures to make the correct
reaction. It was found, however, that allowing the dog to
return to the release box at his own will did away, to a great
extent, with sheepish actions. If the dog was always called
back, after several failures he would become discouraged and
give up trying. If he was left to his own devices, after several
failures he would lie down and rest for perhaps two minutes
and then return of his own free wTill and try over again with
his attention and interest as alert as ever. No sign of sheepish
behavior appeared then.

The records also show the contrast between the different
parts of the experiments, i. e. the routine of leaving the release
box when the door was opened, and that of making the correct
reaction to the stimulus given. Often when he refused, through
discouragement, to make a choice of compartments, he went
through the routine part without a hitch. It was found, how-
ever, that extreme discouragement affected even the routine

284

ARTHUR C. WALTON

part and the dog refused to even leave the release box on the
opening of the door. On command the routine part would
be resumed, but correct reactions, or even attempts at choosing
did not follow such commands. Hunger also caused attention
to vary. When very hungry, the dog was in good attention
and gave good results, and vice-versa.

Another interesting factor in regard to the preference for
any certain compartment was found in the records. A sum-
mary will give a better idea of this preference than can the
mere description above.

TRAINING TRIALS

Condition "A"

— Three

Lights 101 trials

85 correct

85%

No. 1

32 trials

30 correct

94%

No. 2

34 trials

26 correct

76%

*

No. 3

35 trials

29 correct

83%

Condition "B"

— Three

Lights

81 trials

43 correct

53%

No. 1

20 trials

12 correct

60%

No. 2

33 trials

15 correct

45%

No. 3

28 trials

16 correct

57%

DELAY TRIALS

"Three Lights"

Condition "A"

381 trials

249 correct

64%

No. 1

128 trials

87 correct

68%

No. 2

132 trials

77 correct

51%

No. 3

121 trials

85 correct

71%

Condition "B"

211 trials

118 correct

56%

No. 1

68 trials

'36 correct

53%

No. 2

74 trials

46 correct

62%

No. 3

69 trials

36 correct

47%

Condition "C

310 trials

193 correct

64%

No. 1

103 trials

60 correct

59%

No. 2

107 trials

73 correct

68%

No. 3

100 trials

60 correct

60%

"Two Lights"

Condition "A"

95 trials

85 correct

89%

No. 1

46 trials

44 correct

95%

No. 3

49 trials

41 correct

84%

STIMULI DURING DELAYED REACTION IN DOGS

285

Condition "B"

119 trials

78 correct

65%

No. 1

53 trials

39 correct

73%

No. 3

66 trials

39 correct

59%

Condition "C"

141 trials

108 correct

76%

No. 1

69 trials

63 correct

91%

No. 3

72 trials

45 correct

62%

Condition "AD"

17 trials

13 correct

76%

No. 1

8 trials

5 correct

62%

No. 2

9 trials

8 correct

90%

Condition "CD"

51 trials

46 correct

90%

No. 1

30 trials

26 correct

87%

No. 3

21 trials

20 correct

95%

Four Lights"

Condition "C3"

90 trials

71 correct

79%

No. 1

24 trials

21 correct

88%

No. 2

23 trials

13 correct

57%

No. 3

20 trials

16 correct

60%

No. 4

23 trials

21 correct

91%

The above summary shows that the associations toward the
different compartments varied considerably. Any two of the
compartments would have perfect associations while the other
would be neglected. The next day the result would be vice-
versa, and the neglected one would become the compartment
best associated. Thus, while one day's record would show more
trials at one compartment than at another, the whole series
of trials showed about *an equal number of trials on each one.
This variation might be construed as an argument against the
possession of reason by the dog. If the light always meant
the compartment that contained the food in the three light
trial, why did not the dog go to the light when it was placed
over a fourth compartment ? This presupposes that the dog
had mastered the association between the light and reaction
necessary to obtain the food and gave good results in the three
light experiments. The fact is that he did not, of his own accord,
make the new association. Evidently if reason was working
here as a factor in association, seeing the light anywhere over
a dish would cause a motor impulse to go to it. But, as it

28G . ARTHUR C. WALTON

did not, it is evident that reason was not the cause of the for-
mations of the associations. That habit is the cause of associ-
ation being formed is shown by the fact that after being taught
to go to the extra compartment by special training, and the
habit of going there firmly fixed, a series of trials including the
four compartments showed that the association of stimulus and
response is just as perfect for the fourth, or new one, as for any
of the former three. An argument that would seem to point
in just the opposite direction, tending to support the idea of
the functioning of reason, is given in the actions of the dog in
cases of wavering. In some cases it was noticed that the dog
would start for one compartment, and then swerve, often very
sharply to another, sometimes wrong and more often right.
Was it reason that made the dog believe that he had made a
wrong choice and caused him to change his selection, or was it
the motor energy in his muscles that forced him out in which-
ever direction he happened to be facing when released ? Was he
unable to set up the motor reaction connected with going to the
compartment for which he had made the association between the
movement to get the food and the light stimulus until the first
momentum was over ? To the experimenters it seemed that
the use of reason is the most feasible solution, but the psychology
of such a question is left to men more trained in that line than
the writer. A still more striking and less easily explained
action, was manifested when on getting almost to some compart-
ment, the dog would stop, hesitate and then go ahead or choose
another compartment, sometimes wrong, sometimes right. A
few times the dog gave up entirety and, returned to the release
box without even trying. Did the dog 'forget his cues, and
realizing it, attempt to reason out the correct association, and
on failing to do so, would return to the release box; or did he
fail to get the cue and form the association, and, from habit
rushed out when the release box was opened ? That is anothei
question for the trained psychologist to answer.

In condition "Al, Three Lights" it was seen that No. 2 com-
partment was discriminated only SS% as well as No. 1 and
No. 3. Thus it shows that while it was easy to discriminate
two widely separated compartments, the addition of the one in
the middle made it much more difficult to keep its cues separate
from those of the other two.

STIMULI DURING DELAYED REACTION IN DOGS 287

In condition "B, Three Lights," it is noticed that compart-
ments No. 2 and No. 3 are discriminated equally well and that
No. 1 is the one not so well discriminated. This failure on No. 1
was due to a long period of fear of the light there, as the dog
had burnt his nose on it at the beginning of the "B" trials. The
equal discrimination of No. 2 and No. 3 shows that the training
on No. 2 received in condition "A" had borne fruit. In condi-
tion "C — Three Lights," compartment No. 2 was discriminated
25% better than either No. 3 or No. 1 .In both compartments,
the dog had lost the cues to their discrimination several times
and had been given special training on them. The previous
training on No. 2 was shown in the results of the trials. This
trial in the power of discriminating No. 2 from the others is a
proof of the benefit of special training in habit formation, for
the habit of going there on stimulus, had become so firmly
fixed that errors became steadily less, and passed in strength,
the habits that caused him to go to the others on stimulus.

In the "Two Light" experiments, condition "A," "B" and
"C" show better discrimination of No. 1 than of No. 3 by about
18%. This favoritism was due to the fact that the light in
No. 3 was too bright, and after changing to a dimmer one, it
took over a week before the fear of No. 3 was sufficiently over-
come to allow the dog to enter freely whenever the stimulus
was given there. As the "Two Light" trials took place in a
period of only two or three weeks, this trouble with No. 3
materially affected the general results of a large number of trials.

In the trials of condition "AD" and "CD" that took place in the
period between December 12th and 15th, 1913, the results were
reversed and No. 1 was the one that was not so well discrimi-
nated. In condition "AD" the difference was too small to be
noticed but in condition "CD" a difference of 11% was found.
This difference was due to the fact mentioned in the "Three
Light" types, i. e. that the dog had burned his nose on December
15th, and hesitated to go to No. 1 after that. This set of ex-
periments was concluded on this day and the "Three Light"
type resumed, but the fear of No. 1, however, was carried over
and effected the records there. In all these trials, care was
taken that, while rhythmic successions of choices of compart:
ments was avoided as much as possible, the number of chances
was approximately the same for each compartment. The

2SS ARTHUR C. WALTON

usual result was that the compartment that was discriminated
the least accurately received a few more trials than the others.

Another point gained from the records is that the reaction
comes, not from seeing a light over a compartment and then
going there when released, but from the fact that when a light
was shown over a certain compartment to which he had been
trained to go on stimulus, the dog went as a matter of habit.
Hence, a light over a compartment to which he was not in the
habit of going did not set up in the dog's mind the association
of "Light — Movement to Light — Food" or for the incita.tions
to the motor response that comes on release, that the training
to that compartment would. The dog must be in the habit,
gained through thorough training, of going to an indicated
compartment on release, or he would not pay any attention
to it, but on release would go to one of those to which he was
accustomed to go, even though he had received no stimulus
to go there. The mechanical is stronger than the reasoning
in this case. Addition to the number of compartments means
that the dog must have special training on the new one before
it can become one of the several to which he is trained to go on
release after a stimulus had been given.

In the "Three Light" problem, condition "A" shows that
by course of long training a light stimulus can be made effective,
and the dog can remember the cues formed and the associations
set up by the light stimulus for the three compartnemts over
a period of one minute delay between stimulus and release.
The latter part of the records show that the olfactory stimulus
to reaction was not an important factor, as the records were
as good as when the presence of the food in the bowl gave the
possibility of such stimulus.

The records from Condition "B" show that the sight of the
operator placing the food in the bowl and operating the lights
gave no cue that was necessary for correct reactions, as the
general results of "B" are practically the same as those of "A"
while the dog could not see the operator until after the entire
reaction had been completed.

Condition "C" gives results of the effect of orientation and
the retaining of the compartments in view during delay period,
on the correctness of reaction. The records show that the dog

STIMULI DURING DELAYED REACTION IN DOGS 289

did not use orientation cues at all, or that they were of such
minor importance that they were dropped without effecting
his reactions. The turning of the release box during the delay,
thus destroying orientation to the food compartments and the
disturbing effect that a new set of objects before the sight would
have, did not give records any lower than those of condition
"A." In fact the records for the discrimination of the three
lights was better than those of "A," and the delay period reached
was of the same length in both conditions. From these results
the experimenters claim that this dog should be classed with
the group in which Hunter (13) places his raccoons, i. e. the
group that does not depend on the retaining of orientation to
give them the proper cues to obtain correct reaction.

The "Two Light" experiments show that the discrimination
of two compartments is easily within the native capacity of the
dog, for without previous training, once the light association
is formed, he gives 100% results. Perfect mastery is here shown
for all the conditions for delay periods up to one minute for
"A," two minutes for "B" and one minute for "C." Condition
"CD" gives results that show that diverting stimuli, such as
sound, sight, smell, etc., during the delay period of condition
"C," do not materially affect the power of correct discrimination
of the two compartments even though the cues must be retained
over a period of as long as five minutes. In none of the delays
of any condition, was there any sign of -breaking down in the
cues to any compartment, in the longest delay periods used.
No attempt was made to find the limit of the time over which
the dog could retain the association cues, in any of the problems.

The "Four Light" type was tried only in condition "C" and
it was found that through the benefit of previous training, the
dog, after a thorough training on the new compartment, could
discriminate the four compartments up to a one minute delay
as well as he had the three compartments. The first trials
showed, however, that without definite training, and the for-
mation of the habit of going to compartment No. 4 on stimulus,
the dog paid absolutely no attention to the extra compartment,
even though the light was constant, but went to one of the
compartments to which he was accustomed to go on release.

290 ARTHUR C. WALTON

SUMMARY OF RESULTS

(1) The habit of going to a compartment on release must
be formed for each one separately before discrimination of from
two to four can occur.

(2) The discrimination of four compartments was retained
for at least a delay period of one minute, and of a fewer number
of compartments, for a much longer period.

(3) The discrimination of two objects is within the native
capacity of the dog.

(4) Visual and olfactory cues are not necessary for correct
reaction.

(5) Signs of orientation may be prominent in the dog, but
such cues were not important for the success of the delayed
reaction in the animal experimented upon.

(6) Distractions of all kinds, visual, olfactory and auditory,
or such as might arise from the natural behavior of the dog,
may not necessarily interfere with successful delayed reactions.

BIBLIOGRAPHY

1. Ament. Ein Fall von Ueberlegungbeim Hund. Arch. ges. psych., 6, 249,
1905.

2. Carr, H. Orientation in the White Rat. Jour. Comp. Neur. & Psych.,

18, 27, 1908.

3. Cole, L. W. Concerning the Intelligence of Raccoons. Jour. Comp. Neur.
& Psych., 17, 211, 1907.

4. Cole, L. W. Observations of the senses and instincts of the Raccoon. Jour.
Animal Behavior, 2: 5. 299, 1912.

5. Davis, H. B. The Raccoon: A Study in Animal Intelligence. Am. Jour-
Psych., 18, 479, 1907.

6. Franken, A. Instinkt und Intelligenz eines Hundes. Jour. Animal Behavior,
1, 6, 430, 1911.

7. Glaser, O. C. The formation of habits at high speed. Jour. Comp. Neur.,
20, 165, 1910.

8. Haggerty, M. E. Imitation in Monkeys. Jour. Comp. Neur. & Psych.,

19, 337, 1909.

9. Hamilton, G. V. An Experimental Study of an Unusual Type of Reaction
in a Dog. Jour. Comp. Neur. & Psych., 17, 329, 1907.

10. Hamilton, G. V. A Study of Trial and Error Reactions in Mammals. Jour.
Animal Behavior, 33.

11. Hoge & Stocking. Punishment and Reward as motives. Jour. Animal
Behavior, 2, 1, 43, 1912.

12. Holmes, S. J. The Evolution of Animal Intelligence.

13. Hunter, W. S. The Delayed Reaction in Animals and Children. Behavior
Monographs, Vol. 2, No. 1.

14. Johnson, H. M. Audition and Habit Formation in the Dog. Behavior
Monographs, Vol. 2, No. 3.

15. Morgan, C. Lloyd. Habit and Instinct. Animal Behavior.

STIMULI DURING DELAYED REACTION IN DOGS 291

16. Sackett, L. W. A Study of the Learning Process in the Canada Porcupine.
Behavior Monographs, Vol. 2, No. 2.

17. Shepherd. W. T. Imitation in Raccoons. Am. Jour. Psych., 22, 583.

18. Small. Mental Processes of the Rat. Am. Jour. Psych., 11, 112, 1900,
& 12, 233, 1901.

19. Thorndike, E. L. Animal Intelligence. Psych. Rev. Monogr. Suppl., Vol-
2, No. 4, 1898. Psych. Rev., 6, 412, 1899.

20. Washburn, M. The Animal Mind.

21. Watson, J. B. Animal Education.

22. Watson, J. B. Imitation in Monkeys. Psych. Bull., 5, 169, 1908.

23. Yerkes, R. M. The Discrimination Method. Jour. Animal Behavior, 2, 2,
142, 1912.

THE LOCALIZATION OF SOUND IN THE WHITE RAT

ALDA GRACE BARBER
From tne Psychological Laboratory oj the University oj Texas

INTRODUCTION

The experiments presented in the following paper are intended
as a preliminary study of the white rat's ability to localize
sound. Meyer, Johnson, and Szymanski have also made pre-
liminary studies, of less extent, however, upon other animals.

Meyer's1 problem was to investigate (1) when and how local-
ization appears in mammals and (2) the date of the appearance
of the ability to localize correctly. As a result of his work he
concludes that ability to localize depends upon: (1) mediate
factors of vision, tactual sensations, habit and experience; (2)
the immediate factor of hearing. Furthermore, he says true
localization of the second type (hearing) is a function of binaural
hearing, and mentions the factor of intensity. To test the
above problems, he used humans and various species of animals:
47 human nurslings, 16 older children and 100 animals, 9 of
which were less than a year old. With children he found that
the difference between location of familiar and unfamiliar sounds
seemed to be the essential factor. Six stages in the evolution
of hearing were distinguishable in the human nurslings, com-
parable to the stages in the animals tested. The nurslings
localized sounds as early as 7 weeks, although there was con-
siderable variation. By the end of 6 months, however, prac-
tically all of them localized calls and noises. His work with
animals falls into the following groups, a whistle furnishing
the stimulus: (1) 2 dogs (5 days old) gave no reaction; (2) 1
Samali sheep (8 mo. old), 2 bears (6 mo.), attempted to localize
sound but could not; (3) jaguar (5 mo.), elephant (5 mo.),
leopard (13 mo.), panther-leopard, localized quickly and

1 Meyer, Julius. Die Benutzung der Schalllokalisation zum Nachweis von
Hordiff erenzen ; ihre Verwertung als Simulations-probe. Monat. j. Ohrenhk., bd.
46, S. 1-15. 1912.

— — Weitere Beitrage zur Frage der Schalllokalisation.

Untersuchungen an Siiuglingen und Tieren. Monat. j. Ohrenhk., bd. 46, S. 449-
474. 1912.

292

LOCALIZATION OF SOUND IN THE WHITE RAT 293

accurately; (4) older animals, including lions, tigers, panthers,
hyenas, bears, elephants, antelopes, zebras, sheep, angora goat,
various species of apes, land and water turtles, and 2 serpents,
all localized with varying degrees of accuracy. If the animal
oriented to the sound, Meyer presumed that it was endeavoring
to localize. Meyer has made a table cataloguing the reactions
of all these animals. No very definite conclusions were gained
because of the roughness of the experimentation.

Johnson - and Szymanski3 have each made a few tests on the
localization of sound by dogs. (The latter author has worked
with cats also.) Johnson found that his four dogs learned to
go to the source of sound after from 105 to 165 trials. Szyman-
ski's animals failed after from 21 to 30 (?) trials. (S. attributes
the failure to the small size of the experiment box which measured
9m. by 2.7 m. More probable causes are the small number of
trials given and the pernicious position habits that developed.
Johnson's box was differently constructed. He does not give
its dimensions in detail, but I judge it t© have been 24 ft. by
12 ft. The variations in size in the two boxes are thus negli-
gible.) In each experiment, the stimulus consisted of a sound
(a buzzer with J. and a bell with S.) which could be given in
either of two positions in front of and to either side of the sub-
ject. (4 m. away in S's work, about 10 ft. in J's study.) No
attempt was made in either case to increase the number of
positions in which the sound might appear; and in Johnson's
work little or no attempt was made to determine the cues used
in securing the positive results.

In the present paper, I have been concerned primarily with
the following problems: (1) How accurately will white rats
localize sounds ? (2) To what extent does intensity (both
absolute and relative) determine the accuracy of response ?
The results throw additional light upon several supplementary
problems : sensitivity to tone and the nature of the learning pro-
cess. The study was made at the University of Texas during the
session of 1913-14, under the supervision of Prof. W. S. Hunter.

Notes on Animals Used. Seven rats in all were used during
the experiment. Rats No. 4 and No. 6 (male) were obtained

2 Johnson. H. M. Audition and Habit Formation in the Dog. Behav. Mon.
vol. 2, No. 3, 1913. pp. 46-51.

3 Szvmanski, J. S. Lernversuche bei Hunden und Katzen. Pfluger's Arcliiv.,
bd. 152, 1913.

294

ALDA GRACE BARBER

from a dealer, January, 1913. They were approximately 6
weeks old at the time. Rats No. 19, No. 21 (males) and No. 20,
No. 22, No. 23, (females), reared in this laboratory, were about
2 months old at the time the experiment was begun upon them
(October, 1913.) No. 19 was dropped after the first preliminary
trials upon methods of learning, because the method in^which
it had been trained was discontinued. The older rats were
more deliberate in their movements than the younger.

/ B

.

^\^^

10

»C 1

ii

/3^-"^

X... D

l*~

B'

D'

A

K

3?>

E*

E

lit . 19 . 19

H

H

a ra

F

r

wj

h q.X.

Figure 1. Ground plan of apparatus, a, the stimulus board; b, the main
apparatus box; c, outer triangle; d, inner triangle; e, section
(approximately 2 ins. wide).

APPARATUS AND GENERAL METHOD

A. Apparatus. Apparatus Box — The apparatus in the present
study consisted of an eight-sided box surrounded by a stimulus
board. (See Figs. I & II.) All was made of light wood. The floor
of the box was divided into isosceles triangles, lettered A, B, C,.etc,
in order to facilitate the noting of the positions of the rat. The
sides of the box were divided into 32 sections all of which were

LOCALIZATION OF SOUND IN THE WHITE RAT

295

approximately 2 inches wide with the exception of the corner
ones which were from 3 to 4 inches wide. The stimulus board,
2-1/2 inches away from the main box, was fastened with wooden
pegs to the table. This was done to prevent, as far as possible,
the vibrations from passing through the wood between the
point of sounding the stimulus and the point where the rat
was standing. An opaque screen containing peep holes was
erected about the apparatus in order to conceal the experi-

Figure 2. Entire apparatus in perspective, a, main apparatus box; b, the
stimulus board; c, the table; d, two sides of the screen behind which
the experimenter stood.

menter from the view of the rats. Measurements of the appar-
atus are as follows:

Minimal width of box 22 in.

Length of sides 9-9 1/2 in.

Height of sides (inner) 7 7/8 in.

Distance of stimulus board from box 2 1/2 in.

296 ALDA GRACE BARBER

Length of sides of stimulus board 10 1/2-11 1/2 in.

Width of stimulus board 3 in.

Height of stimulus board from table 3 1/4 in.

The box had inevitable defects. (1) The fact that no release
box was used allowed the rat to wander at will, getting the
stimulus from different angles and positions. No constant
standard head position could be gotten. (2) The reflection of
the sound probably differed as the rat was nearer to the center
or to the side of the box. Finally, (3) the sound might be
diffused along the boards and thus prevent very accurate local-
ization. However, in spite of these defects, the localizations
were quickly and comparatively accurately made.

Various methods suggest themselves by which a relatively
better control of the position of the rat with respect to the
point of origin of the sound could be obtained. This of course
is one important feature necessary for a comparison of animal
experimentations with the human work in the localization of
sound so far accomplished. Perhaps Pawlaw's salivary method
would offer the best solution of the difficulty in tests with such
animals as are suited to the method. The animal's head here
could be fixed in a stationary position during the test. Pre-
sumably, after the association of a definite localization of the
sound stimulus with food had been set up, the animal could
be tested for the accuracy of change of localization in the different
planes. This accuracy would be measured in respect to the
quantity and quality of the flow. Monaural hearing should
be tested here also.

Stimuli — The standard instrument for giving the stimulus (a
tapping upon the stimulus board) was a medium weight chisel,
the tapping of which had a predominant pitch between 256
d. v. and 512 d. v. This was determined by the use of Helm-
holtz resonators. Other stimulus sounds were made by: (1)
tapping upon the stimulus board with the rubber of a lead
pencil; (2) sounding a 256 d. v. tuning fork outside the screen;

(3) giving the interrupted tone, 256 d. v., on an organ pipe;

(4) hissing through the teeth; and (5) tapping with a lead pencil
rubber upon the resonator box of a 256 d. v. fork. In giving
this last stimulus, the resonator box was held in the hand outside
the screen, and was tapped on the upper surface 1/4 of the

LOCALIZATION OF SOUND IN THE WHITE RAT 297

distance from the opened to the closed end or half way between
the open end and the fork. The intensity of the resulting sound
was approximately the same as that made by the pencil (6 1/2
gr. weight) when dropped from the height of three inches upon
the resonator at the same point used in the tapping. Here,
as in the giving of the stimulus, the resonator was held in the
hand. The intensity of the sound of the chisel was roughly
the same, while the intensity of the tapping on the stimulus
board with the lead pencil rubber was approximately equal to
that caused by dropping the pencil above used 'on the resonator
box from a height of one inch only.

The interrupted tone on the organ pipe was given for com-
parison with the interrupted noise produced by tapping. The
stimulus from the fork and the hissing were comparable in that
both were continuous in character. To the experimenter, the
sound of the 256 d. v. fork seemed lower (undoubtedly due to
the absence of overtones) than the tapping upon the 256 d. v.
resonator box although both resounded to the Ut 3 Helmholtz
resonator. The former was also decidedly more characterless.

B. Description of Method — The problem which the present
experiment set the rat was the establishment of an association
between the location of a sound (normally the tapping upon
the stimulus board) and food. The experiment fell into three
periods, which may be characterized as follows: (1) a period
in which the rat was fed inside the box in order to accustom him
to the apparatus and the experimenter; (2) a period of learning
the association between tapping and getting food at the point
of tapping; and (3) a control period in which the determining
cues for the behavior were sought.

The procedure of each trial of the regular tests was as follows:

(1) The position of the rat was noted at the moment of tapping.
This included the direction of his head in respect to the section
tapped as well as the absolute position of his body in the box.

(2) The tapping signal was given on the stimulus board at
the middle of a certain section. This tapping was continued
until the rat stood up at some section on the side of the box. (3)
The path of the rat from his starting point to the standing up
point was noted. (4) Finally, the rat was fed at the section
tapped to which he had to come if he had incorrectly localized
elsewhere. No punishment was given if the rat did not react

298 ALDA GRACE BARBER

correctly, with the possible exception of the fact that he was
consequently delayed a moment or two in being fed. As the
rat was allowed only a nibble of the bread held over the side
of the box, his zest for the work was not impaired during the
8 trials given per day. The records were noted in symbols,
e. g. « A' tq B' C D 16-14. Interpreted, this means that

the rat was standing in the inner triangle, A' (see fig. 1), headed
away from the experimenter (^ ) when the signal was given,
turned quickly (tq), went through triangles B', C, D, standing
up finally at section 16 in D, while the experimenter Was at

section 14.

The accuracy of localization is therefore 2. A regular series
of presentations was used, in which each of the 32 sections of
the box (see fig. 1) was given once every four days while each
side of the box was given once every day. The order was
as follows:

1st day

A

D

B

F

C

H

E

G

1

16

8

21

10

30

19

27

2nd day

B

F

D

H

E

G

C

A

6

23

15

32

17

26

9

4

3rd day

C

H

F

A

D

E

G

B

12

29

22

2

13

18

28

7

4th day

D

A

C

H

F

B

G

E

14 3 11 31 24 5 25 20

The capitals stand for the different sides of the box, and the
numbers for the sections. Daily records were tabulated from
the reactions of each rat by averaging the eight trials. The
results are in terms of error, i. e., of accuracy of localization,
denoting how many sections the rat missed the point of tapping.
The reaction of the rat was considered completed when he
stood up, and no further record was made for that test, regard-
less of subsequent behavior.

After the rat had been trained to a degree of accuracy which
was reasonably constant from day to day, whereby the fact
was established that the animal was localizing something, the
next phase of the problem was considered, viz., was the reaction
an auditory one. To establish this point controls were put in

LOCALIZATION OF SOUND IN THE WHITE RAT 299

which eliminated kinaesthetic, olfactory and visual cues. Then,
since the association still persisted, an effort was made to discover
the auditory factors determining the accuracy of localization.

Several difficulties arise under the present plan of experi-
mentation: (1) the rat, although alert and eager to respond,
has to inhibit its own movements; (2) the tendency is to go in
the direction headed (see fig. 3, below p. 303) ; (3) a reflex recoil
is manifest at unwonted, unexpected noises; (4) flightiness or
unstable attention is present; and (5) no punishment was given
for incorrect responses, a condition which probably lessened
accuracy and quickness of learning. These factors are all of
importance in differentiating animal work from that done on
humans. In addition one should note the difference in recording
judgments in rats and humans, for the latter have only to indicate
the point localized or to respond according to a familiarized
chart, while the former have actually to go to the correct section.

EXPERIMENTAL SECTION

A. The learning of the association — The first question, i. e.,
whether the rat could localize the noise, was quickly answered,
for an accuracy which was not improved in degree throughout
the later part of the experiment was obtained within from 40
to 136 trials, i. e., in from 5 to 17 days. Table 1 shows the
number of trials necessary for each rat to reach the standard
reaction, which was considered achieved when the rat did not
vary markedly in response for several days.

TABLE 1

Rat 6 20 4 21 22 23

No. trials on learning 136 40 136 64 48 48

An interesting observation in connection with this table is
that rats 6, 4 and 21 were males, while rats 20, 22 and 23 were
females. This difference in trials on learning may be due to
chance, or to the fact that rats No. 6 and No. 4 were older
than the others.

Records of the average daily error for rats No. 21, No. 22,
and No. 23, for the first 15 days are in Table II.

300 ALDA GRACE BARBER

TABLE

; ii.

Rats

No. 21

No. 22

No. 23

1st day

3 2/7

6 6/8

6/4/8

2nd day

3 2/8

5

6 4/8

3rd day

3 2/8

4 3/8

4 5/8

4th day

4

4 5/8

4 5/8

5th day

1 4/8

1 5/8

6/8

6th day

1 5/8

3 6/8

5 3/8

7th dav

2 5/8

1

1 2/8

8th day

3

7/8

1 7/8

9th day

1 4/8

2 2/8

1 2/8

10th day

2 7/8

1 6/8

4 6/8

11th day

l (D*

1 1/8 (1)*

2 2/8 (I)*

12th day

3 1/8 (II)*

2 3/8 (II)*

1 4/8 (II)*

13th day

1 5/8 (")*

3 1/8 (II)*

1 4/8 (II)*

14th day

2 4/8

6/8

1 5/8

15th day

6/8 .

1 5/8

1

* On these days controls were put in, but as they did not affect the rats' reactions
the trials were considered standard.

The high average of No. 23 on the 10th day was doubtlessly
caused by the noise in the laboratory resulting from an electric
storm. One bad reaction of No. 22 on the 13th day, accounts
for the high average, for the other reactions were up to standard.
The average for No. 21 on the 12th day can be accounted for
in a similar manner.

Throughout the tests the responses of the rats never became
automatic. If a curve were plotted of these normal responses,
it would show marked irregularities throughout its course.
This, contrasts with the regularity of the ordinary maze co-
ordination in rodents — a motor or kinaesthetic habit.4 Other
investigators working with other problems have noted a similar
irregularity in certain sensory habits. For example Vincent5 in
studying the ability of the white rat to learn the maze problem
when olfactory and visual stimuli had been added and utilized
secured results of this type. Watson6 and Hunter7 point out
a similar lack of automaticity in the maze habits of birds. A

4 Watson, J. B. Kinaesthetic and Organic Sensations. Psych. Rev. Mon., vol.
7, No. 2, 1907.

5 Vincent, S. B. Some Sensory Factors in the Maze. Psych. Bull., vol. 10,
p. 67, 1913.

6 Watson, J. B. The Behavior of Noddy and Sooty Terns. Carneg. Inst. Publ.,
No. 103, 1909.

7 Hunter, W. S. Some Labyrinth Habits of the Domestic Pigeon. Jour Animal
Behav., vol. 1, 1911.

LOCALIZATION OF SOUND IN THE WHITE RAT 301

thorough study of the factors governing these curve differences
has not been made at the present time.

The length of the periods of learning the auditory localization
in our problem are interesting when compared with an exper-
iment on the effect of using food as the stimulus object performed
by Mr. A. C. Scott in this laboratory. He had two problems
for comparison. In one the rats set up an association between
the appearance of a light in one of two boxes and being fed at
a point immediately over the light, i. e., a problem in which
the animal learned to eat the light stimulus, we might say.
This is comparable in every way with our problem in which
the rats "ate the auditory stimulus" in so far as they understood
the problem. The association in Mr. Scott's experiment was
learned in 30 trials, the best of our rats learned in from 40 to
64 trials. In Mr. Scott's second problem, the rats were trained
in the same Yerkes discrimination box to respond to the presence
or absence of light by running in the proper direction through
the box. The food was placed in the rear of the home box from
which they started. This association was learned in not less
than 120 trials. It seems reasonable to conclude, therefore,
that one large factor making for rapid learning in our tests
was the use of the food object for the stimulus. There are two
other possibilities which would need to be seriously considered
in an exhaustive study of this matter. The localization of
sound may be largely an instinctive capacity; or it may be a
capacity which was considerably developed in the ordinary life
of the animal before the present tests were begun.

The learning of the association between source of sound and
getting food fell into four main stages. In the first few trials,
the rats apparently disregarded the auditory stimulus while
seeking for some other cue as a guide. Visual (?) cues were
used predominately, i. e., the appearing of the hand over the
side of the box with food (this occurred only after the rat had
made the reaction of standing up at some point) , and movements
of the screen. Olfactory cues seemed to be sought, for the rat
frequently sniffed in all directions before responding. In the
second stage, an awareness of the tapping was evidenced. This
was indicated by a quick onward start when the stimulus was
given. However, the animal did not seem to realize that this
was a cue to the correct direction of the food, merely that it

302 ALDA GRACE BARBER

was a signal for response. The third stage of the learning was
one in which hesitancy was manifested when the stimulus came.
The rat would turn his head in all direct ons before deciding
in which direction to go. During the rest of the reactions
(embracing the fourth division of the learning of the association)
the attention was placed predominately upon the proper stimulus.
The progress during this stage was an increase in accuracy.
B. Control period — Now that the first question of the problem
has been answered, i. e., can the white rat localize noise, the
other two questions arise: (1) Is this an auditory reaction ?
(2) What factors determine accuracy of response ? Twelve
different control tests were put in to investigate these points.

a. Visual controls — To eliminate visual cues which might
have been gotten from the operator, a screen of black cloth was
fastened around the table, as has been indicated. Furthermore,
the operator constantly stood so that the angle from the section
tapped varied from trial to trial. A conclusive proof that the

' rat was not using the operator as a guide occurred elsewhere,
e. g., in control III. when the sound of a vibrating tuning fork
was used as a stimulus. Here the rat broke down entirely.
If the rat had been reacting to a visual cue or even to any type
of cue from the experimenter, the response wTould have been
as accurate as before.

b. Olfactory control (I) — As the rats frequently stood up and
sniffed in all directions before responding, odor was considered
a possible cue in that food was always held in the experimenter's
hand. Accordingly, small pieces of bread soaked with milk
(the food used as the reward) were laid along the edges of the
box in order to distribute the odor uniformly. The reaction
remained normal. The odor appeared possibly to stimulate the
rats in quickness of response, but no confusion arose. To serve
as a further check, throughout the experiment the food was
held at different angles to the point of stimulation. Final proofs
were : ( 1 ) that the rat would respond accurately when the ex-
perimenter had no food in his hand; and (2) that the reaction
broke down when the auditory stimulus suffered certain changes
as recorded below.

c. Kinaesthetic-tactual control (II) — Another possible guiding
cue was the kinaesthetic-tactual sensation gotten from the
vibrations in the floor of the apparatus box when the stimulus

LOCALIZATION OF SOUND IN THE WHITE RAT 303

was given. This had been eliminated as far as possible by
fastening the stimulus board to the table and not to the main
apparatus box. In control II, a layer of cotton batting 1 in.
thick was placed under the apparatus box in order further to
eliminate vibrations. The resulting responses were at normal
accuracy. A final argument to prove conclusively the non-
essential character of the vibratory cue was found in control
III where the substitute stimulus, a resonator box, was held
in the hand outside the screen. Extraneous vibrations were
here eliminated, yet the reactions were made at a normal accuracy.

The elimination of olfactory, kinaesthetic-tactual and visual
cues indicated that the response of the rat was determined by
auditory factors. The problem now concerned the auditory
factors determining the accuracy of localization. Other aud-
itory timbers and pitches, the interrupted character of the
stimulus and intensity were investigated.

d. Auditory controls — For use in later comparison, a pre-
liminary control (III) was put in. A stimulus noise was found
which was of a predominant pitch 256 d. v., and of an interrupted
character. This was the tapping upon a resonator box with
the pencil rubber as described above in the section on apparatus.
The pitch was determined by Helmholtz resonators. The
intensity has also been described previously, and was approx-
imately equal to that of the chisel which gave the normal stim-
ulus. Thus in this control, we have a predominant pitch 256
d. v., the interrupted character of the sound and the standard
intensity. The reactions, which showed no break from the
normal accuracy, were as follows:

TABLE III

Rat

6

20

4

21

22

23

Normal
Con. Ill
Con. Ill

6/8
3

1 7/8

2 1/8
1 5/8
1 3/8

1 1/2

2 1/4
2 1/8

1 5/8
1 1/8
1 1/4

3 3/8

2 1/8
2 1/2

1 2/8
1 3/8

The three series of averages shown, were secured on three
successive days.

Whether or not the pitch element per se of the standard
stimulus was the fundamental factor in determining the locali-

304 ALDA GRACE BARBER

zation was the next problem (control IV.) The stimulus was
given by striking a tuning fork of 256 d. v., attached to its
resonance box. The open end of the resonator was held at the
given section of the apparatus box. Accuracy averages for this
stimulus are given in table IV. The negative results indicate

*

TABLE IV.

Rat

6

20

4

21

22

23

Normal
Con. IV
Con. IV

6/8
4 5/8
8 5/8

1 5/8
5 3/8

7 3/7

1 6/8
8 3/8
7 6/7

6/8

4 1/2
8 1/4

1 5/8
6 3/8
8 1/8

1

11 1/2
6 1/8

that the mere presence of a given pitch was not guiding the
reactions. But more than this, it would seem either that the
animals are unable to localize pure tone or that they are deaf
(absolutely or relatively) to the one here employed under the
present experimental conditions. In the light of Prof. Hunter's
tests, the latter alternative is undoubtedly the correct one.8 It
is important to note here that a response of some accuracy,
i. e., standing up at some point along the side of the box, was
made by the rats throughout the experimentation regardless
of the nature of the stimulus. Thus our method is not crucial
on cases of mere sensitivity because results are stated solely
in terms of accuracy. Inasmuch as the rats had been taught
that food was over the side of the box, they could not be expected
to remain inactive for any considerable interval of time; and,
in fact, they went from one section of the box to another, stand-
ing up each time. A trial was not considered complete until
the rat had stood up in such a manner.

The most significant data are derived from an observation
of the animals' general behavior during the stimulation. Quick-
ness of response, alertness, head-turnings for localization are
all present when the standard stimulus are given. No attention
was paid to the stimulus in control IV. The animals wandered
indifferently about the box exactly as they always did between
the regular tests. Several times the animals jumped when the
fork was struck; however, there were no indications of an effort

8 Hunter, Walter S. The Auditory Sensitivity of the White Rat. Jour. Animal
Behav., vol. 4, No. 3, 1914.

LOCALIZATION OF SOUND IN THE WHITE RAT 305

to localize during the continuance of the remainder of the stim-
ulus. The same response was made when the fork was dampened
and the thud of striking only was given.

It is worth while noting that the pitch in control IV was the
same as the predominant pitch in control III. The intensities
also were as close to equality as possible. Results9 secured
on the rat's ability to discriminate intensities of tone would
suggest a very poor sensitivity to intensity differences. As a
result of these relations, a further question arises in regard to
the physiological basis for the perception of noise and the per-
ception of tone.10 The fact that a tone 256 d. v. is ignored while
a noise 256 d. v. is reacted to accurately may indicate a separate
basis for the two perceptions (or, as stated above, in the light
of other work it may be due to deafness to tones of a certain
pitch). The problem must be carried much further, of course,
before definite conclusions can be drawn.

(Con. V) In order to test the interrupted character of the
stimulus as a predominant factor in governing accuracy of
response, 256 d. v., on an organ pipe was tooted. Although
this too was of the same pitch as the tapping stimulus in control
III and was a klang and not a simple tone, the accuracy of
response was just as disturbed as with control IV. The responses
seem to have been made by chance, for there was much aimless
wandering and apparently no attention was paid to the sound
in the great majority of cases. The reasons for the breakdown
of the reactions may be either (1) inability to hear the tone
256 d. v. no matter whether simple or complex or (2) the fact
that the stimulus was too different from the standard stimulus
to be recognized. It must be noted, however, that the inter-
rupted character of this stimulus elicited no better response
than the continuous tone of the tuning fork while the tapping
on the resonator box gave normal results. This is again in
strict harmony with the results obtained by Dr. Hunter in his
work (p. 221) on the auditory sensitivity of the white rat above
referred to.

(Con. VI) This control, further questioned the interrupted
character of the stimulus as the primary factor. The stimulus
used was hissing through the teeth, a continuous sound. The

9 Hunter, the last article cited, pp. 219-20.

10 Nagel's Handbuch der Physiol, der Menschen, Bd. 3, S. 585, 1905.

306 ALDA GRACE BARBER

matter was not investigated with sufficient thoroughness to
obtain conclusive results because of lack of time. Four rats
evidently heard the sound and endeavored to locate it, although
their attempts were attended with very poor accuracy. The
sound apparently had no meaning for the other two animals.
The reactions of the first four, fall, in accuracy, between those
of control III and those of control V. It seems evident that
the quality of the stimulus aids in the present localizing response.
Whether the rats can actually localize an interrupted sound more
accurately than a continuous one, I am not prepared to say.
The issue in the present case may have been one of familiarity
vs. unfamiliarity.

Our attention was next directed to the place of intensity
among the essential factors, determining the standard accuracy
of response.

Very loud tapping with the chisel was used to test the effect
of strong absolute intensity (con. VII.) The animals were
startled and nervous, but their reactions were up to the normal
accuracy. A light tapping (con. VIII), was next tried of an
intensity not much more than just perceptible to the experi-
menter. Here the rats moved more slowly than usual, but
maintained an attitude of alert attention. They seemed con-
fused and in doubt, though ready to respond. The stimulus
may have been below the threshold in some cases with each
rat, if the matter is to be judged by aimless wandering during
the giving of the stimulus. The accuracy of response was
slightly decreased.

As absolute intensity, within the range used was not the
essential factor, relative intensity was tested. What we were
striving towards was data which would indicate that the rat's
responses were governed by the relative intensity of the sound
to its two ears. In the first control (IX) a double stimulus
was used, necessitating two operators (Hunter and Barber).
Hunter tapped heavily at the allotted section while Barber
tapped lightly directly opposite. The tapping was always
begun when the rat was half way between Hunter and Barber.
The stimuli were given as nearly at the same moment as possible,
but the louder one was always slightly earlier in that it was
used for a signal for Barber to begin the lighter tapping. Thus,
the difference was measured by the length of Barber's reaction

LOCALIZATION OF SOUND IN THE WHITE RAT

307

time. Results, reckoned in accuracy in respect to the sections
tapped by Hunter, are as follows:

TABLE V.

Rats

20

21

22

23

Normal
Con. IX
Con. IX
Con. IX

. 2 3/8

2 7/10
7/8
1 1/2

2
3

2 10/11

3 6/8

2 7/8

2 11/12
6/8

3 1/2

1 1/2

2 9/11
2 6/8

As a rule the rat went to the heavier tapping, as may be seen
from the results.

The question at once arose whether the first tap did not
direct the rat's localization. Accordingly, a similar control was
installed (X) in which the lighter tapping was begun first, acting
as a guiding signal to Hunter. The control was not entirely
comparable to control IX, however, for in order to insure the
fact that the lesser intensity was perceived, the rat was always
allowed to make a decided start towards the lighter tapping
before the heavier was begun. In spite of this decided advantage
for the lesser intensity, the reaction broke down in accuracy,
i. e., they failed to choose the lesser intensity. This shows
that the mere giving of the sound first by Hunter in control IX
did not determine the response to the heavier tapping. Results
reckoned in accuracy in respect to the sections tapped by Barber,
are given in Table VI.

TABLE VI.

