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M..  WiLFORD  PoULSON, 

THE 
UNIVERSITY  OF  CHICAGO 

Founded  by  JOHN  D.  RCXKEFELLER 


The  Delayed  Reaction  in  Animals  and  Children 


A  DISSERTATION 

Submitted  to  the  Faculty  of  the  Graduate  School  of  Arts  and  Literature,  in 
Candidacy  for  the  Degree  of  Doctor  of  Philosophy 

DEPARTMENT  OF  PSYCHOLOGY 


By 
WALTER  S.  HUNTER 


Published 

at  Cambridge,  Boston,  Mass. 

HENRY  HOLT  &  COMPANY 

34  West  33d  Street,  New  York 

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


ACKNOWLEDGMENTS 

It  is  a  pleasure  to  acknowledge  my  deep  obligation  to  Prof. 
Harvey  A.  Carr  both  for  setting  the  problem  and  for  the  careful 
supervision  and  criticism  of  the  work  here  presented.  To  Prof. 
James  R*.  Angell  also  I  owe  much.  Not  only  has  he  subjected 
the  monograph  to  a  searching  analysis;  but,  through  that  im- 
palpable something  called  "laboratory  atmosphere,"  he  has 
influenced  the  tone  of  the  interpretations.  Prof.  John  B.  Watson 
of  Johns  Hopkins  University  has  read  a  first  draft  of  the  theo- 
retical section  of  this  paper.  I  wish  to  add  a  word  of  thanks 
to  Mr.  W.  R.  Hough  and  Dr.  H.  B.  Reed  for  the  guidance  given 
me  by  the  data  which  they  had  accumulated  in  an  early  study 
of  the  present  problem.  Further  notice  of  their  work  is  given 
below.  Mr.  De  Vry,  director  of  the  Zoological  Garden  in  Lincoln 
Park,  Chicago,  and  Dr.  Homaday,  director  of  the  New  York 
Zoological  Garden,  have  both  given  me  information  concerning 
the  habits  of  raccoons. 


TABLE  OF  CONTENTS 

Page 

I.  Introduction 1 

II.  Critical  Review  of  HisTORicAii  Data 2 

1.  Imitation 3 

2.  Use  of  tools 5 

3.  Dreams 8 

4.  Learning  curve 8 

5.  Memory 9 

6.  Thorndike's  test 10 

7.  Learning  by  being  "put  through" 14 

8.  Recognition 16 

9.  Rate  of  forgetting 16 

10.  Association  by  similarity 16 

11.  Reluctance  and  expectancy 17 

12.  Varying  means  to  the  same  end 17 

13.  Reactions  to  a  temporal  series  of  colors 19 

14.  Washburn's  cat  on  the  stairway 20 

III.  Notes  on  the  Animals  and  Children  Tested 21 

IV.  Apparatus  and  General  Method 22 

V,  Experimental  Results 30 

1.  Tests  with  animals 30 

A.  Learning  the  association 30 

(a)  Rats 30 

(b)  Dogs 32 

(c)  Raccoons 33 

(d)  Summary 34 

B.  Maximal  intervals  of  delay  attained 35 

(a)  Group  differences  in  maximal  delay 35 

(b)  Effect  of  size  of  release  upon  delay 37 

(c)  Effect  of  backgrounds  of  diflferent  brightnesses  upon 

delay 38 

(d)  Effect  of  number  of  boxes  upon  delay 39 

(e)  Effect  of  other  conditions  upon  delay 39 

C.  Methods  of  reaction  after  delay  used  by  animals 39 

(a)  Orientation  of  whole  or  part  of  body 40 

(b)  Position  in  the  box 47 

2,  Tests  with  children 52 

A.  Method  of  experimentation 52 

B.  Are  the  results  obtained  from  animals  and  children  *com- 

parable? 53 

C.  Learning 55 

D.  Differences  between  the  learning  of  animals  and  children  ...  55 

E.  Delayed  reactions 57 

VI.  Theoretical  Considerations 62 

1.  The  cues  essential  for  correct  delayed  reactions 62 

A.  Substitutes  derived  from  the  external  env-ironment 63 

B.  Substitutes  derived  from  within  the  subject's  body 67 

(a)  The  type  of  internal  cue  used 67 

(b)  The  mechanism  by  which  internal  cues  guide  behavior  70 

2.  The  place  of  ideas  in  the  grades  of  animal  learning 73 

VII.  Summary  and  Conclusions 79 

VIII.  Appendix 82 

A.  Detailed  records  of  two  rats  and  two  raccoons 82 

B.  Notes  on  raccoons 85 

V 


I.     INTRODUCTION 

The  experiments  in  this  monograph  '  aim  at  an  analysis  of 
typical  mammalian  behavior  imder  conditions  where  the  de- 
termining stimulus  is  absent  at  the  moment  of  response.  Asso- 
ciations were  first  set  up  between  movements  that  led  to  food 
and  a  light  which  might  be  in  any  one  of  three  boxes.  Controls 
were  used  to  make  sure  that  the  position  of  the  light  alone 
determined  the  reactions  of  the  subject.  Tests  were  then  in- 
stituted in  which  the  Hght  was  turned  off  before  the  reaction 
was  made.  The  subject  thus  had  to  respond  in  the  absence  of 
the  stimulus  that  hitherto  had  guided  his  reactions. 

The  nature  of  the  present  experiment  may  be  further  set 
forth  by  contrasting  it  with  the  following  type  of  adjustment: 
A  cat  watches  for  a  mouse  and  sees  it  appear  at  an  open  hole. 
The  mouse  vanishes  before  the  cat  can  react,  yet  the  cat  goes 
over  to  the  hole.  There  can  be  no  question  here  but  that  the 
determining  stimulus  is  absent  at  the  moment  of  response,  pro- 
vided possible  olfactory  stimuH  be  neglected.  Our  experiment 
differs  from  this  in  complexity.  If  there  were  three  holes  that 
differed  only  in  their  several  directions  from  the  cat,  and  if  in 
the  past  the  mouse  had  appeared  an  equal  number  of  times  in 
all  three  holes,  the  conditions  would  be  the  same  as  in  our  tests. 
A  selection  between  the  three  holes  would  need  to  be  made  on 
the  basis  of  the  immediately  previous  presence  of  the  rat,  if 
a  correct  reaction  were  to  occur.  If  an  animal  can  manifest 
behavior  that  does  not  lend  itself  to  a  "stimulus  and  response" 
explanation,  this  is  one  type  of  situation  in  which  that  behavior 
should  appear.  That,  in  fact,  it  is  the  situation  par  excellence 
for  the  eliciting  of  this  behavior  will,  I  believe,  appear  as  this 
monograph  progresses. 

>  Experimentation  on  the  present  problem  was  first  begun  in  the  University  of 
Chicago  laboratory  by  a  graduate  student,  W.  R.  Hough.  The  following  year 
the  work  was  taken  up  and  carried  somewhat  further  by  another  student,  M.  a. 
Reed  Both  students  worked  with  white  rats.  Although  in  each  case  the  results 
obtained  were  in  strict  harmony  with  those  presented  in  this  paper,  m  neither 
ease  were  they  conclusive.  The  chief  value  of  the  work  lay  in  its  suggestiveness 
The  apparatus  used  by  Reed— Prob.  Box  D— is  described  below.  The  present 
investigation  was  carried  on  in  the  same  laboratory  from  October,  1910  to 
April,  1912. 

1 


2  WALTER  S.  HUNTER  , 

In  the  present  experiments,  two  main  factual  questions  arise : 
(i)  How  long  after  the  determining  stimulus  has  disappeared 
can  an  animal  wait  and  still  react  correctly?  (2)  Does  the 
animal  give  any  behavior  cues  as  to  its  method  of  solving  the 
problem?  If  so,  what  are  they?  With  these  data  given,  there 
remains  the  task  of  interpretation.  If  a  selective  response  has 
been  initiated  and  controlled  by  a  certain  stimulus,  and  if  the 
response  can  still  be  made  successfully  in  the  absence  of  that 
stimulus,  then  the  subject  must  be  using  something  that  func- 
tions for  the  stimulus  in  initiating  and  guiding  the  correct 
response.  Our  •  investigation  thus  forces  us  to  the  considera- 
tion of  the  functional  presence  of  a  representative  factor  in  the 
behavior  of  animals  and  children.  Not  only  this,  but  the  prob- 
lem of  the  nature  of  this  representative  factor  confronts  us.  Is 
it  an  overt  motor  attitude,  or  not?  If  not,  is  it  sensory  or  imag- 
nal,  i.e.,  ideational? 