Rats

20

21

22

23

Normal
Con. X
Con. X

2 5/8

8 1/8

11 2/8

1 3/8
7
10

1

8 7/8
10 1/8

7/8

10 7/8

8 5/8

The following reaction is typical of the responses made:

B' on A' A 4 B C D 13 (H 29.) Interpreted, this means
that the rat was in triangle B' (see fig. 1) headed towards the

lesser intensity when the tapping was begun (B'), went on to

308 ALDA GRACE BARBER

A and then hesitated when the heavier tapping was begun
hh

(A), stood up at point of hesitation (4), turned towards the
heavier intensity, and responded accurately to this (D13).
Barber was at H29. The error, which was noted in respect
to the first standing up and not in terms of the final decision
was 7. From these results it is apparent that the first taps do
not determine essentially the final reaction. The table further
makes it clear that the rats went to the loud sound although
headed toward the faint one. This is important when viewed
in the light of the curve in fig. 3 which shows that the rats tended
to go in the direction they were pointing.

A test further questioning the effect of the first few taps
was given in control XI in which alternate tapping was made
the stimulus. Hunter tapped once heavily, and then Barber
tapped once less heavily, etc. The results show that as a whole
the rats chose the stimuli indifferently. However, in two cases
(No. 20 and No. 23) reactions to the heavier tapping predom-
inated. No evidence was obtained that the first tap determined
the point finally localized. A conclusive test of the influence
of the first taps was given by control XII. In this the operator
tapped only three times and then stopped, not continuing until
the rat stood up as in the standard tests. Little of interest
is shown in the results as tabled; however, the experiment was
of importance for the observations made of the rats' reactions.
The rats started as usual for the right point, but then showed
great hesitancy and confusion when the stimulus stopped.
Usually, however, the impetus gotten at first was great enough
to secure a fair accuracy of response. The indications plainly
were that the determination of the general direction of the stim-
ulus was a matter of the first taps, while the accuracy of response
was dependent upon the continued tapping. Evidently the rat
utilized the whole stimulus in making his normal reaction.

Involved necessarily in this question of relative intensity is
the problem of the binaural ratio. In control IX, double stim-
ulus of two intensities, the rat was sideways to each of the
operators at the beginning of the stimulus, but after the first
movement, conditions were changed. Thus, no definite state-
ment can be made in respect to the binaural factor as a cue
throughout the control. A very careful effort was made to

LOCALIZATION OF SOUND IN THE WHITE RAT 309

determine the relative accuracy of the rat during the standard
reactions in regard to the three bodily positions, namely, when
headed towards the operator, when headed away and when
sideways. Many tables and curves were constructed, but no
conclusions bearing upon the ratio in question were reached. (It

If da.y:

Figure 3. Average accuracies per day of rats 21, 22 and 23 showing, a, accuracy

with head pointed away from section tapped, b, accuracy with head pointed

toward section tapped, and, c, accuracy when rat was sideways to the

point of stimulation. A storm occurred at x.

is well in this connection to bear in mind the writer's comments
upon general method made above, pp. 299.) Figure 3 brings
out the not unexpected fact that the rat's greatest accuracy
came when it was oriented toward the source of stimulation.
When the animal was oriented sideways to the stimulus, it
reacted with the next degree of perfection. The least accurate
responses occurred when the animal was headed away from
the stimulus.

C. Tests on Retention — In order to discover the degree of
permanency in the localization-association, memory tests were
made upon the six rats after various intervals in which there
was no training. Rats No. 4 and 6 were tested first after an
interval of 40 days and then after an interval of 38 days. In
each case there was essentially perfect retention. (See table VII.)

TABLE VII.

Rats 4 6

Dec. 18 2 1/2 1 1/2

Jan. 29 4 4/8 1 1/8

Jan. 30 3 6/8 3/8

Mar. 8 2 1/2 2

310 ALDA GRACE BARBER

Rat No. 4 raised his averages, January 29 and 30, by making
three bad reactions each day. The other trials however, were
of normal accuracy. Rats No. 20, 21, 22, 23, were tested after
a rest period of nearly a month (Feb. 11-Mar. 8) Table VIII.

TABLE VIII.

Rats

20

21

22

23

Feb.
Mar.

8
8

3 5/8

2 1/4

1 3/4
3 7/8

1

3 1/8

1

1 1/2

The younger rats, No. 20, 21, 22, 23, seemed less certain of
the correct response than did the older rats, particularly No. 6,
but retention was evidently present. No. 22 broke down on
the first two trials given, making an average of only 5-6 on
the last six. No. 21 seemed indifferent to the stimulus as a
rule, although he made several perfect reactions. The small
number of rats used however will not permit correlation between
age and accuracy of memory. It must be remembered that
although the rats were not tested during the period of rest,
they still had some practice in that they would run to the sides
of the cage when anyone entered the room. This however will
not account for the accuracy manifested in the memory test.

SUMMARY AND CONCLUSIONS

1. The white rat is able to localize a noise with an average
accuracy of from 2 to 4 inches under the conditions of the pre-
sent experiment. This means, of course, 2-4 inches on either
side of the point of stimulation, so that while in a single trial
the accuracy is as just stated, and, let us say, to the right of
the source, the next time it may be an equal distance to the left.
The total space covered is, therefore, from 4 to 8 inches.

2. The association between such an accuracy of localization
and food is established in from 40 to 136 trials.

3. The response is to an auditory cue, for those from vision,
odor and kinaesthetic-tactual sources were eliminated from the
experiment without change in the accuracy of response.

4. The auditory factor which in general determines the accur-
acy of localization is probably the relative intensity of the

LOCALIZATION OF SOUND IN THE WHITE RAT 311

sound to the two ears. Further tests must be made before
this is established beyond question.

5. In control tests, the rats were not only unable to localize
pure tones from tuning forks, but they absolutely ignored them.
The same behavior was manifested toward klangs as sounded
on an organ pipe.

6. A noise of 256 d. v. predominant pitch was localized while
a tone of the same pitch was ignored. This has a bearing upon
the problem of sensitivity to noise with insensitivity to tone,
and with Prof. Hunter's work, it may point to separate bases
for the perception of noise and tone.

7. There is evidence to show that if a rat is trained on an
interrupted noise, it is disturbed in its accuracy of response
by the substitution of a continuous noise. It is impossible to
say at present whether the difference is intrinsic or not.

8. The present localizing-association was retained practically
unimpaired for 40 days during which there was no training.

THE AUDITORY SENSITIVITY OF THE WHITE RAT

WALTER S. HUNTER

The University of Texas

INTRODUCTION

The present paper is a continuation of the research upon the
auditory sensitivity of the white rat reported in volume 4 of
this Journal1. That paper and the present one should be read
in conjunction with an article on the localization of sound in
the rat by Miss Barber2. The three together present a large
array of data upon the sensitivity of the white rat to tones in

X

R

1 1 ^ 1 .. 1 A

Figure 1. (Reprinted from volume 4, page 215, of this Journal.) T shaped
discrimination box. F, food; R, release box; X, tuning fork was held above
this point; A, alley stop, can be placed in either alley; S, switches.

the lower part of the pitch scale. The results have been accumu-
lating since January, 1913, and so far as I can detect are all
consistently opposed to the conclusion that the rats are sen-
sitive to tones of the pitch used. Perhaps I should add "under
the present experimental conditions," but I can see no reason
for doubting that the method employed offered a perfectly fair
test of the rat's ability.

The same apparatus and method were used in the present

1 Hunter, Walter S. The Auditory Sensitivity of the White Rat. Journal
Animal Behavior, vol. 5, no. 4, 1915.

2 Barber, Alda Grace. Localization of Sound in the White Rat. Journal Animal
Behavior, vol. 5„no. 4, 1915.

312

AUDITORY SENSITIVITY OF THE WHITE RAT 313

tests that are described in the earlier account. For the sake
of clearness, it may be well to describe these again. Figure 1
is the T shaped discrimination box. The rat was expected to
associate a turning to the left in order to secure food placed at
F with one stimulus, and the opposite turning with another
stimulus. The forks and whistles of the present tests were
mounted above x. Other stimuli were given just back of the
discrimination box where the experimenter stood. In the present
work, the release box was not used. The animal was placed
in the door at F after the stimulus had been started. Punish-
ment and reward were used with all the rats. Unless otherwise
stated in this paper, the following series of presentations (10
trials daily) were used:

lrllrrrllr The present tests were carried out during the quietest
rlllrrlrrl part of the day under practically ideal conditions so
llrrllrrlr far as extraneous noises were concerned.

rllrrrlllr

EXPERIMENTAL RESULTS

I
Four young untrained rats were tested with the tuning fork
896 d.v. In order to respond correctly in the present test, the
rat should turn through the right pathway when the fork was
sounded and through the left pathway when the fork was not
sounded. 700 trials (70 days) were given; but the rats not
only failed to learn the association, they never improved essen-
tially during the tests. Table 1 gives the number of correct
reactions out of each succeeding fifty of the 700 trials.

Trials

50.
100.
150.
200.
250.
300.
350.
400.
450.
500.
550.
600.
650.
700.

TABLE 1

Rats

29

30

31

32

16

25

23

27

22

26

27

20

24

23

24

25

22

22

17

26

27

22

21

23

24

22

20

23

29

25

27

18

26

27

28

24

26

30

27

27

21

28

18

25

28

25

30

31

25

27

28

26

23

24

27

28

28

27

22

27

314 WALTER S. HUNTER

II
Learning Tuning Fork Chord — Tests were made upon 4 rats
in an attempt to set up an association between turning to the
right and a chord composed of the tones 512 d.v. and 640 d.v.
(both sounded on tuning forks) and between turning to the left
and the absence of the chord. Two of the rats (Nos. 37 and
38) were untrained. The other two (Nos. 31 and 32) had gone
through the tests with the fork 896 d.v. cited above. Table
2 summarizes the results. It will be seen from that that none

TABLE 2

Rats

Trials

31 32 37 38

50 27 30 22 21

100 27 29 26 26

150 26 26 25 23

200 26 26 23 29

250 23 26 23 22

300 22 25 29 25

350 33 31 26 24

400 28 30 21 26

450 35 23 16 19

500 38 31 26 26

550 33 24 24 32

600 31 24 26 27

650 31 31 24 33

of the rats learned the discrimination within the 650 trials
given. During this time there was a slight improvement in
the reactions of numbers 31 and 38; but not in the case of the
other rats. No. 31 ran as high as 76% and No. 38 as high as
66% during a period of 50 trials. Although these rats had
begun the tests with an accuracy of 54% and 60% respectively,
it was deemed advisable to put in controls and attempt to
determine the factors guiding the responses.

Controls — The following controls were used: 1, chord not
sounded. Other conditions as usual. Reaction counted wrong
if it did not fit the series of presentations. 2, end-stops were
placed in each alley as opposed to one alley. The chord was
not sounded. Other conditions as in control 1. Using end-
stops in each alley served to equalize atmospheric conditions
in the two pathways. It appeared to the writer within the
realm of possibility that the rats might be able to detect a fresh-
ness of the air through the open pathway which would not be
present in the closed one. Their behavior was hesitant and

AUDITORY SENSITIVITY OF THE WHITE RAT

315

harmonized a priori with such an hypothesis. As soon as a
rat had chosen the proper pathway, the end-stop on that side
was quickly and noiselessly removed 'so that by the time the
rat reached the alley on the side of the box a free exit was offered
him. 3, no end-stops; no punishment; no chord sounded.
Reactions right when they fit the series of presentations. If
the rat chose wrongly, he was confronted by an open pathway
to the food. In this control, even the punishment due to a
blocked pathway was removed. This and the following control
were used to test the role" of kinaesthetic factors or position
habits. Control 3 sought the character of these habits when
uninfluenced by punishment. 4, conditions the same as in con-
trol 3, save that the electric shock was used when errors occurred
A quick interposition of the end-stop prevented the animal
from reaching, food when it chose the wrong alley. It was
thought that the introduction of such punishments might lead
to changes in the position habit as revealed in control 3. 5, no
end-stops; everything else normal (as in standard learning series.)
The results attending the introduction of the controls are

Nature

of

test

TABLE 3

Number Rats

of

trials 31 32

Con. 1 20

Normal 20

Con. 1 20

Con. 2 20

Con. 3 30

Normal 20

Con. 1 20

Con. 2 20

Con. 2 30

Con. 3 20

Normal 40

Con. 1 10

Con. 4 20

Con. 1 20

Con. 2 40

Normal 50

Con. 1 30

Normal 50

Con. 5 10

Con. 3 20

Con. 1 30

Normal 60

Con. 2.... 20

Records are given in their chronological
in per cents. Rat 37 was not tested.

65%

70%

75%
50%

70%

45%

72%

65%
65%
65%
60%

60%

65%

40%
60%

38

oo70
60%
65%

53%

60%

46%

40%o

52%
68%
63%
74%
80%
65%
66%
70%
60%
order. Correct responses are given

316 WALTER S. HUNTER

given in table 3. The significant fact from the standpoint of
tone sensitivity is that the animals maintained their relatively-
high percentage (60% to 75%) of correct reactions when the
chord was not sounded. This is conclusive proof that the slight
improvement in accuracy found in the learning records in no
way depended upon tone sensitivity. In other words the rats
showed themselves as unable to respond to a fairly complex
klang as to a simple tone.

The remaining controls were not. worked out in detail with
rats 32 and 38. The diary records indicate clearly that the
responses were governed by position habits. Rat 31 was tested
more fully. There are two chief points of interest in the data
secured through these controls, (1) a high percentage of correct
responses can be made on the basis of position (kinaesthetic)
habits even though the series of presentations is" very complex
and cannot be said to be learned; and, (2) simple alternation
seems to be the fundamental position habit. Although data
with control 4 are lamentably lacking, it seems probable, from
reasons given below, that the position habits were affected
by punishment.

Control 2 did not disturb the reactions of rat 32, but did
slightly those of rat 38. Rat 31 was undoubtedly affected by
closing up both alleys. This was not a disturbance due to a
changed visual (brightness) condition in the alleys, because the
relation of the apparatus to the source of light precluded this.
It would seem that normally rat 31, and probably rat 38, was
greatly dependent upon the atmospheric conditions (freshness
and better air circulation) of the two alleys. This is only ad-
vanced as a probability. Tests made directly upon the rat's
ability to discriminate such stimuli offer the only definite ap-
proach to a solution of the question.

Controls 4 and 5 had no effect upon the animals tested. The
poor percentage made by rat 32 with control 4 is to be accounted
for entirely in terms of peculiar position habits. Part of the
time a simple alternation was present; part of the time there
was alternation after a success only. Control 3, by leaving
both alleys of the apparatus open, permitted the rats' position
habits (or kinaesthetic controls) to assert themselves in an un-
modified way. In every case where this control was used, the
rats tended to fall back immediately upon the method of simple

AUDITORY SENSITIVITY OF THE WHITE RAT 317

alternation between the two alleys. For example the series
llrrllrrlr is given and the animal chooses as follows lrlrlrrlr.

The reaction is 70% correct and yet there is only one reversal
(underscored) of the series of alternations. Again the series
rllrrrlllr is given and the rat alternates with no reversal making
60% correct. Another rat given this latter series alternated
regularly save that on the 3rd, 4th and 5th trials he went to
the right hand box. In the regular series (on learning), there
were more reversals and there was also a marked tendency to
reverse after each success only. Inasmuch as this last type of
behavior was not present when punishment and the end-stops
were not used, it seems probable that these factors produced
the behavior by modifying the simple alternation position habit.

The moral of these controls lies in pointing out the necessity
of being on one's guard against complex position habits which
otherwise might be taken as evidence of discriminative ability.

Many tests in comparative psychology which have been in-
tended primarily as tests of discrimination have been vitiated
because they have required the animal to localise the stimulus
in order to give evidence of sensitivity. Hence when negative
results are secured it is not known whether the animal was
insensitive or whether it was simply unable to localize the stim-
ulus. The method adopted in the present tests does not involve
a localization factor (Johnson's work has this merit also.)3
Hence the negative results secured when working with the pure
tones 256 d.v. and 896 d.v. and with the chord 512 d.v. plus
640 d.v. are of great significance.

111

Learning Whistle— Tests were now begun on four . untrained

rats (Nos. 44, 45, 46 and 47) using as a stimulus 3906.17 d.v.
on a Galton whistle. The whistle was held in clamps above
the experiment box where the forks had been and was turned
in such a manner that air currents were not directed downward
upon the animals. It was sounded by blowing (with the ex-
perimenter's mouth) through a long tube. The standard inten-
sity of this tone, when measured with a water manometer, was
secured with a pressure of 16 cm. We may call this whistle,

3 Johnson, H. M. Audition and Habit Formation in the Dog. Behav. Mon.y
vol. 2, no. 3 1913.

318

WALTER S. HUNTER

whistle A. Later during the control tests -another Galton
whistle was used, whistle B. B was a new instrument and was
accepted as standard. Its tonal divisions were lower in pitch
than those of A, so that 3413.3 on A was equaled by 3906.17
on B, using the same air pressure. (These measurements are
very close approximations.) Pitches are always stated in
terms of B.

In these tests the problem set the rat was the associating
of a turn to the right for food with the whistle tone and a turn
to the left for food with the absence of the whistle. 10 trials
daily were given with punishment and reward. The period of
learning plus the control period extended from April 17, 1914
to October 17, 1914.

Table 4 gives the results on learning. Rat 44 was dropped
at the end of 650 trials because of an incurable habit of always
going to the right whether the stimulus was sounded or not.

TABLE 4

Number

of Correct Reactions in

Each Succeeding 50

Rats

44

45

46

47

50

23

21

19

19

100

18

26

21

25

150

28

24

13

22

200

28

32

19

25

250

29

25

14

21

300

28

21

32

28

350

28

26

27

23

400

28

24

33

24

450

29

32

35

23

500

27

27

26

29

550

27

29

28

22

600

32

32

33

39

650......

10

35

34

29

700

35

40

37

750

43

28 of 30 trs.

37

800

39

42

850

41

39

900

36

39

950

46

43

960

10

, .

9

The problem was considered learned by rat 46 at the end of
730 trials, and by rats 45 and 47 at the end of 960 trials. Con-
trols were then instituted.

AUDITORY SENSITIVITY OF THE WHITE RAT 319

Controls — The following is a summary statement of the eleven
controls used in analyzing the animals' reactions:

1. Leave off end-stops. Everything else normal.

2. Do not sound whistle. Everything else normal. Re-
actions correct if they fit the series.

3. Whistle is blown so as to give "rush of air sound" but no
tone. The "rush of air sound" is probably twice as loud as
it is when it accompanies the whistle tone. All else is normal.

4. Make "rush of air sound" with lips. Intensity equal to
that of control 3. Care taken that air currents do not reach rats.

5. Clap hands in place of giving whistle tone. Medium
intensity.

6. Two holes are bored in wall of room. A rubber tube
passes through one from the experimenter to a Galton whistle
placed in the adjoining room. The mouth of the whistle is set
close in front of the second hole with a paper reflector directing
the sound back into the experiment room. The whistle is set
for the tone 3906.17 d.v. and is sounded in place of the whistle
over the apparatus box. Everything else is normal.

7. Whistle over the apparatus box is used at the same in-
tensity as the tone of control 6. The two were matched by
sounding first one and then the other. The pressure in the
water manometer was 4 cm.

8. Fork 1280 d.v. sounded in place of whistle and at a little
more than the intensity of control 7.

9. The whistle over the apparatus box set at 1280 d.v. and
sounded under normal conditions.

10. Fork 1152 d.v. and fork 1280 sounded as a chord in place
of normal whistle tone. Slightly greater intensity than control 8.

11. The whistle used in control 6 was substituted for the
whistle usually sounded over the box. The normal intensity
and pitch were given.

Inasmuch as I regard the full presentation of the records
on these controls as a matter of great importance, tables 5, 6
and 7. are given in the appendix. In these the reader will find
a chronological statement of controls and results for each of
the three rats. Here in the body of the paper, I shall gather
together all of the tests made upon a given control irrespective
of the relative times at which the tests were made.

320

WALTER S. HUNTER

Control 1. — -When the alley-stops were not used the animals
reacted normally.

Control 2. — -All of the rats failed in their reactions when the
whistle was not sounded. This demonstrates clearly that there
was some cue involved in the presentation of the whistle stim-
ulus that determined the reactions. A reference to table 6

Rat 45

20 trials

60% correct

Rat 46

40 trials

52% correct

Rat 47

20 trials

65% correct

(appendix) will reveal the fact that I have not included in No.
46 's record 30 trials secured with this control during which
70% of the reactions were correct. This rat's dependence upon
extra-auditory cues was very temporary. This is indicated by
the fact that only 50% and 60% were made with control 6 just
before and by the further fact that just succeeding the 70%
with control 2 the rat fell back to 55% with the same control.
I do not know what cue was used during that brief period.

Controls 3, 4 and 5. — All of the rats succeeded when the
noise of rushing air was substituted for the whistle tone. One
cannot argue from this that the rats did not hear the tone,
although this is a possibility — in fact a probability when con-
sidered in connection with the other facts here brought together.
Judging from this control alone or in connection with controls
4 and 5, an alternative hypothesis is evident, viz., the rats
reacted to any auditory stimulus which stood out clearly at the
moment of response. An inspection of table 7 (appendix) will

Control 3
Control 4
Control 5

Rat 45
Rat 46
Rat 47

Rat 45
Rat 46
Rat 47

Rat 45
Rat 46
Rat 47

40 trials
40 trials
70 trials

40 trials
30 trials
40 trials

20 trials
50 trials
50 trials

82% correct
82% correct
77% correct

80% correct
86% correct
77% correct

80% correct
80% correct
66% correct

indicate that rat 47 was disturbed slightly at the beginning of
each series of tests with control 3. Each time, however, the
disturbance quickly passed away. There was less disturbance
with control 4. When control 5 was used, there was a complete
breakdown at first ; but later on in an isolated test period of 20
trials, 85% of correct reactions were made.

AUDITORY SENSITIVITY OF THE WHITE RAT 321

Rat 46 (table 6, appendix) was only disturbed with the 5th
control, and this was speedily overcome — raised from 60% to
85%. Rat 45 was not disturbed by either of the three controls.

The net result of these controls is that the rats are able to
respond correctly to two very different noises when these are
given in the place of the standard whistle. So far, then, it is
certain that although the rats were dependent in their reactions
upon the auditory stimulus, this was certainly not of a specific
nature. This is in harmony with the data set forth in the two
companion papers (Hunter and, Barber, above cited). It was
necessary, therefore, to work further in order to show that the
tonal element in the whistle was or was not effective.

Controls 6 and 7. — The only crucial test on the tonal element
that could be made with the whistle depended upon ruling out
any accompanying noise. There was only one method that
was at all feasible. That was to remove the whistle to such a
distance that distance itself would eliminate the extraneous
factors. Such a test can only be suggestive and never conclusive :
(1) It is impossible to tell whether or not the noise has been
eliminated for the rat. (2) Distance not only cuts out the noise,
but also cuts out overtones and lowers the general intensity
of the stimulus. The first is the weighty objection. The second
I believe has little or no weight because: (a) from the work on
chords cited above and to be cited below (control 10), it is
doubtful whether tonal complexity means much for the rat's
reactions ; and (b) control 7 indicates that the lowering of general
intensity is non-effective. This point is made certain for pure
tones, if not for klangs, by (work cited on pp. 219-220 of) the
author's previous paper on the auditory sensitivity of the rat.

Control 6
Control 7

Rat 45
Rat 45

50 trials
70 trials

56%
78%

Control 6
Control 7

Rat 46
Rat 46

90 trials
80 trials

67%
81%

Control 6
Control 7

Rat 47
Rat 47

50 trials
70 trials

60%

71%

The numerical data just given indicate clearly that the rats
broke down for control 6. We have just pointed out the possible
reasons for such behavior, — the most probable one being the
elimination of noise by distance. We must now indicate why

322

WALTER S. HUNTER

rats 45 and 46 were disturbed by control 7 where the normal
whistle stimulus was simply sounded at a less intensity than
usual. When the standard whistle is decreased in intensity
the change is much the same as occurs when the whistle is taken
to a distance, i. e., the noise accompanying the whistle is de-
creased in intensity if not eliminated and similar changes most
probably occur among the overtones. Therefore, even from an
a priori standpoint, one need not be surprised that the reactions
with control 7 were of less than normal accuracy. The import-
ant fact is that they were significantly better than the reactions
with control 6. Inasmuch as the stimuli in the two controls,
were, for the experimenter, extremely similar in respect to in-
tensity magnitude, it seems most probable that the rats were
governed in their responses by the noise usually accompanying
the whistle tone. There is no evidence that the animals heard
the stimulus in control 6.

Controls 8 and 9. — In a previous experiment rats that had
been trained to respond to the noise of handclapping were unable
to make discriminative responses when tones were substituted
for the standard stimulus, although the substitution of other
noises was attended by positive results. The same facts appear
here with the piston whistle tests. It will be seen from the

Control 8
Control 9

Rat 45
Rat 45

70 trials
20 trials

60% correct
90% correct

Control 8
Control 9

Rat 46
Rat 46

70 trials
20 trials

61% correct
85 % correct

Control 8
Control 9

Rat 47
Rat 47

80 trials
20 trials

60%, correct
85% correct

numerical summary here given that all of the rats failed un-
qualifiedly to respond in control 8 to the tuning fork 1280 d.v.
Rat 46's percentage for control 8 would be only 54, if 20 trials
were ruled out when the animal was responding to extra-auditory
cues. (See above page 290, and appendix table 6.)

There was no tuning fork available whose vibration rate was
at or above 2000 d.v. It was therefore impossible to use a fork
of a pitch equal to the standard whistle. However, the next
best thing was done. The whistle pitch was lowered in control
9 to the pitch of the fork used in control 8 (1280 d.v.). The
data given above indicate that the rats reacted as well to this

AUDITORY SENSITIVITY OF THE WHITE RAT 323

whistle pitch as to the standard in spite of the fact that only-
failure attended the use of the tuning fork.

Control 10. — The difference in the results obtained in controls
8 and 9 may have been due to differences in the complexities
of the stimuli. This is true although long tests were made
(as described above) in a fruitless endeavour to set up a dis-
criminative reaction to a common chord, 512 d.v. plus 640 d.v.
In the present control the chord 1152 d.v. plus 1280 d.v. was
sounded on forks in place of using the standard whistle. The
animals again failed in their reactions. If, in spite of the fact
that the results of my experiments indicate that differences in
tonal complexity are not utilized, later studies should show that
my tests did not offer complex enough klangs, they will be very
interesting in establishing a threshold for tonal sensitivity on
the basis of tonal complexity.

Rat 45

50 trials

66%

Rat 46

40 trials

57%

Rat 47

40 trials

57%

Control 11. — This control was introduced to supplement con-
trols 6 and 7. In order to rule out the possibility that the data
there obtained were due to intrinsic differences in the whistles,
the one used in control 6 was placed over the apparatus in place
of the standard whistle and was sounded at the intensity of
control 7. Rat 47 was not tested, but the other two made 90%
and above. It may be concluded from this that for the rat
no intrinsic differences in the whistles were functionally effective.

IV

In instituting and continuing the series of tests with piston
whistles as just set forth, the writer was influenced by two
principle motives: (1) Uniform failure had waited upon all of
the work with tuning forks. It was hoped that with the whistle
positive data might be secured whose analysis would throw
light upon the problem of tone sensitivity. (2) It has been
suggested recently, notably by Yerkes, that where a difficult
discrimination is required of an animal, training should first
begin with a complex easily discriminable and gradually be
directed toward the aspect upon whose presence the problem
centers. When the present whistle tests had been begun pri-

324 . WALTER S. HUNTER

marily with the first intention, it was thought advisable to
extend them in the light of the second.

In the work published in volume 4 of this Journal, rats that
had responded to noise by turning to the left were later given
from 350 to 520 trials in an endeavour to force them to turn
to the right for the tone 256 d.v. sounded on the fork. No one
of the rats showed improvement during this interval.

In the present instance rats 45, 46 and 47 had been trained
to react successfully to the whistle by turning to the right.
They were then given a series of tests with the tuning fork
256 d.v. in an attempt to train them to turn to the right for the
fork tone also. A new series of presentations was employed
as follows :

rllrrrllrl Three hundred trials were given; but there was no
rrlrllrllr improvement in the reactions from first to last. The
lrrlrrlrll following table is a summary of this fact. These re-
Urlrrlrlr suits lend further indirect confirmation to the con-
clusion drawn above that the rats were depending upon noise

TABLE 5
Trials

Rats

45 46 47

50 25 28 27

100 26 32 28

150 29 28 28

200 29 28 27

250 25 23 27

300 27 31 31

in the whistle complex and not upon tone. The present results
are also very striking when we compare them with the rat's
ability to react to noises which are very dissimilar, from the
experimenter's point of view, to those with which it has been
trained. To quote from the previous paper, pages 221-222,
"All of the tones given were for some reason very different

from the noises Inasmuch as the animals reacted

in the same manner to all of the noises, it is certainly a striking
fact that none of the tonal stimuli given were classed as noises."

V

Retention Tests. — Forty-one days (for rats 46 and 47) and
45 days (for rat 45) after the tests on control 11 for rats 45 and

AUDITORY SENSITIVITY OF THE WHITE RAT 325

46 and on control 7 for rat 47, the animals were again tested on
their ability to turn to the right for the whistle tone. During
the interim, the work just described on the fork 256 d.v. was
carried on. Whether this could have affected the retention will
depend upon the rat's sensitivity to the tone in question. If
he can hear the tone, there should at least be no decline in the
accuracy of response due to the training on the fork. If, how-
ever, he cannot hear the tone, the training upon turning to the
right for the fork will tend to break down the normal reaction
of turning to the right for the whistle. The results show a
decrease in accuracy of response for two rats. Rat 47 reacted
normally. These results may be due either to the effect of
time intervals or to habit interference.

Rat 45 Rat 46 Rat 47

Normal, 90% of 10 trs.
Control 11, 90% of 20 trs. Control 11, 100% of 20 trs. Control 7, 80% of 10 trs.

Retention tests; per cent correct of 50 trials given
72% 76% 80%

VI

The most significant data secured in the work upon the audi-
tory capacity of the white rat may be summarized as follows,
(data are here mentioned which were included in the author's
previous paper and in Miss Barber's work.) :

A. Crucial Evidence Upon Tone Sensitivity:

(1) The tone 256 d.v. sounded on the tuning fork was not
discriminated: (a) by 6 untrained rats after 700 trials, (b) after
700 trials, by one rat that had learned to react to hand clapping
within 400 trials; (c) after 350, 410 and 520 trials respectively
by three rats that had been trained previously to respond to
hand claps; (d) after 300 trials by 3 rats that had been trained
to respond to a whistle.

(2) The tone 896 d.v. sounded on a tuning fork was not
discriminated by 4 untrained rats after 700 trials.

(3) The chord 512 d.v. plus 640 d.v. sounded on forks was
not discriminated; (a) by 2 untrained rats after 650 trials; and
(b) after 650 trials by 2 rats that had been trained upon the

326 WALTER S. HUNTER

tone 896 d.v. If we count the difference between that tone
and the present chord as sub-limnal, these 2 rats were given
1350 trials with no evidence of discrimination.
B. Evidence Bearing Upon Tone Sensitivity Which While Not
In Itself Crucial Is Yet Of The Greatest Significance:

(1) Four rats trained to react to a whistle tone of 3906.17
d.v. would not react to a tuning fork chord (1152 d.v. plus 1280
d.v.), or to the fork 1280 d.v. when these were each substituted
for the standard stimulus. When a whistle of the same pitch
was sounded in an adjoining room so that distance probably
eliminated the noise factor, the rats failed; although they made
a significantly larger per cent of correct reactions when the
standard stimulus was decreased in intensity to match the in-
tensity of the distant whistle.

Further these same rats reacted properly when either of the
following noises were substituted for the standard whistle; (a)
the rush of air through the whistle; (b) sound of "rush of air"
made with lips; and (c) clapping of hands. The rats reacted
successfully to 1280 d.v. on the standard whistle but failed when
the same pitch was sounded on a tuning fork.

(2) Three rats trained to react to hand clapping reacted
successfully to the following noises when these were substituted:
rattling of paper, dropping sunflower seed on tin, scratching
on wood, drumming on the table with the fingers, rubbing two
pieces of board together, hissing through the teeth, and rattling
nails in a glass. These rats failed when the following tones were
sounded in place of the hand claps: (a) 1024 d.v. on fork; (b)
256 d.v. on organ pipe sounded steadily; (c) b sounded in toots;
(d) 1024 d.v. sounded steadily on organ pipe; (e) d sounded
in toots; and (f) 341.3 d.v. on the organ pipe sounded steadily.

(3) Six untrained rats failed (after from 575-800 trials) to
discriminate a very intense from a very faint sounding of the
fork 256 d.v.

(4) Rats trained to localize a tapping noise ignored: the
fork 256 d.v.; and the same pitch tooted upon an organ pipe.
They responded to a noise made by tapping with the rubber
end of a lead pencil upon the resonator box of the fork 256 d.v.
This gave an interrupted noise of the same predominant pitch
as the fork.

AUDITORY SENSITIVITY OF THE WHITE RAT

327

CONCLUSIONS

(1) There is a practical insensitivity to many pitches in
the lower region of the scale for the white rat. This apparently
goes along with a sensitivity to noises of the same predominant
pitch.

(2) Differences in tonal complexity and intensity may be
considerable without making discrimination possible.

(3) Apparent reactions to tone are most probably made to
accompanying noises.

(4) If, after all, there is a sensitivity to tonal stimuli as
here tested, then, for the rat, tones and noises are very different
classes of stimuli.

APPENDIX

Chronological statement of controls used with rats in whistle
tests.

TABLE 5

Rat 45

Nature of

Per cenl

test

Trials

correct

Con. 1

10

90

Con. 2

20

60

20

90

Con. 3

20

80

Normal

10

100

Con. 4

20

80

Normal

60

83

Con. 6

10

60

Con. 7

20

85

Normal

10

100

Con. 6

10

60

Con. 8

10

50

Con. 7

10

80

Con. 8

10

50

Con. 6

10

50

30

83

Con. 9

10

90

Con. 8

20

70

Con. 10

50

66

20

95

Con. 8

20

60

Con. 3

20

85

Con. 4

20

80

Con. 5

20

80

Con. 6

20

55

Con. 7

40

75

Con. 11

20

90

328

WALTER S. HUNTER

TABLE 6

Rat 46

Nature of

Per cent

test

Trials

correct

Con. 1

20

90

Con. 2

10

50

Normal

40

77

Con. 2

10

50

Con. 1

10

80

Con. 3

10

70

70

63

last 40

100

10

100

Con. 4

10

100

10

60

Normal

30

90

20

85

10

60

Con. 7

10

50

Normal

10

100

Con. 6

20

75

Con. 7

20

85

10

50

Con. 7

10

80

10

60

Con. 7

10

100

Con. 8.......

20

80*

Con. 2

10

100*

Con. 2

20

70*

Normal

10

80*

Con. 2

20

55*

Con. 8

10

60

Con. 8

20

50

Normal

20

90

Con. 9

20

85

Con. 10

40

57

20

95

Con. 8

20

55

Con. 3

20

80

Con. 4

20

80

Con .5

20

85

40

72

Con. 7

30

83

Con. 11

20

100

* For comments upon these controls see body of text.

AUDITORY SENSITIVITY OF THE WHITE RAT

32^

TABLE 7

Rat 47

Nature of

Per cent

test

Trials

correct

Con. 1

10

80

Con. 2

20

65

Normal

20

90

Con. 3

20

60

Con. 3

20

95

Normal

10

90

Con. 4

10

60

Con. 4

20

85

Con. 6

10

60

Con. 7

10

50

Con. 6

10

60

Con. 7

10

50

Normal

20

80

Con. 7

10

60

Con. 5

10

50

Con. 5

20

55

Normal

20

85

Con. 9

10

90

Con. 8

10

60

Con. 9

10

80

Con. 8

10

60

Con. 10

20

60

Con. 8

10

50

Normal

20

80

Con. 10

20

55

Con. 8

50

62

Con. 3

10

76

Con. 3

20

85

Con. 4

10

80

Con. 5

20

85

Con. 6

30

60

Con. 7

20

100

Normal

20

95

Con. 7

10

60

Normal

10

50

Normal

10

90

Con. 7

10

80

THE RELATION OF STRENGTH OF STIMULUS TO
RAPIDITY OF HABIT-FORMATION IN THE KITTEN

J. D. DODSON

Central College, Pella, Iowa

For this study of the relation of strength of stimulus to rapidity
of learning I have used the method which Yerkes and I found
satisfactory in our similar study of the dancing mouse.1 But
instead of requiring the kitten to choose between white and
black, as in the case of the mouse, I required it to discriminate
between light and dark — that is the kitten had to choose in
the Tight-dark series instead of the white-black series. Irre-
spective of the relative positions of the two boxes the subject
had to choose the light one. Should the kitten enter the dark
box it received an electric shock, and was never allowed to
escape by passing through the same.

The apparatus was very much the same as that used with
the dancer (for general construction see figures 1 and 2, page
460, of the article referred to above). The experiment box
was divided into a nest box, an entrance chamber and two
electric boxes. The entrances and exits to the electric boxes
were 9 by 9 cm. each. The electric boxes were placed in the
circuit of a constant electric current. In this circuit was a
double key by which the experimenter could direct the current
through either box he might wish. The inductorium and re-
sistance coil were placed in an adjoining room thus eliminating
all the noise of the constant buzz of the inductorium. The
current was furnished by a storage battery which was kept
constant at a voltage of 19.5 and amperage of 4. To govern
the amount of light entering the electric boxes, the entire end
of the experiment box containing the electric boxes was covered,
and two openings cut in the cover, one directly over each electric
box. In order to prevent the kitten from seeing the opening
in this cover as it entered the electric box, a platform 25 cm.
wide was placed 12 cm. from the top of the box and directly

1 Jour, of Comp. Neurol, and Psy., 1908, 18, 459-482.

330

RAPIDITY OF HABIT-FORMATION IN THE KITTEN 331

over the wires. The experimenter determined which electric
box should be light and which should be dark by placing a cover
over one of the openings. The cardboard cover was shifted
in the same order as in the experiment with the dancer (table
1, page 461).

The kitten was placed in the nest box by the experimenter
and a plain glass cover put over the box to prevent the kitten's
climbing out at the top. The only way left for the animal to
escape was to pass through an opening into the entrance chamber
and thence through the electric box and out at an exit at the
rear of the experiment box. A mirror was placed so that the
experimenter could see the kitten without the kitten's seeing
the experimenter. The play instinct caused the kitten to be
very restless and, thus, it soon attempted to make its escape.
If it chose the light box it was allowed to pass through undis-
turbed; but should it choose the dark one it received an electric
shock. This shock usually caused a hasty retreat, but should
the animal attempt to pass on over the wires the experimenter
forced it to return into the entrance chamber not allowing it
to escape through the dark box.

Each of the 18 kittens used was given ten tests each day until
it succeeded in choosing the light box correctly for three con-
secutive days. If the kitten should enter far enough into the
dark box to receive a shock it was recorded as a mistake but
in order for the trial to be counted a test the kitten must escape
from the box. The principal motives for the kitten's escape
were the instinct of play and the gregarious instinct. The
animals were given their usual meals during the day, but I
always fed them at the close of the experiment.

Each kitten was just six weeks old when I began to train it.
All were of the same stock of cats. I conducted three sets of
experiments. First set was done with the condition of visual
discrimination rather difficult, using a medium and relatively
strong stimuli. For the second set the condition of discrimi-
nation was less difficult. For the third set the condition of
visual discrimination was fairly easy.

At the beginning of the training of a set of kittens I allowed
each one to pass through the electric boxes a number of times
without turning the electric current in either box. This was
to teach the kitten that there was a way out of the box and also

332 J. D. DODSON

to tend to establish in the animal the habit of escaping. During
this preliminary work I shifted the cardboard from side to side
to determine whether or not the kitten had any preference for
the light or dark box and found no preference shown.

The difference in the amount of light entering the two electric
boxes was that which would pass through an opening in the cover
23.5 by 13 cm. Of this opening 16 by 13 cm. was over the plat-
form which was 12 cm.' below the top of the box. For the
medium stimulus a current with a voltage of 19.5 and an am-
perage of 2.5 was run through an inductorium with a coil set
3.6 cm. from the closed end. For the strong stimulus a
current was used with the voltage and the inductorium the
same as for the medium stimulus but the amperage was 3.5.

Results of experiments of set 1. Tables 1 and 2 show detailed
results of set 1 . At the top of each table are given the numbers
of the kittens which were used under the conditions named
in the heading of the table. The first column gives the number
series; the other columns give the number of errors and the
average of errors made by male and female and also the general
average; while the last line gives the total number of trials
and their average for perfecting the habit.

TABLE 1

The Results of Experiments of Set I, Medium Stimulus

(Volt. 19.5, Amp. 2.5)

Males Females

General

Series No. 1 No. 5 Average No. 2 No. 6 Average Average

1 6 4 5 7 4 5.5 5.25

2 2 2 2 2 3 2.5 2.25

3 4 2 3 6 4 5 4

4 4 2 3 4 3 3.5 3.25

5 13 2 1 2 1.5 1.75

6 0 4 2 1 2 1.5 1.75

7 1 1 1 0 2 1 1

8 11 1 1 2 1.5 1.25

9 0 0 0 0 3 1.5 0.75

10 0 0 0 0 0 0 0

11 0 0 0 0 0 0 0'

12 0 0 0

Total No. of trials. .. . 80 80 80 80 90 85 82.5

RAPIDITY OF HABIT-FORMATION IN THE KITTEN

333

TABLE 2

The Results of Experiments of Set I, Strong Stimulus

(Volt* . 19.5, Amp. 3.5)

Males Females

Series No. 3 No. 7 Average No. 4 No. 8 Average

1 6 4 5 5 4 4.5

2 5 3 4 4 4 4

3 2 3 2.5 4 4 4

4 4 3 3.5 4 2 3

5 7 2 4.5 2 3 2.5

6 3 2 2.5 3 4 3.5

7 2 2 2 2 4 3

8 1 2 1.5 1 4 2.5

9 0 4 2 13 2

10 2 1 1.5 0 1 0.5

11 0 0 0 0 3 1.5

12 0 2 1 0 2 1

13 0 0 0 0 0

14 0 0 0 0

15 0 0 0 0

Total No. of trials.... 100 120 110 90 120 105

General
Average

4.75

4

3.25

3.25

3.5

3

2.5

2

2

1

0.75

1

0

0

0

107.5

Special conditions of set 11. The visual discrimination was
made less difficult by putting a cover over 15 by 40 cm, of the
nest box and by cutting out the openings over the electric boxes
until they were 36 by 13 cm. instead of 23.5 by 13 cm. The
strengths of stimuli were the same as in set 1, but only two
kittens were used for each strength.

TABLE 3

The Results of Experiments of Set II, Medium Stimulus

(Volt. 19.5, Amp. 2.5)

Male,

Female,

Series

No. 9

No. 10

Average

1

5

5

5

2

4

5

4.5

3...,

4

2

3

4...'

3

2

2.5

5

2

1

1.5

6

1

1

1

7

0

0

0

8

0

0

0

9

0

0

0

Total number of trials

60

60

60

334 J. D. DODSON

TABLE 4

Results of Experiments of Set II, Strong Stimulus

(Volt. 19.5, Amp. 3.5)

Male,

Female,

Series

No. 11

No. 12

Average

1

4

6

5

2

4

2

3

3

3

4

3.5

4 :

3

2

2.5

5

3

1

2

6

2

0

1

7

0

0

0

8

0

0

0

9

0

0

Total number of tests

60

50

55

Special conditions of set III. The nest box and entrance
chamber were lined with black cardboard and the electric boxes
were lined with white. The openings over the electric boxes
were cut out till they were 40 by 18 cm. and the nest box and
entrance, chamber were covered with cardboard all but an open-
ing 20 by 40 cm. Thus the condition of visual discrimination
was made fairly easy. The stimuli used were the same as in
the previous experiments, but with one additional stimulus.

TABLE 5

rs of Experiments Set III,

Stimulus Weak (Volt 19.5, Am

Male,

Female,

Series

No. 13

No. 14

Average

1

5

6

5.5

2

5

4

4.5

3

4

4

4

4

3

2

2.5

5

2

3

2.5

6

3

2

2.5

7

1

1

1

8

1

0

0.5

9

0

0

0

10

0

0

0

11

0

0

Total number of trials. .

80

70

75

RAPIDITY OF HABIT-FORMATION IN THE KITTEN 335

TABLE 6

Results of Experiments of Set III, Stimulus Medium

(Volt. 19.5, Amp. 2.5)

Male,

Female,

Series

No. 15

No. 16

Average

1

4

6

5

2

5

4

4.5

3

4

4

3.5

4

4

2

3

5

3

2

2.5

6

0

0

0

7

0

0

0

8

0

0

0

Total number of trials

50

50

50

TABLE 7

Results of Experiments of Set III, Stimulus Strong

(Volt. 19.5, Amp. 3.5)

Male,

Female,

Series

No. 17

No. 18

Average

1

5

4

4.5

2

4

3

3.5

3

1

1

1

4

0

1

0.5

5

0

0

0

6

0

0

0

7

0

0

0

Total number of trials

30

40

35

Possibly no one realizes more fully than the experimenter
certain crudities of method in this experiment, but still there
are some things of interest to the animal psychologist. And
if any conclusions may be drawn from the use of so few animals
those conclusions are in accord with previous findings in the
dancer.

Conclusions. 1. The rapidity with which kittens acquire the
habit of always choosing the light box may be seen from the
following results: Under fairly difficult conditions of learning,
with a medium stimulus it took on the average 82.5 trials for
the kitten to perfect a correct habit, and with a strong stimulus
107.5 trials; under less difficult conditions it took 60 trials with
a medium stimulus, and 55 trials with a strong stimulus; and
under fairly easy conditions it took 75 trials with a weak stim-

336 J. D. DODSON

ulus, 50 trials with a medium stimulus, and 35 trials with a
strong stimulus.

2. The relation of the painfulness of the electrical stimulus
to the rapidity of habit formation depends upon the difficultness
of the visual discrimination.

3. When the discrimination is difficult the medium strength
of stimulus was found to be the more favorable to habit formation ;
but when the discrimination is less difficult the difference between
the unpleasant and the very unpleasant stimuli is not marked.
When the discrimination is. easy the rapidity of habit formation
increases as the unpleasantness of the stimuli is made greater,
at least within certain limits.

NOTES
THE MATING OF LASIUS NIGER L.

, C. H. TURNER
Sumner High School, St. Louis, Mo.

It was three o'clock on the afternoon of September the seven-
teenth, 1913. For two days we had been having frequent
showers; even then, although the sun was shining brightly,
there were numerous clouds in the sky, any one of which, with-
out a moment's notice, might float before the sun. The temper-
ature was only 78 degrees Fahrenheit; but, compared with the
73 degrees of the afternoon of the sixteenth and with the 63
degrees of the afternoon of the fifteenth, it seemed quite warm.
The numerous nests of the ant Lasius Niger L., which had long
existed, unnoticed, beneath the pavements and in the vacant
lots of St. Louis, had suddenly been rendered conspicuous by
the restless myriads of gigantic virgin females, miniature males,
and small workers that were swarming from them and forming
agitated masses of ants about each entrance.

On viewing this periodically repeated phenomenon one is
tempted to assume that the ants have suddenly become nega-
tively geotactic and positively phototactic; and this hypothesis
is strengthened by the fact that, on the evenings following such
an occasion, females of the species may be captured at the
street lights. It may have been a negative geotropism, it cer-
tainly was not a positive phototropism which urged the ants
from the nest; for the sunlight does not penetrate into the nests.
A prolonged and careful observation of the virgin females and
neuters of a nest situated at the foot of a large grape-vine re-
vealed conditions that do not harmonize with so simple an
explanation. If the behavior of these ants were wholly a nega-
tive geotropism, or a positive phototropism, or a combination
of both, then they should have climbed ever upward until the
tips of the twigs were reached; but, that is not the way they
behaved. Along the lower four feet of that vine the females

337

338 C. H. TURNER

and neuters were constantly ascending and descending. To
watch the agitated promenading of these restless ants up and
down the stem, was to be convinced that these activities of the
unmated females and of the neuters were not merely a tropism.
Evidently the physiological changes caused by the maturing of
the sexual powers had initiated a restless meandering.

I am not certain how the behavior of the males should be
interpreted. The leaves of the grapevine and the tops of other
uprights were black with them. The stem of the vine supported
countless numbers of them; but my attention was so completely
concentrated upon the movements of the females and neuters
that I did not notice whether the males were moving ever up-
wards or to and fro.

The concentration of attention upon the virgin females was
for the purpose of observing every detail of their mating behavior.
Several females were watched from the time they left the nest
until they flew away. Both on the ground and on the grapevine,
they roamed in and out among the males, jostling them to the
right and to the left, without stimulating the least response.
One is warranted, then, in concluding, with previous writers,
that the mating of this species does not occur, normally, either
on the ground or on some support.

While watching the females promenade to and fro upon the
grapevine, numerous males and a few females flew away from
the nest. When I had fully satisfied myself that mating occurred
neither 'on the ground nor on a support, I arose and looked about
me. For fifteen to twenty feet above the ground, the air was
thick with the minute, gnat-like, males of this species. Not
only the atmosphere above my yard, but that above all of the
yards of the vicinity was alive with these miniature creatures,
for the males of all of the Lasius nests of the city were having
an aerial dance. They rose and fell, swerved to first one side and
then to the other, occasionally they alighted on the ground,
and, after a short rest, unless captured by the foraging ants
of another genera, arose and repeated over and over again the
maneuvers — thus they performed the prenuptial dance of the
species, and all of the participants were males.

From time to time lone virgin females appeared in the midst
of the dancing bachelors. Starting near the ground, such a
female would corkscrew upwards, sometimes vertically, some-

THE MATING OF LASIUS NIGER L. 339

times obliquely, and disappear above the two-story houses.
Some of these females caused no disturbance of the dance;
others attracted towards them one or more of the participants
which accompanied them beyond the range of human eyes.
Somewhere in the air mating would occur and the female, no
longer a virgin, would return to earth. I did not have the
pleasure of observing a pair at the moment of copulation; but
I captured several of the brides as they descended; each with
her miniature husband attached, appendage like, to the tip
of her abdomen.

The altered appearance caused by the clinging of the male,
made it easy to recognize a newly mated female afar off. Several
were followed until they settled on the plants of my garden.
After alighting and before the male had detached himself, the
female, by means of vigorous strokes of her third pair of legs,
would break off the wings of first one side and then of the other.
These wings were for the honey-moon flight; since the females
of this species mate but once in a life time, they were cast aside
as useless encumbrances. Those wings were badges of virginity;
now that she had become a matron, she discarded those emblems
of maidenhood.

What a feast these marriage festivities furnished the insect-
feeding ants of the community! Around the outskirts of each
band of excited ants, Formica scouts were capturing the male
stragglers and dragging them alive to their nests. All over the
ground beneath the dancing males, active foragers of these
same species of Formica were capturing such ants as happened
to fall to the earth. Even the large females became prey of
these alert ants. Often two and even three ants were observed
dragging off the same female.

At the beginning of these observations, the sun was shining
brightly; later the clouds became so thick that not a ray of sun-
light could reach the earth. The prenuptial dance and the
mating continued, in both sunshine and shadow, until about
the close of day. Then the dancers gradually vanished until
all 'that remained of the countless multitudes were a few strag-
gling males and an occasional female. Even after the last of
these males had disappeared, an occasional lone female would
corkscrew upwards through the air. Poor belated virgins! Too
late to perform the mission of their sex! Some, if not all, haunt-

340 C. H. TURNER

ed the street lights of the city for a night or two ; but the oppor-
tunity to become mothers had passed forever. The wedding
festivities of Lasius niger had closed for the season. No new
festivities could be inaugurated until, in some way not under-
stood, the physiological and meteorological factors had stimu-
lated a future generation of ant maidens and ant bachelors
to wed.

JOURNAL OF ANIMAL BEHAVIOR

Vol. 5 SEPTEMBER-OCTOBER No. 5

THE BEHAVIOR OF FUNDULUS, WITH ESPECIAL

REFERENCE TO OVERLAND ESCAPE FROM

TIDE-POOLS AND LOCOMOTION ON LAND.'

S. O. MAST
From the Zoological Laboratory of the Johns Hopkins University

It is difficult for one not familiar with life in the sea to realize
what a fierce struggle for existence many of the smaller fishes
have to wage. Our common minnows, e. g. Fundulus, are beset
on every side with danger. They are continuously hunted from
below by many predaceous fishes and from above by various
sea-birds. For these creatures the price of existence is indeed
eternal vigilance. Owing to this price, no doubt, they are among
the most wary of fishes. The least disturbance in the water
from below or merely an approaching shadow from above sends
them scurrying for places of safety.

For purposes of protection they are usually found in shallow
water very near the shore-line. As the tide rises they contin-
uously follow the water inland keeping quite" near the edge,
and as it ebbs they follow it out again. On the newly covered
bottom they are frequently seen rooting in the sand, apparently
feeding. Thus the movement in harmony with the tide pro-
bably serves them in securing food as well as in protection
against enemies. But in following the tide aquatic animals
are also exposed to clanger, for with the incoming tide they
are often directed into depressions in the beach which are of
such a nature as to hold water for a considerable time after
the tide recedes but not until it rises again. To linger at the
shore-line in these pools waiting for the water to recede would
mean certain death to most aquatic animals. How does it
happen that Fundulus, which is so frequently found in such

1 Published by permission of the Commissioner of Fisheries.

342 S. O. MAST

pools, and ordinarily does remain at the water's edge is rarely
if ever caught in them.2 It was this question that inspired the
following experimental observations, all of which were made
during the summer of 1914 on a sand beach at Beaufort, N. C.

I shall first give in a general way the results of these obser-
vations, all of which were repeated a considerable number of
times; then I shall present a few experiments in some detail.

If Fundulus gets into a tide-pool while the tide is rising it
usually swims about in a deliberate sort of way, stopping here
and there to root in the sand and to play with its companions.
This behavior continues until the tide turns or at any rate
until it is very nearly high. After that the animals may still
swim about much as they did before, but they invariably, every
few moments, return to the outlet of the pool and swim out and
in again. Thus they continue to test the depth of the water
in the outlet, and as soon as it gets too shallow they leave the
pool and do not return. This accounts for the fact that they
are not caught in these pools under ordinary circumstances.

But what interested me primarily was the behavior observed
in pools in which the outlet had been closed before the fishes
had escaped. Under such conditions it was found that the
behavior depends very largely upon whether the water is running
in or out of the pool at the time it is closed.

If the water is running in, nothing phenomenal occurs. The
animals may swim about rather rapidly for a few moments,
but even if they do, they very soon become quiet and proceed
to feed and play in their accustomed manner. This experiment
was repeated many times and only in one case was the behavior
essentially different from that described, and in this case the
tide was very nearly high at the time the pool was closed. The
response observed under these conditions lead to some important
conclusions that will be stated later in connection with a detailed
description of the experiment.

If the water is running out when the pool is closed the be-
havior of the fish is quite different from what it is if the water
is running in. After the pool is closed under these conditions,
they first swim about rapidly in various directions for a few

2 1 have again and again, during the ebbing tide, examined numerous tide-pools,
but I have never found Fundulus in any of them after the water had stopped flow-
ing out although in some instances they were still 40 to 50 meters long and con-
tained water 20 to 30 cm. deep.

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moments, apparently very much excited; then they usually
swim two or three times entirely around the pool keeping very
close to the edge much as though they were looking for an out-
let; after this a number of them ordinarily crowd together and
wriggle well up on the beach into very shallow water. This

Fig. II. Outline of a portion of a tide-pool with the outlet closed by means of
a board. This pool was 50 meters long, 13 meters wide and about 20 cm.
deep. It contained approximately 300 specimens of Fundulus, all but 75 of
which escaped to the sea by crossing a sand-bar 3 meters wide and fully 10
cm. high. T, tide-pool; o, outlet; S, sea; s, sand-bar; d, dam; r, ridge of sand;
p, small pool; c, m, n, x, y, points mentioned in the description.

usually occurs in the original outlet at either end of the dam
across it. Finally one flops entirely out of the water onto the
sand. Others follow immediately much as sheep follow a leader.
After they have left the water they continue flopping and pro*
ceed directly across the bar which separates the pool from the
sea. (See Fig. I.) Those that are left ordinarily swim about
again for a few moments then collect as before, after which more

THE BEHAVIOR OF FUNDULUS ' 345

escape. This is repeated, one group following another, until
all or nearly all have escaped.

In this way I have seen more than 200 of these fishes leave
a tide-pool 50 meters long, 13 meters wide and 30 cm. deep,
and travel across a sand-bar more than 3 meters wide and 10
cm. high, all in the course of half an hour. And I have seen
them proceed in a fairly direct course toward the sea even against
a moderately strong wind. I have also seen them persistently
attempt, continuously for at least a minute, to go overland
to the sea against a wind so strong that they could make no
headway. When I first saw this performance I was deeply
impressed. I had often seen fishes, when thrown on the land,
flop back into the water in a more or less aimless fashion, but
I had never seen any voluntarily leave a body of water and
travel in a coordinate way on land. Concerning the nature
of this phenomenon and the regulation in direction of locomotion
on land I shall have something to say presently.

The description given above is based upon numerous exper-
imental observations among which the following are typical.

1. On August 30 a tide-pool containing numerous specimens
of Fundulus majalis was discovered on a sandy beach. This
pool, somewhat irregular in outline, had a maximum length
and width of 50 and 13 meters respectively and the water in
much of it was, in places, more than 20 cm. deep. A strong
current about 3 cm. deep was running out through the outlet,
and some of the specimens were continuously passing out or
in through it. At 5 P. M. all in the immediate neighborhood
were driven in and then the outlet was suddenly closed with a
board which extended 5 cm. above the surface of the water.
A ridge of sand 60 cm. long and 10 cm. high was thrown up at
either end of the board. This ridge extending 16 cm. above
the water in the pool, joined on one side of the outlet, a natural
bar of sand of the same elevation, so that the pool was separated
from the sea on this side by a continuous barrier having an
elevation of 15 cm. On the other side however, the natural
bar had an elevation of only 5 cm. On this side in the angle
between the ridge and the outlet, there was a considerable
depression containing a small pool of water connected with the
outlet, as represented in figure 2. The sand-bar was at every
point over three meters wide. The bank at the edge of the pool

346 S. O. MAST

on the sea-side was everywhere very steep, and the water be-
came deep rapidly. On the opposite side the incline was very
gradual, and the water was very shallow.

As soon as the pool was closed the fishes began to swim about
rapidly in an aimless sort of way. They continued for a few
moments, then they came very close to the edge of the water
and swam several times up and down the side of the pool nearest
to the sea. Finally a dense aggregation formed in the outlet
near the dam and soon, three minutes after the outlet was closed,
they began to come out in the angle between the outlet and the
dam represented by y in figure 2. The first group that left
the water consisted of about twelve individuals. All of these
followed the ridge from y to its end, and then turned and went
toward the sea. Other groups soon followed behaving in a
similar way. Many attempted repeatedly to cross the ridge
at y and three actually succeeded although the ridge was fully
10 cm. high and the incline over it formed an angle with the
horizontal of more 'than 45 degrees. After passing the ridge
some went directly across the sand-bar and entered the sea at
m, but many of them got into the small pool p. All of these
swam directly across this pool to the bank at n. Here three
were seen to leave the water again, climb the relatively steep
bank 9 cm. high and then proceed to the sea, although this
pool had a free passage to the outlet through which nearly all
escaped. This seems to indicate that after these creatures once
start in a given direction toward the sea they have a strong
tendency to continue in this direction.

About 25 individuals were seen to leave the tide-pool at c,
but all returned. A few of these reached a point nearly a meter
from the edge of the water before they returned but most of
them went only a few centimeters. Quite a number also left
the pool at x but all of these returned after going a very short
distance.

When the pool was closed there were approximately 300
specimens in it. The following morning 75 dead ones were
found; consequently some 225 must have escaped.

2. In all of the experiments made during the falling tide
behavior similar to that described above was observed. In
some of them, there were, however, additional points of interest.
A detailed description of one of these follows.

THE BEHAVIOR OF FUNDULUS

347

In this experiment a dam was thrown across a long narrow
tide-pool running parallel with the coast-line as shown in figure
3. In this way approximately 150 specimens of Fundulus
majalis of various sizes were enclosed. The sand-bar between
the pool and the sea varied in height from 10 to 15 cm. This
bar rose rapidly along the edge of the pool on the sea side, but
on the opposite edge of the pool the inclines was very gradual :
so that the elevation at the end of the dam on this side was
only 3 cm., while on the sea side it was over 10 cm.

Observations were continued for 20 minutes. During this
time nearly 50 specimens escaped by traveling overland around.

s

Fig. HE Outline of a long, narrow tide-pool with a dam thrown across near the
middle. This pool had a maximum width and length of 2 and 24 meters
respectively. It contained approximately 150 funduli, most of which escaped
by traveling overland, against a moderately strong wind, around the end of
the dam on the land side, xy. T,tide-pool; o, outlet; S, sea; s, sand-bar;
d, dam; m, n, x, y, points mentioned in the description. The arrow indicates
the direction of the wind.

the end of the dam from x to y, i. e. on the land side where the
elevation was least. These specimens were opposed in their
locomotion on land by a fairly strong wind. A few escaped at
the opposite end of the dam, going overland from m to n. And
two crossed the sand-bar taking a direct course to the sea. A
few also came out a short distance elsewhere but all of these
returned to the pool.

The results obtained in these two experiments and others show
that Fundulus tends to leave the tide -pools near the original
outlet. Relatively few were seen to attempt to escape else-
where in spite of the fact that the incline of the bottom was usu-
ally much more gradual in many other places. They also show
that there is a tendency to select the lowest place near the out-
let. This is particularly evident in experiment 2. Ordinarily
these creatures leave the pools on the side of the outlet nearest
the sea but in this case they left on the side nearest the land
where the elevation was much less than on the opposite side.

348 S. O. MAST

The results show, moreover that after the fishes are out on the
land they tend to go directly toward the sea. This is evident
from the persistent attempts made in experiment 1, to cross
the ridge at y, and from the direct course taken after passing
the ridge, especially in the small pool p. They show, further-
more, that the tendency to go toward the sea is not a response
to the light reflected from the water, for in experiment 1, the
fishes, when they were behind the ridge, persistently attempted
to go toward the sea, although in this position, the ridge effect-
tively hid the sea from view while the pool was fully exposed.
In experiment 2 they also proceeded toward the sea under
similar conditions, or rather toward the original outlet of the pool.

3. As previously stated, if the tide flows in when the pool
is closed, nothing out of the ordinary occurs in the reactions
of Fundulus. Only in one experiment, that described below,
was there an exception to this. Unfortunately, owing to other
duties, I was unable to repeat this experiment under the same
conditions.

On September 7, at 10.19 A. M. the outlet of a large tide-pool
(12 by 30 m.) containing about 350 funduli was closed. At
this time there was a strong current of water running into the
pool indicating that the tide was still rising. Immediately after,
the pool was closed, the fishes began to swim about rapidly
being apparently very much excited, and two minutes later
they began to come out of the water. In short, they behaved
precisely as they ordinarily do when the tide is running out,
not at all as they ordinarily do when it is running in. They
continued to come out for some time, most of them, as usual
near the original outlet, but nearly all of them returned to the
pool ; only a few succeeded in crossing the sand-bar which separ-
ated the pool from the sea. The sun was very hot at this time
and the sand on the bar rather dry. This probably accounts
for the fact that nearly all returned to the pool after proceeding
a short distance toward the sea. At 10.40 the tide had un-
questionably turned for the water outside the pool was already
several centimeters lower than that inside. The tide was con-
sequently very nearly high when the pool was first closed and
this no doubt, was the cause of the unusual behavior. If this
is true it must be assumed that in some way these animals know
when the tide is about to turn, for their method of response

THE BEHAVIOR OF FUNDULUS 349

changes from that characteristic of the rising tide to that
characteristic of the falling tide before the tide turns.

At 11.10, i. e. nearly an hour after the pool was closed, the
fishes were much more quiet than they had been earlier, Most
of them were swimming about in a leisurely fashion, some were
feeding and none were coming out of the water. They were
observed for some time after' this, but at no time was there the
slightest indication of an attempt to leave the water, although
various methods were used in trying to make them leave, e. g.,
boards were thrown into the pool, the water was violently dis-
turbed by running around in it and much of it was drawn off.
Later the water in this pool together with the fishes was drained
into a lower pool. In this pool the fishes swam about rapidly
as though they were considerably excited but none of them
left the pool, although a few at different times came out of the
water a short distance. Their behavior in general was markedly
different from that observed in animals suddenly shut in pools
during the ebbing tide . This indicates strongly that the all-
important factor involved in the behavior resulting in the over-
land escape of Fundulus from tide-pools is the sudden closing
of the outlet through which it is accustomed to go. The loca-
tion of this outlet they evidently remember for some time.
The results of this experiment show also that Fundulus becomes
very rapidly acclimated.

The movement of these fishes on land seems to be well co-
ordinated. They travel in fairly direct courses. There is
nothing in the nature of aimless tumbling about as is ordinarily
seen in the behavior of fishes out of water. Locomotion con-
sists of successive leaps due to sudden bending of the body.
When the fish falls after a leap it may be directed toward any
point of the compass, but the succeeding leap carries it on its
course no matter in which direction it may be facing at the time
of the response. Thus before each leap it may be headed in
the direction in which it is traveling or in the opposite direction
or in any other direction. It is really remarkable that the
bending of the body is so regulated that the animal continues
to move in a given direction regardless of its axial position at
the beginning of the successive reactions. As to the mechanics
of the process I am as yet quite in the dark. And I am also
unable to say what factors in the environment serve to direct

350 S. O. MAST

these animals overland to the sea. Vision of the sea seems to
play little or no part in this, for the fishes continue toward the
sea if a screen is so placed that the water can not be seen; or if
conditions are so arranged that the largest surface of water
visible is in the tide-pool. The slope of the beach can also not
serve to guide them, for in crossing the sand-bar they have
to go up grade as well as down. Nor are there any other external
features that seem capable of serving as a guide. The phenom-
enon is consequently probably very largely dependent upon

internal factors.

SUMMARY

1. Fundulus is frequently found in temporary tide-pools,
but rarely if ever after the water is so low that the outlet is
closed. When the tide is falling it swims out and in at short
intervals but as soon as the water in the outlet gets low it does
not return. In this way it avoids being caught in these pools
and killed when they dry during low tide.

2. If the outlet is closed while the tide is rising nothing
out of the ordinary occurs, but if it is closed while the tide is
falling the fishes swim about rapidly in various directions for
a few moments. Then they come out of the water and travel
overland to the sea. Many specimens have been seen thus to
leave large tide-pools and travel across sand-bars more than
3 m. wide and 10 cm. high.

3. Fundulus nearly always leaves the pools on the sea side
near the original outlet. It apparently remembers the location
of the outlet ; and it is the sudden closing of this that constitutes
the principal factor causing these fishes to leave the pools.

4. On land they never travel in the wrong direction any
considerable distance. It is not known how they are guided
in the right direction, but it is known that light reflected from
the water is not a significant factor in the process.

5. Locomotion on land is brought about by successive leaps
due to rapid bending of the body. The course taken is fairly
direct. Every leap carries the animal in the right direction,
although the ax'al position at the beginning of the successive
leaps varies greatly; the fish, at this time, may be headed in the
direction of locomotion or in the opposite direction or in any
other direction. The movements appear to be well coordinated,
but the process involved in thus regulating the direction of
locomotion is not understood.

EXPERIMENTS ON SEX RECOGNITION AND THE

PROBLEM OF SEXUAL SELECTION

IN DROSOPHILA

A. H. STURTEVANT
Columbia University

Much has been written on the subject of sexual selection
since Darwin first developed the theory, and many remarkable
observations have been recorded. There has, however, been
very little experimental work in this field. Darwin and those
who have followed him have obtained much of their evidence
from the insects, and within this group some of the most striking
cases of elaborate mating habits have been reported in the
Diptera, and here too there is to be found a most remarkable
array of secondary sexual characters. Perhaps the most extreme
case is that of the Elaphomyia described by Wallace, in which
the male has long, hornlike processes arising from his head,
which are absent in the female. The families of Platypezidae,
Dolichopodidae, and Empididae are especially rich in secondary
sexual characters, which occur in the legs, wings, antennae,
face, or other parts. In the two latter families some very curious
observations on mating habits have been recorded (see especi-
ally 'Poulton's account ('13) of Hamm's work on Empididae).1

Some of the best experimental evidence in favor of sexual
selection is that obtained by Lutz (1911), who worked with an*
abnormal wing venation in Drosophila ampelophila which he
found to be strongly selected against. To Dr. Lutz is due the
suggestion that the mutants in this fly obtained by Morgan
would form excellent material for the study of the problem.
The method of some of the experiments was also suggested by
Lutz. I took up the matter at the suggestion of Professor
Morgan, to whom I am greatly indebted for most of the material
and for his encouragement and criticisms. Several discussions
of the matter with Dr. Lutz have also been very helpful. Some

1 1 have myself observed courtship in a few Dolichopodidae and in a number of
other Diptera. These observations will be published in full later.

351

352 A. H. STURTEVANT

of the work was done at the Cold Spring Harbor Laboratory in
the summer of 1911, and I wish to express my appreciation of
the interest in the experiment shown by Dr. C. B. Davenport
at that time.

COURTSHIP AND MATING

Most of my observations on courtship in Drosophila have
been made upon D. ampelophila Loew. In general the process
is very similar in D. busckii Coq., but differs in several respects
in D. amoena Loew, D. repleta Woll., and D. funebris Fabr.
The first and most noticeable act in courtship occurs when
the male, being near the female, extends one wing at about
right angles to his body, and vibrates it for a few seconds. The
wing is then returned to the normal position and the process
is repeated, usually with the other wing. But between times
there is a scissors-like movement of the wings repeated several
times. This vibrating of the wings is often repeated many
times, and may be done in any position relative to the female,
though the male a1 ways faces her. Usually, in fact, he swings
quickly around her in a semicircle once or oftener during the
process. Soon the male begins to protrude his genitalia and,
if the female remains quiet, to lick her posterior end. Some
white matter now protrudes from her ovipositor, and other males
in the same vial are usually 'observed to become excited now
and begin courting; indicating odor as a cause of sexual excite-
ment. If the female runs or flies away the male is excited, moves
his wings jerkily, and walks around rapidly, but seems unable
to follow the female accurately or to locate her quickly. The
' penis is directed forward by bending up the abdomen under-
neath, towards the thorax, and is jerked toward the female
(the male always standing facing her at this stage), but not
always toward her genitalia, as I have seen ii strike her in the
eye.2 If it does strike the mark the male mounts on the female's
back, between her wings. Mounting never takes place until
after the actual copulation has occurred, in which respect Droso-
phila differs from some related flies (e.g., Muscidae, Anthomyidae,
Sepsidae, Borboridae, and Ephydridae, so far as my observa-
tions go). In these forms the male flies and lights on the female,

2 The male in this case, however, had white eyes, and so was perhaps blind,
Normally the aim is accurate.

PROBLEM OF SEXUAL SELECTION IN DROSOPHILA 353

after which copulation may or may not take place, probably
depending upon the way the female responds.

Berlese ('02) and Hewett ('08) find that in the house fly the
final step in copulation is taken by the female, which inserts
the ovipositor into the genital opening of the male. I have not
been able to verify this for Drosophila, but it is probably true
here also. In Drosophila, as in some other related flies (I have
examined a few Anthomyids and Sepsis violacea), the ovipositor
enters the male opening, instead of the penis entering the female
duct. But I cannot state positively that the female inserts it
instead of the male drawing it in by means of his genital arma-
ture. In any case, it is certain that the female is not entirely
a passive agent. The time required for copulation to take place
depends largely upon whether she stands quietly and allows the
male to pair, or moves away when he begins to court. In the
latter case very active males have been seen to pair while the
female was walking away, but this is exceptional. Occasion-
ally a female seems to frighten off a male by spreading her
wings and moving quickly toward him.3 When this happens he
moves off, and does not so far as I have seen, then pair with that
female, although she has been known to pair with another male
within a few minutes afterward. That this is really a threat on
the part of the female seems likely from observations of fighting
between males. If two males are courting the same female they
often grow very excited, especially if she is unwilling to stay
quiet. In such cases they may sometimes be seen to spread
their wings, run at each other, and apparently butt heads. One
of them soon gives up and runs away. If the other then runs
at him again within the next few minutes he usually makes off
without showing fight.

The time occupied by the process of courtship varies greatly
with the age and condition of the flies and with the temperature.
Copulation may occur within a few seconds after the flies are
put together, with little preliminary courtship. While experi-
menting with flies about 3 or 4 days old, which had never been
allowed to pair, I have found that 20 minutes or a little less is
about the average length of time before copulation occurs. The
flies may remain in copula for only a few seconds, but so far

3 Compare Howard's ('02, pp. 141 and 145) accounts of Asilid and Empidid
flies eating males which were courting them.

354 A. H. STURTEVANT

as my observation goes this occurs only after a prolonged court-
ship in which the female has seemed unwilling to mate, and is,
I think, due to the male not getting a good -hold. I do not
know whether or not such pairings are successful. Ordinarily
copulation lasts about 20 minutes.4

EXPERIMENTS ON OTHER INSECTS

There is a considerable body of evidence relating to the ques-
tion of sex recognition in the Arthropods. A short review of
the subject and a bibliography are given by Chidester ('11),
so I shall confine myself here to the evidence dealing with
insects. There is evidence from several groups of insects, but
most of it points the same way. Sex recognition at a distance
is by smell, but the actual process of copulation depends upon
the sense of touch.

In the Orthoptera, Stockard ('08) has observed the male
walking stick to pair with the detached abdomen of a female
which was fastened to a stick with wires for legs.

In Coleoptera, Fere ('98) finds that male cockchafers do not
pair if the antennae are removed. Males will sometimes pair
with males, prov ded the latter have just paired with females,
or have been artificially impregnated with female juices.

Mast ('12) shows that in the firefly the males find the females
by means of the flashing lights, signals being made by both
sexes. Tower ('06) reports that in Leptinotarsa males normally
never try to actually copulate with males, but that if the anten-
nae are removed or painted with shellac they will try to pair
with any individual they happen to touch. If this individual
is a female pairing will occur. If the abdomens of females are
removed the males are attracted by them, though not by the
wings, head and thorax. Females with their abdomens coated
with shellac are not attractive to the males.

Fere ('98a) found that in the silkworm moth males will pair
with other males, which have not been given a chance to get
the female odor, if the latter males are sluggish, as after removal
of the antennae. Males without antennae will copulate. Kel-
logg ('07) has since reported that males without antennae find
the females only by chance, while normal ma1es go straight to

4 In 20 cases the duration of copulation was timed with the following result
(minutes): }, 5, 16, 17, 18, 18, 19, 20, 21. 21, 21. 21, 22, 22, 23, 24, 25, 26. 27
33,

PROBLEM OF SEXUAL SELECTION IN DROSOPHILA 355

them. If one antenna be removed the male travels in a circular
path instead of going toward the female. If a male without
antennae happens to touch a female he immediately shows
strong sexual excitement, such as normal males show when
brought near females. Scent glands on the abdomen of the
female were shown to be the seat of the olfactory attraction,
for when the abdomens were removed males were attracted by
them and not by the rest of the female. Blackening the eyes
produced no change in the behavior.

Mayer (1900) performed numerous experiments on the moth
Callosamia Promethea. He showed that it is odor that attracts
the males, and that this odor comes from the abdomen of the
female. Interchanging of wings indicated that the marked
sexual dimorphism in color, which occurs in this species, has no
selective value.

Kirkland (1896)5 showed that in the Gypsy moth odor is
again the main element concerned, but the wings of the female,
as well as her abdomen, have an exciting odor. Mayer and
Soule (1906) tried experiments on this form, which they sup-
posed indicated that normal females discriminated against males
without wings. I find, by applying Yule's (1911) formula for
the standard error of the difference, that the difference between
the per cent of times winged males paired without resistance
and the per cent that wingless males paired without resistance
(the measure of sexual selection used by these authors) is
almost exactly three times the standard error. This means that
the result is not conclusive. Mayer and Soule blinded females
and found this apparent discrimation against wingless males to
disappear, but the per cent of resistance dropped, as a whole,
from 46% in the normal females to 27% in the blinded ones.
This may mean that the blinded ones were too greatly disturbed
by the blinding to pay much attention to what male mated
with them. While I am inclined to suspect that there is some
odor connected with the male's wings, still, as stated above, it is
not certain that any effect at all is produced by removing the
wings of the male. Further evidence against the importance
of sight is furnished by the fact that females did not discrimi-
nate against males with wings painted in unusual colors.

5 I have not seen this paper, but make the statement on the authority of Mayer
and Soule (1906).

356 A. H. STURTEVANT

Federley (1911) gives evidence indicating that odor is a strong
sexual stimulator in the moth Pygaera, and may even cause
males to attempt to pair with the bars of the cage in which they
are confined. Entomological literature contains many accounts
of the remarkable ability of male moths to locate females though
smell. A few of the more striking cases are given by Wash-
burn ('09, pp. 87 and 88.)

SEX RECOGNITION IN DROSOPHILA

It was noted above that when an egg protrudes from the
ovipositor of a female any males in the same bottle usually
become excited and begin courting. When a female is killed
eggs are likely to protrude, and males are often seen vigorously
courting females which have been freshly killed, even though the
killing agent were so strong smelling a substance as ether. In such
cases it is the posterior end of the abdomen which seems to be
the chief focus of attraction. The attraction may last for at
least 30 minutes after death, and probably longer. I have not
as yet been able to cause males to copulate with dead females,
probably because the female normally takes an active part, as
indicated above.

If a male which has just paired is placed with a male which
has been isolated from females for several days he may be
courted by that male, though this is not frequent. If two males
are kept in solitary confinement for four or five days and are
then put together they often court each other, in one case even
the doubling up of the abdomen being seen, and the wing move-
ment {not fighting) being almost invariably observed. Such
mutual courtship between males has not been seen under other
conditions, but a dead male which had not been with females
for two days before killing has been seen to be courteql by other
males. This courting, however, seems more likely to occur when
juices from female abdomens are put on the dead males. In
Psychoda sp. courtship of males by males seems to be very
frequent, and often copulation is attempted. The genitalia even
become attached, and stay so for several seconds. Males have
been seen to mount males in Fucellia marina, Sepsis violacea,
and Sarcophaga sp.

In order to test what part is played by the female juices

PROBLEM OF SEXUAL SELECTION IN DROSOPHILA 357

mentioned above I placed some on bits of filter paper and put
these in the same vial with males. The males paid no atten-
tion to the paper, and showed no signs of excitement, though
that they were sexually ripe was shown by the fact that they
courted and paired with females when they were put in with
them. This experiment has been repeated several times with
the same result. When a female is thoroughly crushed and the
remains heaped up in a little pile the males will sometimes
court slightly, but as a general rule, the more mashed the female
is, the less excited the males become. No great importance is
to be placed upon this latter experiment, as the result is com-
plicated by the presence of so many other body juices. This
objection, however, will hardly hold in the case of the filter
paper impregnated with female juices. The objection that not
enough odor was present may perhaps be justifiable in that
case. But neither of these objections would seem to apply to
the following experiment. Two females were placed in a small,
dark, cloth bag and this was put in a vial with a few males.
The males were close to the females, which they could not see or
touch, but should be able to smell. This experiment was done
three times and in no case did the males show any signs of
sexual excitement, though in all three cases they did court
immediately afterwards when given females in the usual way.

It has been shown by Barrows ('07) that the sense organs
for smell in Drosophila, insofar as one may judge from reactions
to food substances, are located in the terminal antennal joints.
For this reason I was led to perform the following experiments,
in an effort to determine the part played by the sense of smell
in courtship and copulation.

The antennae were removed from several males,6 which were
after several days placed with virgin females. Such males are
very sluggish, and- it was therefore not surprising that no court-
ship was observed. However, one such male was found copu-
lating, and at least three of them left offspring after the opera-
tion. One of the three had white eyes, and was therefore prob-
ably also blind. Courtship has been observed in two males from
which the antennal aristae had been removed. A normal male
has been seen copulating with a female from which the antennae

6 1 have found that antennae may easily be removed without using the complex
method described by Barrows, if the operation be performed on very young flies.

358 A. H. STURTEVANT

had been removed, and this pairing resulted in the production
of offspring.

The above experiments failed to give any evidence demon-
strating that smell alone can cause males to show signs of court-
ship. Another series of experiments, now to be described, has
indicated, however, that smell may be a secondary factor in
causing sexual excitement. Males and virgin females were
isolated for three or four days and were then placed, in pairs,
in clean vials. The length of time before copulation occurred
was recorded; and, after it had taken place, the flies were re-
moved and a new pair was placed in the same vial. The only
difference between the two sets was that one lot was in clean
vials, the other was in vials in which copulation had just occurred.
In these experiments an equal number of each sort was done
on each day (placing a third pair in some vials when necessary
in order to get an equal number), and all flies used on a given
day were as nearly the same age and size as practicable, and
were from the same culture. Table I gives the result of the
experiments. It shows that in the first five or six minutes

TABLE I

Minutes Number of times observed

before — ■

Copulation 1st pair 2nd pair

1-3 13 22

4-6 12 22

7-9 5 7

10-12 7 6

13-15 11 2

16-18 7 5

19-21 8 5

22-24 4 3

25-27 5 3

28-30 2 1

31-33 7 1

34-36 * 2 2

37-39 0 2

40. and more, including failures. 24 25

the flies in the used vials are more likely to copulate than are
those in the clean vials; between ten and twenty minutes there
are more copulations in the clean vials, and after that the two
series are parallel. Apparently there are a certain number of
pairs that are nearly ready to mate, and these will mate more
quickly if another copulation has just occurred in the same
vial. But if much courtship is to be required before copu-

PROBLEM OF SEXUAL SELECTION IN DROSOPHILA 359

tation. then the effect of smell is negligible. It is not clear from
these results whether the effect is produced upon the males,
the females, or both.

In. order to test whether sight is the sense which stimulates
the male I carried out the following experiment. Two vials
having the same bore were filled with cotton up to about three
centimeters from the mouths, and then placed with their mouths
together. A thin glass cover-slip was then placed between them,
and a male fly was placed in one vial, a female in the other.
These flies had been isolated for several days, and were sexually
ripe. The male could see the female, but could not touch or
smell her. Once or twice they met ' ' head on ' ' with only the
cover-slip between them, but the male showed no signs of recog-
nition. After thirty minutes the female was let in the vial
containing the male; and the vials were left in position. He
•courted her writhin two minutes, and paired in five minutes.
The experiment was repeated with the same result, except that
copulation now occurred in three minutes after putting the
flies together.

It is also evident that sight is not necessary for pairing from
the facts that Drosophila breeds freely in the dark (see Payne,
'11), and that pure stock of white-eyed flies (which may be
blind) has been kept for many generations.

In Fucellia marina and in Musca domestica males seem to
see their mates from some distance and fly directly to them,
lighting on the back of the mate. Here sight would seem to
play considerable part, and in Fucellia still more convincing
evidence was obtained from observation of violent courtship
of a fly which was separated by thick glass from the courter.
Not only did this male court the other fly, but when she walked
around rather rapidly, he very accurately followed her on the
other side of the glass. This has been observed twice.

Since the wings play such a conspicuous part in courtship
I was led to try the effect of cutting them off. Two males
of the same age were used, the wings of one being cut off at the
base. These were kept in the same vial for several days, and
then placed with a virgin female several days old. The vial
was then watched until copulation took place. This has been
done 125 times, using different individuals each time. The
normal male paired 72 times, the clipped male 53 times. As

360 • A. H. STURTEVANT

in all the similar experiments here reported care was taken to
have the competing flies as nearly the same age and size as pos-
sible. The result indicates that there is very slight, if any,
selection against the clipped males. It seemed possible that
courtship made the female ready to copulate, but that she
would then mate with either male. To test this hypothesis
another series of experiments was carried out. A single pair
of flies was placed in each vial, using each day an equal number
of normal and of clipped males. The length of time before
copulation was recorded in each case. A preliminary account
of this experiment has been published by Morgan ('13); but the
data used there have been discarded, since two serious sources
of error had not then been recognized. It was not realized
that the time before copulation might be influenced by a pre-
vious copulation having occurred in the same vial ; and sufficient
precautions against drying were not taken — a very important
factor. A new series of experiments, in which these points were
controlled, gave the results shown in table II. As a matter of
fact, however, these data are very similar to the discarded series.

TABLE II

Minutes Number of times observed

before

Copulation Normal <-? Clipped r?

0- 3 15 4

4-6 19 9

7-9 10 7

10-12 15 5

13-15 3 7

16-18 8 4

19-21 3 10

22-24 3 4

25-27 9 4

28^30 2 2

31-33 2 2

34-36 0 4

37-39 1 2

40-42 3 2

43-45 2 1

46 and over, including failures. 43 73

This table seems to justify the suspicion that led to the ex-
periment. Had the females discriminated against the clipped
males to the extent shown above when both kinds were present,
the normal males would certainly have appeared at a greater ad-
vantage. That the result was not due to less activity on the part of
the clipped males is indicated both by the contests described above

PROBLEM OF SEXUAL SELECTION IN DROSOPHILA 361

and by the following observations. In some of the experiments
recorded in table II the number of minutes before courtship
began was observed. Table III indicates that the clipped males
began courting as quickly as did the normals.

TABLE III

Minutes before
Courtship Normal Clipped

1-2 12 9

3-4 2 3

5-6 1 2

7-8 1 2

9-10 0 1

11-12 1 0

• 13 and over 7 7

From these experiments it seems certain that the wings are
of value in courtship; but the effect probably is to produce
sexual excitement in the female, rather than to cause her to
select a male that uses his wings. No " choice " is involved;
but, as pointed out by Watson ('14, p. 173), the effect, in nature,
would be strongly in favor of the normal male.

It seems probable that touch is of considerable importance
in the sexual process, and all my observations are consistent
with that view, but I have no direct experimental evidence to
that effect. It is not possible to get evidence from Drosophila
such as Kellogg obtained from Bombyx, because the flies are
more active, and less easily sexually excited, than is the silk-
worm moth.

Two kinds of experiments have been carried out in an effort
to find out what part of the body is responsible for causing
sexual excitement. A female without an abdomen, but alive
and active, was placed with males that had been isolated from
other females for four days. She was vigorously courted.