In  the  interpretative  study,  I  shall  proceed  on  the  assump- 
tion that  an'mals  are  conscious.  What  the  nature  of  this  con- 
sciousness is,  it  will  be  the  task  of  this  paper  to  help  determine. 
(If  the  reader  does  not  choose  to  follow  this  line  of  interpreta- 
tion, he  may  state  everything  in  neurological  terms  without 
marring  the  significance  of  this  discussion.)  But  a  propos  of 
the  term  "image"  or  "idea,"  let  it  be  said  once  for  all  that 
wherever  these  terms  are  used  by  the  present  writer  with  refer- 
ence to  animal  consciousness,  they  should  be  supplemented  by 
the  phrase  "or  functionally  equivalent  process."  I  use  the 
structural  term  chiefly  for  the  sake  of  its  brevity. 

II.     CRITICAL  REVIEW  OF  HISTORICAL  DATA 

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  sub- 
jects. In  that  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  stim- 


^  In  the  literature,  it  has  been  taken  for  granted  that  the  question  of  the  exist- 
ence of  images  and  that  of  the  existence  of  ideas  in  animal  consciousness  is  the 
same.  I  shall  proceed  on  the  assumption  that  images  are  centrally  aroused  pro- 
cesses, while  ideas  may  be  either  peripherally  or  centrally  conditioned.  The  essence 
of  the  idea  is  not  its  origin  (or  content),  but  its  function.  This  point  will  be  ampli- 
fied in  the  final  divisions  of  this  monograph.  The  present  statement  will  suffice 
for  a  definition  of  terms. 


DELAYED  REACTION  o 

ulus  (object)  or  movement  that  is  represented.  In  the  present 
historical  section  the  attempt  is  made:  (i)To  present  the  main 
types  of  behavior  that  have  been  used  as  evidence  of  the  exist- 
ence of  images  in  animals;  and  (2)  to  show  that  this  evidence 
is  inconclusive,  because  the  behavior  may  be  stated  in  sensori- 
motor terms.  In  the  Hght  of  the  assumption  just  made,  there 
are  two  reasons  why  this  behavior  may  be  so  interpreted:  (i) 
The  stimuH  determining  the  reactions  in  question  have  not  been 
adequately  known;  and  (2)  inasmuch  as  this  is  true,  one  has 
no  right  to  assume  the  absence  of  the  stimuH  which  are  sup- 
posed to  be  represented.  All  of  the  behavior  that  is  summar- 
ized in  this  section  may  have  involved  representative  actors. 
The  point  of  my  criticism  will  be  that  they  need  not  have  in- 
volved such  processes.  It  is  not  merely  a  question  of  the  appH- 
cation  of  the  law  of  parsimony,  as  that  is  usually  stated.  It 
is  also  a  recognition  of  the  fact  that  sensori-motor  behavior 
is  genetically  the  more  fundamental  form. 

The  following  are  the  types  of  evidence  to  be  considered: 
(i)  Imitation;  (2)  use  of  tools;  (3)  dreams;  (4)  nature  of  the 
learning  curve;  (5)  memory;  (6)  Thomdike's  test:  The  imme- 
diate reaction  to  one  stimulus  before  t|ie  appearance  of  a  second 
which  has  always  accompanied  the  first  after  an  interval  of 
a  few  seconds;  (7)  recognition;  (8)  learning  by  being  "put 
through;"  (9)  rate  of  forgetting;  (10)  association  by  similar- 
ity; (11)  reluctancy  and  expectancy  of  .response;  (12)  vary- 
ing'means  to  the  same  end;  (13)  reactions  to  a  temporal  series 
of  colors,  and  (14)  Washburn's  cat  on  the  stairway. 

1.  Imitation 
Thorndike^  is  an  example  of  the  comparative  psychologist 
who  interprets  the  highest  type  of  imitation  as  requiring  the 
presence  of  images  or  ideas.  In  his  experiments,  however,  he 
found  no  evidence  for  the  existence  of  this  kind  of  behavior. 
The  general  character  of  the  imitation  experiment  is  well  known. 
An  animal  that  has  failed  to  solve  a  certain  problem  is  con- 
fined where  it  can  see  another  work  the  mechanism  and  get 
food.  It  is  then  given  an  opportunity  to  make  the  desired 
reaction.  If  the  trial  succeeds  or  if  there  is  a  sudden  improve- 
ment in  the  animal's  behavior,  it  is  said  to  have  profited  by 

^Thorndike,  E.  L.     Animal  Intelligence.     1911,  New  York,  pp.  76-108. 


4  WALTER  S.  HUNTER 

viewing  the  other's  performance.  Haggerty  *  found  this  be- 
havior in  well  controlled  tests  with  monkeys.  He  divides  the 
stimulus  for  that  imitative  behavior  into  three  parts:  (i)  A 
fairly  simple  mechanism;  (2)  the  perception  of  another  animal 
working  at  the  mechanism,  and  (3)  the  perception  of  the  other 
animal  getting  food.  Haggerty  does  not  discuss  the  theoretical 
side  of  imitation  and  argue  for  the  existence  of  images.  He 
simply  presents  the  data.  However,  in  view  of  the  stand  taken 
by  Thorndike  and  others  on  interpretation,  we  shall  neverthe- 
less use  material  drawn  from  Haggerty 's  monograph  for  analysis. 
The  following  criticisms  tell  against  the  use  of  this  type  of 
behavior  as  crucial  evidence  for  images;  The  animal  that  does 
the  imitating  may  make  its  improvement  under  the  incentive 
of  a  social  impulse  rather  than  of  the  apprehension  of  relations. 
This  receives  confirmation  by  the  fact  that  Haggerty 's  monkeys 
did  better  if  the  animal  to  be  imitated  was  a  stranger  and  thus 
aroused  the  imitator  more  strongly  than  a  familiar  animal  would 
have  done.'  This  criticism  is  a  variant  on  the  following  one. 
(2)  The  fact  that  the  sight  of  the  other  animal  being  fed  was  a 
part  of  the  stimulus  makes  it  at  least  possible  that  the  imitator's 
attention  was  simply  drawn  very  vividly  to  the  spot  to  be 
attacked.  Of  course  the  more  complicated  the  reaction  to  be 
made  and  the  more  exact  the  execution  of  this  by  the  imitator, 
the  better  the  argument  for  an  ideational  perception  of  rela- 
tions. However,  the  general  objection  will  always  be  valid  that 
one  can  never  say  that  the  imitating  animal  was  not  guided 
solely  by  stimuli  present  to  sense.  The  determining  factor  in 
the  stimulus  can  not  be  said  to  be  ideational.  Once  the  animal's 
attention  is  vividly  focused  upon  the  objective  seqvience  "pull- 
ing string — getting  food,"  e.g.,  the  necessary  reaction  may  fol- 
low by  association  when  the  opportunity  presents  itself.  Mon- 
keys in  particular  have  such  an  enormous  repertoire  of  reactions 
that  it  is  very  tempting  to  analyze  such  imitative  reactions  as 
Haggerty  presents  on  a  purely  "stimulus  and  response"  basis. 
That  author  says  of  one  of  his  typical  experiments  (Chute 
Experiment  A) :  "In  order  to  secure  the  food,  the  monkey  must 
leap  from  the  wire  part  of  the  cage  to  the  chute,  and,  while 

^  Haggerty,  M.  E.    Imitation  in  Monkeys.    Jour,  of  Comp.  Neur.  and  Psy.,  1909j 
vol.  19. 

5  Op.  cit.,  p.  436.      ■'  i^ 


DELAYED  REACTION  5 

holding  to  it,  must  thrust  a  hand  up  inside  and  pull  the  string, 
thereby  releasing  the  small  door  in  the  top  of  the  cage  and 
allowing  food  which  had  been  placed  on  it  to  fall  to  the  floor. 
He  must  then  descend  to  the  floor  to  get  the  food."  •  After 
the  imitator's  attention  is  focused  upon  the  hole  at  the  chute's  end 
due  to  the  action  of  the  imitatee,  what  is  more  natural  than 
that  it  should  jump  to  the  chute?  The  hole  has  "caught  its 
eye"  before  the  jump,  so  the  hand  goes  in  almost  reflexly,  as 
reflexly  closes  about  the  string  and  pulls.  Food  falls  and  is 
eaten.  If  the  animal  is  attentive  to  the  movements  during  the 
performance,  the  chances  are  that  it  will  henceforth  succeed.' 

2.    Use  of  Tools 

A  second  argument  for  the  presence  of  ideas  is  the  use  of 
tools  by  animals.  In  view  of  the  fact  that  such  behavior  has 
at  times  been  exclusively  claimed  for  man,  students  of  animal 
behavior  have  long  sought  for  conclusive  evidence  on  this  ques- 
tion.' We  shall  take  typical  data  presented  by  Hobhouse  for 
consideration.  This  will  also  lead  to  an  understanding  of  that 
author's  attitude  on  the  question  of  images.  Hobhouse  treats 
such  behavior  largely  under  the  heading  "Articulate  Ideas." 
An  example  will  best  lead  us  to  an  understanding  of  his  posi- 
tion. The  animals  used  were  monkeys,  one  a  Rhesus  and  the 
other  a  chimpanzee.  The  latter  had  already  learned  to  throw 
a  rug  over  food  placed  at  a  distance  in  order  to  rake  in  the 
.latter.  He  was  then  taught  to  substitute  a  stick  for  the  rug. 
Quotations  from  the  author  will  now  indicate  the  animal's  prog- 
ress. "Next  day,  the  chimpanzee  learnt  to  use  a  short  stick 
in  order  to  reach  a  larger  one,  with  which  in  turn  he  could  reach 
the  banana."  »  "One  day  I  gave  him  a  rope  with  a  noose  to 
throw  over  the  box  in  place  of  his  stick."  (The  banana  was 
placed  in  a  cigar  box.)  "I  did  not  give  him  any  hint,  but  he 
soon  tried  it  in  a  vague  way.  He  did  not,  however,  understand 
the  matter  very  well,   for  when  he  succeeded  in  getting   the 

'  Op.  cit.,  p.  355. 

'Vide     Hobhouse,  L.  T.     Mind  in  Evolution.     London,  1901,  p.  202  for  place 
of  accident  in  learning. 

'  Lindsay,  W.   Lauder.     Mind   in  the  Lower  Animals  in   Health  and  Disease. 
London,  1879,  vol.  I,  chaps.  23  and  24. 
Hobhouse,  L.  T.    Op.  cit.,  chap.  10. 
Also  many  recent  studies  in  imitation. 
•  Op.  cit.,  p.  236. 


6  WALTER  S.  HUNTER 

rope  round  the  box,  he  did  not  seem  aware  of  his  advantage, 
flung  it  away,  went  off  for  his  shawl,  and  used  it  very  success- 
fully. I  then  tied  a  block  of  wood  to  the  rope  to  assist  in  throw- 
ing it.  He  attempted  this  spontaneously,  at  first  without  suc- 
cess. Presently,  however,  he  happened  to  pitch  the  block  right 
into  the  box,  which  today  was  open,  pulled  it  in,  and  got  the 
banana.  Notwithstanding  this  signal  success,  he  never  took  to 
this  trick."  ^^  "In  the  experiment  to  which  I  have  already 
referred,  when  the  box  was  tied  to  a  rope,  the  further  end  of 
which  was  passed  over  a  stanchion  several  feet  from  the  cage, 
he  failed,  as  I  shall  mention  later,  to  find  the  right  method, 
but  was  fertile  in  devising  wrong  ones.  He  would  shake  the 
rope  violently,  so  that  the  banana  would  fall  out  of  the  box. 
He  would  then  swing  the  rope  to  and  fro,  swishing  the  banana 
about  from  side  to  side,  until  by  degrees  it  would  come  within 
his  reach,  in  a  way  which  I  should  have  thought  beforehand  to 
be  quite  impossible."  "  "In  these  tests,"  says  Hobhouse,  "it 
was  necessary  that  [the  monkeys]  should  grasp  how  the  stick 
and  the  food  stood  in  relation  to  them;  that  they  should  get 
the  stick  at  the  food  and  beyond  it."  ^^  "A  form  of  'analogical 
extension'  is  also  strongly  marked  in  the  use  of  substitutes 
differing  very  widely  in  appearance  and  the  manner  of  use 
from  the  object  first  employed."  '^  These  illustrations  of  the 
use  of  tools  are  examples  and  proofs  of  the  existence  in  monkeys 
of  what  Hobhouse  means  by  the  practical  judgment,  where  artic- 
ulate ideas  are  employed."  The  author  explains  articulate  ideas 
as  follows:  "  By  a  more  articulate  idea,  is  meant  one  in  which 
comparatively  distinct  elements  are  held  in  a  comparatively 
distinct  relation."  '^  The  nature  of  the  practical  judgment  is 
set  forth  as  follows:  "It  is  more  than  assimilation,  because 
what  is  revived  is  an  idea,  a  definite  reference  to  something 
unperceived.  It  is  more  than  association,  because  relation  be- 
tween the  'revived'  idea  and  the  given  perception  is  an  essen- 
tial part  of  it,  and  it  is  less  than  analytic  thought,  because  the 
relations  involved  are  not  dissected  out  as  distinct  elements  in 


i»Op 
"  Op.  c 
"  Op.  c 
"Op 
"  Op.  c 
«  Op.  c 


it.,  pp.  237-8. 
It.,  p.  238. 
it.,  p.  241. 

pp.  241-2. 
...,  p.  269. 
It.,  p.  234. 


DELAYED  REACTION  7 

consciousness."  *«  "The  practical  judgment  is  not  independent 
of  associations,  for  association  supplies  the  whole  of  its  material. 
But  out  of  that  material,  it  selects  what  it  wants,  and  shapes  it 
as  required."^'  This  "material"  that  association  presents  is 
ideational  as  the  quotation  from  page  117  indicates.  It  seems, 
though  I  would  not  be  sure,  as  if  Hobhouse  assumed  the  exist- 
ence of  ideas  and  is  only  concerned  with  the  possibiHty  of  their 
functioning  in  behavior.  As  a  basis  for  this  imputation,  I 
point  to  his  discussion  of  the  association  of  ideas  on  page  114 
and  to  that  on  pages  200-1.  In  the  latter  place,  he  makes 
clear  (?)  that  what  he  does  not  wish  to  attribute  to  animals  is 
the  conscious  analysis  of  the  perceptual  order.  Such  a  dis- 
tinction between  existence  and  efficient  functioning  in  behavior 
seems  to  be  theoretically  permissible. »«  Images,  ideas  may 
exist  sporadically  as  has  been  claimed  in  the  case  of  animal 
dreams.  But  comparative  psychologists  have  neither  the  right 
nor  the  need  to  assume  the  existence  of  such  processes  save  as 
that  may  be  forced  upon  them  by  the  evidences  of  behavior. 

The  question  now  is :  Does  the  use  of  tools  i"  such  as  described 
imply  the  presence  of  a  centrally  aroused  factor?  In  the  light 
of  the  above  analysis  of  imitation,  the  reply  is  no.  Even  if 
Hobhouse 's  results  be  fully  accepted  without  raising  the  ques- 
tion of  careful  controls,  one  need  not  accept  his  interpretations. 
The  behavior  may  have  been  controlled  entirely  by  sensory 
factors.  As  to  the  fertility  shown  by  the  animals  in  devising 
methods,  (see  above,  p.  6),  this  was  very  probably  but  a  ran- 
dom use  of  acquired  co-ordinations.  The  use  of  the  tools  was 
acquired  as  any  habit  and  the  sight  of  the  individual  objects 
(ropes,  etc.)  aroused  the  type  of  reaction  that  had  been  taught. 
This  shows  a  higher  grade  of  inteUigent  adaptability  in  the 
animal  than  if  it  had  been  limited  to  the  use  of  one  object,  but 
it  does  not  prove  the  existence  of  a  central  conscious  factor. 
It  may  be  that  such  animals  as  the  primates  are  able  to  give 
similar  responses  to  different  sensory  stimuH  on  account  of  a 
factor  of  "hyper-excitability."  I  hesitate  to  use  such  a  term, 
but  the  general  type  of  case  held  in  mind  is  illustrated  by  the 

18  Op.  cit.,  p.  117. 
"  Op.  cit.,  p.  264. 

18  We  shall  see  below  (p.  9)  that  Morgan  makes  the  same  assumption. 

19  Hobhouse  cities  (op.  cit.,  p.  258)  only  one  well  authenticated  case  of  the  mak- 
ing of  a  tool  by  an  animal.    The  tool  in  this  case  was,  as  he  notes,  a  very  simple  one. 


8  WALTER  S.  HUNTER 

animal  that  is  supposed  to  react  to  a  certain  stimulus,  but,  being 
on  the  qui  vive,  reacts  to  anything  that  occurs  at  the  proper 
moment.  This  behavior  is  familiar  in  human  reaction  experi- 
ments. If,  now,  we  subtract  the  possible  emotional  disturb- 
ances (and  I  doubt  whether  that  even  is  necessary),  we  have 
the  type  of  case,  I  believe,  that  the  experiments  of  Hobhouse 
present. 