Three gynandromorphs have been tested to determine their
sexual behavior. None showed any certain indications of male
behavior, but all were vigorously courted by males. Of these
three gynandromorphs the external characters were as follows:

(A) All female, except one side of the head, which was male;

(B) female on one side of the whole body, male on the other
side; (C) female, except the genitalia, which were male. It is
doubtful what conclusion, if any, is to be drawn from these
few observations.

362 A. H. STURTEVANT

SEXUAL SELECTION— ARTIFICIAL ABNORMALITIES

The male of Drosophila ampelophila bears a small comb on
his front metatarsi, a secondary sexual character not found in
most species of the genus.7 Lutz ('11) has shown that the
removal ' of this comb has no effect upon the availability of
males for copulation. That is, the females were not influenced
by the sex-comb in their choice of mates.

It sometimes seems to be difficult for the male to get the
wings of the female out of his way so that he can mount her.
For this reason I carried out an experiment the converse of
one recorded above; using two virgin females of the same age,
one with normal wings, the other with wings removed. These
were put with a normal male. In 52 successful trials the normal
female was paired with 25 times, the clipped one 27. Again it
would seem as though clipping the wings has very little if
any effect.

SEXUAL SELECTION— MUTANTS

Lutz ('11) found that certain slight abnormalities in wing
venation were selected against both 'by normal and abnormal
flies of both sexes. The abnormal flies were not noticeably
different from the normals in behavior, so that it seems quite
unlikely that the results were due to a difference in the activity
of the two types. Moreover, if, let us say, the normal male
was more active than the abnormal, so that he would be more
likely to pair first, it would seem that the normal female would
not be so easily paired with as the abnormal; or vice versa, if
we suppose the abnormal female to be less active and therefore
more likely to be paired with, it is hard to see why the abnormal
male should be at a disadvantage. Further evidence bearing
out this view of the effect of differences in activity will be given
below. Lutz suggested that it seems unlikely that sight could
have any influence, and that perhaps there is some unpleasant
smell correlated with the abnormality, this being the basis of
selection.

I have conducted a series of experiments upon some of Mor-
gan's Drosophila mutants, in an effort to find if there was any
selective mating in connection with them. The following
mutants were used:

7 So far as my observation goes it is present only in D. ampelophila, D. confusa^
D. obscura, and three or four undescribed species.

PROBLEM OF SEXUAL SELECTION IN DROSOPHILA 363

(1) White eyes. This form was first described by Morgan
('10). There is no color in the eye. This probably means that
the fly is blind, and it has often been observed to be less strongly
phototactic than the wild fly. White eyed flies are also less
active and vigorous than normals.

(2) Yellow body color. Described by Morgan ('11). The
whole body of this fly is lighter than that of the normals, and
there is a distinct yellow color to the wings. Sight seems to be
normal, but again the flies are not so active as are the normals.

(3) Curved wings. The main interest of this form in this
connection is that the wings are always held extended, in some-
what the same position as that of the courting males. The
flies are perhaps a little less active than the normals

(4) Vermilion eyes. Described first by Morgan ('11a). These
flies differ from the normals in that the eyes are of a brighter
and less intense red. Their vigor and activity is very little, if
at all, inferior to that of the normals.

Some of the flies used had yellow bodies and white eyes,
and in one experiment a few vermilion eyed yellow black col-
ored females were used. This latter combination was at the
time considered one of the weakest stocks in the laboratory,
and was used for that reason.

The method of the experiment was as described above for the
wing clipping experiment. For instance, a white eyed female
would be given her choice between a red male and a white one
of the same age and size. Then the experimenter simply watched
until pairing was seen, and the flies were then thrown away.
The following table (IV) gives the results obtained.

TABLE IV

Red vs.

white

eyes. (Normal body color.)

"Chooser'

9

"Chosen"

Number of cases

Red cT

(Red 9
1 White 9

54

82

White o71

(Red 9
(White 9

40
93

Red 9

(Red o71
j White c?

53

14

White 9

(Red c?

62

J White d 19

364 A. H. STURTEVANT

TABLE IV— Continued
Gray (normal) vs. yellow body color. (Red eyes.)

Gray d* iGray 9 25

(Yellow 9 31

Yellow cT i Gray 9 12

} Yellow 9 30

Grav 9 I Gray d1 60

"(Yellow c? 12

Yellow 9 \ Gray c? 25

"j Yellow cT 8

Vermilion \ Red-gray d1 13

Black-yellow 9 ( White-gray d1 1

Gray and yellow body colors. (White eyes.)

Gray d1 J Gray 9 11

1 Yellow 9 4

Gray 9 I Gray cT 21

I Yellow c? 3

Red and white eyes. (Yellow body color.)

Red cT j Red 9 3

/White 9 4

White cT I Red 9 9

) White 9 9

Red 9 J Red d1 9

J White d"' 2

Wrhite 9 i Red d" 21

j White c? 1

Red and vermilion eyes. (Gray body color.)

Red c? j Red 9 7

( Vermilion 9 , 5

Vermilion c? ) Red 9 4

(Vermilion 9 4

Red 9 ( Red cT 11

(Vermilion d1 14

Long and curved wings. (Other characters normal.)

Long c? i Long 9 10

(Curved 9 13

Curved d1 ^Long 9 5

"(Curved $ 3

. Long 9 J Long cT _ 14

I Curved cT 4

Curved 9 \ Long c? _ 9

} Curved d"' 5

PROBLEM OF SEXUAL SELECTION IN DROSOPHILA 365

It appears that sexual selection is not involved in any of
these cases. The impression gained from observation of over
1,000 " contests " of this sort is that the outcome is not a matter
of choice. A female, in the great majority of cases, seems to
allow the first active amorous male that comes along to pair
with her; or, if she is disinclined to mate, resists all males appar-
ently indifferently. When a male is sexually excited he pairs
with the first female he finds which will allow him to. As a
result, the more active and vigorous males are likely to win
their contests, and the greater the difference in vigor, the greater
the proportion of times the better male wins. This is just what
the results show to happen. So far as the small numbers show,
the vermilion male is at no disadvantage and the curved male
is not quite able to hold his own, while it is certain that the
yellow and white are far behind their normal opponents.

In the converse case, a less vigorous female will be less likely
to resist or escape from the male successfully if she be disin-
clined to mate. But this influence should have less effect on
the result than the one discussed above, since both females
will often be willing to mate and will not try to escape. This
again agrees exactly with the facts as given above.

The two results of unequal vigor discussed above seem to
me quite adequate to explain all the results obtained. There
is no evidence of any ' choice ' on the part either of males
or of females. Unlike the abnormal venation studied by Lutz,
these mutants probably have no significance from the point of
view of sexual selection, in the narrower sense of that term.

SUMMARY

Experiments indicate that sight is not essential in sex recog-
nition in Drosophlia. The olfactory and tactile senses are prob-
ably both concerned, as in most other insects.

The wings of the male play a conspicuous part in normal
courtship. Experiments with males from which the wings had
been removed indicated that the function of these organs in
courtship is the production of sexual excitement in the female.

Experiments were carried out with four mutants (white eyes,
vermilion eyes, yellow body color, and curved wings), involving
the observation of 839 contested matings.

As a result of these experiments it seems probable that the

366 A. H. STURTEVANT

four characters involved have no selective value, except in so
far as results from the fact that at least two of these classes are
less active then normals.

In general it is probable that, in Drosophila, neither sex exer-
cises any " choice " in the selection of a mate. A female that
is ready to mate will accept any male, and a male that is ready
to mate will do so with the first female that will allow him to.

LITERATURE CITED

Barrows, W. M. The reactions of the pomace fly, Drosophila ampelophila, to

1907. odorous substances. Jour. Exper. Zooi, IV.

Berlese, A. L'accoppiamento della Mosca domestica. Rev. Patol. Veg., IX. 1902.
Chidester, F. E. The mating habits of four species of the Brachyura. Biol.

1911. Bull, XXI.
Darwin, C. The descent of man and selection in relation to sex. 2nd edition. 1874.
Federley, H. Vererbungsstudien an der Lepidopteren-gattung Pygaera. Arch.

1911. Ross. u. Ges.-Biol., VIII.
Fere, C. Experiences relatives aux rapports homosexuels chez les hammetons.

1898. C. R. Soc. Biol., V.

1898a. Experiences relatives a l'instinct sexuel chez le bombyx du murier.
C. R. Soc. Biol., V.
Hewett, C. G. Structure, development, and bionomics of the housefly. Quart.

1908. Jour. Micr. Set., LII.
Howard, L. O. The insect book, New York.

1902.
Kellogg, V. L. Some silkworm moth reflexes. Biol. Bull., XII.

1907.
Kirkland, G. H. Assembling of the gypsy moth. Gypsy Moth Report, Mass.

1896. Board. Agr.
Lutz, F. E. Experiments with Drosophila ampelophila concerning evolution.

1911. Carnegie Inst. Wash. publ. 143.

Mast, S. O. Behavior of fire-flies (Photinus pyralis) with special reference to

1912. the problem of orientation. Jour. Animal Behav., II.
Mayer, A. G. On the mating instinct in moths. Ann. Mag. Nat. H., V.

1900.
Mayer, A. G. and C. G. Soule. Some reactions of caterpillars and moths. Jour.

1906. Exper. Zool., III.
Morgan, T. H. Sex-limited inheritance in Drosophila. Science, XXXII. 1910

1911. The origin of nine wing-mutations in Drosophila. Science, XXXIII.

1911a. The origin of five mutations in eye-color in Drosophila, etc. Science,
XXXIII.

1913. Heredity and sex. New York.

Payne, F. Drosophila ampelophila bred in the dark for sixty-nine generations.

1911. Biol. Bull., XXI.
Poulton, E. B. Empidae and their prey in relation to courtship. Entom. Mag.,

1913. XXIV.
Stockard, C. R. Habits, reactions and mating instincts of the walking stick,

1908. Aplopus mayeri. Carnegie hist. Wash. publ. 103.
Tower, W. L. An investigation of evolution in Chrysomelid beetles of the genus

1906. Leptinotarsa. Carnegie Inst. Wash. publ. 48.
Washburn, M. F. The animal mind. New York.

1909.
Watson, J. B. Behavior. New York.

1914.
Yule, G. U. An introduction to the theory of statistics. London.

1911.

THE WHITE RAT AND THE MAZE PROBLEM

IV. THE NUMBER AND DISTRIBUTION OF
ERRORS— A COMPARATIVE STUDY

STELLA B. VINCENT

Chicago Normal College

What is the maze problem ? It is the learning of a difficult
path, having many blind alleys, under a stimulus so strong
and certain that finally, when put into the labyrinth, the animal
runs swiftly and surely to the goal without error. It consists
of a series of movements which tend toward a definite end and
which are so ordered that the position and the direction of the
turns seem to be the all important factors. The animal's task
is to learn this motor co-ordination, ours, if possible, to find
out how it does it.

In the learning of the maze we find not a single problem
but a complex of many and much light has been thrown upon
them through the work of Small, Watson, Richardson, Carr
and others. Some of the questions which arise in the course
of such investigations are, however, still without satisfactory
answers. The preceding numbers of this series have dealt with
the problems of sensory control in the maze. This paper at-
tempts to deal, briefly, with some of the more general features
of the maze problem in the light of that experimentation. One
question which immediately suggested itself concerned the rela-
tive value of the different senses when directive in such a problem.

THE RELATIVE EFFECTIVENESS OF THE DIFFERENT SENSES

AS MODES OF CONTROL

This comparison is not an easy one to make since any one
sense factor is never isolated but only emphasized in the sensory
complex. The following table (I) shows factual data taken
in different ways from the learning scores. If we turn this into
terms of per cent, making the lowest and therefore best score
always 100, and basing the others on this we get table II. By
normal maze is meant the unpainted wooden maze where the

367

368

STELLA B. VINCENT

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THE WHITE RAT AND THE MAZE PROBLEM 369

TABLE II

Comparison of Normal, Black-white and Olfactory Mazes

Time of learning

Olfactory 100%, Normal 145%, Black-white 175%

* Initial— Olfactory 100%, Black-white 130%, Normal 370%
Final— Olfactory 100%, Normal 250%, Black-white 750%
Total— Olfactory 100%, Black-white 175%, Normal 330%

Time

Initial— Black- white 100%, Olfactory 115%, Normal 215%
Final— Olfactory 100%, Normal 110%, Black-white 143%
Surplus— Black-white 100%, Olfactory 138%, Normal 190%,

Comparison of Open Maze with Enclosed Normal Maze of Same Pattern

Time of learning

Open maze 100%, Normal 100%

Accuracy

Initial— Open maze 100%, Normal 150%
Final— Open maze 100%,, Normal 225%
Total— Open maze 100%, Normal 140%

Time

Initial— Normal 100%, Open maze 105%
Final— Open maze 100%, Normal 120%
Total— Open maze 100%, Normal 110%

sides to the alleys were high enough to prevent any outlook
to the neighboring runways and the light and odor were as
evenly distributed as possible. The second maze was of the
same plan but the true and the false paths were made to differ
decidedly in brightness values. The third maze, again of the
same pattern, had an olfactory trail in the true path.1 The
figures from the open maze are not compared directly with the
others but with the score from the same maze when the re-
straining walls to the alleys were in place.2

We will not stop to comment upon the time of learning, as
the chief differences are seen in the accuracy records. The
olfactory maze heads the list in this respect both in initial, final
and total accuracy within the limits of the experiment. The
black- white maze follows second in initial accuracy and in total,
because of the initial, but falls far behind in final accuracy.

1 In these tables the combined black-white figures are used, i.e., two groups of
animals of five each where the true path was white and the cul de sacs black, and
two groups of the same size where the conditions were reversed. The olfactory
records are those where the trail was in the true path since this seemed most typical
for our purpose. The combined olfactory scores make but little difference in the
rating, they simply somewhat lowered the scores in the early trials and raised them
in the final. For full details consult the previous papers.

2 These mazes are all described in previous papers.

370 STELLA B. VINCENT

The reasons for this have been discussed in another paper.
The time records are almost a direct reflection of the accuracy
for, although the final scores distinctly favor the olfactory and
black- white mazes, the advantage is but slight. The cutaneous
open maze is also better than the normal in all of the accuracy
counts, and also in final and total time. The small differences
in time again are probably more or less an expression of the
accuracy with a balance in favor of the open maze.

In these results, then, the olfactory maze leads, the open
maze stands next in order while the black-white and the normal
mazes approach each other very closely if all of the counts are
considered. It will be seen that the big advantages which these
sensory mazes offer are found in the early trials, in the setting
up of the automatisms, and that the apparent total gain is due,
for the most part, to the gain in the early trials. The estab-
lished habit is practically the same no matter under what sen-
sory conditions it is set up. The distracting effects of some
of these sensory situations which affect the final scores are
discussed in the previous papers.

Why some experimental workers should choose to neglect the
error records is still a mystery to some of us. Certainly the
real differences in the bits of learning given above are not shown
by the time records. It is more essential in the normal life of
a rat that it should be able to thread a beam or a cornice
without falling, to jump from one projection to another with-
out missing, to avoid being cornered and to strike its hole
exactly when pursued by its enemies than to run a certain
number of feet per second. The total distance which has been
a measurement warmly advocated has advantages but it does
not show really significant variations from the true path, although
there is always, we will grant, a relation between the total num-
ber and amount of the errors and this total distance. If a rat
always took the shortest way home, if it did not have its own
peculiar way of getting out from its hole, perhaps this measure
would express the facts more truly. The animal runs out into
the maze a little way, runs back, runs out a little farther and
then back, etc. This is a purely instinctive activity quite on a
par with those natural movements in and about a rat's hole
that insure it an open way home and such actions may
not at all signify that the path as far as traversed is not familiar.

THE WHITE RAT AND THE MAZE PROBLEM 371

These runs then, which are included in the total distance, are
not of the same nature as those other errors which take it en-
tirely off the trail. They indicate its method of learning. They
are interesting of course, and perhaps valuable for learning but
they are not of the same class as the others. In all of this
work, since our interest lay in the ability which the animals
possessed to follow or to neglect a certain sensory stimulus, the
errors consisted in leaving the true path. But it is not alone
the number and kind of errors which excite our interest in this
problem but also the distribution of the errors within the maze

itself.

DISTRIBUTION OF ERRORS

The following tables show the distribution of errors in the
different mazes. Whether a cut de sac will be entered or not
depends upon the general direction in which it extends, its
relation to the food box and whether it is so placed that the
animal enters it headlong, etc., etc. For these reasons and for
the sake of fairness we have chosen to compare the total scores
of alleys 1, 2 and 3 with the corresponding error scores of 5, ^
and 7,3 in the Hampton Court Maze. The normal maze record
shows a greater score on every count for the first three than
for the last three alleys. The combined black-white maze table
reveals the same thing, as does also the cutaneous normal
records. In the cutaneous maze, alleys 4 and 5 were very near
to the food box, so near that in the open maze the animals
sometimes succeeded in jumping across. For this reason these
alleys were very attractive and the different results in the open
maze may, perhaps, be explained in this way. It will be ob-
served, however, that in the last three counts in the open maze
also, when the automatism is beginning to be perfected, favor
the final alleys. The olfactory maze, where the trail is in the
true path, gives a record where the conditions are reversed, but
when the trail is in the alleys the normal standard is again
approached although the degree of difference between the first
three and the last three alleys is less. The elimination of the
final members of the series first is not only true of the groups
as a whole but also of the individual animals. The records of
41 rats in the normal, black-white and cutaneous groups were
gone over and only five rats found where the relation was re-

3 The cid de sacs are numbered in the order in which they occur in the maze.

372

STELLA B. VINCENT

versed and two where they were the same. The number might
have been easily doubled but it seemed useless to do so.

TABLE III
Distribution of Errors, Normal Maze

Alley

Alley

Alley

Alley

Alley

Alley

Alley Allevs

Allevs

1

2

3

4

5

6

7 1,2,3

5,6,7

Total errors

81

112

146

82

68

121

25

309

214

Trial at which the error

was not made three

times in succession by

any rat

18

21

26

5

13

16

11

31.6

. 13—

Average errors per rat

after 10th trial

1.1

1.5

2.2

.7

1.2

1.

.6

.9

Average error per rat

from 20th to 35th trial.

.3

.9

1.

.3

.2

.1

.1

.7

.1

TABLE IV
Distribution of Errors, Black-white Maze

Total errors

Trial at which the error
was not made three
times in succession by
any rat

Average errors per rat
after the 10th trial

Average errors per rat
from 20th to 35th trial.

Alley Alley
1 2

31 55

16

.6
.2

19
1.7

.6

Alley
3

45

7.5
.8
.3

Alley
4

43

.6
.5

Alley
5

11

4.5

.1

i

Alley
6

24

6
.1
.05

Alley Alleys Allevs
7 ' 1, 2, 3 5, 6, 7

131

2.5 14.2
.1 1.
.15 .36

40

4.3

.11
.1

TABLE V
Distribution of Errors, Olfactory Maze, Trail in True Path

Alley
1

Allev
2

Alley
3

Alley
4

Alley
5

Allev
6 *

Alley
7

Allevs
1,2,3

Allevs
5,6,7

Total errors

1
1

14
11

12
17

16

16

14
10

36

14

17
9

27

9 +

57

Trial at which the error
was not made by any
rat three times in suc-
cession

11

Average errors per rat
after the 10th trial

0

0

1.1

.9

0

.3

.3

.4—

.3—

Average errors per rat
from 20th to 35th trial.

0

0

.5

.1

0

0

.1

.16

.03

THE WHITE RAT AND THE MAZE PROBLEM

373

TABLE VI
Distribution of Errors, Olfactory Maze, Trail in the Cul dc sacs

Alley

Alley Alley

Alley

Alley

Alley

Alley

Alleys

Alleys

1

2 3

4

5

6

7

1,2,3

5,6,7

Total errors

0

40

59

62

35

73

22

99

130

Trial at which the error

was not made by any

rat three times in suc-

cession

0

7

32

6

5

10

8

13

7+

Average errors per rat

after the 10th trial

0

2.1

2.3

5.3

2.3

1.6

.3

1.46

1.4

Average error per rat

from the 20th to the

35th trial

0

1

1.5

4.6

1.1

1.

.1

.83

.7

TABLE VII

Distribution of Errors, Cutaneous Maze — Sides Enclosed

Alley
1

Alley
2

Alley
3

Alley

4

Alley
5

Alley
6

Alleys
1,2,3

Alleys
4,5,6

Total errors

Trial at which the error was
not made three times in

succession by any rat

Average errors per rat after
*the 10th trial

53

26
2.6
.8

25

17

.8
0

52

18
1.6
.6

60

23
2.1
.6

19

8

.5
0

1

2

.1
0

130

20.3

1.6

.5

80

11.
9

Average errors per rat from the
20th to the 35th trial

.2

TABLE VIII
Distribution of Errors, Cutaneous, Open Maze

Alley
1

Alley
2

Alley
3

Alley
4

Alley
5

Alley
6

Alleys
1,2,3

Alleys
4,5,6

Total errors

30

33
3
1.6

29

17
2.5
1.3

48

17
2.3
1.3

66

25
3.1
.6

37

10
2.6
1.1

4

2

.3
0

107

22.3
2.6

1.4

107

Trial at which the error was
not made by any rat three
times in succession

12.3

Average errors per rat after
the 10th trial

2

Average errors per rat from the
20th to the 35th trial

.5 +

In a normal maze, when the cul de sacs are at all comparable,
the number and persistence of the errors of the first part of the
series may be explained by the laws of association, i.e., they are

374 STELLA B. VINCENT

made first, made most frequently and therefore persist longer.
On the other hand, it may be that the food box as the final
and probably the strongest member of the motor series may
become more directive and react back into and help to organize
the later members of the series most closely connected with it
in time much as other memory series — not motor — are known
to be organized.

The black-white maze influenced the distribution of errors
but as the rat's vision is notoriously poor the influence was
chiefly seen in the smaller amount of difference between the
records of the first and the last cut de sacs as the character of
the distribution remained the same.

In the open maze the errors were more evenly distributed
for the reasons given above. The animals in the olfactory maze
were really learning to follow a trail and incidentally learning a
motor series. The incidental errors increased toward the end
of the series although the last two counts show a balance in
favor of 5, 6 and 7. The experiment when the trail was in the
cul de sacs gave a situation where the true path resembled that
of the normal maze but the cul de sacs were made more attrac-
tive because of the odor and thus influenced the totals. The
last three counts, however, are lower for 5, 6 and 7 in this
experiment also.

Sensory clues in these mazes, not only favor accuracy but
also affect the distribution of the errors among the members
of the series of blind alleys. The influence is seen both in the
degree of difference and in the character of the distribution.
The distribution could be said to be less mechanical and not
quite so predictable as in the normal maze although on the
whole the relations were similar in all of the mazes.4 The final
members of the cul de sacs were entered less frequently and elimin-
ated first.

4 Since making these tabulations and comparisons Miss Hubbert's paper has
appeared, " Elimination of errors in the maze," Jour. Animal Behav., Vol. 5, No. 1.
Her results contradict those reported here, but this work must stand on its own
merits. I cannot at this place enter into a discussion of Miss H's. paper. It
scarcely seems fair, however, when there are so few cul de sacs, to eliminate the
first and the last, where the chief differences are seen, from the comparison. There
is always overlapping in the middle of any series. If the nature of the maze com-
pelled this elimination then no general conclusions should be drawn.

Contributions from the Zoological Laboratory of the Museum of Comparative
Zoology at Harvard College, No. 262

THE GRASPING ORGAN OF DENDROCOELUM

LACTEUM

ELIZABETH S. P. REDFIELD

The grasping organ of Dendrocoelum lacteum is situated on
the ventral surface of the anterior part of the head of this worm,
between its two auricular appendages.

Ijima ('84) records this organ as used for locomotion against
currents. Gamble ('96, pp. 35-48) describes this species as
' affixing a sucker, placed on the under side of the head, to
the substratum, and pulling the posterior end close to this.
The sucker, discovered by Leydig, is even better developed in
(Planaria) punctata, P. mrazekii, and P. cavatica, and is an
efficient adhering-organ, which has probably been developed
from a similar but simpler structure, found in a considerable
number of both fresh-water and marine Triclads."

How far these interpretations apply to Dendrocoelum lacteum,
will appear in the following account. This paper is based on an
experimental study of the function of the grasping organ in
Dendrocoelum lacteum, and I wish to thank Dr. G. H. Parker,
under whom the work has been done, for his kind assistance.

STRUCTURE OF THE GRASPING ORGAN

The grasping organ of Dendrocoelum lacteum, when studied
under a low power of the microscope, appears as two symmet-
rically placed opaque thickenings, near the middle of the anterior
margin of the head. In the resting condition, these structures
project forward very slightly, forming a pair of rounded lobes,
as shown in figure 1, A.

As the planarian moves about in ordinary locomotion, this
organ is in continual activity, stretching out, contracting, now
grasping an object, now rejecting it. When grasping at materials
these lobes are stretched forward fully twice their resting length
and press the object, one on each side (fig. 1, B). The form of

375

376

ELIZABETH S. P. REDFIELD

A

C.

Figure 1. Head of Dendrocoelum; A and B, dorsal views; A, grasping organ
contracted; B, grasping organ expanded; C and D, lateral views; C, grasping
organ contracted; D, grasping organ expanded. Magnified 25 diam.

pmcL

--prncl.

Figure 2. Ventral view of grasping organ expanded; drawn from a wax recon-
struction; a, anterior; p, posterior; prnd, graspers. Magnified 50 diam.

GRASPING ORGAN OF DENDROCOELUM LACTEUM

377

the grasping organ as seen in surface view, is well represented
in figure 2. It was with great difficulty that a planarian was
killed with the grasping organ extended, and the preparation
from which figure 2 was drawn was the only one in perhaps a
hundred to show the organ favorably.

The organ consists of two ridges on the ventral side of the
head, which converge abruptly and meet as two thickened, club-
shaped lips at the anterior end. Posteriorly the ridges become
broad and low, and merge into the ventral surfaces of the head.

Evidently this specimen was fixed in a condition of semi-
extension, for a transverse section of another Dendrocoelum
(fig. 3) shows the median groove to be greatly narrowed and
the ridges on either side to be folded together.

mu. cr

7im. crc.-->-

^mu. Ig.

Figure 3. Transverse section .of grasping organ showing musculature; mu. crc.
circular muscles; e'th. epithelium; mu. Ig. longitudinal muscles. Magnified
75 diam.

There are no rigid structures to be discovered in sections of
the grasping organ. Such sections show an abundance of mus-
cular tissue (fig. 3). It would appear probable that the grasping
organ is extended through the action of these muscles upon the
body fluids, thus producing a pressure which would stretch the
anterior part of the ridges and perhaps give to the head an upward
turn, thus bringing the ventral ridges into an anterior position.
Figure 1, C and D, illustrate how this action may take place.
The movement is too quick to allow of very accurate analysis,
but it is evident from the way in which this organ is used and
from the structure as seen in figure 1, that it is more appro-
priately designated a grasping organ, than a sucker.

378 ELIZABETH S. P. REDFIELD

FUNCTIONS OF THE GRASPING ORGAN

Certain classes of materials, such as substances suitable for
food, call forth in Dendrocoelum a very striking reaction, which
involves the grasping organ. If, for example, a pair of forceps
which has been dipped in a twenty per cent cane-sugar solu-
tion is held in front of a Dendrocoelum, the animal will suddenly
dart its head forward and seize the forceps with the grasping
organ, and adhere to them so firmly that the creature can be
shaken loose only with difficulty. The word ' pounce ' de-
scribes this reaction more vividly than any other, and the idea
of a pouncing worm can surprise the reader no more than the
reaction did the author.

A moving bait will call forth this reaction more readily than
a motionless one. Living Hydra, and pieces of meat are seized
by Dendrocoelum lacteum in this manner. These facts suggest
that the grasping organ is used to capture and hold the prey of
the planarian, until the pharynx can be affixed and feeding
begin. To ascertain whether the grasping organ was primarily
concerned with feeding, the following experiment was tried. A
solution of brown sugar, which was visible in water, was applied
by a capillary tube to various regions on the surface of the
worm. On stimulating the lateral edges there was a local
expansion of the body, a condition to be observed anywhere"
between the posterior end and any point almost as far anterior
as the auricular appendages. In the neighborhood of these
appendages, the application of the sugar solution caused the
head to be turned towards the region of stimulation, the grasping
organ to seize the end of the capillary tube, and feeding to begin.

Animals tested in this way with a capillary tube containing
only water instead of brown-sugar solution, gave no reaction,
and consequently the responses to the sugar solution could not
be regarded as due to the mechanical disturbance produced by
the slight current of water. From this experiment, it seems
clear that the receptors which initiate the feeding reaction of
the worm are located upon its head.

As a further test of this conclusion, the following experiments
were made. Worms from which the brain, eyes, and auricular
appendages had been removed by decapitation, were put each
in a Syracuse watch-glass full of water and left standing twenty-
four hours. A twenty per cent brown-sugar solution was then

GRASPING ORGAN OF DENDROCOELUM LACTEUM 379

applied from a capillary tube to their lateral margins. In no
case was there a response of the whole worm, as when feeding
begins, though in each instance a local expansion of the side
of the body occurred where the sugar solution had been applied.
As a preliminary experiment, before removing their heads, all
the worms were tested with a brown-sugar solution, and found
to feed upon it in a normal manner. The heads of the decapi-
tated worms were kept, each in a watch glass, and subjected to
the same stimulus as that used on the trunk of the worm. They
responded by coming up to the tube and remaining close to it,
the grasping organ being agitated in the same manner as in the
normal worm about to begin feeding. Occasionally a head
would circle away from the tube but it always came back again.

These experiments confirm the previous one, in that they
show that the receptors for the feeding reactions are located
upon the head of the worm. One might object to drawing this
conclusion on the grounds that animals whose heads had been
removed might be expected, as a result of the operation, to fail
to respond normally; but since the heads, which had been sub-
jected to as great a shock as the trunks, if not a greater one,
reacted normally, this objection can have no weight. In order
to determine whether the grasping organ itself, or the auricular
appendages were the receptors, the following experiment was tried.

The grasping organ, after having been stimulated to action,
was removed by catching it with forceps and pulling it out.
The results were surprisingly uniform; worms without the grasp-
ing organ did not attempt to feed. It would appear from this
experiment that the receptors for the feeding reflex, are located
probably on the sucker itself.

Mechanical and certain chemical stimuli (as a twenty per
cent solution of sodium chloride) call forth a rapid forward
movement of the animal, like that of some leeches, produced
by (1) extending the body, (2) attaching the grasping organ to
the substratum, (3) releasing the posterior end, contracting the
body, (4) attaching the posterior end, and then again (5) carry-
ing the body forward, thus repeating the whole operation. If
the grasping organ is removed, the animal may still progress
in a leech-like manner, attaching itself by the action of the
general ventral surface of the anterior end combined with that
of the margins of the body in the same region. If the head is

380 ELIZABETH S. P. REDFIELD

cut off, the animal can also still progress in a leech-like manner.
Consequently the grasping organ is not essential for this mode
of locomotion. Animals in a dish of water held in a current,
attach themselves to the substratum by the tail, but not by the
grasping organ, thus showing that the grasping organ is not
used to prevent the animal from being washed away.

In my own experiments, however, there is nothing to show
that the grasping organ may not be used for locomotion; the
point insisted upon is the importance of its relation to feeding.'

SUMMARY

From the foregoing it is evident that the grasping organ of
Dendrocoelum lacteum is primarily employed by the animal in
feeding. This grasping organ is used to seize and hold material
on which Dendrocoelum lacteum feeds. It is stimulated to
activity by appropriate materials applied to the receptors located
on the anterior part of the worm. The grasping organ may be
used in certain forms of locomotion, but it is not essential to
this operation.

POSTSCRIPT

Since the completion of this paper, a note by Julius Wilhelmi,
Einige biologische Beobachtungen an Siisswassertricladen, has
been published in the Zoologischer Anzeiger, Bd. 45, pp. 475-479,
in which these grasping reactions are recorded.

BIBLIOGRAPHY

Gamble, F. W. 1896. Platyhelminthes and Mesozoa. The Cambridge Natural

History, London, vol. 2, pp. 1-96.
Ijima, I. 1884. Untersuchungen liber den Bau und die Entwicklungsgeschichte

der Susswasser-Dendrocoelen (Tricladen). Zeitschrijt jiir wissenscliaftliche

Zoologie, Bd. 40, pp. 359-464, Taf. 20-23.

THE HABITS AND NATURAL HISTORY OF THE
BACKSWIMMERS NOTONECTIDAE

CHRISTINE ESSENBERG

From the Zoological Laboratory oj the University of California

The purpose of this article is to record observations made
on the aquatic Hemiptera Notonectidae. These insects were
chosen for the experimental work because they are found in
great abundance and because very little is known about their
behavior. The work was done in the Zoological Laboratory of
the University of California under Professor S. J. Holmes, to
whom I wish to express my gratitude for kind suggestions, and
criticisms. Thanks are also due to Professor C. E. Van Dyke
for his help in determining the species.

The Notonectidae are commonly known as backswimmers
from their habit of swimming on their backs. They are widely
distributed, extending from the arctic to the tropical regions.
Kirkaldy has recorded about twenty different species of Noto-
nectas. According to J. R. de la Torre, Bueno, twelve of these
species are peculiar to America. The bugs here described were
collected in a small pond on the university grounds, the species
identified being four in number, Notonecta insulata Kirby,
Notonecta undulata, variety Charon, Notonecta indica, and an
unidentified spec es. The last named is most abundantly rep-
resented. Notonecta insulata is the largest of the four species,
ranging in size from five to five-tenths mm. in width. It is
usually of a dark or bluish-black color. Notonecta undulata
and Notonecta indica are smaller and more slender than Noto-
necta insulata. Notonectas show many striking adaptations to
aquatic life : their backs are convex and boat-shaped, the ventral
surface being flat. The hind legs are long, specially flattened
and fringed, thus serving as oars. The two pairs of forelegs
are sparsely covered with hairs and are provided with claws.
The latter serve for the capture of food and for attachment to
the surface film, from which they hang with their heads down-
ward, the posterior part of the ventral surface being exposed

381

382 CHRISTINE ESSENBERG

to the air. When in this position the fore- and middle-legs are
slightly bent so that the claws are at the surface. The insects
often rest at the bottom, clinging to sticks or weeds.

It is also interesting to note that the hairs of the body are
so arranged as to facilitate respiration. On the forelegs are
two rows of hairs pointing in opposite directions, and partly
covering the spiracles on the thorax. The ventral surface of
the thorax has a double row of thick hairs on both sides of the
margin, pointing posteriorly and meeting the hairs of the abdo-
men. There is also a double row of hairs on each lateral margin
of the abdomen; the hairs of the outer rows increase in length
as they approach the posterior end of the abdomen, where they
end in one row of long tufts. The inner rows of marginal hairs
cover the pleura and can be napped back by the contraction of
the abdomen. The carina or the ventral midpart of the abdo-
men is thickly covered with hairs which extend laterally on both
sides and overlap the hairs from the lateral margin, which
extend toward the middle line. Thus the rows of hairs form a
waterproof covering over the gutters which he one on each side
of the carina and serve for the conveyance of air. In addition
to the rows of long hairs described, the whole surface of the
abdomen is covered with short hairs. On the dorsal surface,
beneath the wings, there is a row of hairs between each segment,
pointing posteriorly, while fine hairs cover the entire dorsal
surface of the abdomen. The hairs are covered with an oily
secretion which prevents their getting wet.

Three pairs of spiracles are found on the thorax, and a pair
on each segment of the abdomen in the pleura. The air finds
entrance to the spiracles from the posterior end of the body,
where an opening is formed by the tufts of hairs as soon as the
animal reaches the surface of the water. The hairs cling together
and close the opening as soon as the animal is submerged. Some-
times the whole fringe is lifted like a lid from the pleura when
the animal reaches the surface of the water, closing again as soon
as it sinks. The bug comes to the surface to receive a fresh sup-
ply of oxygen and to emit carbon dioxide. The bug being sur-
rounded by air, is lighter than the water so that it is compelled
to keep the rowing legs in constant motion in order to keep
beneath the surface. As soon as the leg-motion ceases, the air
buoys the insect up until it meets the surface film. As soon as

THE HABITS OF NOTONECTIDAE 383

the animal is suspended by the surface film, it begins to move
its forelegs. Hoppe suggests that by moving the legs the insect
forces the air into the spiracles in the thorax. I am rather
inclined to believe that it is trying to straighten out the hairs
and to brush away the impurities, because the animal performs
these movements every time some foreign substance is dropped
on the thorax. If a small particle of asphalt be placed on the
thorax, the animal moves the legs in an effort to free itself from
it, and if it can reach the part, will also use the beak for the
same purpose. It brushes the ventral and dorsal surfaces of
the abdomen with the hind legs, and especially the tip and
lateral margins.

Notonecta, if sealed in water, dies within from three to five
hours. In this case it hangs to the surface film all the time
with its body covered with gas bubbles. If a drop of oil is
put on the ventral surface of its body, the creature dies imme-
diately. If the backswimmer is sealed in the water from which
the oxygen has been expelled by boiling, death results in from
five to ten minutes. If the water is left exposed to the air, the
insect clings to the surface film almost constantly, with the
fringes lifted and the breathing pores exposed, while under
ordinary circumstances it comes to the surface only once in
every thirty or forty minutes. On a dry substratum, if exposed
to sunshine, the insect dies within forty or fifty minutes; in a
cool and shady place it can live much longer.

In several books on insects the statement is made that Noto-
nectidae bury their eggs in the stems of plants. I have found
that this is not the case in any one of the species studied. The
ova are usually deposited and glued on sticks or on the stems
of plants. Very often I have found the eggs deposited on the
backs of other insects, such as dragonfly larvae, and on the
walls of the aquarium. Soft sticks were placed in the aquarium.
The eggs, however, were never found buried in the stems, but
were always deposited in rows around the sticks. In the pro-
cess of ovoposition, the female attaches herself to the lower
surface of the stick and moves the posterior segments very
vigorously until the egg is extruded and attached, then she
moves away. Frequently embryos are found in a row with
their heads pointing in the same direction. If the eggs are
examined immediately after they have been deposited, the sur-

384 CHRISTINE ESSENBERG

rounding gluing substance is very plainly seen. The eggs are
beautifully white, elongated, and cylindrical, with the attached
side slightly flattened. The chorion is decorated with small
depressions. The eggs of Notoneda insulata are about two
mm. long. Those of smaller species are slightly smaller in size.
After an incubation period of twenty days, the chorion splits
at the anterior end and the nymph crawls out. In working
out from the envelope the nymph first gets its head out, con-
tracting and expanding the body and bending over it pulls itself
out of the case, sometimes stopping to rest, then continuing the
process again. Inside the coarse egg envelope and surrounding
the nymph is a thin transparent membrane which occasionally
breaks, allowing the animal to escape while the membrane
remains attached to the outer envelope, but often the nymph
is still surrounded by the membrane after leaving the egg-case
and must work its way out from it. As soon as the nymph is
free it goes to the bottom and rests a while and then begins
to move about actively, searching for food. The nymphs are
very beautiful, with large compound eyes which are conspicu-
ously red. The body is transparent white. The long hairs are
well developed on the lateral margins and over the pleura,
which are shallower than in the adult; the hairs on the middle
carina are short and irregular. After from seven to ten days
the first moult takes place. Hoppe states that there are five
complete series of moultings in Notoneda glauca, and J. R.
de la Torre, Bueno, thinks that there are about five moultings
in all the species. I have not been able to follow the complete
series of moultings, because it is extremely difficult to raise
nymphs in an aquarium owing to the fact that they attack one
another even in the presence of an abundance of food. They
are very sensitive to foul air and contaminated water. The
nymphs differ from adults in their behavior in that they come
more frequently to the surface, about once in every three or
five minutes, and the fringes are usually flapped back, while
in the adult the fringes are lifted only when the insect is in
great need of oxygen.

The food of Notonectas consist of animal matter, chiefly,
living or dead insects, but they do not hesitate to attack other
animals. Thus Bueno has observed the nymphs of Notoneda

THE HABITS OF NOTONECTIDAE 385

undulata kill and suck the juices of young fish which had just
emerged from the eggs. I have seen the nymphs and adults kill
young Diemyctylus torosus as soon as they emerged from the
gelatinous envelope. I have also observed a nymph dragging
a Diemycty'us larva which was about three times its own size.
The nymphs usually attack May-fly larvae and drag them about,
although the latter are. twice the size of the aggressor. The larger
species usually attack the smaller ones and the young are eaten
by the adults, being seemingly preferred to other kinds of food.
Notonecta nymphs of equal age and size attack each other
and suck each others juices during their attack until one or
both are dead. They often attack dragonfly nymphs, which
are many times their own size, usually approaching from beneath,
grasping them with the forelegs and piercing the body with the
proboscis. The nymph has no chance of escape from the insect,
the latter continuing its hold no matter what position the victim
may assume. The dragonfly nymph does not die from the first
attack but only after a number of punctures. Notonecta is also
destructive to young fish.

The Notonectidae are not easily affected by chemicals, as
they may live in strong sodium chloride solution without showing
any change in activity. They can live in five per cent alcohol
for days. They become drowsy in twenty per cent alcohol, but
if put in pure water they revive again. Several specimens were
kept in strong copper sulphate solution for several weeks and
did not suffer from it, while other animals dropped in the same
liquid died within a few minutes. A Notonecta insulata was
kept alive in Gilson's fixing fluid over two hours.

Notonectas are positively phototactic and can be led by the
light in any direction. If an aquarium containing Notonectas
is left in the sunshine, the bugs move quickly to the lighted
end of the tank, and fly toward the light, producing a buzzing
sound. If the aquarium is placed between two lights of different
intensities, the Notonectas usually collect near the light of
greater intensity, as is shown in the following table:

Two lights, one of one hundred candle power, the other of
thirty-two candle power, were placed one at each end of the
aquarium. Every five minutes the lights were reversed and the
insects moving toward each light counted.

386

CHRISTINE ESSENBERG

One hundred candle power

29
30
29
27
34
30
29
24
31
30
25
21
25
23
23
26
28
31
• 20

Thirty-two candle power

5

4

5

7

0

4

5
10

3

0

9
13

9
11
11

8

6

3
14

If Notonectas are put in a high jar and light admitted from
below, the bugs are more numerous at the bottom. If the
light shines from above, the bugs are more numerous on the
surface. This proves that Notonectas have a strong positive
phototaxis. However, their phototaxis may be modified by
some such factors as temperature. Thus, an increase in tem-
perature results in an increase in phototaxis, as shown in table
following :

Number of Notonectas, thirty-four. Two lights, one sixteen
candle power, the other one hundred candle power, were placed
at either end of the aquarium and were turned on alternately
every five minutes and the animals counted. The number
moving toward the light is indicated by a plus sign, those moving
away or at random, by a minus sign. Temperature increased
gradually.