3.     Dreams 

A  third  argument  used  for  ideas  is  the  supposed  fact  of  an  mal 
dreams.  The  usual  criticism  of  this — to  which  I  subscribe — is 
that  the  law  of  parsimony  forces  one  to  recognise  that  the  inter- 
pretation of  the  facts  may  as  well  or  better  be  physiological  than 
ideational. 

4.     Learning  Curve 

A  fourth  argument  used  in  the  discussion  as  to  the  presence 
of  ideas  is  the  nature  of  the  learning  curve.  In  1898,  Thorn- 
dike'' "  presented  data  for  cats  which  when  plotted  gave  what  the 
author  termed  a  "gradual  slope."  "The  gradual  slope  of  the 
time  curve, — shows  the  absence  of  reasoning."  It  represents 
"the  wearing  smooth  of  a  path  in  the  brain,  not  the  decisions 
of  a  rational  consciousness."  There  seems  to  be  no  doubt  but 
that  Thomdike  meant  that  had  ideas  been  present  to  guide  the 
reactions  that  the  latter  would  have  succeeded  within  a  few 
trials.  Hobhouse  would  seem  to  agree  with  Thorndike  that 
such  a  curve  as  the  latter  claimed  to  present  was  evidence  of 
the  absence  of  imagery.  His  criticism  of  Thomdike  is  to  the 
effect  that  the  former's  curves  are  not  gradual — "unless  the 
slope  of  a  church  steeple  is  gradual." 

The  (apparently)  common  assumption  of  these  writers  has 
been  questioned  effectively  both  by  Watson^'  and  by  Hicks  and 
Carr."  The  criticism  of  the  latter  authors  is  factual  and  is 
summed  up  as  follows :  "  Our  results  indicate  that  any  inference 
from  such  a  general  characteristic  of  a  curve  is  not  feasible, 
because  we  are  dealing  with  a  complex  phenomenon  due  to 
several  independently  variable  factors.    Our  results  indicate  that 

^^  Thomdike,  E.  L.  Animal  Intelligence.  Psy.  Rev.  Mon.  Supp.,  1898,  vol. 
2,  p.  45. 

^^  Watson,  J.  B.  Kinaesthetic  and  Organic  Sensations.  Psy.  Rev.  Mon.  Supp., 
1907,  vol.  8,  pp.  23-4. 

"  Hicks,  V.  C.  and  Carr,  H.  A.  Human  Reactions  in  a  Maze.  Jour,  of  Animal 
Behavior,  1912,  vol.  2,  pp.  116-118. 


DELAYED  REACTION  9 

the  rational  status  of  a  group  of  animals  can  not  be  inferred 
from  the  slope  of  a  curve  in  so  far  as  this  slope  is  dependent 
upon  the  number  of  trials  or  the  relative  rate  of  elimination. 
They  indicate,  moreover,  that  inferences  as  to  intelligent  status 
are  legitimate  in  so  far  as  the  slope  is  determined  by  the  factor 
of  total  values  eliminated,  but  that  the  relation  between  the 
abruptness  of  slope  and  the  degree  of  rational  ability  is  just  the 
inverse  of  that  assumed  by  Thorndike  and  Hobhouse." 

5.  Memory 
Arguments  for  the  existence  of  ideas,  have  also  been  drawn 
from  behavior  purporting  to  be  guided  by  memory — in  the 
psychological  sense.  Let  us  use  an  example  from  Lloyd  Mor- 
gan. The  quotation  of  a  few  sentences  will  adequately  represent 
his  position  when  the  Introduction  to  Comparative  Psychology 
was  written.  "In  the  first  place  we  may  notice  that  the  exist- 
ence of  memory  is  implied  in  the  association  of  ideas ;  or  rather 
in  the  occurrence  of  ideas  at  all."  "If,  therefore,  animals  have 
ideas  at  all — and  if  they  have  not  we  need  not  attempt  to  carry 
any  further  our  investigations  into  zoological  psychology — they 
must  have  memory,  and  there  must  be  in  them,  as  in  us,  some 
anatomical  and  physiological  basis  for  what  is  popularly  termed 
the  retention  of  ideas."  "  By  idea  Morgan  understands  any 
centrally  aroused  conscious  process.  Of  course  Thorndike 's 
results  showed  long  ago  that  the  presence  of  ideas  in  an  animal 
requires  vigorous  proof  rather  than  mere  assumption.  Now  for 
a  concrete  example:  "When  I  was  at  the  cape  I  used  to  take 
my  two  dogs  up  the  Devil's  Peak,  an  outlying  point  of  Table 
Mountain.  There  were  several  places  at  which  it  was  necessary 
that  I  should  lift  them  from  ledge  to  ledge  since  they  could  not 
scramble  up  by  themselves.  After  the  first  ascent  they  always 
remembered  these  places  and  waited  patiently  to  be  lifted  up. 
On  one  of  our  first  ascents  one  of  them  put  up  a  young  coney 
and  they  both  gave  chase.  Subsequently,  they  always  hurried 
on  to  this  spot,  and  though  they  never  saw  another  coney  there, 
reiterated  disappointment  did  not  efface  the  memory  of  that 
first  chase,  or  so  it  seemed.  I  think  the  last  time  I  took  them 
up  must  have  been  about  three  and  a  half  years  after  the  coney 

»  Morgan,  Lloyd.  Intro,  to  Comp.  Psych.  London,  1898,  p.  117.  Thus  Mor- 
gan, as  we  noted  for  Hobhouse,  seems  to  assume  that  ideas  exist  whether  they 
function  in  behavior  or  not. 


10  WALTER  S.  HUNTER 

hunt :    so  long  had  the  memory  endured  and  the  association 
remained  uneffaced."  ^' 

This  is  a  fairly  well  known  example  of  the  type  of  proof  used 
by  the  "anecdotal  psychologists."  To  some  it  may  seem  too 
trivial  either  for  serious  analysis  or  notice.  But  such  a  judg- 
ment is  ill  informed.  We  shall  find  similar  arguments  as  late 
as  Cole's  paper  on  the  Intelligence  of  Raccoons.  The  obvious 
criticism  of  Morgan's  illustrations  is  that  they  may  be  simply 
cases  of  sensory  recognition  of  the  commonest  kind.  A  further 
word  will  be  said  in  connection  with  the  criticism  of  Cole's  work. 

6.     Thorndike's  Test 

A  great  many  of  the  experiments  which  Thomdike  presents 
in  his  recent  book  on  Animal  Intelligence"  involve  more  or  less 
intimately  the  question  of  the  existence  of  images.  However, 
I  shall  limit  my  analysis  to  the  case  in  which  the  problem  of  the 
fact  of  images  is  most  crucially  attacked.  The  case  I  choose 
is  the  famous  one  reported  in  the  first  monograph  of  Animal 
Intelligence.  I  shall  term  it  the  "hand-clapping  test"  with 
cats.  Thorndike's  own  words  are  such  an  excellent  example  of 
scientific  description  that  I  shall  quote  them  at  length:^'  "The 
only  logical  way  to  go  at  this  question  and  settle  it  is,  I  think,  to 
find  some  associations  the  formation  of  which  requires  the  pres- 
ence of  images,  of  ideas.  You  have  to  give  an  animal  a  chance 
to  associate  sense-impression  A  with  sense-impression  B  and 
then  to  associate  B  with  some  act  C  so  that  the  presence  of  B 
in  the  mind  will  lead  to  the  performance  of  C.  Presumably  the 
representation  of  B,  if  present,  will  lead  to  C  just  as  the  sense- 
impression  B  did.  Now,  if  the  chance  to  associate  B  with  A 
has  been  improved,  you  ought,  when  the  animal  is  confronted 
with  the  sense-impression  A,  to  get  a  revival  of  B  and  so  the 
act  C.  Such  a  result  would,  if  all  chance  to  associate  C  with 
A  had  been, eliminated,  demonstrate  the  presence  of  represent- 
tions  and  their  associations.  I  performed  such  an  experiment 
in  a  form  modified  so  as  to  make  it  practicable  with  my  animals 
and  resources.  Unfortunately,  this  modification  spoils  the  cru- 
cial nature  of  the  experiment  and  robs  it  of  much  of  its  author- 
ity.    The  experiment  was  as  follows: 

2^  Ibid,  p.  118. 

25  Thorndike,  E.  L.    Animal  Intelligence.    New  York,  1911. 

^Ubid,  pp.  110-112. 