Weak light Temperature Strong light

+

—

+

—

18

16

16°

30

4

15

23

24

10

28

6

18°

30

4

30

0

29

5

32

2

20°

33

1

32

2

• 34

0

33

1

22°

34

0

32

2

34

0

34

0

24°

34

0

34

0

34

0

34

0

26°

34

0

THE HABITS OF NOTONECTIDAE 387

34

0

34

0

34

0

28°

34

0

34

0

34

0

34

0

30°

34

0

34

0

34

0

34

0

32°

34

0

34

0

34

0

At temperature of sixteen to eighteen degrees the insects are
slower in their motions. At a temperature of twenty to twenty-
two degrees they become more active, and with a further increase
of temperature they are still more active, moving toward the
light hurriedly and remaining crowded there. In a temperature
of thirty-two degrees and above, the water bugs are slower in
their movements, dying in a temperature of forty to forty-
two degrees.

With increasing need for oxygen as is the case when Noto-
nectas are placed in a high jar which is kept in diffused light
and the temperature gradually increased, the bugs always come
to the surface. But if the jar, containing the insects, is put
in a dark room and a light is placed below the jar and then the
temperature gradually increased as before, the bugs, attracted
by the light, remain at the bottom, becoming more and more
positively phototactic with the increase of the temperature,
beating their heads against the bottom of the aquarium until
they die in an effort to get nearer the light. Rarely one or
more escape from the center of attraction and rise to the surface.
If, however, two lights are placed, one above, the other below
the aquarium, and the temperature gradually increased, the
backswimmers rise to the surface and remain there even after
the light above has been turned off, regardless of the fact that
the light below is still shining. The last experiment indicates
that although the creatures are strongly positively phototactic,
after they have departed once from the source of light, the need
of oxygen overcomes their phototaxis.

The question arises, Why do the insects rise to the surface
with the increase of temperature ? As I have explained above,
the animals carry air under the hair surrounding the body and
in the spacious air tubes. Thus they are rendered lighter than
the water and must keep their appendages in motion in order
to keep beneath the surface. The increase in temperature
brings with it an increase in the activity of the animal with a

388 CHRISTINE ESSENBERG

resultant greater need for oxygen for the metabolic changes
which are taking place, hence the bugs rise to the surface in
order to obtain the oxygen from the atmosphere. That the
bugs remain at the bottom of the aquarium in spite of the high
temperature, indicates that there are two opposite forces in
action, viz., the need of oxygen and the positive phototaxis.
The latter is increased with the increase of the temperature
and is evidently so strong that the animals, after they have
once been attracted by the light, can not depart, but struggle
to get to the light at the bottom until they die, while, after
they have once departed from the source of light the tendency
of the bugs, with the increase in temperature, is to gather at
the upper light. And even after the upper light is extinguished
and the lower light is shining, the bugs still persist in remaining
at the surface, because the demand for oxygen is greater than
the positive phototaxis. The bugs are probably led by instinct
to seek the surface when they become aware of the need of
oxygen, and again they are only led by their strong positive
phototaxis to go to the bottom of the aqtiarium. In normal
conditions the Notonectas rise to the surface at more or less
regular intervals. The same is true in diffused light when the
temperature is increased, the bugs always rise to the surface
and remain there. The buoyant force plays an important role
here, but it may be of secondary importance only.

If the insects are sealed in ordinary water, they first swim
about, but later they remain at the surface all the time. They
may go down for a moment but return immediately to the
surface, usually remaining there until they die.

If Notonectas are sealed in water from which the oxygen has
been expelled by boiling, the air carried by the bugs is absorbed
by the water, hence the insects drop to the bottom and do not
rise, although they try hard to reach the surface. In this con-
dition they die in from five to ten minutes. In this case buoyant
force is of least importance and it is only this specific response
which leads the animals to the surface in their quest for oxygen.

If Notonectas are placed in boiled water in an open dish they
immediately come to the surface, remaining there until the
amount of oxygen in the water has increased. When a light was
placed below the aquarium containing boiled water, the Noto-
nectas collected around it, the majority of them dying in a few

THE HABITS OF NOTONECTIDAE 389

minutes, while a few repeatedly returned to the surface for
oxygen, sometimes picking up their dead companions on the
way and carrying them to the surface. These experiments
were tried with adult Notonectas and with nymphs with the
same results.

Cold does not destroy the phototaxis of Notonectas, but when
the insects become chilled, they move more slowly toward the
light. If kept in ice-water for some time, the insects become
so chilled that they drop to the bottom. If the water is shallow'
the insects come to the surface when the temperature is increased
but if the water is from fifteen to thirty cm. in depth, while they
show signs of life as soon as the temperature of the water is
increased, they fail in their attempts to reach the surface. Some-
times they succeed in rising a few inches, swimming obliquely,
falling back after each successive effort. It is an interesting
fact that, while under ordinary circumstances the bugs must be
in a constant motion in order to remain beneath the surface,
here the reverse is true, the bugs working in the greatest effort
to reach the surface and falling back each time. Evidently they
have lost their air in some way or another. Thus the animals
may lie until an increase in temperature arouses them to greater
activity. Metabolism goes on, the remaining oxygen is used
up, and when the animals attempt to rise there is no surround-
ing air to buoy them up, and death from lack of oxygen is the
result. While in shallower water they have more access to free
oxygen and can more easily reach the surface of the water.
Hoppe believes that the cold water dissolves the carbon dioxide
more readily and that, therefore, the animals, losing the sur-
rounding gas, are rendered heavier and sink down. The fact
of the bugs' trying to reach the surface, leads one to believe
that the effort is an instinctive one when the animals are in
need of oxygen.

If Notonectas are exposed to an arc light they first show a
tendency to negative phototaxis for a moment, then they fly
to the light and are burned. Young nymphs are positively
phototactic from the very first day. I have experimented with
light reactions on Notonecta insulata which were only three
or four hours old. When exposed to light in a dark room, they
crowded to the lighted side of the aquarium.

Notonectas are negatively geotropic and are usually found at

390 CHRISTINE ESSENBERG

the surface when at rest. This, however, may be due to the
fact that in an aquarium without any weeds or sticks the sur-
face film serves as the only medium of attachment. A stronger
evidence in favor of negative geotropism is that the bugs, when
placed on the wall, always crawl upward. Again, when the bugs
are placed in a high jar which is kept in diffused light or in
perfect darkness, they always rise to the top as soon as the jar
is reversed. But here we have to deal with two factors, the
need of oxygen in the closed jar, and the negative geotaxis.

Notonectas are positively rheotactic, always swimming against
the current. They have positive thigmotaxis and usually are
attached to some object when at rest. Sometimes they are
attached to one another, three or four in number.

SUMMARY

Notonectas are widely distributed. They are very voracious
and attack animals many times their own size. The insects
are well protected by the thick layer of surrounding air, hence
chemicals have very little influence on them. Notonectas have
a strong positive phototaxis. The phototaxis increases with the
increase of the temperature and with greater light intensity.
When exposed to arc light or to bright sunlight, they imme-
idately take to their wings, flying toward the light. At a tem-
perature of zero centigrade they become chilled, lose their air,
and drop to the bottom of the aquarium and die if the aquarium
is deep. They are positively rheotactic, always swimming against
the current. The young hatch within twenty days and are well
adapted to their environment from their very first day of life.
They resemble the adults in their behavior and instincts.

LITERATURE CITED

Kirkaldy, G. W. Miscellaneous Rhynchotalia. The Entomologist, 34, 5-6.

1897. Revision of the Notonectidae. Trans. Entom. Soc, London, 4, 392-426.
Buena, J. R. de la Torre. The Genus Notonecta in America, North of Mexico.

1905. Journ. N. Y. Entom. Soc, 13, 143-167.

1908. Concerning the Notonectidae and Some Recent Writers on Hemipter-
ology. Canad. Entom., 40, 210-211.
Delcourt, A. De l'influence de la temperature sur le development de Notonecta.

1908. C. R. Ass. France Av. Sc. Sess., 36, 244-245.
Holmes, S. J. Phototaxis in Ranatra. Journ. Cotnp. Neur. and Psvch., 15, 305.

1904.
Hoppe, Julian. Die Atmung von Notonecta glauca. Zool. Jahrb. Allg. Zool.

1912. & Physiol, 31, 189-224.
Severin, Henry H. P., and Harry C. Severin. Notonecta undulata Say preying

1910. on the eggs of Belostoma (Zaitha auct.) flumineum Say. Canad.
Entom., 42, 340.

SOME OBSERVATIONS ON THE INTELLIGENCE
OF THE CHIMPANZEE

W. T. SHEPHERD

Waynesburg College

The observations reported in this paper were made on two
chimpanzees; Peter, an ape on the vaudeville stage a few years
ago, and Consul, also lately, and I believe still, on the stage.
However, the writer is not certain that the latter ape exhibited
on the stage as Consul and observed by the writer was the
Consul extensively mentioned in the newspapers when brought
from Europe a few years ago. The manager represented the
latter vaudeville star to be the original Consul.

The observations made on Peter included those made at two
performances by him on the stage and in one private examina-
tion of him. The observations on Consul included seeing him
perform on the stage once and a private examination of him
by the writer. In the cases of both Peter and Consul the ob-
server questioned the keepers concerning the animal's perform-
ances, habits and training.

Of course, had it been practicable, observations should have
been made much more extensively to give satisfactory results.
But we believe that the observations reported warrant at least
a partial explanation of the apparently superior intelligence
exhibited by these and similar animals.

We shall first give a syllabus of the conclusions to which the
observations appear to lead, and the indications to which the
observed reactions seem to lead.

The writer believes that the apparently superior intelligence
of the apes is principally accounted for by:

1. The superior motor-equipment of the animals

2. The training which all show animals receive.

3. The semi-erect carriage of apes.
We note also that :

4. There are indications of intelligent imitation in the mental
make-up of the animals.

391

392 . W. T. SHEPHERD

5. There are indications of a low form of reasoning, or of
crude ideas in the apes.

6. There are indications of more human-like emotions than
monkeys such as the Rhesus manifest, e.g., sympathy.

7. They show superior capacity for intelligent reactions to
that of any of the lower orders of animals. Probably, largely
on account of superior motor-equipment and their upright
carriage.

8. With all allowances made, apes are superior in intelligence
to all sub-humans and so are nearer to man than any of the
other lower animals.

OBSERVATION OF PETER ON THE STAGE

>

Peter, dressed like a man, sat down to a table, put on a napkin
and ate food with a knife and fork. After eating, he struck a
match, lighted a candle, lighted a cigarette and smoked. He gave
his keeper, McArdle, a light for the latter's cigarette from his own.

Upon command from the keeper, the ape danced on the stage
fairly well, much like a man, a sort of jig-dance.

When roller-skates were put on his feet, he skated around
the stage skilfully. He appeared to skate as well as a girl whom
he chased around the stage.

The animal got upon a bicycle himself and rode it around the
stage. He chased the girl around the stage while riding the
wheel. While riding, he drank water from a cup handed him.
Then he skilfully rode between a number of bottles and cut a
sort of figure 8 while riding between the bottles. The ape
picked up a bottle and drank out of it while riding.

The animal rode the bicycle up an inclined plane on the
stage. I noticed that he always increased his speed just before
coming to the inclined plane.

After performing these feats, Peter undressed and went to
bed, very much like a man does.

PRIVATE EXAMINATION OF THE APE

Upon command from the keeper, Peter took up a hammer
and a nail and drove the nail into the wall, quickly and without
observable awkwardness.

THE INTELLIGENCE OF THE CHIMPANZEE 393

IMITATION

As a test of imitation, I took out my watch and pressed on
the stem, slowly, and opened the watch three times while Peter
watched my actions with attention and apparently with interest.
Then I reached it to him: he held it and pressed on the stem
correctly several times, as if to open it. However, he did not press
hard enough, and the watch did not open. He thereupon at-
tempted to open it with his finger nails. The keeper stated to
me that the ape. had not received any training on that act.

APE WRITING

I held out a writing tablet and a pencil to Peter. He at
once seized them and began scribbling, i.e., making irregular
marks on the tablet. I made, in his sight, the letter T; a very
plain T, with simply one vertical and one horizontal stroke of
the pencil. The ape made a rather poor T, the first time shown.
He also made a W when I showed him once. Peter seemed to
like to use the pencil and tablet.

Upon being ordered by his keeper, the animal put a handker-
chief around my neck and tied it quickly and correctly when told
to do so. He also untied the knot quickly.

He came and slapped me on the lower limb when the keeper
bade him, though apparently with some reluctance. The animal
would lie down and sit up when ordered to do so.

APE LANGUAGE

When told to do so, Peter articulated the word ' mama."
The ape spoke the word something like a foreigner speaks it.
I noted, however, that the wife of the keeper pressed her fingers
against the ape's under lip when he spoke the word mentioned.

Now, let us attempt to analyze the factors in the apparently
superior intelligence shown in the actions of the ape, just recited.
In these acts, it seems we may see in the superior motor-equip-
ment of the animal one of the principal factors. Peter's com-
paratively perfect hands enabled him to use the knife and fork
in eating and to handle a cup in drinking. His man-like lower
limbs, his hands and his upright figure enabled him to ride the
bicycle, to pick up a bottle and drink while riding, etc. His
superior motor-equipment was also, as it seems to the writer,

394 W. T. SHEPHERD

a principal factor in such feats as driving a nail, tying a handker-
chief in a knot and untying it, etc., Dogs and other animals,
if they had the intelligence, lack the requisite motor-apparatus
to do such acts.

Another principal factor in all these acts was, doubtless,
training. We know that horses, dogs, and even pigs may be
trained to do many feats.

In the writing by the ape, his man-like hands together with
training, probably accounts for it, though imitation is possibly
a factor here. What accounts for his seeming eagerness to mark
on the paper might, however, be an interesting question. It
might be interesting also to test how far the ape might be taught
to carry his writing.

Peter's articulation of the word " mama " was very possibly
quite mechanical and parrot-like, perhaps not understood by
himself. However, it would be interesting to test how far such
speaking by apes might be carried.

Peter's correct attempt to open the watch looks like intelligent
imitation. However, though the keeper assured me that the ape
had had no training in that act, we might doubt the statement.
Then, perhaps, we could account for the reaction by the ape's
hands, his training and the well known curiosity of all monkeys.
If the veracity of the keeper can be relied upon, we have here,
as it appears to the writer, a case of intelligent imitation.

In the matter of the ape increasing speed to ride up the in-
clined plane, if training does not account for it, we appear to
see evidence of something very like ideation or reasoning of a
low order. If in this instance ideas are present, they are per-
haps what Hobhouse has named 'practical ideas," i.e., crude
and unanalyzed ideas. The writer is inclined to believe that
the latter together with motor-equipment and training are the
factors involved.

OBSERVATION OF CONSUL ON THE STAGE

Consul did most of the feats which Peter had done, such as
putting on a napkin and eating at a table, getting upon a bicycle
and riding around the stage, riding between nine bottles, riding
up an inclined plane. Consul did these acts in a similar manner.

The latter ape also performed some other feats: He poured
out his coffee, picked his teeth, cleaned his teeth with a brush,

THE INTELLIGENCE OF THE CHIMPANZEE 395

cleaned his tooth-brush. He rode a wheel with a lamp on his
head, held by himself while riding; he bored with an augur,
put the rounds in and fitted together a ladder, with some help.
He took a tablet and pencil and wrote, or the keeper said he
wrote; I do not know what he wrote. He took down the re-
ceiver of a telephone and listened, or appeared to listen. The
ape used a typewriter, that is, he pressed on the keys, so far
as the writer could judge, and can remember, perhaps without
knowing what he wrote.

Consul threaded a needle, cut paper into strips with scissors.
He took a key and locked and unlocked a padlock, and did other
acts requiring similar intelligence.

These acts by Consul, like similar acts by Peter, are perhaps
accounted for principally by the animals' motor-equipment,
erect carriage, and training. Some of them, such as riding up
the inclined plane and increasing his speed to go up, again raise
the question of ideation or a lower form of reasoning in the
animals' mental make-up.

IN PRIVATE EXAMINATION

The writer did not note in Consul the good nature and sym-
pathy shown by Peter. The former ape showed the brute in
him by a certain roughness of manner and by not obeying his
keeper very readily, etc.

In this connection we might mention that Peter showed evi-
dences of affection for his keeper by such acts as putting his
arm around the latter in a very human-like manner and kissing
him. When I questioned Peter's keeper as to sympathy, etc.,
in apes, to let me see for myself, the keeper, in the ape's sight,
pretended to have hurt his hand, whereupon Peter went to him,
put his arm around McArdle, and by his acts gave very evident
signs of ape sympathy. Peter acted in a similar manner when
I also pretended to have hurt my hand.

From the actions which have been enumerated of these two
chimpanzees, we may, as the writer believes, venture to con-
clude that:

1. The apparently superior intelligence of the chimpanzee is
accounted for principally by;

(a) Superior motor-equipment.

(b) Training.

396 W. T. SHEPHERD

(c) Their semi-erect and biped position.1

2. There are some indications of ideas of a crude and un-
analyzed character or of a lower form of reasoning in their men-
tal equipment.

3. That whatever are the factors involved in their reactions,
apes such as the chimpanzee are the most intelligent sub-humans
of which we have knowledge. As anatomically they are superior
to the lower orders of animals, by the criterion of structure as
indication of intelligence, they should be more intelligent than
their humbler congeners.

We must, as already stated, admit that more extensive obser-
vations should have been made on the individuals we have
considered. More individuals should also be observed and
experimented upon before drawing final conclusions on some of
the points at least involved.

However, the present writer cannot but believe that these'
and similar apes are the most intelligent of the sub-humans.
We feel that anyone who has observed their actions, who bears
in mind their anatomical superiority — their physical structure
as compared to that of any lower forms on the one hand and
to that of man on the other — who has noted their semi-human
looks and actions in general, cannot but agree with this latter
conclusion.

'Note. — As a corollary from (a) and (c) doubtless, the superior intelligence of
other lower species of monkeys is accounted for in part by their motor-equipment.

THE HABITS OF THE WATER-STRIDER
GERRIS REMIGES

CHRISTINE ESSENBERG

From the Zoological Laboratory of the University of California

CONTENTS

Introduction.

General Description of Gerris Remiges.

Locomotion.

Food Habits.

Cleaning Habits.

Death Feigning.

Phototaxis.

Thigmotaxis.

Rheo taxis.

Geotaxis.

Sense of Smell.

Sense of Hearing.
General Summary.
Literature Cited.

INTRODUCTION

The purpose of this article is to report the results of obser-
vations made of the aquatic Hemipteran Gerris remiges. This
work was carried on in the Zoological Laboratory of the Uni-
versity of California under the direction of Professor Samuel
J. Holmes, to whom I am indebted for many valuable sugges-
tions and criticisms. I also wish to express my gratitude to
Professor C. E. Van Dyke for help given in determining the
species.

The Gerridae, commonly known as water-striders, are of
world-wide distribution and include many different species.
The specimens were collected from small pools in Strawberry
Canyon, near the University Campus, Berkeley. They are
dark brown in color, the dorsal surface of the abdomen being
red. The ventral surface is usually gray and is furnished with
a plush-like coating which repels the water. The nymphs are
much shorter with bodies closely resembling those of adults,
but with the plush-like coating not so well developed. The
water-striders pass the winter as adults, hibernating under logs,
rocks, rubbish, and in other sheltered places. In the early

397

398 CHRISTINE ESSENBERG

spring they emerge, lay eggs along the edge of grasses growing
under water but near the surface, fastening them with a water-
proof glue. The eggs hatch within three weeks.

These insects move backward and forward with equal facility,
though the usual direction of locomotion is forward; but if the
animal is approached from the front it moves backward very
swiftly. It can also float on its back as has been observed
taking place in the aquarium during and after the cleaning
process of the insect, when it lies on its back for a considerable
time and is carried by the water, moving its legs or else keeping
perfectly quiet. When disturbed while on the water the insects
betake themselves quickly to the land or among the weeds, and
hide by clinging to the lower surface of the leaves or by lying
quietly on the ground.

For its food supply the water-strider depends upon such living
or dead insects as it finds floating on the surface of the water.
Sometimes it catches mosquitoes flying above the water. In
the latter case it sits quietly upon some aquatic plant and, as
soon as the mosquito approaches, makes a swift leap and catches
the insect, or when a mosquito is discovered at some distance
on the surface of the water, the water-strider moves very
swiftly towards it until it reaches its victim, when it seizes it
with its raptorial forefeet. The food is never taken from under
the water. Several individuals were kept in an aquarium
thickly populated with mosquito larvae, although the insects
had not received any food for several days and were in a starv-
ing condition, they did not touch the mosquito larvae, but as
soon as a mosquito emerged from the pupa case it was caught
and eaten. Gerris remiges is very voracious and will eat any
animal matter, not disdaining its own kind. It does not hesitate
to attack animals many times its own size. In the aquarium,
where there is less chance of escape, the young nymphs usually
fall victims to the adults, and the stronger ones, as a rule, feed
upon their weaker companions. In the laboratory the water-
striders were fed mostly upon flies, they being most easily ob-
tained, but they ate other animal matter, such as ants, bees,
butterflies, moths, Jerusalem crickets, etc. Gerris remiges is
not particular in its choice of food and its sense of taste is not
well developed. Upon different occasions the insects were fed
flies, some of which had been previously soaked in quinine and

HABIT OF THE WATER-STRIDER GERRIS REMIGES 399

alcohol and some, in coal oil. They first approached the flies
carefully, then left them, but soon returned and attacked them
in spite of the taste or odor. Three days later these same insects
were fed flies which had been soaked in ammonia for twenty- .
four hours. The following morning they were dead. The
insect attacks fresh and decaying matter indiscriminately.

Gerris remiges can live on land as well as in water. It runs
with a jerking motion, making from four to six jumps in succes-
sion and then making a short stop. Very often it turns a som-
mersault and continues running without interrupting its course
until it reaches a place of safety. There it lies quietly for from
fifteen to twenty-five minutes, then suddenly begins its race
again. The insect can right itself when placed on its back by
turning over longitudinally, resting its body on the head or
abdomen. If a water-strider is held up by some of its legs, it
tries to free itself by pushing the object holding it with the
remaining free legs, at the same time pulling the legs which are
being held.

The water-strider is accustomed to cleaning itself and some
times is engaged in this occupation for hours. It rubs one leg
with another, then it rubs its proboscis and the ventral and
dorsal surface of the body interchangeably. Very often it rolls
over in the water during the cleaning process. If some foreign
substance, such as dust or asphalt is put on the dorsal surface
of the body the animal dives and rubs itself in the greatest
effort to get rid of the substance. If the insect is left in a weak
light it remains quiet excepting that it rubs its legs; if brought
into a strong light, it swims towards the source of light as nearly
as possible, and rubs its legs.

Feigning death is a characteristic of this insect, which is
especially well developed in some individuals. In accomplishing
this feat it crosses its forelegs and becomes perfectly rigid. It
may be rolled on the floor, picked up and held by one leg, dashed
with water, exposed to considerable heat or to strong light
without showing any signs of life. If left alone it lies quietly
for ten or fifteen minutes, then gradually livens up and begins
to run. If touched, it again feigns death, and thus it may
continue for hours. The insect can be artificially made to as-
sume this condition by putting it on its back and holding the
hind legs, at the same time gently tapping it on its ventral

400 CHRISTINE ESSENBERG

surface, or by holding it down and pressing on the dorsal surface.
The first sign of death feigning is usually the crossing of the
forelegs, then the body becomes rigid and the legs are drawn
up close to it so that the whole body assumes a compact shape.
The water-strider has been made to assume this position thirteen
times in succession. Later it did not so readily respond to the
stimulus and the successive periods of death feigning gradually
decreased in length, the first periods lasting for from twenty-six
to twenty-five minutes and the last periods lasting for from six
to five minutes, only. The larvae of these insects are especi-
ally prone to feign death. When taken from the water they
sometimes feign death and do not recover for an hour or longer.
Feigning death is evidently not a voluntary act on the part of
the animal, this condition being brought about by some physi-
ological change. Professor S. J. Holmes cites similar experi-
ences with Ranatra jusca also with some birds from which he
pulled feathers while the birds were in this condition without
producing any response.

Gerris remiges is positively phototactic. If it takes to its
wings once in a while it always flies toward the light, producing
a buzzing sound as it flies. When placed in an aquarium it
swims toward light. It is more phototactic in strong light and
in high temperature, less so in a weaker light.

Gerris remiges is negatively geotropic. If an individual is
left in an empty jar it always crawls upward. If placed on
the wall it crawls upward, never downward, although it may
jump or fly to the ground. The same is true when it retires to
sleep on plants, attaching itself to the lower surface of the
plants, with head pointing upward. Although very swift of
motion when on water, the insect remains perfectly motionless
on plants and makes no effort to escape when picked up. Blind
individuals act in the same way as do the normal ones in regard
to geotropism, i.e., they crawl upward or opposite to the source
of gravity.

Water-striders are positively thigmotactic, piling up in three
or four layers, sometimes becoming so tangled up in their long
legs that it becomes difficult for those in the middle to disen-
tangle from the others. They also crowd together when fright-
ened and when hibernating in the winter.

The water-striders are positively rheotactic and always swim

HABIT OF THE WATER-STRIDER GERRIS REMIGES 401

■

against the current. Experiments have been tried with indi-
viduals in which one or both eyes were destroyed. When water
was rotated in a dish they swam against the current.

The sense of smell of the water-strider was tested in the fol-
lowing way: A small drop of coal oil was placed on the upper
edge of the wall of the aquarium upon which the insects were
trying to climb. When they had almost reached the oil, which
was gradually moving downward, they stopped, moved their
antennae, bent backward and plunged into the water. This
experiment was tried with coal oil and ammonia water inter-
changeably, the insects commonly responding in the same way.
A drop of coal oil was placed on the surface of the water in a
corner of the aquarium. When the insects, in calmly gliding
around occasionally came near the oil, they stopped, moved
their antennae, then retreated. When frightened and in rapid
motion they sometimes came directly into the field of the oil,
when they would swim back excitedly and try to escape by
jumping at the walls of the aquarium at the opposite end.

These insects seem to have a sense of hearing. When, for
instance, a door is slammed, or some loud metallic sound is pro-
duced, the animals immediately respond by moving backward.
When wingless flies are dropped into the water and are buzzing,
the water-striders hurriedly move toward them, while a dead
fly may float for a considerable length of time without being
discovered. This experiment was tried with Gerris remiges
whose eyes had been destroyed, with the same result, the blind
insects moving from all directions toward the source of sound.
However, they do not respond to all sound equally well. A
tuning pipe was attached to one end of a wire, the other- end of
which was in the aquarium. The tuning pipe was then blown,
but it had little or no effect on the water-striders, which con-
tinued their movements at random on the surface of the water.

SUMMARY

Gerris remiges are very common and are widely distributed.
They are found almost everywhere on the surface of the water,
beneath the rocks and in crevices. They are swift of motion,
moving forward and backward with equal facility. They are
very voracious and carniverous, although they never attack
animals below the surface of the water, but only those on the

402 CHRISTINE ESSENBERG

surface or on plants. They show no particular choice in the
selection of food, eating any dead or living animal matter. If
nothing is obtainab'e, they can live without food for weeks
or months. They are specially given to the cleaning habit
and may be engaged in this process for hours in succession.
They are prone to feign death and may be artificially stimu-
lated to do so several times in succession. They are positively
phototactic.

Gerris remiges is positively thigmotactic, hence, usually found
in groups or piles beneath rubbish and rocks. The insects also
crowd together on the surface of the water. They are positively
rheotactic and negative y geotactic.

They seem to have some sense of smell. Their sense of
hearing is not well developed, but they detect a sudden jar,
such as the slamming of a door, or drumming on the edge of
the aquarium, etc.

The sense of sight is keenly developed, the insects detecting
a moving object or a shadow very quickly.

In considering the economic aspect,' these insects may be
useful because of their contribution to the reduction of the
number of mosquitoes which lay their eggs on the surface of
the water, also because of their destroying the emerging young
mosquito.

LITERATURE CITED

Bueno, J. R. de la Torre. The Gerridae of the Atlantic States. Trans. Amer.

1911. Ent. Soc, 37, 243-252.

1911. On the Aquatic and Semi-aquatic Hemiptera Collected by Professor
T. S. Hine in Guatemala. Ohio Naturalist, 8, 370-382.
Douglas, J. W. Notes on Gerris thoracica. Entom. Mo. Mag., 16.

1870.
Holmes, S. J. Death- feigning in Ranatra. Journ. Comp. Neurol, and Psvchol.,

1906. 16, 200-216.
Kirkaldy, C. W. A New Species of Gerris. Entom. News, 22, 246.

1911.
Miall, L. C. Natural History of Aquatic Insects. Macmillan and Co., London.

1895.
Severin, H. P. and Severin, H. C. An Experimental Study on the Death-feigning
of Belostoma (Zaitha aucct.) fiumineum Say and Nepa apiculata
Uhler. Behavior Monograph, 1, 11-85.

NOTES
MATERNAL INSTINCT IN A MONKEY

ROBERT M. YERKES

To my friend and fellow investigator, Doctor G. V. Hamilton,
I owe the opportunity to make the observations of the behavior
of monkeys which it is the purpose of this note to report. Gladly
I avail myself of this chance to thank him publicly for his gener-
osity in placing his animals and experimental equipment wholly
at my disposal during the present year, and for his unfailing
kindness and sympathy.

On February 27 one of the monkeys of our collection gave
birth, in the cages at Montecito, to a male infant. The mother
is a Macacus cynomolgus rhesus who has been described by
Hamilton1 as " Monkey 9, Gertie, M. cynomolgus rhesus. Age
3 years, 2 months. (She is now, May 1, 1915, 4 years and 6
months). Daughter of monkeys 3 and 10. First pregnancy
began September, 1913." The result of this pregnancy was, I
am informed, a still-birth.

The second pregnancy, which shall now especially concern us,
resulted likewise in a still-birth. Parturition occurred Saturday
night, and the writer first observed the behavior of the mother
the following Monday morning. In the meantime the laboratory
attendant had obtained the data upon which I base the above
statements.

At the time of parturition Gertie was in a 6 by 6 by 12 foot
out-door cage containing a small shelter box, with an excep-
tionally quiet and gentle male (not the father of the infant)
who is designated in Hamilton's paper as Monkey 28, Scotty.

My notes record the following, exceptionally interesting and
genetically important behavior. On March 1, when I approached
her cage, Gertie was sitting on the floor with the infant held in
one hand while she fingered its eyelids and eyes with the other.

1 Hamilton, G. V. A study of sexual tendencies in monkeys and baboons. Jour,
of Animal Behavior, 1914, 5, 298.

403

404 ROBERT M. YERKES

Scotty sat close beside her watching intently. When disturbed
by me the mother carried her infant to a shelf at the top of
the cage. Repeatedly attempts were made to remove the dead
baby, but they were futile because Gertie either held it in her
hands or sat close beside it ready to seize it at the slightest
disturbance.

Especially noteworthy on this, the second day after the birth
of the infant, are the male's, as well as the female's, keen inter-
est in the body and their frequent examinations of the eyes, as
if in attempts to open them. Often, also, the mother searched
the body for fleas.

Observations were made from day to day, and each day
opportunity was sought to remove the body without seriously
frightening or exciting the female. No such opportunity came,
and during the second week the corpse so far decomposed that,
with constant handling and licking by the adults, it rapidly
wore away. By the third week there remained only the shriv-
eled skin covering a few fragments of bone, and the open skull
from the cavity of which the brain had been removed. This
the mother never lost sight of: even when eating she either held
it in one hand or foot, or laid it beside her within easy reach.

Gradually this remnant became still further reduced until
on March 31 there existed only a strip of dry skin about four
inches long with a tail-like appendage of nearly the same length.

'The male, Scotty, on this date was removed to another cage.
Gertie made a great fuss, jumping about excitedly and uttering
plaintive cries when she discovered that her mate was gone.
Whenever I approached her cage she scurried into the shelter
box and stayed there while I was near. This behavior I never
before had observed. It continued for two days. On April 2,
it was noted that she had lost her recently acquired shyness
and she no longer made any attempts to avoid me. As usual,
on this date, she was carrying the remnant about with her.

The following day, April 3, Gertie was lured from her cage to
a large adjoining compartment for certain experimental obser-
vations. After she had been returned to her own cage the
remnant was noticed on the floor of the large cage. I picked it
up. Gertie evidently noticed my act, for although at a distance
of at least ten feet from me, she made a sharp outcry and sprang,
to the side of the cage nearest me. I held the piece of skin (it

MATERNAL INSTINCT IN A MONKEY 405

looked more like a bit of rat skin than the remains of a monkey)
out to her and she immediately seized it and rushed with it to
the shelf at the top of the cage.

Two days later the remnant was missing, and careful search
failed to discover it in the cage. It is probable that Gertie had
carelessly left it lying on the floor whence it was washed out
when the cages were cleaned. On this date Gertie seemed
quieter than for weeks previously.

Thus it appears that during a period of five weeks the in-
stinct to protect her offspring impelled this monkey to carry its
gradually vanishing remains about with her and to watch over
them so assiduously that it was utterly impossible to take them
from her except by force.

After reading this note in manuscript, Doctor Hamilton
informed me that Gertie had behaved toward her first still-
birth as toward her second. And, further, that Grace, a baboon,
also carried a still-birth about for weeks.

I am now heartily glad that my early efforts to remove the
corpse were futile, for this record of the persistence of maternal
behavior seems to me of very unusual interest to the genetic
psychologist.

A REPLY TO PROFESSOR COLE

WALTER S. HUNTER

I cannot permit Professor L. W. Cole's recent article in the
Mar. — Apr. number of this Journal, entitled "The Chicago ex-
periments with raccoons" to stand unprotested. Abstracting
from the deplorable tone of the publication, I should like to
draw attention to one or two points only. (1) Professor Cole
interprets my position as a desertion of the sensory-motor
hypothesis in favor of some vague imageless thought construct.
I tried strenuously in the monograph on Delayed Reactions to
make clear that the ideational function ascribed to raccoons and
to the child F was of a strictly sensory content. This content
in any case need not be visual. It is not necessary that mental
content copy the stimulus in order to represent it. In the
Delayed Reaction experiments the content could not be visual
because a visual sensation cannot be revived or reproduced.
The content of the representative factor was very probably
kinaesthetic (Delayed Reaction, p. 75) and was associated with
the light. These kinaesthetic sensations could be revived and
used as cues to differential responses. This is mentioned in
many places in the monograph and is summarized finally in the
classes of animal learning on page 79. I can see no grounds
for so odd a misinterpretation of my attitude. (2) Professor
Cole is aghast at the use of the term "steeple" for "staple" on
page 18 of my monograph. This error was probably due to a
slip in the proof reading. Had Professor Cole read a few lines
further down the same page, he would have found the perfectly
proper usage. (3) On page 167 of his article, by quoting a
portion only of a sentence which in its turn was in a vital con-
text, Professor Cole grossly misrepresents my statements con-
cerning odor controls. It is to be noted that a very different
criticism is involved to that offered elsewhere by Professor
Watson. (4) The only confirmation that my work offers of
Professor Cole's is, I still believe, the agreement indicated on
page 20 of my monograph.

I see no need for further comments either upon the Delayed
Reaction or upon the work by Gregg and McPheeters.

406

JOURNAL OF ANIMAL BEHAVIOR

Vol. 5 NOVEMBER-DECEMBER No. 6

LITERATURE FOR 1914 ON THE BEHAVIOR OF
THE LOWER INVERTEBRATES

S. J. HOLMES

The University of California

Allee (1) has tested the relation of rheotaxis in Asellus to
metabolism, measuring the latter by means of the duration of
life of the animal in solutions of KCN. As animals having a
high degree of metabolism die more quickly in KCN a means
is afforded of testing the metabolism of different lots. Those
which showed the most strongly positive rheotaxis were those
in which, other things equal, the degree of metabolism is the
greatest. Certain modifying factors must be taken into con-
sideration and for an account of these reference must be made
to the original paper.

In another paper Allee (2) points out that the rheotactic
response is especially adaptive in stream isopods and is more
pronounced in Asellus communis from streams than in the same
species from ponds. The distribution of stream isopods is largely
accounted for by their rheotactic and thigmotactic reactions.

Allee and Tashiro (3) have studied the relations between
rheotaxis in Asellus and the rate of production of C02, and
find that in a given individual the reaction is positive when
the C02 production is rapid and indifferent when the C02 pro-
duction is low. Resistance to KCN is in inverse proportion to
the production of C02. There are great differences in the reac-
tions of different individuals and ' the rheotactic reaction is
an expression, not of the absolute metabolic rate of the animal,
but of the relative metabolic rate to which the isopod is accli-
mated for the time being."

408 S. J. HOLMES

In a paper in general ecology of Folliculina Andrews (4)
records a number of observations on the behavior of this form.
Ordinarily the species lives in tubes secreted by its body, but
it often leaves these and swims through the water; it is posi-
tively phototactic and thigmotactic, and these traits lead it to
settle down upon the younger parts of plants to which it is
usually found attached. There is a strong tendency for indi-
viduals to aggregate in groups.

Baunacke (5) has considered various organs which might pos-
sibly occasion the orientation of Limax and other mollusks to
gravity. He excludes light, tactual, and chemical stimuli and
finds that orientation occurs in a medium of the same specific
gravity as that of the animals. The statocyst alone is con-
sidered to be the organ directly concerned in orientation to
gravity. Mollusks from which this organ has been removed
are unable to orient themselves to gravity in the normal way.

The orientation of crustaceans to gravity forms the subject
of an extended discussion by Buddenbrock (7) who recognizes
three distinct factors which conspire to preserve the normal
position of these animals. There is (1) the tendency to present
the dorsal surface to the light (Lichtriickenreflex) which the
author rinds to be widespread among pelagic crustaceans. Then
there is (2) the orienting function of the statocysts, and (3) a
general reflex dependent upon no particular organ which leads
the animal to keep the ventral surface below. In some crusta-
ceans orientation to gravity may persist after the destruction of
both statocysts and eyes.

According to Cowles (8) the starfish Ecinaster spinosus moves
toward a white wall and away from a black one.

Dice (9) has analyzed the factors involved in the vertical
migrations of Daphnia pulex. At 20° C. Daphnias are normally
positive to weak light but indifferent to light of higher intensity.
Increase of temperature makes them less positive, while decrease
of temperature makes them more so. Light of high intensity
makes Daphnias positively geotactic, while a decrease of light
intensity has the reverse effect. These responses help to explain
the diurnal movements of these forms. During the day Daph-
nias, at least in certain localities, are found more in deeper
water while they commonly rise to the surface at night. This
migration is due in part to the direct influence of light, but

BEHAVIOR OF THE LOWER INVERTEBRATES 409

more to the effect of light upon geotaxis. Temperature also is
a factor, as Daphnias tend to become positively geotactic in
high temperatures and negatively geotactic in low. This has
a marked influence in the seasonal migration of these animals.
Other minor factors of migration are discussed, such as age
and wave action. There is no diurnal rhythm independent of
the direct action of orienting agencies.

Ewald (10) finds that Daphnia has two distinct modes of
reaction to the light, the orienting response and a response to
change in light intensity. By subjecting Daphnias to inter-
mittent light Ewald found that the orienting response was not
effected by the frequency of interruption, provided that the
same amount of light was received in a given time. For the
shock reaction, interrupted light affords a much more effective
stimulus. Both types of response harmonize with the Bunsen-
Roscoe law. Daphnias respond to different colors, and not
only to light intensity.

Fasten (11), in an account of fertilization in a species of cope-
pods, describes the copulatory activities of the male.

Galiano (12) has described, without indicating any general
conclusions or discussing his results, a number of experiments
on the chemotaxis of Paramecium. Reagents were used similar
to those which Paramecium encounters under natural conditions,
i.e., culture fluids, distilled water, and dilute alkaline solutions.

Herwerden (13) placed Daphnias in a horizontal glass vessel
one end of which was closed by quartz. When ultra-violet
light was passed through the quartz into the water the Daph-
nias became negative; when a piece of glass was interposed the
reaction was discontinued. In specimens in which the eye was
destroyed there was no negative reaction.

Hess (16) finds that the ambulacral feet of the starfish Astro-
pecten retract under the influence of light. If only a small
extent of the ventral surface of one ray is illuminated the feet
struck by the light rays retract while the others are extended.
The oral tentacles of Holothoria show a similar reaction. In
both cases red light has little effect but blue and green readily
evoke the response. Serpulas (14) react to change in light
intensity like color-blind people, i.e., without regard to wave
lengths of differently colored lights. Balanus reacts in similar
way, ceasing its movements upon a diminution of the light.

410 S. J. HOLMES

fL Jordan (17) has studied in detail the function of the con-
tractile fibers of the body wall of holothurians. Holothurians,
actinians, annelid worms and many other forms are grouped in
a division which Jordan calls hollow organ animals. In these
forms the absence of internal or external skeleton is in a way
compensated for by the presence of fluids within the animal
which, when under pressure, afford a certain rigidity to the
body. There is a detailed study of the general physiological
properties of the muscles of holothurians as well as certain
fibers of the skin which while different from other muscle fibers
are shown to be contractile. These latter Jordan thinks have
a special function of maintaining the tonus of the body, while
all the more nearly typical muscles have their function limited
to simple contractility. There is thus a separation of functions
performed by striated muscles of higher forms similar to that
which Von Uexkiill describes for the two sets of fibers supply-
ing the spines of the sea urchin.

Just (18) finds that at Woods Hole, Massachusetts, the swim-
ming of Platynereis me galops occurs in July and August in the
dark of the moon. The breeding activities may be studied in
the laboratory although the males are rather delicate and as a
rule live only a few days in receptacles of sea water. The male
in swimming coils spirally about the body of the female and
works forward until he gets into a position in which the female
may seize his tail in her jaws. Just thinks that the sperms
are swallowed by the female and fertilize the eggs internally,
after which ovulation takes place by the rupture of the body
wall. After copulation sperm may be found in the pharynx
" whence they escape through lesions in the pharyngeal wall to
the coelom."

Kafka (19) has given a valuable and welcome summary of
work on the sensory reactions of the invertebrates.

Kanda (20) finds that the anterior end of Paramecium cau-
datum and Spirorostum teres is heavier than the posterior end
and therefore the orientation to gravity shown by these forms
cannot be a merely mechanical one. Differences in pressure of
water on the two ends or sides of the body are so slight as to
be negligible, and besides both these forms orient negatively to
gravity in solutions of greater specific gravity than their body.

BEHAVIOR OF THE LOWER INVERTEBRATES 411

After excluding other theories, Kanda concludes that the stato-
cyst theory of geotropism is the most tenable.

Kanda (21) has also studied the geotropism of Arenicola
larvae, subjected them to various salts solutions isotonic with
sea water and noted the influence of different media on the
sense of the response. Calcium and magnesium ions tend to
reverse the normally negative response, but their action tends
to be neutralized by sodium. The metallic ions are considered
to be the influential elements in reversing geotropism. The
usual positive phototaxis of the larvae may be reversed by the
addition of sodium chloride or potassium chloride, but the action
of these salts may be antagonized by calcium chloride or mag-
nesium chloride.

In a paper on the biology of the snail (Helix) Kiihn (22)
treats of hibernation, loss of weight in winter, and reactions to
drought in summer. Helix can be made to come out of its
closed shell when placed under moist conditions. It does not
take dry food if its body does not contain a considerable amount
of water.