DELAYED  REACTION  11 

"A  cat  was  in  the  big  box  where  they  were  kept  (see  p.  90) 
very  hungry.  As  I  had  been  for  a  long  time  the  source  of  all 
food,  the  cats  had  grown  to  watch  me  very  carefully.  I  sat 
during  the  experiment,  about  eight  feet  from  the  box,  and  would 
at  intervals  of  two  minutes  clap  my  hands  four  times  and  say, 
'I  must  feed  those  cats.'  Of  course  the  cat  would  at  first  feel 
no  impulse  except  perhaps  to  watch  me  more  closely  when  this 
signal  was  given.  After  ten  seconds  had  elapsed  I  would  take 
a  piece  of  fish,  go  up  to  the  cage  and  hold  it  through  the  wire 
netting,  three  feet  from  the  floor.  The  cat  would  then,  of  course, 
feel'  the  impulse  to  climb  up  the  front  of  the  cage.  In  fact, 
experience  had  previously  estabHshed  the  habit  of  cHmbing 
up  whenever  I  moved  toward  the  cage,  so  that  in  the  experi-. 
ment  the  cat  did  not  ordinarily  wait  until  I  arrived  there  with 
the  fish.     In  this  experiment 

A=The  sense -impression  of  my  movements  and  voice  when 

giving  the  signal 
B=The  sense-impression  of  my  movements  in  taking  fish, 

rising,  walking  to  box,  etc. 
C=The  act  of  climbing  up,  with  the  impulse  leading  there- 
unto. 

"The  question  was  whether  after  a  while  A  would  remind 
the  cat  of  B,  and  cause  him  to  do  C  before  he  got  the  sense- 
impression  of  B,  that  is,  before  the  ten  seconds  were  up.  If  A 
leads  to  C  through  a  memory  of  B,  animals  surely  can  have 
association  of  ideas  proper,  and  probably  often  do.  Now,  as  a 
fact,  after  from  thirty  to  sixty  trials,  the  cat  does  peform  C 
immediately  on  being  confronted  by  A  or  some  seconds  later, 
at  all  events  before  B  is  presented.  And  it  is  my  present  opinion 
that  their  action  is  to  be  explained  by  the  presence,  through 
association,  of  the  idea  B.  But  it  is  not  impossible  that  A  was 
associated  directly  with  the  impulse  to  C,  although  that  impulse 
was  removed  from  it  by  ten  seconds  of  time.  Such  an  associa- 
tion is,  it  seems  to  me,  highly  improbable,  unless  the  neurosis 
of  A,  and  with  it  the  psychosis,  continues  until  the  impulse  to 
C  appears  But  if  it  does  so  continue  during  the  ten  seconds, 
and  thus  get  directly  linked  to  C,  we  have  exactly  a  represen- 
tation, an  image,  a  memory,  in  the  mind  for  eight  of  those  ten 
seconds.     It  does  not  help  the  deni-rs  of  images  to  substitute 


12  WALTER  S.  HUNTER 

an  image  of  A  for  an  image  of  B.  Yet,  unless  they  do  this, 
they  have  to  suppose  that  A  comes  and  goes,  and  that  after  ten 
seconds  C  comes,  and,  passing  over  the  intervening  B  blank, 
willfully  chooses  out  A  and  associates  itself  with  it.  There  are 
some  other  considerations  regarding  the  behavior  of  the  cats 
from  the  time  the  signal  was  given  till  they  climbed  up,  which 
may  be  omitted  in  the  hope  that  it  will  soon  be  possible  to 
perform  a  decisive  experiment.  If  an  observer  can  make  sure 
of  the  animal's  attention  to  a  sequence  A-B,  where  B  does  not 
arouse  any  impulse  to  act,  and  then  later  get  the  animal  to 
associate  B  with  C,  leaving  A  out  this  time,  he  may  then,  if 
A,  when  presented  anew,  arouses  C,  bid  the  deniers  of  represen- 
tations to  forever  hold  their  peace." 

First  as  to  the  data  obtained,  Thorndike's  results  indicate 
only  the  magnitude  of  the  interval  between  two  stimuli  which 
association  can  bridge.  Using  his  symbols,  B  and  C  have  been 
associated  before  this  experiment  was  begun.  The  hand  clap- 
ping, A,  now  precedes  B  by  ten  seconds.  At  the  end  of  from 
thirty  to  sixty  trials,  the  cat  climbs  up  at  A  rather  than  waiting 
until  B  appears.  Now  must  we  assume  either  that  the  "A" 
neurosis,  and  hence  the  "A"  psychosis,  persists  or  that  A  has 
resulted  in  the  central  arousal  of  B?  Not  at  all.  There  is  good 
evidence  to  show  that  association  in  animals  can  bridge  an 
interval  of  ten  seconds  and  more.  Nearly  all  behavior  experi- 
ments cover  at  least  ten  seconds  from  the  beginning  of  the 
test  to  the  acquisition  of  food.  Yet  it  is  necessary  that  the 
first  and  the  last  of  the  test  be  associated  in  order  to  provide 
a  motive  for  the  complete  reaction.  In  no  case — Thorndike's 
not  excepted — ^is  the  ten  seconds  a  sheer  gap.  (Thorndike  did 
not  describe  the  behavior  of  the  cats  during  the  interval,  although 
he  did  refer  to  it.)  The  animal  is  reacting  during  the  interval. 
Motor  attitudes  at  least  are  present  to  fill  the  gap.  An  animal 
as  high  in  the  scale  as  a  cat  could  certainly  form  this  simple 
association  between  a  sound  and  a  single  reaction  within  sixty 
trials.  Moreover,  it  is  to  be  remembered  that  only  two  cats 
succeeded  within  this  time.  Two  others  were  tested  for  one 
hundred  and  thirty-five  trials,  but  uniform  reactions  were  not 
secured.  The  situation  would  have  been  quite  different  had 
there  been  two  or  more  signals,   "A's,"  and  as  many  difterent 


DELAYED  REACTION  13 

responses.     But  even  under  such  conditions,  one  would  still  be 
studying  the  association  of  stimulus  and  response.    This  would 
remain  true  as  long  as  it  was  the  feeding  and  not  the  animal's 
reactions  that  were  delayed.     On  the  other  hand,  if  both  the 
feeding  and  the  reactions  were  delayed  after  the  stimulus  had 
been  given,  then  if  there  were  such  states  as  ideas  one  would 
expect  them  to  function  here.     Furthermore  the  need  for  ideas 
would  increase  with  the  number  of  different  stimuH  and  reactions. 
Just   a  word   now   concerning   Thorndike's   formula  for  the 
study  of  imagery.     The  fact  that  he  himself  was  unable  to 
carry  out  experiments  in  conformity  with  it,   and  that  none 
have  been  carried  out  since  his  attempt,  does  not  speak  very 
well  for  the  formula.     I  must    confess  my  own  failure  as  yet  to. 
perfect  a  technique  by  which  the  formula  might  be  applied  to 
animals.     In  order  to  associate  A  and  B,  it  will  be  necessary 
that  they  be  followed  by  a  reaction  x.    A,  B  and  x  are  now  asso- 
ciated.   B  and  C  may  now  be  linked  together  through  a  second 
reaction  y.    Even  granting  the  ideational  character  of  reactions 
carried  out  according  to  the  formula,  one  would  have  to  know 
the  following  facts  concerning  the  above  test:     (i)   Did  the 
animal  discriminate  between  A  and  B,  between  B  and  C,  and 
between  A  and  C  ?    If  the  first  and  second  discriminations  were 
not  made,  A  and  B  or  C  would  have  been  directly  associated 
through  X  or  y.     If  A  and  C  were  not  discriminated,  the  asso- 
ciation B-C  would  have  been  useless.     Difficulties  such  as  these 
lead  me  to  believe  that  the  goal  aimed  at  is  unattainable.     In 
fact,  Thomdike  states  that  the  formula  is  valid  only  when  B 
arouses  no  impulse  to  activity;   this  is  the  essential  weakness 
of  the  formula,  for  one  can  never  be  certain  of  the  absence  of 
these  intervening  mediating  motor  tendencies.     In  fact  their 
presence  is  extremely  probable.     It  cannot  be  too  often  reiter- 
ated that  structural  psychology  has  no  place  in  the  study  of 
animal  behavior.     One  must  speak  in  terms  of  function.  ■  It  is 
impossible  to  tell  whether  an  image  is  present  or  not.     The 
most  that  one  can  ever  say  is  that  some  process  other  than 
overt  motor  activity  is  present  which  functions  as  an  image 
might  in  human  consciousness.     This  amounts  to  an  accept- 
ance of  Hobhouse's  statement  (although  I  do  not  feel  that  he 
always  limits  himself  to  this)  that  the  ideas  we  deal  with  are 


14  WALTER  S.  HUNTER 

"practical  ideas,"  understanding  by  this  a  function  which  does 
for  animals  that  which  practical  ideas  do  for  human  behavior." 

7.     Learning  BY  Being  "Put  Through" 

Perhaps  the  most  important  and  best  known  piece  of  work 
on  the  presence  of  imagery  in  animals  is  that  by  Cole  on  the 
Intelligence  of  Raccoons.  Let  us  consider  the  evidence  which 
Cole  presents.  The  argument  derived  from  an  animal's  learning 
a  problem  by  being  "put  through"  may  be  analyzed  first.  Cole 
writes  in  particular  reference  to  Thorndike,  saying  "It  would 
seem  that  nine-tenths  of  the  experimental  evidence  for  the 
absence  of  ideas  in  dogs  and  cats  comes  from  their  inability  to 
learn  from  being  put  through."^*  Again,  "If  inability  thus  to 
learn  is  evidence  against  the  presence  of  ideas,  then  ability  to 
do  so  should  be  equally  strong  evidence  for  it."^*  In  an  earlier 
paper,  2'  I  have  discussed  some  aspects  of  this  problem  in  the 
light  of  experiments  carried  out  upon  the  white  rat.  This  phase 
of  the  question  need  not  be  gone  into  more  fully  here.  Whether 
or  not  it  seems  probable,  from  a  speculative  point  of  view,  that 
an  animal  must  use  "free  impulses"  or  images  in  order  to  learn 
from  being  "put  through,"  we  need  not  consider.  My  conten- 
tion in  the  paper  mentioned  is  that  the  data  so  far  at  hand 
do  not  warrant  conclusions  as  to  the  presence  of  imagery. 
Furthermore  I  indicated  that  the  behavior  could  be  explained 
better  in  other  terms.  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  con- 
cerned. Some  raccoons  at  least  appear  to  learn  by  being  "put 
through."  Whether  all  raccoons  would  do  so  is,  of  course, 
quite  another  matter.  But  given  the  fact,  it  does  not  follow 
that  one  must  necessarily  interpret  it  as  an  evidence  of  the 
presence  of  images.  Cole  seems  to  have  carried  over  this  inter- 
pretation rather  uncritically  from  Thorndike.  The  entire  pro- 
cess can  be  adequately  stated  in  sensational  terms.     Certain 

"  Hobhouse,  L.  T.  Mind  in  Evolution.  New  York,  1901,  p.  283.  That  Hob- 
house  does  not  limit  himself  strictly  to  this  may  be  seen  by  reading  the  first  few 
sentences  on  p.  284. 

'*  Cole,  L.  W.  Concerning  the  Intelligence  of  Raccoons.  Jour,  of  Comp.  New. 
and  Psych.,  vol.  17,  1907,  p.  249. 

"  Hunter,  W.  S.  A  Note  on  the  Behavior  of  the  White  Rat.  Jour,  of  Animal 
Behavior,  vol.  2,  1912. 


DELAYED  REACTION  15 

stimuli,  X,  y,  and  z,  e.g.,  are  made  prominent  by  directing  the 
animal's  attention  to  them.  These  stimuli  occur  in  connection 
with  one  another  and  with  certain  movements,  kinaesthetically 
reported,  and  are  followed  by  the  acquisition  of  food.  What 
could  be  more  natural,  then,  than  that  the  cognizance  of  the 
stimuli  should  set  off  the  associated  movements?  The  behavior 
noted  by  Cole  bears  out  this  contention.  All  four  raccoons, 
both  the  pair  put  through  and  the  pair  not  put  through,  solved 
the  problem  of  escaping  from  the  box  (No.  4)  by  working  the 
fastenings  at  one  trial  in  one  manner  and  at  another  in  another 
fashion.^"  This  need  mean  no  more  than  that  several  responses, 
as  opposed  to  a  fixed  series,  might  follow  upon  certain  stimuli. 
This  would  be  a  higher  type  of  behavior,  to  be  sure,  than  where 
only  one  response  was  given,  but  it  would  not  therefore  involve 
a  new  type  of  conscious  process.  "If  the  act  which  he  (the 
raccoon)  is  put  through  is  the  one  which  will  remain  the  easiest 
and  the  most  convenient  for  him  throughout  the  tests,  irre- 
spective of  his  position  in  the  box,  he  will  never  vary  from  it. 
If  not,  he  will  employ  your  act  when  his  position  makes  it  con- 
venient and  he  is  looking  at  the  latch  you  began  with.""  We 
are  not  told  whether  the  raccoon  learned  which  was  the  easiest 
way  by  trial  and  error  or  not.  But  it  is  to  be  inferred  from 
the  behavior  of  raccoon  No.  2  that  such  was  the  case."  The 
behavior  thus  described  is  interesting,  but  entirely  inadequate 
as  far  as  the  presence  of  imagery  is  concerned.  It  may  well 
be  that  "animals  which,  so  far  as  we  know  at  present,  are 
utterly  unable  to  learn  save  by  innervating  their  own  muscles ' ' 
are  devoid  of  ideas,  without  its  following  that  if  this  type  of 
learning  is  present,  the  animal  possesses  imagery.  Hence  assum- 
ing the  facts  that  Thorndike  and  Cole  present  to  be  unquestion- 
able, it  need  only  follow  that  the  raccoon  exhibits  more  com- 
plex 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. 

Cole  adduces  further  evidence  for  the  presence  of  imagery." 
These  may  be- listed  as  he  himself  presented  them:  (a)  Recog- 
nition of  objects;    (b)  forgetting;    (c)  variability;    (d)  associa- 

3"  Op.  cit.,  p.  243. 
"  Op.  cit.,  pp.  245-6. 
S2  Op.  cit.,  p.  246. 
»3  Op.  cit.,  p.  251,  S. 


16  WALTER  S.  HUNTER 

tion  by  similarity;  (e)  reluctance  and  expectancy;  (f)  var5ring 
means  to  the  same  end,  and  (g)  reactions  to  colors  presented 
in  a  temporal  series,  (c  was  treated  under  7,  above.)  Most 
of  these  arguments  can  be  dismissed  summarily.  It  should 
never  be  forgotten  that  although  almost  any  type  of  behavior 
may  involve  imagery,  the  comparative  psychologist  is  seeking 
for  behavior  whose  explanation  requires  the  assumption  of  such 
a  function,  even  under  the  law  of  parsimony.  Is  the  determin- 
ing sensory  stimulus  present  or  absent  at  the  moment  of  re- 
sponse? If  it  is  present,  why  should  the  animal  use  a  represen- 
tative factor?  These  are  the  questions  that  every  investigation 
as  to  the  presence  of  images  in  animal  consciousness  must  face. 

8.     Recognition 

It  seems  to  me  extremely  obvious  that  the  fact  of  the  recog- 
nition of  a  food  bottle  need  not  be  interpreted  as  presupposing 
imagery.  In  fact  it  is  hard  to  understand  how  imagery  would 
function  in  such  a  situation!  Recognition  of  this  type  does  not 
necessarily  imply  memory  or  the  dating  of  an  experience  in 
one's  past.  On  this  basis  all  animals  must  be  granted  the  pos- 
session of  images. 

9.     Rate  of  Forgetting 

The  fact  that  some  of  the  raccoons  forgot  the  solution  of 
the  boxes  after  an  interval  of  three  days  does  indeed  indicate, 
as  Cole  claims,  that  automatisms  had  not  been  set  up.  But 
one  must  not  infer  therefore  that  images  were  involved.  There 
is  no  factual  support  for  the  assumption  that  imaginal  forgetting 
is  more  rapid  than  sensory.  The  same  is  true  of  the  variable 
nature  of  the  raccoons'  behavior  discussed  above.  This  very 
probably  indicates  a  high  order  of  adjustive  ability  on  ,  the 
sensori-motor  level,  but  not  necessarily  an  "imaginative"  ad- 
justment. Mere  variability  of  response  is  present  in  all  animals. 
Do  all  animals,  then,  possess  images? 

10.     Association  by  Similarity 
"Association  by  similarity,"  or  the  fact  that  a  raccoon  will 
attack  a  certain  fastening  even  after  its  location  in  the  box 
has  been  changed,  when  contrasted  with  the  activity  of  cats^* 

^'  Cole,  L.  W.     Op.  cit.,  p.  253. 