The death feigning reflex of arthropods is described by Lohner
(23), who not only reviews a considerable amount of literature
on the subject but describes several experiments of his own
on different species of diplopods. 'The destruction of the brain
or decapitation makes the reaction much more difficult to elicit,
but these operations do not destroy it entirely. If the nerve
cord is cut the part anterior to the cut can be made to perform
this reflex. The reflex is not shown by an isolated part of the
body behind the fifth segment.

The reactions of Bursaria to food and the processes of diges-
tion in this species have been carefully studied by Lund (24).
Bursaria may reject certain kinds of solid materials while it
takes in others, depending on the action of the ciliary mechanism
of the oral cavity. Large particles either do not enter the oral
sinus or are rejected before reaching the latter, while small
particles may be carried into the deepest part of the sinus and
then carried out in a stream which passes backward on the
ventral side of the body. The amount and rate of food taking
depends on the condition of the animal. Bursaria appears to
have a faculty analagous to the sense of taste, as it rejects food

412 S. J. HOLMES

particles impregnated with various chemicals. There is a selec-
tive elimination of the contents of food vacuoles, as indigestible
substances that have been taken in are soon gotten rid of.

Mast (25) has made an extended reply to a paper on Euglena
by Bancroft, which was reviewed in this journal last year. The
question at issue concerns the method of orientation, Mast up-
holding the previous contention of Jenning's and himself that
it is brought about through a more or less modified form of
the ' motor reaction." It is impossible to give an adequate
presentation of the arguments of Mast in a short space, and
reference must be made to the original paper.

Metalnikov (26) finds that Paramecia that had injected
Sudan powder so that they contained an average of 20 food
vacuoles enclosing this substance, almost completely failed to
take in Sudan on the following day, although they had been
kept in the meantime in a fresh hay infusion. They took in
other substances, such as carmin, sepia and egg albumen in
abundance. If a mixture of nutritive and non-nutritive sub-
stances be given the Paramecium takes both at first, but later
rejects the non-nutritive and continues to take nutritive material.

Orton (27) gives an account of the feeding mechanism and
feeding reactions in brachiopods and certain polychaetes and
discusses the evolution of similar food-taking mechanisms and
their reactions in unrelated groups of animals.

Echinus miliaris were found by Orton (28) to aggregate into
groups in the period of sexual maturity. Males and females
were most frequently associated, but groups were not infre-
quently found containing but one sex.

In an extensive review of work on actinians Pax (29) has
given a very useful resume of investigations on the reactions
and natural history of these animals.

The Smithsonian Institution has reprinted a paper by Pearse
(30) on the habits of fiddler crabs, which was reviewed in an
account of the literature for 1912 published in this journal
last year.

Powers (31) has experimented on the reactions of four species
of crayfish (Cambarus) to C02, HC1 and acetic acid. In C02
the species die in the following order: virilis, propinquus, diog-
enes, immunis. All four species react more strongly to HC1
than to acetic, and more strongly to acetic acid than to C02.

BEHAVIOR OF THE LOWER INVERTEBRATES 413

There seems to be a correlation between the specific reactions
of the species and their habitats. In all the species the behavior
is repeatedly modified owing, in the opinion of the author, to
" increased sensitiveness on the part of the animals."

Putter (32) has given a resume of experimental work on the
irritability of protozoans.

In the course of a detailed study of the structure of the in-
fusorian Diplodinium, Sharp (33) records several observations
on locomotor activity and the action of the membranellae.

Torrey and Hays (34) find that Porcellio scaber is negative
in its reaction to light and may be driven about in any direc-
tion by light coming from behind. The first reaction of the
animal when light is suddenly flashed upon it is to turn directly
away. Orientation, the authors conclude, is direct although the
method may be obscured by various random movements.

In the course of an account of the influence of various chem-
icals on Colpidium colpoda, Weyland (35) describes results of
experiments on the chemotaxis of the species in relation to a
considerable variety of compounds.

Zagorowsky (36) finds that Paramecia are positively thermo-
tactic up to 32° C. but at 33° C. and above they become nega-
tive. The rate of swimming increases with rise of temperature
up to 49° C. after which it rapidly falls and ceases at 55° C.

REFERENCES

1. Allee, W. C. Certain Relations between Rheotaxis and Resistance to Potas-

sium Cyanide. Jour. Exp. Zool, 16, 397-412.

2. Allee, W. C. The Ecological Importance of the Rheotactic Reaction of

Stream Isopods. Biol. Bull., 27, 52-66.

3. Allee, W. C. and Tashiro, S. Some Relations between Rheotaxis and the

Rate of Carbon Dioxide Production of Isopods. Jour. Animal Behav., 4,
204-213.

4. Andrews, E. A. The Bottle-Animalcule, Folliculina; Oecological Notes.

Biol. Bull., 26, 262-285.

5. Batjnacke, W. Studien zur Frage nach der Statocystenfunktion. LL Noch

einmal die Geotaxis der Mollusken. Biol. Cent., 34, 371-385, 479-523.

6. Batjnacke, W. Gleichgewicht; " Gleichgewichtsorgane " bei niederen Tieren.

Umschau, 18.

7. Buddenbrock, W. v. Ueber die Orientierung der Krebse im Raum. Zool.

Jahrb. Abt. f. Zool. u. Physiol, 34, 479-514.

8. Cowles, R. P. The Influence of White and Black Walls on the Direction of

Locomotion of the Starfish. Jour. Am. Behav., 4, 380-382.

9. Dice, L. R. The Factors Determining the Vertical Movements of Daphnia.

Jour. Animal Behav., 4, 229-265.
10. Ewald, W. F. Versuche zur Analyse der Licht- und Farbenreaktionen eines
Wirbellosen (Daphnia pulex). Zeit. f. Sinnesphysiol., 48, 285-324.

414 S. J. HOLMES

11. Fasten, N. Fertilization in the Parasitic Copepod. Lernaeopoda Edwardsii

Olsson. Biol. Bull, 27, 115-126.

12. Galiano, F. F. Beitrag zur Untersuchung der Chemotaxis der Paramacien.

Zeit. f. allg. Physiol., 16, 359-372.

13. Herwerden, M. A. v. Ueber die Perzeptionsfiihigkeit des Daphnienauges

fur ultra-violette Strahlen. Biol. Cent., 34, 213-216.

14. Hess, C. Untersuchungcn iiber den Lichtsinn mariner Wiirmer und Krebse.

Arch. ges. Physiol, 155, 421-435.

15. Hess, C. Eine neue Methode zur Untersuchungen des Lichtsinnes bei Kreb-

sen. Arch. f. vergl. Ophlhalm., 4.

16. Hess, C. Untersuchungen iiber den Lichtsinn bei Echinodermen. Arch.

ges. Physiol, 160, 1-26.

17. Jordan, H. Ueber " reflexarme " Tiere. IV. Die Holothurien. Zool. Jahrb.

Abt. f. allg. Zool. u. Physiol, 34, 365-436.

18. Just, E. E. Breeding Habits of the Heteronereis Form of Platynereis megalops

at Woods Hole, Mass. Biol. Bull, 27, 201-212.

19. Kafka, G. Einfuhrung in die Tierpsychologie. Bd. 1. Die Sinne der Wirbel-

losen. Barth, Leipzig, 1914. xii+594 pp.

20. Kanda, S. On the Geotropism of Paramecium and Spirostomum. Biol

_ Bull, 26, 1-24.

21. Kanda, S. The Reversibility of the Geotropism of Arenicola Larvae by Salts.

Amer. Jour. Physiol, 25, 162-176.

22. KtJHN, W. Beitrage zur Biologie der Weinbergschnecke {Helix pomatia L.).

Zeit. wiss. Zool, 109, 128-184.

23. Lohner, L. Untersuchungen iiber den sogenannten Totstellreflex der Arth-

ropoden. Zeit. allg. Physiol, 16, 373-418.

24. Lund, E. J. The Relations of Bursaria to Food. Jour. Exp. Zool, 16, 1-52;

17, 1-43.

25. Mast, S. O. Orientation in Euglena with some Remarks on Tropisms. Biol

Cent., 34, 641-664.

26. Metalnikov, S. Les infusoires peuvent-ils apprendre a choisir leur nourri-

ture ? Arch. f. Protisl, 34, 60-78.

27. Orton, J. H. On Ciliary Mechanisms in Brachiopods and some Polychaetes,

with a Comparison of the Ciliary Mechanisms on the Gills of Molluscs,
Protochordata, Brafchiopods, Cryptocephalous Polychaetes, and an Account
of the Endostyle of Crepidula and its Allies. Jour. Mar. Biol. Ass. n. s.,
10, 283-311.

28. Orton, J. H. On the Breeding Habits of Echinus miliaris, with a Note on

the Feeding Habits of Patella vulgata. Jour. Mar. Biol Ass. n. s., 10,
254-257.

29. Pax, F. Die Actinien. Ergebnisse und Fortschritte der Zoologie, 4, 339-642.

30. Pearse, A.'S. Habits of Fiddler Crabs. Report of Smithsonian Institution

for 1913, 415-428.

31. Powers, E. B. The Reactions of Crayfishes to Gradients of Dissolved Carbon

Dioxide and Acetic and Hydrochloric Acids. Biol Bull, 27, 177-200.

32. Putter, A. Die Anfange der Sinnestatigkeit bei Protozoen. Umschau, 87-94.

33. Sharp, R. G. Diplodinium ecaudatum with an Account of its Neuromotor

Apparatus. Univ. of Calif. Publ, 13, 43-122.

34. Torrey, H. B. and Hays, G. P. The Role of Random Movements in the

Orientation of Porcellio scaber to Light. Jour. Animal Behav., 4, 110-120.

35. Weyland, H. Versuche iiber das Verhalten von Colpidium colpoda gegen-

iiber reizenden und Liihmenden Stoffen. Zeit. (dig. Physiol, 16, 123-162.
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LITERATURE FOR 1914 ON THE BEHAVIOR OF
SPIDERS AND INSECTS OTHER THAN ANTS

C. H. TURNER

Sumner High School, St. Louis, Mo.

TROPISMS

1. Chemotropism. — By attaching shallow pans, containing
kerosene, to the branches of trees, Severin and Severin (77)
were able to catch large numbers of the Mediterranean fruit
fly (Ceratitis capitata). Out of 5,490 flies trapped in eighteen
days only thirty were females. As these authors say, "It is
certainly peculiar that the Mediterranean fruit fly plunges into
kerosene to its own destruction." By using pans of four different
colors (white, black, blue and orange) they demonstrated that
the number of flies secured was not determined by the color
of the pan. They think it highly probable that the sense of
smell plays an important role in attracting the flies, and admit
that it might be a positive chemotaxis due to one or more hydro-
carbons or to the impurities of the petroleum oils. "Again,
the hydrocarbons of the oil may act as an anesthetic, and stupify
the insects whenever they remain within its influence." Neither
of these suppositions, however, accounts for the preponderance
of males. For a period of eight months these flies were trapped
daily. During that time only three victims out of every thousand
were females. Admitting that the proof is not conclusive, these
investigators believe that the kerosene emits a scent similar to
" some sexual odor of the female which in natural conditions
serves to guide the male to her." This harmonizes with Hew-
lett's interpretation* of the reaction of Dacus zonatus to the
oil of citronella.

In another paper (78) these two investigators have discussed
the relative attractiveness of vegetable and petroleum oils for
the Mediterranean fruit fly.

2. Hydrotropism. — In two different species of water beetles,

* Hewlett, F. H. The Effects of Oil of Citronella on Two Species of Dacus.
Trans. Ent. Soc, London, 1912, pt. II, pp. 412-418.

415

416 C. H. TURNER

that inhabit a pond of about 300 square feet, Weiss (98) ob-
served interesting cases of what he calls positive hydrotropism.
When the wingless beetles Gerris marginatus were removed one
to nine yards from the pond they immediately returned to it.
When removed ten yards from the water they had some trouble
in getting started in the right direction; but finally reached
the pond. Thirty yards from the water they seemed to be
lost. The case of Dineutes assimilis, a winged beetle, is even
more interesting. When removed nine or ten feet from the
water, it tried to walk to the pond, then arose and flew directly
to it. When removed to a distance of seventy-five feet, it walked
about in all directions, then arose, on its wings, to a height
of twenty feet and flew directly to the water. When removed
half a mile from the pond, it soared in a widening sub-spiral to
a height of seventy-five feet and flew off in the direction of the
water. He does not know whether they reached the water or not.
3. Phototropism. — Beutel-Reepen (6) does not think swarming
honey bees are positively heliotropic.

OLIGOTROPISM

Robertson (75) does not accept the opinion that " Therefore
the entomophilous flora of a region, as a whole, is not better
pollinated because a part of the bees are oligotropic than it
would be if they were all poly tropic." He writes: ' My view
is that the bee fauna is all that the flora will support, that there
is a constant competition between bees, and that natural selec-
tion favors those which are the most diversified, i.e., the least
competitive in food habits." He believes that short flight is a
result of oligotropy. To show the reasonableness of his con-
tention he insists that if a bee limits itself to a given species of
flowers it gains the immediate advantage of being able to antici-
pate others in their visits to the chosen plant. By locating near
the flowers, it may augment this advantage, and, by concen-
trating its attention on that flower, learn to manipulate its
pollen to greater advantage and even develop special structures
which will increase this advantage. In support of this last
statement, he cites the following examples: — (1) Bees that collect
large pollen have loosely plumose scopae, while others which
collect from the compositae have densely plumose scopae. (2)

BEHAVIOR OF SPIDERS AND OTHER INSECTS 417

Oenothera, the evening primrose, has its pollen grains connected
by threads. Anthedon compta, an oligotrope of this plant, un-
like its nearest relatives, has scopae of long single bristles. The
bee goes to the stem and turns head downward, so as to work
the cob-webby pollen into the scopae. (3) The anthers of Ver-
bena are included in a slender tube and above them is a circle
of hairs which impresses one with the thought that they were
intended to prevent the extraction of the pollen. Verbenapsis
verbenae, the oligotrope of this flower, has her front tarsi pro-
vided with curled bristles. The bee thrusts both front feet into
the corolla and drags out the pollen with her front tarsi.

According to Robertson, there are 223 indigenous nest-making
bees. One species flying the entire season, and fitted about as
Apis, might collect nearly as much pollen and support nearly
as many individuals. It would be to its advantage to be as
poly tropic as possible. ; The ecological specialization exhibited
by Anthedon, verbenapsis and other oligotropes is a fairly cer-
tain indication of the pressure of competition." The long-
tongued pygidial bees were developed as competitors of the
bumble bees, the first on the ground and the most poly tropic
of all bees. This explains their short and rapid flight and their
oligotropic habits. Likewise the Andrenidae, the Panurgidae
and related groups, which are often oligotropic, were probably
preceded by the Halictidae, the most polytropic of all short-
tongued bees. There are forty species of Halictidae flying through-
out the season. There are ninety-four other short-tongued bees
occupying the same region. It would be a hard matter for all
to fly throughout the season and compete with the Halictidae.
They have short times of flight, so distributed that not more
than fifty-two are flying in any month and these only in the
spring, when the Halictidae are the least abundant. All these
bees are least abundant when the Halictidae are most abundant.
" The early maximum flight, the non-competitive phenological
distribution, and the frequent oligotropic habits indicate that
these bees have managed to hold their own only by dividing
up the remaining field and occupying the most favorable corners
left by their polytropic competitors."

Lovell's views upon the origin of oligotropism are diametri-
cally opposed to those of Robertson. In his recent reply (52)
he makes the following criticisms: —

418 C. H. TURNER

1. There is no evidence to support Robertson's contention
that Epiolus is a parasitic genus.

2. To Robertson's assertion that a strenuous struggle for food
is the determining factor in the evolution of the habits of bees,
he replies that the size of the bee fauna is limited by other
factors than the food supply. He insists that the commonness
of an insect species does not depend alone on the quantity of
available food, and gives the following specific proofs that only
part of the available food is gathered by bees: — (a) In River-
side County, California, the orange bloom secretes nectar so
freely that it drops upon the teams and clothing of the pruners
in such copious amounts that, at the close of the day, it is neces-
sary to wash the horses and the harness, (b) Hundreds of acres
of the sandy coastal plain of Georgia are covered with bushes
of the common gallberry (Ibex glabra). It is in bloom for a
month and secretes nectar constantly. According to J. J. Wilder
these flowers are seldom visited by bees.

3 To Robertson's hypothesis that, in the remote past, oligo-
tropism arose through the competition of the long-tongued
pygidial bees with the Bombidae, and of the Andrenidae with
the Halictidae, Lovell replies : ' This highly imaginative suppo-
sition cannot be supported by historical data, and would appear
to be neither probable nor necessary." The polytropism of
Halictus is due to its peculiar economy. The impregnated
females hibernate and appear the following spring. The new
generation flies during the latter part of the season. " This
economy has no special advantage, for Halictus is greatly sur-
passed by Andrena in both species and individuals; while Sphe-
codes, which has essentially the same economy as Halictus, is
represented by comparatively few species and individuals.

It is an advantage for a social bee to maintain its organiza-
tion throughout the season; but for a solitary insect it is desir-
able that it mate and deposit its eggs as soon as possible. The
longer the female flies before this happens the greater the prob-
ability that she will be destroyed by some one of many causes.
* * * Since many polytropic bees have either a short term of
flight, or one which does not exceed a hundred days, it is clear
that a shorter term of flight is not necessarily correlated with
oligotropism."

4. If severe competition did exist among solitary bees the

BEHAVIOR OF SPIDERS AND OTHER INSECTS 419

oligotropic habit would not be desirable. It is not an advan-
tage for a bee to confine its food to one kind of plant unless it
is always certain to obtain the supply it needs. By overstock-
ing a locality oligotropic bees would disappear or become poly-
tropic.

5. The genus Perdita contains about 150 species, practically
all of which are oligotropic. An examination of the habits and
characteristics of the genus should throw some light upon the
origin of oligotropism. The facts are these: (a) the species
are mostly small; (b) they do not take long flights; (c) a part
of the species are vernal, but the majority fly in late summer
and autumn; (d) many visit the Compositae; (e) oligotropism
is as pronounced where there is only one or a few species as
where there are many; (f) many flowers are visited by more
than one species of Perdita; (g) the length of the tongues of
bees limit them to certain flowers, " thus it is the tube-length
of the flower, not competition, which is the factor limiting the
visits of many species of Perdita; (h) female inquiline bees do
not gather pollen and nectar for brood-raising and require only
nectar for themselves; nevertheless, many such bees, with short
terms of flight, visit only the Compositae.

Lovell concludes: "According to the theory proposed by the
writer certain bees have become oligotropic because of the
direct advantage gained, combined with the fact that their
flight was synchronous, or nearly so, with the period of in-
florescence of the plant to which they restricted their visits.
This theory offers an explanation of the rise of oligotropism by
the observation of existing conditions. There may be, and often
are, accessory factors, but they are of secondary importance.
* * * Robertson concedes all that is required when he says,
' The average flight is shorter and there are more of them with

a short flight.' "

AUDITORY SENSATIONS

Hitherto the contributions to the experimental study of the
sense of hearing of butterflies and moths have been fragmentary.
As far as the moths are concerned, Turner and Schwarz (89)
and Turner (86) have attempted to remedy this defect. In
their joint paper (89) these investigators report the results of
laboratory experiments with Catocala unijuga and field experi-
ments with C. flebelis, C. habilis, C. neogama, C. piatrix, C.

420 C. H. TURNER

retecta, var. luctuosa, C. robinsona, C. vidua, C. arnica, C. epione,
C. neogama, C. ilia, and C. innubens. The human voice, the
Galton whistle and organ pipes were used to produce sounds.
Except for special reasons, these instruments were always sounded
where they could not be seen by the insect. To test the ability
of the moths to respond to sounds to which they were usually
passive, the following method was employed. Simultaneously
with the sounding of the note the moth was gently touched.
This was repeated one or more times and then the pitch was
sounded without the tactile sensation. These authors reached
the following conclusions: — " 1. Our field experiments demon-
strate that several different species of Catocala moths respond
to certain high pitched notes of the Galton whistle; but that
they do not usually respond to notes of low pitch, such as the
rumbling of trains, etc. 2. Most specimens responded to a high
note by flying to a nearby tree*; but some, and this was especially
true of C. retecta, responded by making quivering movements with
its wings. 3. The degree of responsiveness was not the same for
all species. Among the least responsive were C. vidua, C. neo-
gama; and at the other extreme were C. flebelis, C. kahilis and
C. Robinsoni. 4. We do not consider the failure of these moths
to respond to certain sounds of a low pitch a proof that they
do not hear such sounds; indeed, we are inclined to believe
that these creatures respond only to such sounds as have a
life significance. Three things render this last supposition prob-
able: (1) the fact that unijuga, which at first did not respond
to whistling, did so readily after once a blast of air had been
allowed to strike her body simultaneously with the sounding
of the whistle; (2) that most of the natural enemies of these
moths produce high pitched sounds and trains and brass bands
and other producers of low pitched sounds do not directly affect
the survival of these moths; and (3) by carefully conducted
field experiments we were able to induce three specimens of
C. neogama to respond to sounds to which the species does not
usually react."

Turner (86) reports the results of laboratory experiments with
79 specimens of Samia cecropia Linn., 104 of Philosamia cynthia
Drury, 41 of Callosamia promethca Drury, and 81 of Telea poly-
phemus Cramer. These experiments were conducted in a build-
ing so constructed that it was impossible for the vibrations of

BEHAVIOR OF SPIDERS AND OTHER INSECTS 421

the sounding body to reach the specimens by any medium other
than the air. For producing the tones, the following instruments
were used: an adjustable organ pipe, an adjustable pitch-pipe,
and an Edelmann's Galton whistle. The moths were confined
beneath wire dish covers. Preliminary experiments demonstrated
that each of the instruments could be held a short distance
from the moths without causing a response, hence it was un-
necessary to hide the instruments ; precautions were taken, how-
ever, to prevent drafts caused by the instruments from im-
pinging on the moths. To all ordinary tones Telea polyphemus
is non-responsive. To see if this was due to deafness or merely
to a refusal to respond to the stimulus, the following method
was employed. " The organ-pipe was sounded five times in
rapid succession. Immediately thereafter the insect was roughly
handled for a few minutes. It was tossed about, gently squeezed
and thrown upon its back. This was repeated over and over
again, sometimes in one order and sometimes in another. After
the moth had quieted down the whistle was sounded again five
times in rapid succession. At each sound of the pipe the moth
would wave its wings. The author has tabulated the effects
of age, temperature and sex upon the responses. The paper
concludes as follows: — " 1. It seems certain that all four species
of the giant silk-worm moths investigated can hear. Three of
the species respond to a large range of sounds. The third,
Telea polyphemus, normally does not respond to sounds, unless
remaining as immobile as possible be considered a response. By
experimentally causing the moth to associate some disagreeable
experience with certain sounds, it can be induced to respond
to these sounds., 2. There is much evidence that the response
of moths to stimuli is an expression of emotion. The fact that
an insect does not respond to a sound is no sign that it does
not hear it. The response depends upon whether or no the
sound has a life significance."

OLFACTORY SENSATIONS
See Severin and Severin under chemotropism.

Beutel-Reepen (6) discusses the olfactory sense of the honey
bee and thinks Forel's flasks are olfactory organs.

In a series of papers Mclndoo (56, 57, 58) has made a sub-
stantial contribution to our knowledge of the olfactory sense

*

422 C. H. TURNER

and of the olfactory organs of insects. He experimented with
honey bees, hornets, ants and spiders. The following odors
were used: oil of peppermint, oil of thyme, oil of wintergreen,
bee food, pollen from old combs, parts of plants, flowers of the
honeysuckle, leaves and stems of pennyroyal, spearmint, scarlet
sage and bee stings. The odoriferous substances were isolated
in stoppered vials. These vials were opened near, and usually
below, the insects. Under normal conditions all of these crea-
tures responded to the odors; usually by moving away from them.
Evidently all of these forms can smell.

Mclndoo thinks he has settled the debated question as to the
location of the olfactory organs of insects. The belief that the
antennae are the olfactory organs of insects is so widely spread
that few except specialists know that the location of these
organs is a debatable question. The following epitome of Mc-
lndoo's extensive bibliography will give an idea of the diversity
of opinion on this subject. The seat of the olfactory organ is
supposed to be in the spiracles by Sulzer (1761), Dumeril (1797),
DuBois (1890), Hermbstadt (1811), Baster (1798), Lehmann
(1799), Cuvier (1805), Straus-Durckheim (1828), Lacordaire
(1838), Brulle (1840); located near the spiracles by Joseph
(1877) ; in the glands of the head and body by Ramdohr (1811) ;
in the oesophagus by Treviranus (1816); in the folded skin of
the forehead by Rosenthal (1811); in the rhinarium by Kirby
and Spence (1826) ; near the eye by Paasch (1873) ; in the mouth
cavity by Huber (1814); in the epipharynx by Wolff (1875); in
the palpi by Lyonnet (1745), Bonnsdorf (1792), Knoch (1798),
Marcel de Serres (1811), Newport (1838), Driesch (1839),
Perris (1850), Cornalia (1856), Weismann (18g9); in antennae
(belief based on structure) by Reaumur (1734), Lesser (1745),
Sulzer (1776), Fabricius (1778), Bonnet (1781), Olivier (1789),
Latreille (1804), Samonelle (1819), De Blainville (1822), Robi-
neau Desvoidy (1828), Carus (1838), Percheron (1841), Goureau
(1841), Pierret (1841), Robineau-Desvois (1842), Slater (1848),
Dufour (1850), Claparede (1858), Donhoff (1816) Noll (1869),
Wonfor (1879), Henneguy (1904); in antennae (belief founded
on experiments) by Duges (1838), Lefebvre (1838), Kuster (1844),
Perris (1850), Cornalia (1856), Gardnier (1860) Balbini (1866),
Forel (1874, 1885, 1908), Trouvelot (1877), Layard (1878),
Slater (1878), Chatin (1880), Lubbock (1882), Plateau (1886),

BEHAVIOR OF SPIDERS AND OTHER INSECTS 42$

Graber (1887), Dubois (1895), Fielde (1901, 1903, 1905), Pieron
(1906), Wheeler (1910), Barrows (1907), Kellogg (1907), Sher-
man (1909); in various structures on the antennae by Erichson
(1847), Burmeister (1848), Vogt (1851), Wonfor (1874), Berg-
mann and Leucjhart (1852), Leydig (1860, 1886), Lowne (1870),
Claus (1872), Mayer (1878, 1879), Reichenbach (1879), Hauser
(1888), Kraepelin (1883), Schiemenz (1883), Sazepin (1884),
vom Rath (1887, 1888), Ruland (1888), Nagel (1892, 1894, 1909),
Dahlgren and Kepner (1908), Borner (1902), Schenk (1903),
Rohler (1905), Cottreau (1905); Berlese (1906) in the caudal
stylets by Paxkard (1870) ; on the base of the wings and on the
legs by Hicks (1857, 1859, 1860), Boiled, Lee (1885), Hauser,
Janet (1904, 1907).

To settle experimentally the question Mclndoo amputated the
antennae of certain bees, wasps and ants and covered the anten-
nae of others with shellac or celloidin. Such mutilated bees were
abnormal in their behavior; sometimes they would respond to
odors and sometimes they would not. Bees with maxillae and
labial palps removed responded to odors the same as normal
bees. Bees with the proboscis removed, bees with the mandibles
amputated and bees with the buccal cavity plugged with paste
responded to odors. When the bases of the wings were glued
and when the legs were covered with vaseline and beeswax the
insects were much slower than usual in responding to scents.
These experiments caused Mclndoo to agree with Hicks that
certain peculiar pores found on the base of each wing and on
the legs are the olfactory organs. In his latest paper, Mclndoo
(56) makes the following criticisms of the researches of most of
his predecessors: — (1) Most investigators study the behavior
in captivity for only a short time and others did not investigate
the behavior of the unmutilated individuals. (2) When the
antennae are injured or removed the insect is no longer normal.
(3) In the honey bee the pore plates can scarcely be considered
olfactory, for the male has eight times as many as the female,
but responds to odors less frequently. (4) The pegs may be
eliminated because they do not occur in the drones. (5) Pore-
plates are not the olfactory apparatus of insects, for they are
entirely absent in the Lepidoptera. (6) Spiders smell; yet they
have neither antennae nor any organ that corresponds to them.
He closes with the following sentence: " In conclusion, it seems

424 C. H. TURNER

that the organs called olfactory pores by the author are the

true olfactory apparatus in the Hymenoptera and possibly in

all insects and that the antennae play no part in receiving the

stimuli."

VISUAL SENSATIONS

See Severin and Severin under chemotropisrn.

Beutel-Reepen (6) thinks colors and odors attract bees to
flowers.

Lovell (53) cites several examples of black animals and of
people clothed in black being attacked by bees; while wThite
animals, in the same situations, were unharmed, thus supporting
the apiarists' belief that a beekeeper receives more stings when
clothed in black than when dressed in white. In one experi-
ment he wore a black veil and a white suit, with a black band
on one of the sleeves. When the bees were disturbed they
attacked the black veil and the black band, but not the white
clothing. He repeated the experiment using a white veil and a
black suit, with a white band on one sleeve. This time the
bees attacked the black suit, but neither the veil nor the white
band.

In another contribution (51), he makes the following objections
to Plateau's statement that the odor of nectar is necessary to
attract bees to flowers: — (1) " The cornflower and several gen-
tians have odorless, conspicuous, nectiferous blossoms, which
are visited by numerous insects. (2) The nectarless and odor-
less wind-pollinated flowers of the elm are visited by countless
numbers of pollen-seeking honey bees. (3) The highly scented
and conspicuous flowers of the sweet-pea and of certain varieties
of Pelargonium are not visited by insects. Plateau claims that
the odorless, but conspicuous, blossoms of the following plants
are not visited by bees : Clematis Jackmanni, Pelargonium zonale,
Willd., Lilium candidum L., Pisum sativum, Passiflora adeno-
phylla Mostera, Oenothera speciosa Nuttall, Linum candidum.
Discovering that the placing of the oil of anisette on these
flowers would cause insects to visit them induced Plateau to
conclude that it was the odor that attracted them. Lovell
found that the placing of odorless sugar water on these flowers
causes them to be visited by insects. According to Lovell, a
certain man had two apiaries situated two miles apart. In the
fields of one frequent rains had produced an abundance of clover

BEHAVIOR OF SPIDERS AND OTHER INSECTS 425

with long corollas ; in the fields of the other a drought had caused
the clover to have short corollas. In the second clover-field the
bees were so abundant that they stung the men who attempted
to mow the clover. In the first field there were practically no
bees. Evidently, the presence of the bees in the former field
was caused by neither the color nor by the odor, but by the
accessibility of the nectar. Lovell's paper closes with the fol-
lowing conclusions: — " Entomophilous flowers are usually char-
acterized by the possession of either bright coloration, or odor,
or both, although apparently to some extent the two qualities
are mutually exclusive. Both allurements are useful in attract-
ing the attention of insects; but the absence of either conspicu-
ousness, or odor, or both, will not necessarily cause a flower
to be neglected if it contains an ample supply of nectar or pollen.
But under similar conditions, small, green, odorless flowers, even
if rich in nectar, will not be discovered as quickly as nectiferous
flowers, which are conspicuous or agreeably scented. On the
other hand, the possession of both color and odor will not ensure
frequent visits in the absence of available food materials. The
experiments afford no evidence that bees visit flowers for the
purpose of experiencing an aesthetic pleasure. Insects, especially
bees, occasionally examine the neglected conspicuous flowers of
cultivation; but, obtaining no food materials, or very little, they
do not often repeat their visits. Many neglected flowers are
pleasantly scented and the addition of another agreeable odor
is neither necessary nor beneficial. When odoriferous fruit syrups
are introduced into conspicuous flowers, commonly neglected, a
group of miscellaneous insects, especially Diptera, will be at-
tracted; but the inference that, therefore, color is no advantage
and an agreeable odor is required is fallacious. For the intro-
duction of an odorless syrup into similar flowers will induce
insect visits in large numbers; also when flowers, with the nectar
inaccessible to honey bees and, consequently, seldom visited by
them, have the nectaries artificially punctured, or the floral
tubes shortened by drought, they are then visited by bees in
countless thousands without the addition of either an agreeable
odor or a sweet liquid. Flowers which in one locality freely
secrete nectar and are visited by numerous insects are sometimes
in other localities nectarless and almost entirely neglected. In-
sects, therefore, perceive the colors and forms of neglected flowers,

426 C. H. TURNER

and the rarity of their visit is the result of their memory of the
absence of food materials, not because the flowers lack an agree-
able odor, which is often not the fact. The flowers into which
Plateau introduced odoriferous sweet liquids were thus arti-
ficially converted into distinct physiological varieties. Since
flowers possessing conspicuousness, an agreeable odor, and a
liquid food are opposed to flowers possessing only conspicuousr
ness, it is clear that color was never brought into competition
with odor— the latter was invariably given the advantage. Colors
and odors attract the attention of insects, but bees in their
visits to flowers previously examined by them, are guided largely
by the memory of past experience; they are able to associate
different sense impressions and unconsciously make analogous

inferences."

MATING INSTINCTS

McDermott (55) gives a resume of the literature showing that
in the Annelid worms and in the Lampyrid beetles phosphor-
escence is a mating behavior. He relates that the habits of the
phosphorescent Elaterid genera Pyrophorus and Photoporus are
unknown; and that Bolitophila luminosa is the only known self-
luminous fly.

According to King (47), the littoral mite, Gamasus immanis
Berl., mates the latter part of August, in a manner similar to
that recorded for G. terribilis by Michael in 1886.

Triggerson (85) observed that the male of Dryophanta ericacea
begins courtship by striking the female several times with his
antennae. These taps quiet the female and render her sub-
missive.

NEST BUILDING AND MATERNAL INSTINCTS

Detailed descriptions of the nesting and maternal habits of
the mason bees of his part of France are given by Fabre (23).*

* The small space given to the discussion of Fabre's work is due not to a lack
of appreciation for him on the part of the reviewer; but to the fact that these articles
were originally published, in the French, several years ago, and it is believed that
most students of animal behavior are familiar with them in the original. The
reading of all of Fabre's works will well repay any student of animal behavior.
One will not always agree with his interpretation of the facts; for, to the day of
his death, he was uncompromisingly opposed to the theory of evolution. He
stands toward the animal behavior men of today in the same relation as did the
elder Agassiz to the morphologists of his day. Agassiz had collected a wealth of
material which he interpreted in terms of types of created things; but which his fol-
lowers, assisted by additional researches, interpreted in terms of morphological evo-
lution. Likewise Fabre has collected a wealth of material which he interprets in
terms of preestablished and unchangeable instincts; but which his followers, assisted
by additional researches, will interpret in terms of mental evolution.

BEHAVIOR OF SPIDERS AND OTHER INSECTS 427

Branch (10) states that Entyla sinuata, one of the Membra-
cidae, oviposits in a slit which the female makes in the midrib
of the underside of the leaf of the thistle Cnicus altissimus.

Weiss (99) informs us that the nest of Paratenodera sinensis
consists of a horny core containing eggs, surrounded by a rind,
which undoubtedly protects the egg from moisture and frorn
sudden changes of temperature. By a long series of tests, he
proved that the eggs were not subject to sudden changes of
temperature.

Williams (102) has given us the following interesting facts
about the behavior of certain Hymenoptera. The nest of Mimesa
argentifrons is a vertical funnel surmounted by a frail cone of
agglutinated grains of sand. Priononyx thomae Fab. deposits her
prey in a place of safety while she constructs her one-celled
burrow. Priononyx atrata St. Farg. digs its burrow with jaws
and forefeet. When the time comes to close the burrow, the
wasp fills it by backing in and throwing in dirt at the same time.
After using her clypeus and jaws as a packer or ram the wasp
smoothes over the burrow with strokes of her feet and then
covers it with bits of soil, sticks, etc.

In another paper (101), he informs us that the Larridae of
Kansas are partial to sandy situations and that they almost
invariably excavate their own nests. Occasionally they build
in brambles; but the majority of the species mine in the ground.
With the exception of Miscophus, the egg is placed transversely.

Strand (83) discusses the nest of an American Eumenid wasp
and its inhabitants.

Dwight Isely (43) describes the nesting habits of six mining
and two mason wasps of the family Eumenidae. The mining
wasps belonged to the genus Odynerus. Each moistens the clay
in which it is going to excavate with water brought, in periodic
trips, from a nearby pond or stream; but, there is a marked
contrast between their nests. The striking thing about many
of these nests is the turret built around the entrance, out of a
portion of the materials removed from the burrow. Odynarus
papagorum Viereck constructs a turret which is durable under
all ordinary conditions. The turret of Odynerus arvensis Sauss.
is so frail that even a light rain destroys it. When the burrow
of this species has been stocked, the wasp demolishes the turret
and throws it, piece by piece, into the burrow. Odynarus dor-

428

C. H. TURNER

salts Fab. does not construct a turret. Odynarus annulatus is
variable in its habits. Sometimes it constructs a burrow with
a turret and sometimes it uses an abandoned nest of Pelopeus.
All of these burrowing species make locality studies before
beginning their excavations. Many of these forms suspend the
egg from the ceiling by a thread. Fabre thought this a device
to prevent the egg from coming in contact with the squirming
larvae. As Isely says, this cannot be true in all cases, for often
the caterpillars are packed closely about the egg.

Beutel-Reepen (7) is convinced that the bees have ascended
from forms having the habits of the digger wasps, and he crys-
tallizes his opinion in the following table:

BIOLOGICAL ANCESTRAL TREE OF BEES

Meliponidae

(Stingless bees)
Melipone and Trigonae
about 170 species

Apidae

Bombidae

(Bumble bees)
about 250 species

Apinae

(Honey bees)
(Apis mellifica)
(A. indica)
(A.florea
(A. dorsata)

Honey-comb-

?emales (old) and unfertilized young females bearing partheno-
genetic eggs working together in the old nest. Beginning
of the one-family colony.

(?)

females see the brood emerge. Guard the nest,
like arrangement of cells.

(Halictus quadricinctus)

females see brood emerge. Guard the nest.

(Halictus sexcinctus)

females, two and more, occupy a burrow in common, but each
cares only for its own young.

(Panurgus, Halictus, Osmia, Eucera, etc.)

females, or females and males over-winter together.
(Halictus, Ceratina, Xylocopa, etc.)

females, independently of each other, construct colonies of simple
nests. Beginning of the first social instinct.

(Andrena, Anthophora, Chalcidoma, Osmia, etc.)

emales construct isolated single nests.

(Prosopis, Osmia papaveris, etc.)

According to the Severins and Hartung (79), the melon fly
(Dacus curcubitae Cog.) oviposits in the stem, petiole, flowers
and fruit of pumpkins.

Herrick (33) reports that the apple pest (Xylena antennata)

Females die be-
fore the brood
emerges.

BEHAVIOR OF SPIDERS AND OTHER INSECTS 429

deposits its eggs in the leaf -scars before the leaves appear. He
finds that, in confinement, Ypsolophus pometellus oviposits in
the latter part of May.

Emery (22) discovered that Simulium vittatum breeds only in
running water. The female attaches strings of 200 to 300 eggs
to the rocks. There are three broods a year.

Bloeser (8) states that Siphona plusiae deposits one or more
eggs on the outside of the Phrygnidian larva.

Welch (100) reports that the fly Hydromyda confluens Loew.
constructs a gall on the submerged petiole of the water lily.
He thinks the fly crawls down the stem and oviposits beneath
the water.

Palmer (67) describes the laying habits of certain lady beetles.

FOOD PROCURING AND DEFENSIVE INSTINCTS

Campion (14) describes the feeding behavior of some dragon
flies; Coad (16) of the boll- weevil and Houser (37) of Con-
wentzia hageni.

According to Bloeser (8) the larva of Siphona plusiae pene-
trates the body wall of the Phrygnidian larva and feeds upon
its entrails. In ten days it is mature.

Branch (10) asserts that Entylia sinuata, a Membracid, feeds
on the thistle {Cnicus altissimus).

By capturing flies and removing their prey from them, Brom-
ley (11) has made a careful study of the food of eighteen species
of Asilidae. He gives a list of prey that covers nearly six pages.

Emery (22) finds that the buffalo gnat {Simulium vittatum)
will bite before ovipositing.

Girault (26) deprived half grown ant lion larvae of food for
twenty-five days and found them still alive.

Guyenot (28A) found that the little fruit fly (Drosophila
ampeliophila) develops normally when fed on sterilized yeast.

Heath (32) records an instance of a phalangid drinking milk.

The investigations of Hewitt (34) show that the dung fly
Scatophaga stercoraria L. destroys large number of flies, especi-
ally Muscoid flies, by seizing the victim with its legs and pierc-
ing the neck with a thrust of the proboscis from below. After
a moment's sucking, the fly is turned over and the proboscis
thrust between the abdominal segments.

In another paper (35) he states that he could not get the

430 C. H. TURNER

•stable fly to bite until twenty-four hours after emerging from
the pupa. [Mitzmain got them to bite at the end of eight
hours.] Usually it feeds not oftener than once in twenty-four
hours.

Hueguenin (41) informs us that a Noctuid moth (Heliothis
dispaceus), which feeds on the tar weed, also feeds on the larva
of Pontia rapae.

Isely (43) reports that the young of all the Eumenidae studied
by him feed on the plant-feeding larvae of other insects.

King (47) finds that the mite Gemasus immanis Berl. feeds on
Oligochaetes. Truessart claims that Molgus littoralis feeds on
■Collembola; but King could not induce this mite to do so. He
found it feeding on living Diptera.

Merrill (60) found a Clerid larva eating the caterpillars of
the codling moth. Palmer (67) finds that the amount eaten
by the larvae of the lady beetles varies with the weather and
the size of the larva; and that the quantity eaten by the adult
varies with the weather and the egg-laying activity. None feeds
on vegetable matter; all eat plant lice.

The Severins and Hartung (79) find that the melon fly (Dacus
curcibitae) feeds upon the cucumber, egg-plant, kohlrabi, musk-
melon, pumpkin, squash, string bean, tomato, watermelon, wild
cucurbit, mango, orange (?), and papaya. They feed from sun-
rise until 10 A. M., and rest during the hottest part of the day.

Venerables (91) finds the adult saw-fly Tenthredo variegatus
feeds upon small Dipterous insects.

According to Welch (100) the young of Hydromyza confluens
.Loew. feeds on the waterlily.

Williams' investigations (103) show that the larva of the
tiger beetle, Amblychila cylindriformis Say, comes to the sur-
face at night and feeds on a variety of insects. It rejects dis-
tasteful ones, sometimes relinquishes an . edible insect that it
cannot subdue, and is occasionally overcome by its intended
prey.

In another paper on solitary wasps, Williams (102) states that
Harpactus gyponae stocks its nest with Gyoina cineres, a Jassid;
that Mimesa argentifrons stocks its nest with Athysanus exitiosa,
another Jassid; and that Priononyx rufiventris feeds its young
on several species of short-horned grasshoppers.

In the following table Williams (101) has condensed much of

BEHAVIOR OF SPIDERS AND OTHER INSECTS

431

the information gleaned from his investigations of the food habits
of the Larridae of Kansas.