DELAYED  REACTION  '  17 

and  rats"  that  attack  the  old  position  rather  than  the  old  fasten- 
ing, proves  for  raccoons  only  the  superior  importance  of  "ob- 
jects,"— or  the  form,  size  and  quality  aspects  of  the  stimulus,— 
over  kinaesthetic  space  controls,  i.e.,  the  position  aspects  of  the 
stimulus.  In  addition,  it  should  be  noted  that  Davis  in  his 
study  of  raccoons^"  obtained  data  of  the  opposite  nature.  His 
animals  would  claw  at  the  spot  where  the  fastening  had  been. 
But  aside  from  all  this,  I  see  no  reason  why  "association  by 
similarity"  should  not  be  purely  perceptual  and  hence  be  simply 
a  type  of  recognition.  As  a  matter  of  fact,  all  animals  have 
responses  (instinctive  reactions  for  example)  that  are  applied 
to  classes  of  objects.  Someone  also  has  well  said  that  animals, 
in  cases  like  the  present  ones,  simply  fail  to  see  the  difference 
between  two  objects  and  hence  react  as  though  the  two  were 
the  same. 

11.  Reluct ANCY  and  Expectancy 
Is  the  "reluctancy"  or  the  "expectancy"  which  appears  to 
be  manifested  in  an  animal's  behavior  toward  a  difficult  and  an 
easy  box  respectively  to  be  taken  as  evidence  of  the  presence 
of  imagery?  Cole,  e.g.,  says  "no  one  who  saw  the  animals 
resist  being  put  into  a  box  failed  to  credit  them  with  a  rather 
distinct  memory  of  the  difficulty  of  escape. "^^^  By  "distinct 
memory"  Cole  undoubtedly  means  an  imaginal  process.  But 
do  the  facts  prove  this?  Is  the  case  not  perfectly  amenable  to 
a  "stimulus  and  response"  explanation?  The  raccoon  has  asso- 
ciated a  certain  box  with  a  certain  displeasure  until  the  presen- 
tation of  the  box  arouses  immediately  the  negative  reaction* 
The  raccoon  may  have  had  images  of  his  previous  experiences, 
but  the  facts  do  not  prove  it.  One  does  not  need  images  to 
explain  this  behavior  any  more  than  to  explain  a  child's  refusal 
to  take  a  second  dose  of  bitter  medicine. 

12.     Varying  Means  to  the  Same  End 

The   data   presented   by   Cole   under   the   heading    "varying 

means  to  the  same  end"  are  just  as  inconclusive  as  that  pre- 

.  sented  above,   although  they  are  more  suggestive.     We  have 

'  here  the  activity  of  four  raccoons  directed  toward  entering  a 

35  Richardson,  Florence.  A  Study  of  the  Sensory  Control  in  the  Rat.  Psych. 
Rev.  Mon.  Supp.,  yo\.  12,  1909,  p.  38,  e.g.       .      .    .      ,  ^  ,  „.  .  , 

3«  Davis,  h!  B.  The  Raccoon:  a  Study  in  Animal  Intelligence.  Amer.  Jour. 
Psych.,  vol.  18,  1907,  p.  470. 

38^  Op.  cit.,  p.  253. 


18  WALTER  S.  HUNTER 

box  containing  an  apple.  The  raccoons  were  accustomed  to 
reaching  through  a  hole  in  the  top  of  the  box  in  order  to  pro- 
cure the  fruit.  When  a  block  with  a  steeple  in  it  was  placed 
in  the  hole,  one  raccoon  immediately  clawed  out  the  block  and 
ate  the  apple.  "  She  seemed  to  work  as  if  actuated  by  a  thought 
of  the  apple  in  the  box.  It  was  not  done  by  random  clawing, 
nor  could  she  smell  or  otherwise  perceive  the  piece  of  the  apple 
in  the  box.""  We  are  not  informed  why  the  animal  could  not 
smell  the  apple.  The  fact  that  the  fruit  odor  was  in  the  room 
will  not  suffice.  But  even  assuming  this  to  have  been  con- 
trolled, we  need  not  attribute  an  image  of  the  apple  to  the 
animal.  Habit  got  the  raccoon  to  the  hole  and  started  her  paw, 
and  the  contact  (?)  of  the  staple  initiated  the  claw  reflex.  This 
plus  the  pleasurable  results  associated  with  the  box  are  suffi- 
cient to  explain  the  activity.  In  a  slightly  different  experi- 
ment, the  animals  crawled  through  a  hole  in  the  top  of  the 
box  in  order  to  procure  the  apple.  I  now  quote  Cole:  "The 
box  had  no  bottom  and  instead  of  resting  directly  on  the 
floor  it  rested  on  a  row  of  bricks.  Removing  one  of  these  made 
an  opening  under  the  lower  edge  of  the  box  through  which  the 
raccoon  might  crawl.  The  opening  in  the  top  was  now  closed 
and  nailed  fast.  No.  i  was  freed,  went  to  the  top  of  the  box 
and  tried  to  claw  out  the  block.  He  then  walked  about  the 
room,  then  tried  the  block  again.  He  then  went  to  the  opening 
made  by  removing  the  brick,  stopped  a  moment,  then  crawled 
in.""  To  argue  that  this  means  image  of  apple  is  certainly 
naive,  at  least.  Could  the  raccoon  not  sense  the  apple  when 
its  nose  was  within  a  foot  (see  description  of  box  i8,  op.  cit., 
p.  215)  of  it?  Again  where  the  animal  climbed  up  and  over  a 
roll  of  poultry  wire  in  order  to  descend  into  the  box,  the  possi- 
bility of  the  presence  of  imagery  is  only  suggested,  not  proved. 
The  opening  into  the  box,  as  well  as  the  odor  of  the  food,  was 
there  impelling  the  raccoon  to  approach.  What  more  natural, 
then,  than  that  the  animals  should  climb  the  wire  and  thus 
reach  the  food.  Such  behavior  is  what  would  be  expected  of 
raccoons  that  lived  in  a  wire  cage.  The  case  of  raccoon  No.  4 
is  somewhat  different.  With  the  box  which  possessed  two 
openings,  he  went  directly  into  the  lower  of  the  two  at  the 

"  Op.  cit.,  pp.  254-5. 
"  Op.  cit.,  p.  255. 


DELAYED  REACTION  19 

first  trial.    What  influence  his  starting  point  in  approaching  the 
box  had  upon  his  success,  we  are  not  told. 

Logically,  the  position  taken  by  Cole  in  his  illustrations 
would  require  him  to  argue  that  ideas  are  present  wherever 
"motor  excess "  in  learning  occurs.  There  a  sensorially  reported 
situation  calls  out  in  succession  the  animal's  repertoire  of  in- 
stinctive and  habitual  acts.  This  is  a  variation  of  means  toward 
the  attainment  of  an  end,  and  is  on  a  par  with  the  "variability 
of  response"  argument  discussed  above. 

13.  Reactions  to  a  Temporal  Series  of  Colors 
It  is  only  fair  to  Cole  to  note  that  his  main  emphasis  does 
not  rest  upon  the  above  data,  but  upon  a  series  of  tests  that 
he  made  with  colors  presented  in  a  temporal  series.  Three 
colors,  white,  blue  and  red,  were  placed  upon  three  levers  which 
in  turn  were  secured  by  a  single  pivot  on  the  back  side  of  a 
board  one  foot  high.  When  the  colors  were  presented  in  the 
order  W,  B,  R,  the  animal  was  to  secure  food  by  climbing  upon 
a  box.  When  R,  R,  R  was  given,  no  feaction  should  be  made. 
Now  since  the  terminal  stimulus  was  identical  in  each  case, 
Cole  argues,  the  only  means  by  which  the  animals  could  react 
discriminatingly  is  by  remembering  what  colors  of  the  series 
had  preceded.  The  fact  that  the  raccoons  clawed  up  the  cards 
from  behind  the  screen,  reacting  only  when  the  proper  one 
appeared,  was  also  used  as  evidence  of  images.  Believing  that 
these  tests  were  almost  absolutely  uncontrolled  and  that  the 
interpretations  were  invalid  as  far  as  the  data  presented  were 
concerned,  I  set  two  graduate  students,  F.  M.  Gregg  and  C.  A. 
McPheeters  at  work  upon  this  problem.  Their  purpose  was: 
(i)  to  duplicate  as  nearly  as  possible  Cole's  results  under  ade- 
quately controlled  conditions,  and  (2)  having  set  up  the  dis- 
crimination, to  determine  and  not  to  assume  its  basis.  Their 
results  will  soon  appear  in  the  Journal  of  Animal  Behavior  under 
the  title  Some  Reactions  of  Raccoons  to  a  Temporal  Series  of 
Stimuli.  I  shall  only  note  here  that  they  found;  (i)  that  dis- 
crimination was  not  based  upon  the  cards — ^in  fact  the  discrim- 
ination was  not  even  visual,  and  (2)  that  practically  the  entire 
discrimination  was  made  on  the  basis  of  the  first  lever  and  not 
on  the  basis  of  all  levers  as  Cole  assumed.  (Since  all  levers 
were  influential,   in  Cole's  opinion,   it   had  been  necessary  to 


20  WALTER  S.  HUNTER 

assume  that  the  first  two  were  represented  imaginally  when  the 
last  was  presented.) 