TABLE TO SHOW THE PREY OF THE LARRIDAE

Wasp

Prey

Order to

which prey

belongs

•
Gryllidae

Larra anathema (Europe)

N otoconia agentata . . ,

Mole crickets (Gryllidae)

Immature Gryllus (Gryllidae)

Ceutophilus sp. (Locustidae)

Immature Tettiginae and Acridiinae

Various Melanopli, M . ferum-rub-
rum, usually immature; Ageneo-
tettix deorum, mature (Acridiinea
and Tryxalinae)

Mature Alpha crenulata (Tryxal-
inae)

Larropsis divisa. .

Tachytes abdominalis . .

Tachytes distinctus

Tachytes fulviventris

Tachytes harpax \ . . .

Niphidium brevipenne (Locustidae)
Niphidium and im. Orchelimum. . .
Immature Tettiginae

Tachytes ynandibularis

Tachytes mergus

Almost

Tachytes obductus

Immature Tettiginae

exclusively

Tachytes obsoletus (Europe)

Tachytes pompilijormis (Europe)

Young Oedipodinae

Orthoptera;

the two

exceptions

are.

Immature Gryllus rufus, grasshop-
pers (Choiptusr) ; lepidopterous
larvae

Tachytes rufofascialus

Immature Melanoplus cyanipes, ma-
ture and immature Melanopli
(Acridiinae)

Lepidoptera

and
Diptera. (*)

Tachytes tarsina (Europe)

Tachysphex fusus

Immature Acridiinae

Immature Melanopli (Acridiinae) .

Immature Litaneutria minor (Man-

tidae)

Tachysphex hitei

Tachysphex panzer (Europe) ....

Tachysphex plenoculiformis

Trachysphex propinquus

Acridiinae

Immature Traxalinae

Mature Alpha crenidata, Ageneo-
tettix deorum and Mestobregma
kiowa; immature Opeia sp. (Tryx-
alinae and Oedipodinae

Tachysphea quebecensis

Immature Acridiinae

Tachysphex semirufa

Immature Melanoplus sprelus

Immature Acridiinae, Tryxalinae
and Oedipodinae

Tachysphex tarsatus

Tachysphex terminatus

Chortophaga viridifasciata, imma-
ture Tryxalinae

Trachysphex texanus

Lyorda subita

Immature Oedipodinae (Diptera)*.
Nemobius ; small crickets (Gryllidae)
Mature and immature Atomoscelis

sp. (Capsidae)

Immature Pamera sp. (Lygaeidae).
Immature Oedipodinae f

Plenoculus apicalis ■

Hemiptera.

Plenocidus peckhami

Exceptions :
Orthoptera

Niteliopsis fossor

and

Niteliopsis inerme .

Immature Capsidae

Arachnida

Miscophus spp. (Europe)

Various small spiders, Epeiridaef. .

J (t)

432 C. H. TURNER

Miss Alice Noyes (65) has made a careful study of the net-
spinning Trichoptera of Cascadilla Creek. She confirms Siltala's
statement that the food of Hydropsyche is both animal and
vegetable. In the fall and winter diatoms form the bulk of
their food; in the spring and summer animal food predominates.
The members of the family Polycentropidae have an animal
diet. Chimamba alterrima of the family Philopotamidae, feeds
exclusively on plants. She makes the following conclusions: —
1. Many forms construct their nets only at night; but Hydro-
psyche spins by either night or day. 2. Two and a half to three
hours is the average time required to weave a net. 3. Different
species build similar dwellings. 4. Unlike the orb-weaving spi-
ders, they do not spin preliminary construction threads. 5.
There is no definite order followed in spinning the threads.
6. The mouthparts, not the tufts of hair on the anal legs, are
used to remove particles from the nets. 7. Its front legs and
mandibles are used for seizing and holding in place until fast-
ened any bits that the insect intends to weave into the net.
8. It is never too intent on its weaving to pick up bits of food
that become entangled in the nets. 9. Food captured in the
net is dragged inward, killed and swallowed whole.

HIBERNATION

Houser (37) states that Conwentzia hageni hibernates in the
larval stage.

Palmer (67) says all lady beetles hibernate in the adult form.

F. E. Lillie (48) thinks that some individuals of the monarch
butterfly hibernate in the adult form, although she could not
obtain confirmatory evidence of this. Indeed, all attempts to
induce them to hibernate by keeping them in a cool, dark place
failed; but in May she found adults with unfrayed wings.

King (47) does not say that the mite Bdella longicornis hiber-
nates; but he states that it constructs a web in which it appar-
ently spends the winter.

Baumberger (4) reviews, at length, the literature on hibernation
of insects and reaches the following conclusion: — " 1. That
temperature is but a single factor and not necessarily the con-
trolling one in hibernation. 2. That hibernation is usually
concomitant with overfeeding and may be the result of that
condition or the result of accumulation of inactive substances

BEHAVIOR OF SPIDERS AND OTHER INSECTS 433

in the cytoplasm of the cell due to the feeding on innutritive
food. 3. That the loss of water which is general in hibernation
probably results in a discharge of insoluble alveolar cytoplasmic
structures which have accumulated and produced premature
senility with an accompanying lowering of the rate of metabolic
processes. 4. That starvation during hibernation together with
this loss of water may result in rejuvenation, when aided by
histolysis, and in increased permeability. 5. That this re-
juvenated condition and increased permeability, will, if stim-
ulated to activity by heat, permit pupation in codling moth
larvae, which in this case is the termination of the hibernating

condition."

LOCOMOTION

Branch (10) relates that Entyla sinuata, a Membracid studied
by him, exhibits no jumping activities in its nymphal stages.

The Severins and Hartung (79) tell us that the nearly full-
grown larvae of the melon fly (Dacus curcubitae Coq.) exhibit
a jumping activity which is never seen in the younger stages.
The insect curls its body into a circle with its jaws attached
to the tip of its abdomen. Then, by suddenly relaxing, it
springs six or eight inches into the air.

Becker (5) describes a rather interesting migratory procession
of the larvae of the fungus gnat (Sciara congregata Johannsen).
Such a procession was observed June 6, 1912 and again July
16, 1913. At first glance it resembled a dead snake. The
procession observed in 1912 was five feet long and tapered
toward each end from the middle, which was three inches wide.
There were several layers of larvae, tapering from eight deep
in the middle to each extremity. The whole procession was
moving forward; but the maggots on top moved much faster
than those on the bottom, hence the insects of the upper layers
were constantly advancing beyond the front, to be immediately
covered by others coming from the rear. In its wake the pro-
cession left a trail resembling that of a snake. The procession
of 1913 was only three feet long.

ECOLOGY

By exposing laboratory animals to controlled stimuli similar
to those of their natural habitats, Shelf ord (81) has been able
to analyze the behavior of animals forming communities and

434 C. H. TURNER

has reached the following conclusions: — " 1. The animals of a
community are in agreement in the reaction to certain inten-
sities of two or more factors. These reactions may be used to
designate them. Thus the rapids community may be designated
as litho-rheotactic, meaning that the animals are arranged with
reference to current and stones of considerable size. 2. Animals
living in the same or comparable situations within the community
habitat are in agreement and the animals of different situations
react differently to these additional factors. Similar differences
are the physiological basis of strata and consocies though the
smaller number of species make the latter not easily distin-
guishable here. 3. Single species found in any community occur
in other situations where they are governed chiefly by stimuli
towards which there is not agreement of reaction throughout
the community to which they primarily belong."

Wolcott (104) discusses the ecology of the parasitic wasp
Tiphia inomata.

See McDermott under mating instincts.

DISEASE SPREADING ACTIVITIES

The papers of Graham-Smith (27), Harms (30), Lloyd (49,50),
Ludlow (54), Riley (74) and Webster (95) will be of interest
to physicians.

Zetek (106) has demonstrated that the typhoid fever spread-
ing fly visits houses 2,500 feet away from the feeding places
of its larvae.

Three theories have been proposed to account for the spread
of pellagra: (1) the zeistic theory, based on the work of Ballardini,
which appeared in 1895, which claims that it is a poisoning
due to the excessive use of the products of corn; (2) Mizell's
theory, proposed in 1911, which holds that it is poisoning due
to the use of cotton-seed products; Sambon's theory, dating
from 1910, which holds that it is spread by the sand-fly. Sambon
bases his theory upon the following statements: (1) the endemic
action in Italy has remained the same since the disease first
appeared; (2) the season of recurrence coincides with and fluctu-
ates with the season of the appearance of the adult sand-fly:
(3) in the center of infection whole families are attacked sim-
ultaneously; (4) in non-pellagrous districts the disease never

BEHAVIOR OF SPIDERS AND OTHER INSECTS 435

spreads to others on the advent of pellagrins; (5) in families
moving into non-pellagrous districts, children born in the former
district are pellagrous, while others are not; (6) the disease
is not hereditary; (7) it is not contagious. The advent of
pellagra in Kansas gave Hunter (42) an opportunity to conduct
a series of experiments which yielded the following results: — "(1)
the number of sand-flies is directly proportional to the number
of cases of pellagra; (2) the appearance of the cases of pellagra
is coincident with the principal broods; (3) just succeeding the
time of the principal broods the flies seem to bite more vigor-
ously; (4) sand-flies which have fed on human blood live several
days longer than those which have not been so nourished, thus
favoring an incubation theory for a parasite, if such there be;
(5) pellagra, thus far in Kansas, has appeared almost entirely
in one restricted locality; of nine cases recorded last year five
were traced back to one town; in this region flies are widely
distributed; (6) no direct evidence has yet been found which
would in any way warrant any conclusion with reference to an
association of the sand-fly in the determination of the etiology
of pellagra." Hunter hopes to continue his researches until
the problem is solved.

PARASITISM

Cummins (18) describes a sarcoptid mite of the cat; Howard
(37) several mites of the gypsy moth; and Bloeser (8) a hymen-
opterous hyper-parasite of Siphona plusiae Coq.

Triggerson (85) gives a list of the numerous parasites of
Dryophanta erinacei.

Isely (43) tells us that the Eumenidae of Kansas are parasi-
tized by the Bombilidae, the Tachinidae, the Ichneumonidae,
the Braconidae, the Mutilidae, the Myrmicidae and the Asilidae;
but that the most persistent parasites belong to the Chrysididae.
He believes that the turrets constructed about the entrances
of so many burrows of this group of insects are to prevent the
entrance of parasites.

Muir (61) discusses the effect of parasites on the struggle
for existence.

Fabre (23) describes the parasites of the mason-bees of his
part of France and states that he does not believe that parasitic
habits result from a love of inactivity ; for he finds that parasites

436

C. H. TURNER

work hard. The parasite Stelis must break through walls as
hard as concrete to deposit its eggs.

Waterson (94) discusses the bird-lice of five species of English
auks. In addition to a parasite peculiar to it, each often has
one or more other parasites. He has epitomized his conclusions
in the following table.

D. acutipectus, Kell

D. calvus, Kell

D. celedoxus, N

D. megacephalus, D . . . .

D. merguli, D

D. iderodes, N

D. cardiceps, P

o

11 birds

Ud) (S)

'a

HO

6 birds

fx(6)
U(l) (S)

x(DO)

e

6 birds

x(6)

CO

SI,

a.

so

11 birds

CO

3
3

so

10 birds

x(H)

fx(10)

1

U(i)(S)

e

e

CO
CO

1 bird

x

CD CO

(S)

a

CD

^2

'— a
a

GO £

CO

CD ..

a-s

An x denotes the occurrence of Docophorus on bird species. The number in
brackets indicates how often the parasite has occurred on the host species.

The long brackets with their numbers show how often and how many species
have occurred together on an individual host.

(S) = straggler.

Thus, column one reads: "Of Uria troile, 11 birds have been examined and on
all D. calvus has been taken. In two cases D. calvus has been found with D. cele-
doxus, and once with D. merguli. This last, however, seems a case of straggling.

SOUND PRODUCING ACTIVITIES

Regen (72) mentions the enticement of the female of a cricket
(Gryllus campcstris) by the stridulations of the male.

Mrs. Comstock.(17) discusses, in a popular vein, the stridu-
lations of crickets and gives directions for keeping the insects
in confinement.

Aubin (2) has performed some experiments which cause him
to assert that the high-pitched note produced by flies is due

BEHAVIOR OF SPIDERS AND OTHER INSECTS 437

neither to the vibrations of the wings, nor to the pulsations
of the thorax, nor to special modifications of the occlusor appar-
atus of the stigmata, nor to movements of the halteres; but,
to a special sound-producing apparatus which is situated, on
each side of the thorax, near the base of the wings. This con-
sists of a membrane-lined depression which is traversed diagon-
ally by two ridges or ribs. When the wings are vibrated rapidly
a chitinous structure on the base of each strikes against one of
the ridges of the apparatus just described and induces the mem-
brane to vibrate. This produces the high pitched sound we call
buzzing. The following results of his experiments on the drone-
fly (Eristalis tenax) seem to justify his conclusion: — 1. The fly
may be held in the fingers in any way but one without appre-
ciably affecting the buzzing; press the shoulders of the wings
to the body and the buzzing ceases immediately. 2. Each or
all of the following parts may be removed without noticeably
affecting the sound; halteres, squama, ante-squama, aulet and
nine-tenths of the wing. If the entire wing is removed the
sound ceases. 3. If the vibrations of the aulets be checked
by a needle applied at tKe convexity of the chitinous part, the
sound continues. 4. If, while the fly is buzzing, a needle is
inserted between the chitinous part of the wing base and the
ribs on the body of the fly, although the parts are uninjured,
the buzzing ceases. 5. A minute spear of tissue paper inserted
between the chitinous portion of the base of the wing and the
ribs on the thorax subdues the sound. 6. If pins be so placed
that, without injuring the wings, they prevent them from closing
closer than 45° with the axis of the body, no buzzing is heard.
Evidently this organ is of a higher order than the striduiating
apparatus of the Orthoptera. Since a portion of it consists
of a vibrating membrane, Aubin is inclined to believe that it
is a sound-receptor as well as a sound-producer.

In the discussion which followed the reading of this paper
before the Royal Microscopical Society of London, a Mr. Hop-
kins arose and stated that, eighty years age, Burmeister had
performed similar experiments which yielded identical results,
and he wondered why Aubin had not cited Burmeister's ex-
periments. At this writing, Burmeister's original paper is not
accessible to the present writer; but, judging from the quotation
made at the meeting of the society, Burmeister held that certain

438 C. H. TURNER

folds connected with the spiracles were the cause of the sound.
Unless the reviewer entirely misunderstands Aubin's words and
illustrations, his apparatus is not connected with the spiracles.
It does, however, seem strange that Aubin makes no mention
of the work of Pemberton* which was reviewed in this journal
about three years agof. Pemberton, as a result of his exper-
iments, insisted that there is no spiracular voice in insects
and that the high-pitched notes of the Diptera and the Hymen-
optera are caused by the striking of the bases of the vibrating
wings against the sides of the thorax. Apparently he over-
looked the ridges against which the wings impinge and the
vibratile membranes connected with these ridges.

DURATION OF LIFE

Baumberger (4) found that, when exposed to constant tem-
peratures, the longevity of insects varies, approximately, in-
versely with the temperature; when exposed to variable temper-
atures, a high or low temperature followed by medium tem-
peratures favors a lengthening of life; exposure to a medium
temperature at the beginning shortens life.

By crossing a short-lived strain of the fruit-fly (Drosophila
ampelophila) with a long-lived strain, offspring were obtained
which were longer lived than either of the parents. In the
second generation some reverted to the short-lived condition.
He thinks there is a physiological connection between the length
of life and the coming into maturity of the germ cells.

Sanderson and Peairs (76) give a table showing the relation
of temperature to the duration of life. The table was compiled
from more than 400 separate experiments involving 390,000
individuals.

Phillips and Demuth (70) assert that the length of life of
bees varies inversely with the amount of work they do; hence,
to secure vigorous bees for the spring, the work to be done in
winter should be reduced to a minimum.

Phil and Nellie Rau (71) have made extended studies of the
longevity of the following Saturnid moths: Philosamia cynthia,
Telea Polyphemus, Callosamia promethea, Samia californica, and

* Pemberton, C. E. Sound Producing Diptera and Hymenoptera. Psyche,
vol. 18, pp. 82-83, 1911.

t Jour, of Animal Behav., vol. 2, p. 396, 1912.

BEHAVIOR OF SPIDERS AND OTHER INSECTS 439

Samia cecropia. They tested both mated and unmated indi-
viduals. In all they studied 3,569 individuals. The following
are some of their conclusions: (1) mating does not significantly
shorten or lengthen the life of the male ; (2) the unmated female
lives longer than the mated: (3) a low temperature lengthens
the life of 5. cecropia and of T. polyphemus.

MISCELLANEOUS
Shelf ord (81) discusses the importance of evaporation in
insect behavior.

1. Migration. Lillie (48) records the well known fact that
the monarch butterflies of Minnesota and of New York migrate
southward in vast swarms each fall; and Davidson (19) discusses
the migration of certain plant lice.

See Becker under locomotion.

2. Pain. Weiss (97) reviews the arguments that have been
produced as proof that insects do not feel pain and concludes
that " The evidence for assuming that insects do not suffer
acute pain is not by any means complete. We simply do not
know and have no reliable means at present of finding out."

3. Pollenization. Mrs. Howard (38) has experimentally proven
that bees are needed to pollenize certain plants. She covered
100 clover blossoms with netting and left 100 exposed to the
bees. From the uncovered blossoms she obtained 2,720 seed;
none of the covered blossoms produced seed. Of 2,586 covered
apple blossoms only three matured.

4. Sleeping habits. According to Beutel-Reepen (7) the males
of several species of solitary bees spend the night congregated
in large clusters.

Williams (102) states that large groups of the males of the
wasp Priononyx tkomae spend the nights and unfavorable weather
on the weeds.

Frohawk (24) describes the sleeping habits of the butterflies
of the family Lyncaenidae.

5. Temperature. In an extended study of the temperature
of the bee-hive, Gates (25) discovered that, even in cold weather,
the bees are neither torpid nor semi-quiescent. There is a
constant interchange of individuals between the outside and
the inside of the cluster. Even in the coldest weather, they
groom and comb one another.

440 C. H. TURNER

MEMORY AND ASSOCIATION

Beutel-Reepen (6) believes that bees have a memory picture
of the environment which guides them home.

Fabre (23) insists that it is not memory, but, a special sense
which guides insects home.

Hudson (39) gives a short note on the memory of a Pompilid
wasp.

Lovell (51) says; ' Experiment and studies of the honey-
plants show that honey-bees learn from observation and are
guided by the memory of past experience. Flowers rich in acces-
sible food supplies receive numerous visits, but if for any reason
the flow of nectar suddenly ceases the bees immediately discon-
tinue their visits."

See Lovell under visual sensations.

TECHNIQUE

O'Kane (66) describes the construction of an outdoor insec-
tary, with a conservatory roof, which has screen sides for summer
and glass sides for winter.

Shelford (8) discusses the importance of using atommeters in
studying insect behavior.

Wolff (105) discusses methods of investigating the temperature
reactions of butterflies.

Mrs. Comstock (17) redescribes a method, well known to
students of insects, of keeping crickets in large lamp chimmeys
resting in flower pots.

Phillips and Demuth (70) describe a method of investigating
bee hives by means of electrical thermometers.

Draper (20) has devised a convenient live box for studying
insects under the lowest powers of the microscope. A piece
of glass tubing one-third of an inch deep and two-thirds of an
inch in diameter is cemented to a standard microscopic slide.
A circular piece of glass, of larger diameter than the cell, serves
as a cover. Near the circumference of this cover and equi-
spaced, three pins are attached to the underside. The collar
by which each pin is attached to the cover prevents it from
touching the top of the cell and thus insures ventilation. A
false bottom permits regulation of the depth of the cell.

Baumberger (4) describes a convenient net for securing large
quantities of live insects. The net is constructed in the follow-

BEHAVIOR OF SPIDERS AND OTHER INSECTS 441

ing manner: "A strong piece of iron wire, three feet, eight
inches long, is bent into a circle with one foot diameter — the
ends are then bent at right engles so as to lie adjacent and
parallel to each other. The ends are inserted into the small
end of a six inch ferule and soldered fast. A short two foot
handle will be found best for sweeping. The net consists of
white muslin — a conical bag about eighteen inches deep. The
tip is cut off where the circumference of the bag measures about
three inches and is replaced by a cloth bag four by six and a
half inches. This small bag is sewed to the point at which the
circumference of the large net is four inches, thus, leaving a
sleeve which hangs down into the small bag — this small bag
will just hold a quarter pound paper bag. The sleeve of the
large net fits into the paper bag. When filled from a minute's
sweeping, the paper bag is pinched at the opening, taken out
of the net and placed in a botanical can. Upon the return to
the laboratory the bag is opened at a well lighted window and
the contents picked over for specimens."

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LITERATURE FOR 1914 ON THE BEHAVIOR OF

VERTEBRATES

STELLA B. VINCENT

Chicago Normal College

VISION

Mammals. — Both Bingham (3) and Johnson (15) reply to
Hunter's criticism of last year, in which he insists that form
must be considered as a part of a pattern — that the stimulus
object is seen against a visual background. The former urges
first, that his apparatus was in a dark room which enabled him
to control conditions of setting and second, that a distinction
must be made between form and shape, i. e., two similar tri-
angles, the one upright and the other inverted, would be alike
in form but differ in shape. In his experiments he got a rela-
tively low per cent of correct choices when the triangle was
inverted; obviously, then, form was not the basis of choice.
The perception of shape, for Bingham, is based upon an unequal
stimulation of different parts of the retina.

Johnson argues that to change, as Hunter suggests, the alleys
in the Yerkes' experiment box to hollow cylinders or triangles
would also change the tactual and probably the olfactory qual-
ities. Admitting that the background changes according as the
stimulus object occupies the right or the left position respec-
tively, he insists that if the stimulus form is as effective in one
setting as in the other the conclusion is justified that the animal
is really reacting to the constant form difference and disre-
garding the variable " pattern " difference.

The best articles on vision in the year 1914 are those of John-
son, beginning his series on Pattern Discrimination in Verte-
brates (16), (17). The first paper deals with the standard
methods of studying vision, the elementary problems in pattern
discrimination and the apparatus and methods. The author
defines pattern discrimination as a discrimination between
visual fields equal in outline, area and average brightness and
differing only in the disposition of their brightness. Four

446

BEHAVIOR OF VERTEBRATES 447

problems are then outlined: (1) the stimulus threshold for stri-
ation, i. e., the width of the individual bands on one field to
insure discrimination between it and another sensibly uniform
field; (2) the threshold difference for size and conversely for
nurnber of individual bands; (3) the difference threshold for
direction of bands; (4) the difference threshold for contrast
which is really the threshold for brightness.

To produce the pattern two glasses were ruled with fine opaque
lines so that the width of the lines and the clear spaces were
equal. When these plates were rotated over each other there
was shown a series of dark and bright bands of equal width.
It is Cobb's apparatus slightly changed. With this was 'used
a modification of the Yerkes — Watson double photometer box.
The whole apparatus is excellent in conception and control,
but for the exact details the reader must consult the original
papers.

In attacking the first problem mentioned above, Johnson
used a series of black and white horizontal bands of equal width
with respect to each other but whose absolute width could be
varied from one which was invisible to one which was plainly
visible without changing any other factor. The task set was to
distinguish this pattern field from a plain field having the same
area, form, range of wave lengths and luminous intensity. The
subjects used were dogs, monkeys and chicks. The details of
the experiments are full of interest. No positive results were
obtained from the dog as his behavior showed no sensitiveness
to differences of detail in visual objects. The experimenter,
however, reserves his conclusions on this subject. The visual
acuity of the monkey was very like that of the human subjects
used for comparison. The acuity of the chick was about one-
fourth that of the monkey. The author raised further questions
as to the method of experimentation the most significant of
which, it seemed to the reviewer, was that relating to the optimal
distance of the test field from the animal. The distance used
in the work reported was, uniformly, 60 cm.

In some experimentation not nearly so well controlled as to
the different factors involved, Szymanski (35) reports some
work on the learning process in white rats. The apparatus
consisted of three connected parts, but, as parts one and two
were so very simple and gave such inconclusive results they

448 STELLA B. VINCENT

may be neglected. In the third part, the animals were required
to go to the right or to the left according to a visual clue. Lamps
of 10 and 2 c. p. were used as stimuli. The temperature was
controlled. After 30 trials punishment was introduced and
after 50 trials the 2 cp. lamp was discarded and the discrimination
was made between the 10 c. p. light and darkness. The rats
had from 93 to 109 trials and only 2 out of 14 animals learned
to follow the light. These two animals made percentages
ranging from 60 to 100. In five other instances the percentages
were rising, although the fact is not mentioned, and probably
further trials might have trained these also as Foley's work
with sparrows, reported below, shows. The work was stopped
too soon. One animal persistently chose the dark way. Many
set up position habits. Numbers 4, 5, 13 and 14 went three
times as often to the left as to the right and number 12 went
four times as often to the right as to the left.

" The understanding of an organism " the same author says,
(34) " is won through an analysis of its motor activities." This
analysis falls into two chief parts: first, the conditions which
influence the general motor activity positively or negatively —
conditions which may be outside or may lie within the organism
and second, the study of the organized movements going on
under the influence of determined and directed stimuli. " In
reality," he says, "the course has been reversed and investigators
have begun with a study of organized activities and only here
and there have sought to clear up the variability of the reaction
to a determined stimulus by reference to the changing conditions
of the organism or of the environment especially the temporal
environment." By means of a bit of apparatus which is called
an aktograph, he records the activities of a series of animals
through the entire course of a series of days including days
chosen at different times of the year. The apparatus was so
arranged as to connect with a Marey tambour and make a
kymograph tracing. Among other animals white and gray mice
were used. No division of activities dependent upon light and
darkness was seen in these animals. The white mice showed
16 periods of activity averaging 45 minutes each, the gray 19
such periods averaging 37.9 minutes each. These periods were
fairly evenly distributed between night and day. He says, "It
appears as if the division of rest and activity periods should

BEHAVIOR OF VERTEBRATES 449

depend upon the preponderance of this or that sense in the
life of the species. If the eye plays the chief role in the life of
the species it is light which regulates the relations of rest and
activity; if other senses have the preponderance, smell, hearing,
kinaesthesis, these are the factors which lead to a different
division."

Amphibians. — Laurens (19) investigated the reactions of nor-
mal and eyeless amphibian larvae to light. The forms which
he used were Rana pipiens, R. sylvatica and Ambly stoma punc-
tatus. Neither normal nor blinded frog tadpoles gave any re-
sponse to light stimulation. The behavior of Amblystoma,
however, was different. Both normal and blinded individuals
were found to be positively phototropic. These reactions, as
proved by operative surgery, were not due to direct stimulation
of the central nervous system but by stimulation of nerve ter-
minals in the skin.

Fish.^*-M.ore work on the color adaptations of fish has been
done by Freytag (6). He used Phoxinus laevis, von Frisch's
best subject, and tried it over many backgrounds. His exper-
iments lasted a year and he used in all 100 animals. These
animals were described minutely before and after the experiments
and sometimes they were kept for 24 hours on the same back-
ground. There were always control animals. As a result of
this work Freytag thinks that the adaptations are to brightness
and not to color at all. There is no doubt he says that the
brightness affects the animals, but no law can be formulated.
Not infrequently was there no change and quite as frequently
was the change in the opposite direction from what was to be
expected. The yellow and red markings showed very incon-
stant changes and never was yellow or red the rule. On the
other hand these colors were often seen when the fish were over
other colors or over gray. He thinks the changes which do
occur are not a response to background alone but are due to
other conditions as well. The enemies of the fish do not all
come from above. It is quite as possible that the adaptation
may be to the brightness of the water in which it swims. None
of the work speaks for a color sense for Pfrille.

Two other investigators (9) in the main confirm the findings
of von Frisch.

450 STELLA B. VINCENT

The aktograph records of Szymanski (34) showed that the
periods of activity of the fish were regulated by light. They
began about one hour before sunrise and ended about one and
one-half hour after sunset.

Birds. — Light discrimination in the English sparrow was the
object of Tugman's (37) experiments and the main attempt
was to find the threshold of brightness. The Yerkes-Watson
brightness apparatus and experiment box was used. The birds
were kept in darkness before the beginning of the work. Correct
choices for two days (30 trials) were counted as a correct dis-
crimination and then the difference between the standard .098
and the variable was decreased and the tests were resumed.
The discrimination differences attempted ranged from .096 to
.009 and the estimated thresholds for four birds were, .015,
.035, .03, .022 c-. p. The estimated thresholds for some human
subjects were .013, .009, .013 c. p. The author says, " One of
the most striking facts is the very large number of trials neces-
sary to bring the animal to the threshold. The three animals
for which the threshold was determined averaged 2,420 trials
each. For the discrimination of the lowest threshold they
averaged 480 trials each ; one of them discriminated only after
615 trials.

As will be seen we are at last getting some well controlled
work on sensory discrimination in animals. The first of the
studies from the Franklin Field Station which Yerkes describes
in the same journal (41) is reported by Coburn (4). He gives
a preliminary study of the crow's ability to discriminate bright-
ness, size and form. In the investigation he used but two
birds. The apparatus was a modified form of the discrimination
box used by Breed and Cole in their study of the visual re-
actions of chicks and the stimulus plates were the Standard
plates of the Yerkes-Watson apparatus. Both method and
apparatus are carefully described in the report. The crows
learned to discriminate between an opal flashed glass and an
opal flashed glass backed first by two milk glasses, second, by
one milk glass; third, by a sheet of paper. These roughly in-
dicate the crows' ability to distinguish differences in illumination.
Then they learned to discriminate between a 9 cm. and a 2 cm.
circle; between a 5 cm. and a 3 cm. circle and between a 3 cm.,

BEHAVIOR OF VERTEBRATES 451

and a 2 cm. circle. Another series of experiments, however,
showed that the crows were reacting not to absolute size but
to relative, i. e. to the larger circle. They also learned to dis-
tinguish a circle from a triangle and from a hexagon under
conditions where form was the only constant factor.

Szymanski's (34) aktograph curve for birds shows a high
degree of activity for the morning hours. In the hours imme-
diately after noon the activity decreased and then with great
constancy rose again just before the beginning of the night
rest. In this respect it resembles the waking (day) curve of
men given by Helpach. The movements of the birds can be
inhibited not entirely but greatly in intensity and also in general
nature by darkness.

SOUND

Mammals. — There are only three papers to report on auditory
sensitivity in connection with vertebrates this year. Shepherd
(31) using the method which he had previously employed with
raccoons and monkeys investigated sound discrimination in cats.
The notes were blown on an ordinary harmonica or sounded
on a piano. The animals were to climb up in a cage for food
at one note or refrain from climbing when another was sounded.
He thinks that he found positive proof of pitch discrimination
as well as discrimination of intensity in noise. The constant
presence of the experimenter makes possible other clues and
renders these results doubtful as Johnson's work with dogs
has shown.

Considering the work mentioned above and other similar
studies the following report by Morgulis (23) seems almost
incredible yet perhaps our apparatus or methods are at fault.
He discusses clearly and concisely the Pawlow method and
makes a brief report on Usiewitch's study of the auditory re-
actions of the dog by this method. He found an auditory
faculty much keener than man's. The dog perceived one-eighth
of a tone and tones of a frequency of vibration quite beyond
human reach. He found absolute memory for sounds and his
dogs could distinguish the shortening of an interval by less than
one-fortieth to one-forty- third of a second.

Hunter (12) has less startling results in a report which he
makes upon some studies of the auditory sensitivity of the
white rat which are now in progress at the University of Texas.

452 STELLA B. VINCENT

A 512 c' fork was used for the tone stimulus and the alternate
noise stimulus was hand clapping. The animals were to go to
the right or to the left respectively at the stimulus. Under
the conditions the errors steadily decreased but when the tone
was withheld the reaction remained the same proving that the
animals were reacting to noise only. None of seven rats in 700
trials learned to react to tone. There was also failure to dis-
criminate between different intensities of c'. Many noises were
substituted successfully for hand clapping with another set of
animals. Interrupted tones gave no better results. The author
concludes that either the rats cannot hear c' or that their sen-
sitivity to this tone is extremely slight.

OLFACTION AND CHEMICAL SENSITIVITY

Mammals. — A note on the supposed hunting response of the
dog by Johnson (15) is a brief but interesting bit of analysis
of some of the theories adduced to account for the ability of
the dog to trail his master or track his prey.

Amphibians. — Risser (27) studied the toad in its reactions to
natural or artificial food odor in living or dead animals. Odor
streams were tried and the experiments were repeated in dark-
ness. The species used was Bnfo americanus Le Conte. His
conclusions are that the visual is the sole stimulus which arouses
the food response of the toad and that this is effective only when
the food is in motion. Rejection of food, he thinks, is due to
mechanical or tactual stimulation and the gustatory function
is negligible. No positive conclusions are drawn as to olfaction
yet he found it difficult to establish any connection between the
seeking of food and inherent food odors. Odor streams caused
definite motor activities which were proven by operative pro-
cedure to have an olfactory stimulus. The reactions which
were inhibited by section of the olfactory tract were not affected
by section of the trigeminal nerve. Tadpoles appear to use
olfaction in discrimination of foods. The author says, "In the
metamorphosed toad the visual stimulus is the principal and
guiding factor in procuring food. Therefore it is inhibitory in
relation to other stimuli and their resultant reactions."

Rapid modification of behavior was noted by Shelford (30)
in experiments designed to test the sensibility of amphibians to

BEHAVIOR OF VERTEBRATES 453

variations in the evaporating power of air. In this case the
conditions were such as would tend to dilute or concentrate
the plasma either in the peripheral sense organs or in the animal
as a whole. Though associations are formed, Shelford says,
they go hand in hand with and can hardly be distinguished
from other type modifications * * * There is no reason to
assume that associative memory is essentially different from
the type of modification here described. * * * It seems probable
that many of the simple problems of associative memory must
be referred to the bio-chemist for solution."

Fish. — Shelford (29) also has published an elaborate bit of
experimentation with different kinds of fish. They exhibited
distinct differences in behavior in the presence of modified water.
He inclines to the belief that the changes in activity are due to
physiological conditions in many cases connected with C02
relations and do not necessarily involve associative memory at
all. The stimuli which gave rise to the modifications most
quickly are those most commonly encountered by the fish in
water — a disturbance of neutrality either in the direction of
acidity or alkalinity.

INSTINCTS AND HABITS

Mammals. — In the hope of coming to a better understanding
of abnormal human sexual behavior, Hamilton (10) has made
an excellent study of sexual behavior in monkeys. The obser-
vations included twenty animals mature, immature and eunuchs
and were made under the varied conditions of confinement and •
free range which a California laboratory permits. For the many
suggestive details the original paper must be consulted. The
author regards behavior as an expression of reactive tendencies
which have specific representation in structure. He says, "The
essential factors in the behavior phenomena are (a) the action
of a physiological process usually operating in conjunction with
environmental forces, in the production of (b) hungers which
impel the individual to manifest (c) activities, the particular
types or modes of which are to be ascribed to (d) specific organic
properties (reactive tendencies)." He recognizes three hungers
which normally impel the macaque to manifest sexual behavior,
viz: hunger for sexual satisfaction, hunger for escape from danger
and possibly hunger for access to an enemy.

454 STELLA B. VINCENT

Lashley (18) gives us a note on the persistence of an instinct
and Hahn (8) a popular account of the hibernation of certain
animals. Among them are the bear, woodchuck and ground
squirrel.

Amphibians. — The only article on the instinctive behavior of
amphibians is that of Banta (1) who gives some interesting
notes and careful observations of the mating behavior of wood
frogs which he watched at Cut off Pond, Cold Springs Harbor.

Birds. — To observe the very first performance of the social
activities of an adult one must rear the animal in isolation and
then allow it, while under close observation, to come in contact
with another animal. Craig (5) does this and gives an inter-
esting account of the behavior of three male doves which he has
thus brought up apart from their fellows. He concludes, among
other things, that display behavior needs social stimulation;
that the motor aspect of the sexual reaction is definitely provided
for by inheritance but that what he calls the 'sensory inlet' is
not complete and is supplemented by experience; and that one
finds surprise, hesitation and even fear in the first performance
of an instinctive act while ease, skill and intelligent adaptation
are the gift of experience.

Another paper which deals with sexual reactions also is that
of Huxley (13). He recounts in elaborate detail the very dra-
matic courtship or love habits of the Grebe. After describing
the bird and giving its animal history, he turns to the real interest
of the stud}^ — the relation of the sexes, (a) in the act of pairing,
(b) courtship, (c) nest building, (d) the relation of different
pairs, (e) other activities. In the discussion which follows, the
author tries to explain what he calls the facultative reversal of
the sexes in the act of pairing — a subject which is interesting
many investigators at the present time — and he then elaborates
a modification of the sexual selection theory which he calls
mutual selection. He says, " Where combined courtship actions
exist and a variation in the direction of bright color or strange
structure occurred it would make the actions more exciting and
enjoyable and those birds which showed the new variation first
would pair up first and peg out their 'territories' for nesting
before the others could get mates." * * * As to the courtship
activities he says, " These actions are much too elaborate and

BEHAVIOR OF VERTEBRATES 455

•

much too specialized to be considered as the immediate outcome"
of any form of physiological excitement. They obviously have
a long and complicated evolution behind them and as they can
only be performed by two birds together there is nothing to
account for them as they now stand but some such process as
I have just sketched under the name of mutual selection. The
second part of the paper gives in detail some of the material
worked up in the first as well as some notes on various points
not connected with the main interest of the study.

Pearl (26) gives us, in the seventh paper of his series, a dis-
cussion of the brooding instinct which is very much changed
possibly under domestication and certainly very much curtailed
under the methods employed at the Agricultural Experiment
Station. He concludes, however, (1) that it occurs with greater
or less regularity following periods of egg laying. (2) that it
varies in intensity at different times in the same individual.
(3) that it is not necessarily connected with any season and may
occur out of breeding season. (4) that it is ordinarily but not
necessarily preceded by the laying of a clutch of eggs. (5)
that it is apparently closely connected with the functions of
the ovary although the precise nature of the connection has
not yet been analyzed.

The flocking habits of migratory birds is the subject of Trow-
bridge's (36) paper. He analyzes the automatic protection
which a large flock affords as follows: A single bird might be in
error from (a) confusion with regard to proper direction of flight,
(b) effect of heavy winds or thick fogs acting as a temporary
confusing factor while migrating, (c) gradual deviation from
the course due to unequal wing power. A large flock eliminates
these causes of error to a large extent and the origin of the
flock is probably due to the fact that it is protective. The
errors are averaged by numbers. He does not attempt to ex-
plain the 'sense of direction' but rather the mechanism to avoid
getting lost. Night migratory calls are discussed and the pro-
tective form of certain flight formations as e. g., the echelon.
This he thinks is not taken to prevent any interference but
so that each bird may see both forward and to the side at the
same time. Birds instinctively follow one another.

Some experiments in feeding humming birds which were
continued for seven summers are described by Sherman (32).

456 STELLA B. VINCENT

•

The birds learned to sip sirup from bottles concealed in flower
forms and from an unconcealed bottle fastened to a post. The
amount of sugar taken by a bird per day amounted to 110 to
120 minims. From the behavior observations it seemed prob-
able that the same birds were coming back summer after summer.
They nested in a near by wood and only came to the garden
for their food. All the birds which fed from the bottles were
females.

Strong (33) studied the Herring Gulls both in their breeding
places and in confinement at the University of Chicago and has
written up his results in two papers and Tyler (38) has published
some notes on the nest life of the Brown Creeper in Massa-
chusetts.

LEARNING

Many of the studies in animal learning have been noticed
under the head of the particular sense control which was in-
volved. The articles are not so numerous as in 1913. Basset's
(2) study of habit formation in a strain of rats of less than normal
brain weight may be mentioned. The rats were some derived
from experimental inbreeding at the Wistar Institute of Anat-
omy and Biology and their relative brain weight (relative to
body length) was 6| per cent, less than that of their normal
controls. Basset worked with several' generations of these for
over two years on maze and puzzle box problems and he used
in all 62 inbred animals and 62 normal controls. Tests were
made not only for learning but also for retention and for re-
learning. In all of the experiments the rats of lesser brain weight
did poorer work on an average than did the normal control
series. The inbred rats of the seventh generation worked less
well than those of the sixth and those of the eighth generation
not so well as those of the seventh. " It would seem," the
author says, "although lessening brain weight had ceased after
the fourth generation that the ability to form habits lessened
progressively with successive generations of inbreeding. The
writer nowhere urges that this lesser ability is due to the in-
breeding per se.

Of a different type and far less well controlled is some work
which is reported in a paper on learning and relearning which
comes from the Bedford College for Women, University of
London (20). The work was under the immediate control of

BEHAVIOR OF VERTEBRATES 457

two students but was also used for class demonstration. As is
clearly stated the work is a repetition of old problems and makes
no pretence to originality. The straight and square mazes
described by Yerkes in the Dancing Mouse were the mazes
used and in addition a maze in five sections which was built
for this experiment. There were only two mice used on this
apparatus. Mouse 'M' learned the straight maze, then the
same maze reversed, then the square maze, then this maze re-
versed and then relearned both of these mazes at varying in-
tervals in their original positions. Mouse 'S' followed the same
order, only it began with the square maze. Both learned the
•sectional maze, relearned it and learned it in reversed position.
Many individual learning curves and much data are given.
Three rats worked on two of Small's puzzle boxes. The general
conclusions are as follows: (1) With renewed repetitions there
is a steady advance in learning. This advance, however, bears
no direct relation to the interval which elapses between one
series of repetitions and another. (2) With sufficient repetition
the successful response may become so " well known " as to be
unaffected by the lapse of long intervals. (3) The successful
response is developed in connection with the general meaning
of the situation. The experiments do not warrant us in saying
in what experiences this general meaning consists. Retention
of it, however, is of even greater importance in influencing the
progress of relearning on a subsequent occasion than retention
of the series of successful movements. Thus the learning does
not fall entirely under the law of habit. The successful move-
ments acquired in learning one maze do not hinder the mice in
learning another which demands a different series of turns;
on the contrary, learning which takes place after practice on
other work is more successful than relearning which follows
on a period of idleness. * * * The influence of the general
meaning of the situation is more marked in the learning of the
puzzle boxes by the rats than in the learning of mazes by the
mice."

The Elberfeld horses still continue to engage the attention
of our friends across the water. Moekel (22) thinks the Mann-
heim dog's behavior much more spontaneous than that of the
horses. Maday (21) attempts an elaborate analysis of the
mental functions of man, their forms and the conditions which

458 STELLA B. VINCENT

evoke them and then examines the proof of the same in the
Elberfeld horses. Pi6ron (25) whose ideas on the subject are
a little more sane than those of some other investigators gives
an excellent review of the situation with a very complete
bibliography.

A careful report by Haenel (7) shows that the horses seem
to have lost ground during the year. Krall attributes this to
the almost unbroken succession of visitors and their many
questions. Krall admitted that the vocabulary of Zarif had
decidedly suffered and that many of the arithmetical operations
which Muhammed formerly performed were now beyond him.
Barto, the blind horse, which had previously acquired the
foundations of arithmetic in a few days, had, in the summer,
after five weeks vacation, forgotten it all, and learned it the
second time with much greater difficulty than at first and had
not yet acquired his former facility. All of the first horses
which Krall undertook to train were teachable — had under-
standing as he thought. But during 1914 he had three horses
from the stud of the King of Wurtemberg and after three or
four weeks endeavor he was forced to confess that he. could teach
them nothing and had to send them back as unlearned as they
came. He has similarly failed with a young female elephant.
Those who were inclined, with Krall, to rate the intelligence
of the horse very high wonder now if these horses have reached
the limit of their ability. Others ask, is it not possible that
the criticism which has been made upon these claims has influ-
enced Krall so that clues which the horses could use in their train-
ing, possibly unconscious to Krall himself, are being excluded.

One of the best articles on the subject is a critical paper by
Schroeder (28) which not only inquires into the proof of the
facts but also into the philosophical and scientific implications
of the theories which have arisen in their explanation.

GENERAL PAPERS

Besides these articles reported above there are others of a
more general nature which do not properly belong under any
of the above headings. Hubbert .(11) discusses the value of
units of time versus units of distance in learning. In the way
of apparatus four graphic methods of recording maze reactions
are described by Yerkes and Kellogg (40) which they designate

BEHAVIOR OF VERTEBRATES 459

as (a) the direct method, (b) the simple reflection method,
(c) the double reflection method of Watson and (d) the double
reflection method of Kellogg. The authors discuss the advan-
tages and disadvantages of each scheme and their paper is
followed in the same journal by one by Watson (39) in which
he describes his own recording device in greater detail. His
circular maze is a maze so planned as to make it very easy to
increase the complexity by adding new units, etc., and with
this maze goes his excellent recording device.

A sympathetic description of the Pawlow method with animals
is found in Morgulis' paper (24). The article is devoted
chiefly to the neuro-psychical phases but the method with its
implications is of interest to all who work with vertebrate
animals.

Similarly the article by Carr (3a) on the Principles of Selec-
tion in Animal Learning will attract all who attempt to analyze
animal behavior or to explain their mode of learning. It is
impossible to summarize an article which is itself so compact.
The author says, " Selection and elimination are the diverse
effects of a single process or mechanism. All connections tend
to be preserved; all develop in strength and functional efficiency
during the learning process, but their development proceeds
unequally. The unsuccessful tendencies are not eliminated in
the sense of being torn out by the roots; they are eliminated
only in the sense of not being aroused in that situation. The
strongest and most prepotent tendencies of the group function
first and dominate the situation. The successful act is selected
because it finally becomes the most prepotent in the group; all
others are eliminated, or better are 'suppressed' because of
their lesser development in functional efficiency.

1 ' The problem of determining the various principles of selection
thus resolves itself into a search for those factors which favor
the retentive development of the successful act at the expense
of the many failures. These principles are relative recency,
relative frequency, and relative intensity."

These principles are then applied in a careful analysis to
three types of animal problems. The paper concludes with a
brief comparison of these selective principles with that of
pleasure-pain which has been advocated so frequently by others.

460 STELLA B. VINCENT

REFERENCES

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Rana sylvatica. Biol. Bull., 26, 171-184.

2. Basset, Gardner Cheney. Habit Formation in a Strain of Albino Rats

of Less than Normal Brain Weight. Behav. Monog., 2, 1-46.

3. Bingham, H. C. A Definition of Form. Jour. Animal Behav., 4, 136-142.
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4. Cobtjrn, Chas. A. The Behavior of the Crow — Corvus Americanus Aud.

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5. Craig, Wallace. Male Doves Reared in Isolation. Jour. Animal Behav.,

4, 121-134.

6. Freytag, G. Lichtsinnuntersuchungen bei Tieren. I. Fische Phoxinus Laevis

(Ellritze Pfrille). Archiv. f. vergl. Opth., 4, 68-83.

7. Haenel, Hans. Neu Beobachtungen an den Elberfelder Pferden. Zeit. f.

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8. Hahn, W. L. The Hibernation of Certain Animals. Pop. Sci. Mo., 84, 147-

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9. Haempel, O. and Kolmer, W. Ein Beitrag Zur Hellig Keito — und Fachen-

anpassung bei Fishen. Biol. Ceutrbl, 34, 450-458.

10. Hamilton, G. V. A Study of Sexual Tendencies in Monkeys and Baboons.

Jour. Animal Behav'., 4, 295-319.

11. Hubbert, Helen B. Time versus Distance in Learning. Jour. Animal

Behav., 4, 60-70.

12. Hunter, W. S. The Auditory Sensitivity of the White Rat. Jour. Animal

Behav., 4, 215-223.

13. Huxley, Julian. The Courtship Habits of the Great Crested Grebe (Podiceps

Christatus). With an Addition to the Theory of Sexual Selection. Proc.
of the Zool. Soc, London.

14. Johnson, H. M. A Note on the Supposed Olfactory Hunting Reactions of

the Dog. Jour. Animal Behav., 4, 76-78.

15. Johnson, H. M. Hunter on the Question of Form Perception in Animals.

Jour. Animal Behav., 4, 134-136.

16. Johnson, H. M. Visual Pattern Discrimination in Vertebrates. I. Problems

and Methods. Jour. Animal Behav., 4, 319-340.

17. Johnson, H. M. Visual Pattern Discrimination in the Vertebrates. II. Com-

parative Visual Acuity in the Dog, the Monkey, and the Chick. Jour.
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18. Lashley, K. S. A Note on the Persistence of an Instinct. Jour. Animal

Behav., 4, 293-294.

19. Laurens, Henry. The Reactions of Normal and Eyeless Amphibian Larvae

to Light. Jour. Exper. Zool., 16, 195-211.

20. MacGregor, M. and Schinz, J. A Study of Learning and Re-learning in

Mice and Rats. Psychol. Studies from Bedford College for Women, Uni-
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21. Mad ay, Stefan v. Begriffsbildung und Denken biem Menschen und beim

Pferde. Arch. f. d. ges. Psychol, 32, 342-391.

22. Moekel, Paula. Rolf der Hund von Mannheim. Tierseele. Zeitschr. f.

vergl. Seelkunde. 1. Rev. Meurnann, Arch. f. d. ges. Psychol, 32, 63-65.

23. Morgulis, Sergius. The Auditory Reactions of the Dog Studied by the

Pawlow Method. Jour. Animal Behav., 4, 142-145.

24. Morgulis, Sergius. Pawlow's Theory of the Function of the Central Nerv-

ous System and a Digest of Some of the More Recent Contributions from
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25. Pieron, H. Le Probleme des animaux Pensants. L'Annee Psychologique, 20,

218-228.

26. Pearl, Raymond. Studies on the Physiology of Reproduction in the Domestic

Fowl. VII. Data Regarding the Brooding Instinct in Its Relation to Egg
Production. Jour. Animal Behav., 4, 266-289.

BEHAVIOR OF VERTEBRATES 461

27. Risser, Jonathan. Olfactory Reactions in Amphibians. Jour. Exper. Zool.,

16, 615-652.

28. Schroeder, Christoph. Die rechenden Pferde. Biol. Central., 34, 594-614.

29. Shelford, Victor and Allee, W. C. Rapid Modification of the Behavior of

Fishes by Contact with Modified Water. Jour. Animal Behav., 4, 1-31.

30. Shelford, Victor E. Modification of the Behavior of Land Animals by

Contact with Air of High Evaporating Power. Jour. Animal Behav., 4,
31-50.

31. Shepherd, W. T. On Sound Discrimination by Cats. Jour. Animal Behav.,

4, 70-76.

32. Sherman, Althea. Experiments in Feeding Humming Birds During Seven

Summers. Wilson Bull., Dec, 1913.

33. Strong, R. M. On the Habits and Behavior of the Herring Gull — Larus

Argenlatus Pont. The Auk, 31, 22-49, 78-200.

34. Sztmanski, J. S. Eine Methode zur Untersuchung der Ruhe und Aktivitats

Perioden bei Tieren. Pfluger's Archiv f. d. ges. Physiol., 158, 343-385.

35. Szymanski, J. S. Lernversuche bei weissen Ratten. Pfluger's Archiv. f. d.

ges. Physiol, 158, 386-418.

36. Trowbridge, C. C. On the Origin of the Flocking Habits of Migratory Birds.

Pop. Sci. Mo., 84, 209-217.

37. Tcgman, Eupha Foley. Light Discrimination in the English Sparrow. Jour.

Animal Behav., 4, 79-110.

38. Tyler, Winsor M. Notes on the Nest Life of the Brown Creeper in Mass.

The Auk, 31, 50-62.

39. Watson, J. B. A Circular Maze with Camera Lucida Attachment. Jour.

Animal Behav., 4, 56-60.

40. Yerkes, R. M. and Kellogg, C. E. A Graphic Method of Recording Maze-

Reactions. Jour. Animal Behav., 4, 50-56.

41. Yerkes, R. M. The Harvard Laboratory of Animal Psychology and the

Franklin Field Station. Jour. Animal Behav., 4, 176-185.

WATSON'S "BEHAVIOR"^

E. L. THORNDIKE AND C. J. HERRICK

Professor Watson's ' Behavior ' is not only an admirable
introduction to comparative psychology; it is also an important
record of the methods and ideals of investigation approved by
a leading investigator and a stimulating account of his views on
the general problems of animal life and intelligence.

Examining it from the first point of view, one finds a clear
and readable statement of representative problems, of apparatus
and methods, of what is known and opined concerning instinctive
tendencies, habit formation, imitation and other possible sec-
ondary sorts of learning, of the limits of educability, of the
relation of human behavior to that of other animals, and of
the sense-powers of animals. Every teacher of psychology who
acknowledges the need of providing knowledge concerning animal
psychology is in Watson's debt. With Washburn's book for
the analysts, Watson's for the behaviorists, and both together
for the ordinary matter-of-fact psychologist, the teaching of
•animal psychology should be notably efficient. It is interesting
to note that animal psychology is now in a position to mete
out to the anecdotal school the strongest form of denial — neglect.
Watson, if I remember correctly, nowhere quotes or refers to
^Romanes or any of his like. This is probably wise, though
pedagogically the contrast in question is one of the best begin-
nings for a student.

There are three topics which the reviewer at least wishes
Watson might have included for the student's sake and one
which might perhaps better have been left out. First, the
behavior of the micro-organisms should, I think, have had a
special chapter in addition to the incidental references made.
Indeed some of these references are likely, as they stand, to be
unintelligible to many students. Second, concrete cases of the
phylogeny of behavior, such as Whitman's story of incubation

1 Behavior: An Introduction to Comparative Psychology. By John B. Watson,
JSTew York, 1914, xh+439 pp.

* 462

WATSON'S "BEHAVIOR" 463

or the course of the scratch reflex, with a discussion of the prob-
lems of tracing the growth and differentiation of behavior as a
fact, seem to me among the most stimulating facts of animal
psychology. The arguments concerning the causes of variation
in general and the potency of sexual selection in general might
well be omitted in favor of the more specific and more relevant
concrete story of behavior's natural history in the world. In
the third place, I regret the omission of a chapter concerning
objective methods and results in human psychology. The
student is likely, as Watson's book stands, to be left with the
impression that mental chemistry — the analysis of conscious
states into elements and the construction of cross-sections of
a stream of consciousness out of sensations, affections, and
other Wundtian myths — has been the regular, orthodox thing
in human psychology. On the contrary, objective methods and
results have characterized a very large proportion of the work
of recognized psychologists for thirty years. Ebbinghaus'
Memory and Cattell's studies of reaction- time, for example,
are as 'behavioristic' or objective as Bassett's study of rats
or Yerkes' study of frogs.

Watson has, throughout the book, freely joined to the descrip-
tion of the status of animal psychology a plea for rigorous control
of conditions and steady aim at prophesy of behavior as a test
of the truth of conclusions. One feels the zeal of the investi-
gator for sound research and the faith of the scientific man in
matter of fact control and prediction as the justification of science.
There is also the healthy insistence that our eventual ideal
must be an explanation of intellect, character and skill in terms
of known neural mechanisms. All this, though perhaps some-
what over the heads of students, is healthy, and helps to make
the book a truer picture of the status of animal psychology,
whose workers have worked in comparative freedom from
obscurantist conventions.

The third contribution of the book is the systematic expression
of Watson's views of the folly of introspective analysis, the
non-existence of centrally initiated processes, the relation of
pleasure to afferent impulses from the erogenic zones, the ade-
quacy of speech movements and other muscular responses to
account for what is commonly meant by 'thought,' the struc-
tural unmodifiability of the neurones from soon after birth,

464 E. L. THORNDIKE AND C. J. HERRICK

and the adequacy of frequency and recency to explain all the
dynamics of learning. These views will interest psychologists
even though they know or care little about the details of animal
activities. It is, of course, impossible to do justice to them
either in description or evaluation within the limits of these
pages. In the reviewer's opinion all of them are important,
but also, with one exception, are too extreme to be correct
as stated.

Watson seems to me to neglect the facts that a human being
can observe himself not only as he observes another human
being but also by other avenues, and that this information
about oneself, got irrespective of sense-organs, may well play
some part in science. It is a minor part, but not necessarily
zero. That "there are no centrally initiated processes" seems
flatly false at its face-value, and, even when interpreted by a
conservative understanding of Watson's account of implicit
behavior — that is, of the procedure occurring in very long-
delayed reactions — seems to imply that all the hundreds of
millions of secondary circuits of associative neurones are doomed
to inactivity except when stimulated within a half-second or
so by sensory neurones. Perhaps I have misunderstood his
position on this point. The limitation of pleasure to stimuli
from the sex zones seems dubious in view of the apparently
closer attachment of pleasure to tastes and smells and its appar-
ent lack of any such rise and fall as the sex-zone sensitivities
show. The doctrine that the neurones stay the same struc-
turally from birth, or soon thereafter, is, I am aware, fashionable,
but it is speculative, and the opposite speculation — that the
terminal arborizations and collaterals of the neurones grow here
and dwindle there — seems to me more in accord with known
facts of growth, degeneration and regeneration. Theories of
behavior should not pin their faith to either theory.

The doctrine that the 'successful' response is selected and
associated with the situation, not because of its success, but be-
cause it has been made as a response to that situation oftener
than any other one response, seems substantially identical with
the similar doctrine of Stevenson Smith. The argument holds,
as I have shown in discussing Stevenson Smith's presentation of
it, only if by original nature the 'successful' response has nearly

WATSON'S "BEHAVIOR"

465

as great a probability of occurrence as any other one. Watson,
like Smith, neglects the common case of learning of the type: —

S, '

' 2,

" 2,

1, 1, 1, 2, 2,

1.

2,

3,

5,1,4

(4 bringing food)

s,

' 3,

" 3,

1, 2, 1, 1, 6,

1,

3,

1,

4

(4 bringing food)

s,

' 4,

" 4,

1, 1, 2, 1, 4

(4 bringing food)

s,

' 5,

" 5,

1, 3, 1, 1, 4

(4 bringing food)

s,

' 6,

" 6,

1, 2, 1, 3, 4

(4 bringing food)

s,

' 7,

» 7,

1, 2, 1, 4

(4 bringing food)

s,

" 8,

" 8,

1,4

(4 bringing food)

s,

" 9,

" 9,

4

(4 bringing food)

s,

' io,

" 10,

' 4

(4 bringing food)

Here response 1 starts out with a frequency of 8 to 1 and
yet loses in the end. Such cases are very common in learning.

I have registered these objections to Watson's views largely
because it seems desirable to keep the general aims and methods
of objective psychology distinct from the particular explanatory
hypotheses of any one of us who are studying it.

In his emphasis on the prevalence of actual speech move-
ments as the body, and perhaps even the soul, of thought, Wat-
son seems to be following a much more hopeful hypothesis.
Thought does seem to be in the beginning, as Cooley has said,
"a species of conversation" and throughout life what many
introspectionists call images of words are almost certainly often
actual partial enunciations. The time-honored 'think bubble'
experiment, for example, is not a test of the presence of kines-
thetic images, but of actual movements — evidence of a kines-
thetic image would be found rather if one could think of saying
the word without moving the mouth-parts. Human behavior
in thinking does consist of muscular responses, the sensations
thereof, further responses excited thereby, and so on, to a much
greater extent than the older "train of thought" metaphors
suggested. A large residuum of thought that involves only
intracerebral neurones does, in my opinion, exist, as witnessed
in the mental manipulation of space relations in geometry,
engineering, and the like, or sound relations in musical compo-
sition; but Watson has exposed a weak spot in psychology's
neglect of the actual muscular action that goes on in thought
and confusion of it and sensations due to it with kinesthetic
images.

A reviewer of this book is presumably expected to make
some estimate of Watson's contrast of the general merits of the

466 E. L. THORNDIKE AND C. J. HERRICK

study of consciousness and the study of behavior, as means to
the progress of science. Watson seems to me to offer the right
criterion in power of prophecy. The proper criticism of the
analysis of conscious states and synthesis of supposed conscious
elements at which gifted followers of Wundt have busied them-
selves for a generation seems to be that these labors have so
seldom enabled us to prophecy what any animal, human or
other, would actually think or feel or do in even a dozen situ-
ations. Where we do find power of prophecy attained, we
commonly find that objective study of what the subjects of the
experiments have said or done has given it. The trouble seems
to be, not that pure psychics, or the inner life of a man as he
feels it, does not exist and give facts, but that it gives facts to
only one observer, and that, first, we get on much better by
using his testimony about these facts (which is, of course, his
behavior, verbal or otherwise) by the ordinary methods of
science than we do by leaving him to try to draw inferences
from it in some more direct way. In fact, he himself does as
well or better by. reporting the inspections of himself which he
makes without using his sense organs to himself by inner speech
and the like and using them thereafter as he would use the
reports of any other man. In the second place, these one-man,
unverifiable observations do not work as well in science as
observations made via sense organs which many of us can make
together and which we can repeat.

Watson is probably right, also, in asserting that straight-
forward objective work has been more or less hampered by the
fashion in psychology of attempting always to say something
about some purely psychical fact. The protocols on the
conscious accompaniments of reaction-time experiments, dis-
criminations of sensory differences, and measurements of 'thres-
holds' of intensity, for example, it might be torture for Watson
to write, collect or read; and if his book relieves future Watsons
from being conscience-smitten at not contributing to knowledge
of how a frog feels to himself when he croaks or what the stream
of a rat's consciousness is as he scampers through the maze,
it will serve thereby a worthy end.

In any case the spirit of psychology in America seems now
to be in a healthy condition in encouraging individuals each to
do the work he thinks best in the way that he thinks best, and

WATSON'S "BEHAVIOR" 467

in judging work by the truth and usefulness of its results rather
than by the orthodoxy of its presuppositions or methods. For
students of the subjective side of the world by personal inspec-
tion of one's own inner life to regard their work as that of a
psychological elite, pure-breds, untainted by physiology, sociol-
ogy, psychiatry or education, would now be amusing rather
than objectionable. For students of objective behavior to re-
gard themselves as martyrs, heroes or prophets is now unneces-
sary. E. L. Thorndike.

The writer has been asked to add some comments from the
biological standpoint to Professor Thorndike's review of Wat-
son's Behavior. It is a pleasure to do this, for Doctor Watson's
biological training, wide reading and accurate scholarship are
everywhere reflected in this work. There are only a few addi-
tional points where comment from the biological side suggests
itself to me.

The first point is a very minor one, which suggests, however,
some reflections of wider import. In commenting upon the
backward condition of the anatomy and physiology of the
nervous system, a number of interesting problems are suggested,
such as the nature of nervous impulses, the processes which
make for the adaptation of sense organs and the like. Then
follows the rather disquieting statement, "In this day of ad-
vanced physiological and neurological technique surely the only
difficulty in obtaining satisfactory answers to these questions
is the lack of sufficient interest on the part of the men who are
competent to carry out such researches."

The fact is that the number of researches directed toward
such neurological problems is fairly large — far greater than one
man who devotes his whole time to neurological work can master
if he attempts any original work himself. Must we then infer
that the fundamental difficulty is that so few of these numerous
workers are really "competent to carry out such researches"?
Possibly; but the real explanation for the relative sterility of
so much of this arduous labor lies in the fact that the "advanced
physiological and neurological technique" of today is wholly
inadequate to open up most of the problems mentioned. "If
the iron be blunt, and he do not whet the edge, then must he
put to more strength." We need to whet the edge of our neuro-

468 E. L. THORNDIKE AND C. J. HERRICK

logical endeavors by the acquisition of new points of view.
The study of familiar facts in a new setting is often all that
is necessary to point the way to entirely new methods of attack.

A review of neurological literature, especially in the field of
comparative neurology, reveals a prodigious amount of research
from which surprisingly few generalizations can be deduced
which are of great interest to students of either animal behavior
or human psychology. This literature has its own problems,
in the solution of which it has not been wholly unsuccessful;
but these problems have always been sharply circumscribed by
the limitations of technique, not the least of which has been the
failure of investigators in this field to make a correlated study
of both the structure and the functions of their objects of re-
search. Doctor Watson's recommendation that extensive pro-
grams of research be carried out with the cooperation of behav-
iorists, experimental physiologists and neurologists is a sug-
gestion of constructive value. In short, while the technique of
each discipline needs improvement, the greatest need is for a
technique of cooperation.

In the discussion of instinct, biologists, behaviorists and
psychologists all claim an interest. All behavior is complex,
and it has been common for each student of animal life to select
from this complex the particular factors which seemed best to
fit into his own philosophical preconceptions and to use these
factors only in formulating his conception of instinct.

In contrasting instinct and habit (p. 185) Doctor Watson
clearly states the cardinal principle which alone can bring order
out of the chaotic and hazy notions which are current. This
principle is the sharp distinction between the innate and the
acquired factors in behavior. All agree that a reflex is the
function of an innate mechanism. Now when reflexes are
combined, as we always find them in behavior complexes, the
order and pattern of their combination may likewise be deter-
mined by the hereditary organization, or this pattern may be
acquired during the individual life of the animal. In the former
case we are .dealing with a pure instinct; in the latter case with
a pure habit. This is Watson's terminology. I would add,
that, in any concrete example of behavior in a higher animal,
both of these types are almost certain to be present, and so the
particular act cannot as a rule be classified off-hand as instinc-

WATSON'S "BEHAVIOR" 469

tive or habitual. The best that we can hope to do is to analyze
the act into its elements and then determine which factors
are innate and which are acquired.

It has been my conviction for several years that the term
instinct has outlived its usefulness in science. All behavior of
organisms can be classed under two heads. It is either the
function of an innate mechanism and therefore determined by
the hereditary organization (reflexes, 'instincts'), or else it ex-
hibits new combinations of elements whose pattern has been
individually acquired. Habit is only a terminal phase of this
individual modifiability. Both innate and individually variable
action are found in some measure in all organisms, and, as
stated above, in almost every act of the higher animals; and
a more detailed consideration of the relations of these two
factors at the beginning of the discussion of instinct might
profitably replace some of the discussion of moot questions of
general evolutionary theory in Chapter V.

There is a third topic in Doctor Watson's book about which
it may be presumptuous for a mere biologist to express an
opinion, though it most assuredfy has a biological aspect. The
new school of experimentalists has sought to rescue the study
of animal behavior from the slough of anectodage and uncritical
anthropomorphism into which it had fallen and to establish
it on the secure scientific basis of objective and verifiable obser-
vation. In this their labors have already been crowned with
a gratifying measure of success, and the, future promises still
greater gains. In such a book as this one, the author, accord-
ingly, does well to adhere strictly to the program which has
been so abundantly justified by results and to limit his discus-
sions to what is objectively verifiable, leaving quite out of
account, observations and speculations about possible mental
processes of men or other animals. This is a sound scientific
procedure.

But when he goes further and says that because the phenomena
of consciousness as introspectively experienced are irrelevant to
his special program, therefore they are everywhere else irrelevant
and negligible, he seems to have thrown out the babe with the
bath, and the biologist should be the first to protest. The
new psychology may perhaps be able to dispense with con-
sciousness, but biology cannot do so.

470 E. L. THORNDIKE AND C. J. HERRICK

One hesitates to utter his convictions on the last point, for
he is certain to be misunderstood. But conscious processes are
realities which cannot be ignored in a comprehensive scheme
of things. They are, moreover, positive biological factors in
human evolution; and the biologist can see no reason why they
should not be observed in the only way open to him, namely,
by introspection.

Is there not, therefore, abundant justification for including
consciousness, as introspectively known, as one of the elements
of human behavior (and inferentially of the behavior of some
other animals also), and should not any comprehensive scheme
of behavior studies include this factor for what it is worth ?
The fact that in the past the uncritical use of these data and of
hypotheses based thereon has often led us astray is no justifi-
cation for denying their validity and practical value when
properly used. Whether in any given program of research it
is expedient to use these data, is a quite different question, which
must be decided on its own merits in each case.

C. J. Herrick.

DUNLAP'S "AN OUTLINE OF PSYCHOBIOLOGY"*

C. JUDSON HERRICK

At the present time there is an active demand for a brief
untechnical introduction to the structure and functions of the
nervous system adapted for the use of students of psychology
and education who have no biological training. It is the purpose
of this little book on Psychobiology to fill this need. Every
experienced teacher will recognize that the difficulties in the
way of such an enterprise are almost insuperable, and any
intelligently directed effort in this field should, accordingly, be
judged leniently.

There are nine chapters in Dr. Dunlap's work, of which one
is devoted to the cell, one to a survey of the tissues of the adult
human body, one to muscular tissue, one to glandular tissue,
and the remainder to the nervous system.

The discussion of the cell and tissues is in general correctly
stated, but is rather schematic and lacking in functional coloring.
The critical student will note a number of minor errors, not
all of which can be explained as due to the condensed form
necessary in a work of this sort. A few examples are given.

On page 11 we read, "Every plant and every animal com-
mences its individual life as a single cell." Exception should, of
course, be made of the very large numbers of species which
may be propagated by fission and budding. On page 26: "Vas-
cular tissue; This includes the blood and lymph, the lymph
glands and the red marrow of the bones, and develops from the
endoderm." The endodermal origin of the blood cells is con-
troverted, but there is no controversy regarding the mesodermal
origin of some of the other tissues here mentioned. On page
29 the nuclei of pale striated muscle fibers are said to be mar-
ginal, while those of dark striated muscle fibers are located more
centrally, embedded among the fibrils. The converse is true,
as illustrated by the figure of human muscle printed on the

1 Knight Dunlap. An Outline of Psychobiology. Baltimore, The Johns Hop-
kins Press, 1914, 121 pages, price $1.25.

471

472 C. JUDSON HERRICK

same page. On page 41 the cochlea and possibly the sensory
surfaces of the organs of smell and taste are said to migrate
outward from the anterior part of the medullary tube. On
page 58, line 2 from the bottom, for "spinal" ganglion of the
cochlea, read spiral ganglion.

The chapters on the nervous tissues comprise a total of 62
pages. There are numerous good figures illustrating the nervous
system and its elements, accompanied by a running description
and lists of names of the parts figured; but here again there is
a dearth of functional interpretation, and the reader who
attempts to assimilate this description with no previous prepar-
ation in biology may find it rather indigestible. The neurological
chapters contain a few infelicitous expressions, such as the
following :

There are several places in the descriptions of the nerves
where the terms afferent and efferent are confused, some of
these apparently being misprints. On page 82 we read, "Only
four of the cranial nerves are, like the spinal, 'mixed nerves.'
Of the other eight, three are pure afferent, or 'sensory,' and
five are efferent, or 'motor'." But in the enumeration which
follows the I, II and VIII pairs are described as afferent and
the III, IV, V. VI, VII, and IX pairs are correctly described as
mixed. There is no mention here of afferent fibers in the vagus
and the "afferent axons of the spinal accessory" are said to
supply the sterno-mastoid and trapezius muscles. On page 90,
however, the afferent fibers of the vagus are referred to. On
the page last mentioned the account of visceral fibers of the
VII and X nerves is incorrect. The recent studies of Molhant,
Yagita, Kosaka and others have clarified the relations of these
systems.

The final chapter on the Functional Interrelation of Receptors,
Neurons and Effectors is a very successful application of the
author's cardinal principle (as stated in the Preface), that the
body must be considered as a functional unit, and that this is
even more important for psychology than for physiology. It
is to be regretted that this principle, which is so well stated
in general terms in this chapter, was not applied more explicitly
and concretely in the descriptive part of the work. This brief
final chapter alone is worth the price of the book.

HACHET-SOUPLET'S "DE L' ANIMAL A L'ENFANT"i

WALTER S. HUNTER

The University of Texas

In the present volume the author attempts to set forth the
main outlines of an embryo science, that of comparative edu-
cation. This discipline is to be based upon an experimental
study of animals and children as opposed to the hitherto current
a priori ideas. The child presents only a difference in degree
and not in nature with respect to the higher animals. Hence
methods of training suitable to the latter are applicable to the
former. And Hachet-Souplet has had long experience in the
training of animals.

In the elaboration of this program, the author treats first,
animals and then children. His standard, however, is the child
and animal life is interpreted in terms of this. The chapter
headings and some of the topics of the first part are as follows:
(1). Experimental study of sensations in animals. In addition
to comments of a general nature, tests on pitch and visual
intensity discrimination are described. Pigeons tested on the
last problem gave results verifying Fechner's law — "du moins
grossierment," writes Hachet-Souplet. And one may well accept
the qualification, for the most elementary precautions are ignored
in the work which is hardly so scientific as the tests Galton
once made with his whistle. (2). Fundamental and derived
instincts. Hunger and fear (primitively the rejection of food)
are fundamental and unmodifiable. Derived instincts are habits.
It is interesting to note that the author does not follow Bergson
in relating instinct and intelligence as opposites. (3) and (4).
The experimental study of derived instincts. (5). The principal
laws of the association of sensations. The chief law here is
that of recurrence. Stimuli d c b a precede the reaction r. The
associations formed remount from a to d. This law makes
anticipation possible in that d or c can lead to r before b or a
appears. At the close of this chapter the author announces

1 Hachet-Souplet, P. De 1' Animal a l'Enfant. Pp. 176. Paris, Alcan. 1913.

473

474 WALTER S. HUNTER

that "des experiences, poursuivies pendant dix ans a Vlnstitut
de psychologie zoologique, ont permis d'etablir que les habitudes
imposees aux animaux sont transmissibles par heredite." The
following six chapters deal with intellectual activity, the notion
of causality, the notion of the physical me, abstraction, aesthetic
taste and persuasion as a method of education. The discussion
of causality centers on the use of tools and the devising of novel
methods of securing results. Hachet-Souplet claims to have
established the existence of these types of activity in animals.
The presence of an idea of the physical me in phyla below man is
asserted on the basis of two tests: (I) A dog that responds
readily to the command "come" when alone will refuse to do
so if he sits in company with other dogs. He will respond,
however, when his name is called. He knows that there are
other dogs present. (2) Monkeys will amuse themselves and
grimace before a mirror. Critical comment is unnecessary here.

The second part of the book dealing with children includes
four chapters : animal traits in children, punishment and reward,
moral training, and instruction properly speaking. A firm dis-
cipline, a sort of "dressage" should be applied in early infancy
in the light of the "law of recurrence."

It is unfortunate that rigorous scientific methods could not
be applied where the opportunities are so great as they seem
to be at the Institut de psychologie zoologique. In the reviewer's
opinion attempts to combine behavior work and education in
any intimate manner are at present far-fetched and are likely
to result in the deterioration of the scientific character of the work. ■

KAFKA'S " EINFUHRUNG IN DIE
TIERPSYCHOLOGIE " i *

WALTER S. HUNTER

The University of Texas

If not an encyclopedia, Kafka's work is at least a very ex-
tensive compendium of the literature on invertebrate behavior.
His sources are almost entirely experimental. A second volume
is promised which will consider the senses of vertebrates and
the development of the higher psychic capacities in the animal
kingdom (instinct, memory, intelligence, etc.). It is that volume
to which students will turn for Kafka's theoretical discussions
which are to be based upon a wide survey of experimental facts.
It is to be hoped that the war in Europe will not cause undue
delay in this scientific enterprise, for the spirit of the first volume
leads one to expect a sane handling of the literature and problems
of the higher functional activities in the second volume.

The present work emphasizes the sensory processes of inverte-
brates, and the material is organized upon this basis. Touch
(117 pages), the static sense (41 pages), hearing (33 pages),
the temperature sense (15 pages), the chemical sense (97 pages),
vision (156 pages), the space sense (53 pages) and the time sense
(20 pages) are the chapter headings and the amounts of space
allotted to each topic. In each of the above divisions the data
are grouped according to animal phyla and genera — protozoa,
coelenterates, worms, mollusks and arthropodes. This method
of presentation has its defects as well as its advantages. It
offers readier reference advantages to the zoologist who is in-
terested in phyla than it does to the behaviorist who is interested
in activities. The scheme allows no place for a summary of
data bearing, e. g., upon tropisms and of the various theories
thereof. Nor does it open the way to a statement of the essen-
tial facts of nervous integration. Such facts as are just indicated
are to be found scattered throughout a large volume, if they

1 Kafka, Gustav. Einfuhruns; in die Tierpsychologie. Bd. 1, S. xii+593.
Leipzig, Barth, 1914.

475

476 WALTER S. HUNTER

are found at all. In some cases they are not even brought
to the reader's attention in the subject index. One such case
is that of tactile and auditory hairs. A volume placing emphasis
upon sensory discrimination should contain a discussion or a
summary of methods with evaluating comments thereon. This
would give the reader a guide to the reliability of the data
presented. An actual examination reveals that the method of
general response is very universally applied. This can be
supplemented by extirpation studies with certain forms. The
association method in any definite form has not been so ex-
tensively used with the invertebrates. Further criticism in this
same vein may be directed against the author's bibliography.
Although this does not aim at completeness, it does aim at the
inclusion of the most important works and of the most repre-
sentative general references. The list given covers 28 pages.
In the general list one misses such titles as: Wheeler "Ants";
Holmes "Evolution of Animal Intelligence"; and Max Meyer's
"Laws of Human Behavior," — which last deserves a place equally
with many that are included. Other sins of omission might
be indicated here and in the bibliographies in special subjects.
I will call attention only to the lack of reference to Mclndoo's
"Lyriform Organs and Tactile Hairs of Araneads" and to the
articles on taste and smell mentioned below. American inves-
tigations are referred to with great frequency.

One of the very excellent features of Kafka's work is the
large number of illustrations given, — a total of 362 figures.
These present the gross bodily appearance, the detailed anatomy
of the sense organs and certain types of reactions of the animals
concerned. Comparative psychologists will welcome a conven-
ient summary of invertebrate sense organs. The teaching of
the subject will gain by this emphasis upon structure even if
research work does not need correction and an added incentive.
Pedagogically important also are the references to the tropic
activities of bacteria and the sex cells.

The intimate relations between touch and hearing are pointed
out. The existence of auditory hairs furnishes supporting
evidence here. No claim is made that the phenomena treated
under audition are to be interpreted as essentially different
from those of touch. The differentiation must be in terms of
stimuli and these are proverbially hard to control. The general

KAFKA'S "EINFUHRUNG IN DIE TIERPSYCHOLOGIE" 477

problem of the criteria for distinguishing sense fields is not
taken up. A special case that is considered is the relation of
taste and smell. The differentiation here is on the basis of the
topographical relations of the sense organs which lead to func-
tional differences. Taste functions in the immediate taking of
food while smell leads to the search for food. [In other words,
it is a difference of extero and intero-ceptors.] If the question
of the relation of taste and smell was to be handled at all, the
author should by no means have ignored the work on this topic
by C. J. Herrick, Parker and Parker and Stabler. The antennae
of insects are held to contain the olfactory organs. Miss Fielde's
work on the detailed anatomy of the antennae of ants is quoted
with approval (?). In his discussion of the study of smell by
extirpation methods, Kafka makes the very valuable suggestion
that the presence of inadequate but effective stimuli must be
reckoned with both in so far as they may affect cutaneous nerves
and in so far as they may arouse activities in taste. The presence
of this source of error is very probable where intense stimuli are
used [and really can only be thoroughly guarded against when
data on threshold sensitivities are at hand.]

In discussing the factors that cause insects to seek flowers,
the author opposes Plateau's odor theory and supports Forel
and others who find vision and habit the main factors. The
recent work of Lovell furnishes additional confirmation of the
truth of this point of view.

The treatment of vision is well executed. Phototropisms are
discussed in detail and are interpreted from the standpoint of
"trial and error" rather than from Loeb's point of view. The
author points out (page 321) "dass die 'Richtung der Licht-
strahlen' an sich ein ebenso 'metaphysisches' Erklarungsprincip
darstellt wie etwa die ' Willenstatigkeit,' gegen deren Heranzie-
hung gerade die Vertreter der Tropismenlehre so energischen
Einspruch erheben. Denn wie die Einstellung eines Organismus
durch die Richtung bestimmt werden soil, in der die Lichtstrahlen
seine Kor per substance durchsetzen (Sachs), bleibt ratsel-
haft * * *." This chapter contains a large number of diagrams
illustrating the discussion of the evolution of the invertebrate
eye. In the presentation of the much be-labored field of insect
color-vision, the author leans toward the interpretation that
the behavior in question is guided by brightness only. Kafka

478 WALTER S. HUNTER

rarely introduces theoretical psychological comments and dis-
cussions into the text. It is a pleasure, however, here in the
account of color-vision, to meet the following statement: "Die
Vergleichende Psychologie vermag daher auf objectiven Wege
das Problem des Farbensinnes der Insekten nur bis zu der
Feststellung zu fordern, dass jedenfalls verschiedene Strahlen-
gattungen verschiedene objective Wirkungen hervorbringen, sie
kann dagegen auf die subjektiven Phanomene im tierischen
Bewusstsein wiederum nur aus der Analogie der objektiven
Vorgange im menschlichen und im tierischen Organismus schlies-
sen." (S. 473). Such analogies, the author further points out,
are hindered by our lack of information concerning retinal
processes in man.

American readers will note with interest Kafka's Introduction
dealing with the aims and principles of comparative psychology.1
It was written prior to the publication in this country of the
many recent "Behavior" papers. In the present book, the dis-
cussion covers 16 pages only out of a total of 549. The "specu-
lative tendency" thus plays no overshadowing role here.

The fact that comparative psychology has manifested an
anthropomorphic tendency cannot be used as a final argument
against the possibility of its being thoroughly scientific. Biology,
physics and chemistry have passed through similar stages. Yet
reacting against anthropomorphism, natural science tends to
seek all explanation in physical and chemical terms or at most
in the teleological conditioning of reactions. Conscious pro-
cesses, since they cannot be "observed" are ruled out of the
subject matter. There is no doubt that the rapid progress made
by comparative physiology and biology within recent years has
been largely due to the insistence that objective processes be
stated in terms of objective factors. Appeals to psychic pro-
cesses have most often indicated only the faliure to analyze
properly a causal nexus. Yet that this physico-chemical state-
ment is not exhaustive is testified to by the consciousness that
each one has of mental concomitants of bodily activity as well
as by the appeal to introspection which physiology makes in
its studies of brain functions. The inaccessibilitv to immediate

1 This chapter appeared, prior to the publication of the book, under the title
''' Ueber Grundlagen und Ziele einer wissenschaftlichen Tierpsychologie," Arch,
f. d. ges. Psych., Bd. 29, 1913.

KAFKA'S "EINFUHRUNG IN DIE TIERPSYCHOLOGIE" 479

experience of the facts for which comparative psychology seeks
is no more a criticism of the scientific character of the field than
is the impossibility of an immediate experience of the center
of the earth and of the back side of the moon an objection to
the sciences there concerned.

There is as much justification for attributing consciousness
to animals as to one's fellow men. In neither case can immediate
experience be had. It is useless to seek for objective criteria
of consciousness, although one feels impelled to do so. One
of the most important criteria proposed is the "associative
memory" of Loeb and Bethe. This, however, assumes that
memory is the first thing in the way of consciousness, — a theory
which can be traced as far back as Hobbes and Locke. [K.
does not mention the fact, but this criticism has been urged by
other writers, S. J. Holmes, et. al.] Other criteria based upon
the analogies of human and animal sense organs and nervous
systerns ignore the possibility of the existence of consciousnesses
different from the human. The legitimate use of analogy directs
attention to the similarity throughout the animal kingdom with
respect to biological adjustments : self-preservation, continuation
of the species, avoidance of pain and the seeking of pleasure.
The continuity of life on the physical side suggests a similar
continuity on the mental side. The psychologist's task is to
trace origins and growths within the subjective realm which
it is necessary to posit beside the physical world. From the
uncertainty which attaches to any subject matter not open to
immediate experience, comparative psychology derives only the
"Verpflichtung, sich streng an die Ergebnisse der objektiven
Forschung als ihre einzige Grundlage zu halten, ohne sich dazu
verleiten zu lassen, psychologische Interpretationen als kausale
Erklarungen der physischen Phanomene auszugeben." (S. 13).

The reviewer can heartily commend Kafka's general point of
view. A safe middle ground is held with respect to a question
where extreme doctrines are only too frequently current.

CESARESCO'S PSYCHOLOGY AND TRAINING OF

THE HORSE*

Carl Rahn
University of Illinois

This work represents the product of life-long study and
practice of the art of horsemanship. The first volume deals
with the mental and physical nature of the horse; the remaining
three volumes are devoted to the methods of training.

We are told that " the horse's intelligence is limited, but the
animal is intelligent enough to understand that it must have
regard for what happens in its environment, and for its rider, — to
feel the justice or injustice of the punishments inflicted, — to try
to oppose, anticipate, and neutralize the efforts of its rider, — and
to choose that moment for injuring its master when the latter
is not looking." ' The horse," furthermore, " has a highly
developed imagination," and this combined with its great sus-
ceptibility to fear, makes the animal readily amenable to our
attempts to train it, for the one "enables it to grasp readily
the idea of our superiority" and the other "gives value to the
slightest stimulus or chastisement."

In whatever way we may react to these psychological inter-
pretations, the account of the methods of training will possess
a positive value for the student of animal behavior, viz.: as a
stimulus toward the formulation of specific problems in con-
nection with the behavior of the horse. Such a student will
miss with regret, at times, the minute analyses of stimulus and
the significant classifications and tabulations of responses which,
e. g., make the work of Pfungst so valuable. Thus the changes
in the voice of the rider are emphasized as one of the most
effective helps, or means of control, and it would have been
highly desirable to have had an analysis of the kinds of quali-
tative or other changes in the form of stimulation that constitute
the really effective factor. At other points in the treatise

1 Cesaresco, Count Eugenio Mantinengo: L'Arte Di Cavalcare, Con Aggiunto: II
Cavallo Attaccato Alia Carrozza. Devoti, Salo, 1914.

480

CESARESCO'S PSYCHOLOGY AND TRAINING OF HORSE 481

such a criticism will not, of course, hold: for instance in the
description of gestures and caresses as inducing stimuli. In
the main, however, the reader is left with a feeling that the
description is couched too often in subjective terms such as:
"approval," "disapproval," "menacing." .... But the student
will find suggested, on the other hand, a wealth of problems
peculiarly significant. And their significance lies in this: that
the horse presents, probably more favorably than any other
form, opportunities for studying a mechanism of stimulus and
response approximating very closely the typical social situation.

If Pfungst's work establishes the fact of a fine perception
of minimal movements of all kinds, as involved in the functionally
effective stimulus for responses in the horse, the treatise of
Cesaresco indicates what appears to be the salient characteristic
of the responsive phase, viz. : a finely balanced inhibition-
mechanism. It is this fact, plus the sensitiveness of the horse
to minimal changes in stimulation while the response is in prog-
ress, that makes its behavior so closely analogous to the reaction
of the human individual in the social situation.

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