The  criticisms  on  Cole's  entire  work  as  outlined  above  reduce 
to  these:  (i)  The  facts  are  either  inconclusive  or  irrelevant. 
And  (2),  there  is  no  evidence  of  adequate  controls.  On  the 
positive  side,  the  work  suggests  that  the  raccoon  is  more  in- 
telligent than  the  dog  and  cat,  but  it  does  not  determine  wherein 
this  superiority  lies. 

14.    Washbuhn's  Cat  on  the  Stairway 

There  is  one  other  t5^e  of  behavior  that  deserves  mention. 
Again,  it  was  not  and  need  not  be  interpreted  as  necessarily 
involving  the  presence  of  imagery.  The  illustration  follows: 
"A  cat,  indeed,  once  observed  by  the  writer,  did  behave  as  a 
human  being  would  do  to  whom  any  idea  had  occurred,  when, 
on  coming  into  the  house  for  the  first  time  after  she  had  moved 
her  kittens  from  an  upper  story  to  the  ground  floor,  she  started 
upstairs  to  the  old  nest,  stopped  halfway  up,  turned  and  ran 
down  to  the  new  one.  But  errors  of  interpretation  are  possible 
at  every  turn  of  such  observations."^' 

This  is  an  excellent  illustration  of  the  type  of  argument  that 
would  use  "hesitation"  and  "wavering"  as  an  evidence  for 
the  presence  of  ideas.  It  is  a  mode  of  behavior  that  is  found 
almost  everywhere  in  animal  studies.  A  rat,  e.g.,  hesitates  at 
a  division  point  of  the  maze  and  finally  selects  the  right  path- 
way, or  it  runs  half  the  length  of  a  blind  alley  and  then  turns 
back.  Was  it  guided  by  an  ideational  representation  of  the 
movements  to  be  made  and  their  consequences?  Not  neces- 
sarily. Accidental  stimuli  may  have  initiated  the  new  reaction 
and  any  conflict  present  may  have  been  resolved  on  a  purely 
sensory-motor  level.  The  experimental  technique  for  the  con- 
trol of  such  reactions  will  be  discussed  below  (see  p.  74). 

There  is  very  little  that  needs  to  be  said  in  the  way  of  a  sum- 
mary of  this  historical  review.  All  of  the  arguments  for  the 
presence  of  imagery  in  animals  that  we  have  examined  have 
been  found  inconclusive.  It  is  not  that  the  various  types  of 
behavior  may  not  have  involved  a  representative  factor.  The 
point  is  that  this  possibility  is  nowhere  proved  necessary.  The 
fault  does  not  lie  in  the  exhaustiveness  of  the  data.    The  vavi- 

3»  Washburn,  M.  F.    The  Animal  Mind.    New  York,  1909,  p.  272. 


*  DELAYED  REACTION  21 

ous  methods  have  been  made  to  yield  ample  returns  for  this 
purpose.  The  crux  of  the  matter  is  that  the  methods  them- 
selves are  inadequate  for  the  solution  of  the  problem.  Let 
me  re-emphasize  the  fact  that  if  comparative  psychology  is  to 
postulate  a  representative  factor,  it  is  necessary  that  the  stim- 
ulus represented  be  absent  at  the  moment  of  response.  If  it 
is  not  absent,  the  reaction  may  be  stated  in  sensori-motor 
terms.  But  in  order  to  know  that  the  stimulus  is  absent,  it 
is  first  necessary  to  determine  carefully  what  the  stimulus  is. 
None  of  the  methods  reviewed,  I  believe,  meet  these  require- 
ments. Whether  the  tests  presented  in  this  monograph  do  or 
not,  the  reader  himself  may  judge. 

III.     NOTES  ON  THE  ANIMALS  AND  CHILDREN  TESTED 

Four  classes  of  re -agents  were  used  in  the  experiments  whose 
description  is  to  follow:  white  rats,  dogs,  raccoons  (Procyon 
lotor)  and  children.     A  few  words  descriptive  of  these  subjects 

will  not  be  amiss. 

1.  Rats 

Twenty-two  rats  were  used  during  the  entire  course  of  the 
experiments.  Five  of  these  were  normal  adults  and  were  used 
only  in  preliminary  tests  in  which  the  purpose  was  the  perfec- 
tion of  a  method.  The  remaining  seventeen  (normal)  were  all 
started  in  the  experiments  when  approximately  four  weeks  old. 
All  were  vigorous,  healthy  animals  whose  records  may  stand 
as  typical. 

2.  Dogs 

The  two  dogs  tested  were  mongrels  in  whom  the  rat  terrier 
strain  was  dominant.  They  were  very  bright  and  intelligent 
looking,  very  active,  playful  and  affectionate, — indeed  they 
seemed  to  possess  all  the  qualities  that  are  attributed  to  intel- 
ligent dogs  in  countless  anecdotes.  This  was  the  unanimous 
testimony  of  many  observers.  The  two  dogs,  .Blackie  and 
Brownie,  both  females  of  the  same  litter,  were  secured  from 
an  animal  dealer  when  they  were  small  puppies  and  were  started 
on  the  preliminary  tests  at  about  the  age  of  five  months.  They 
were  usually  kept  in  a  kennel  out  of  doors  and  remained  in 
excellent  condition  during  the  experiments.  Of  the  two.  Brownie 
was  the  more  aggressive  and,  to  the  ordinary  observer,  appeared 
possibly  the  more  intelligent. 


22  WALTER  S.  HUNTER 

3.  Raccoons 

Four  raccoons,  two  males — Bob  and  Jack — and  two  females 
— Betty  and  Jill,  were  tested.  Bob  and  Betty  had  been  pets 
and  were  secured  from  their  owner  when  about  five  or  six  months 
old.  Jack  and  Jill  were  caught  in  the  woods  when  about  two 
and  a  half  months  old.  Preliminary  experiments  were  started 
almost  immediately  with  all  four.  The  raccoons  were  and 
remained  in  perfect  health  throughout  the  experiments.  The 
only  physical  defects  possessed  by  any  of  them  were  the  cata- 
racts which  developed  in  Bob's  eyes  about  a  month  after  his 
purchase.  Although  this  interfered  with  his  accurate  vision  of 
objects  and  resulted  in  his  colliding  frequently  with  them,  he 
was  able  to  distinguish  such  changes  in  brightness  as  were 
necessary  in  the  experiments.  This  fact  was  demonstrated 
conclusively  by  many  control  tests  which  will  be  described 
later.  Of  the  four,  Betty  was  the  quietest  and  most  timid. 
She  was  the  least  promising  subject  among  them.  Further 
facts  about  these  animals  are  given  in  the  appendix. 

4.  Children 

Five  children  were  used  in  the  course  of  the  present  tests: 
two  boys,  Hd  and  L,  and  three  girls,  F,  M,  and  H.  H,  Hd 
and  L  were  each  approximately  six  years  old.  M  was  about 
eight  years  old;  and  F,  about  two  and  a  half.  Hd  and  L  were 
in  kindergarten  work,  and  M  and  H  were  in  the  graded  schools. 
The  indications  were  that  they  were  children  both  of  normal 
ability  and  of  normal  intellectual  advancement  for  their  ages. 
F  was  a  bright  little  girl  and  made  an  excellent  subject.  All 
of  the  children  were  more  or  less  timid  at  first;  but  this  was 
overcome,  in  all  save  possibly  H's  case,  before  tests  were  begun. 
Particular  pains  were  taken  with  F.  The  experimenter  was  in 
her  company  a  great  deal,  and  by  the  beginning  of  the  tests 
was  a  gladly,  accepted  play-fellow. 

IV.     APPARATUS  AND  GENERAL  METHOD 

The  plan  of  box  A  is  presented  in  Fig.  i.  (This  box  was  used 
for  the  raccoons.)  The  box  is  made  of  I"  boards  and  is  2^  high 
with  doors  yl"  wide  and  13"  high.  The  light  stimulus  came 
from  3  c.p.  8  volt  miniature  carbon  lamps,  so  wired  that  they 
might  be  switched  on  one  at  a  time.     The  current  was  obtained 


DELAYED  REACTION 


23 


from  a  220  volt  lighting  circuit  and  was  passed  through  a  lamp 
rheostat  before  reaching  the  discrimination  box.  The  release 
box  R  was  raised  by  means  of  a  cord  passed  over  a  pulley  in 
the  ceiling  and  back  to  the  experimenter  at  E.  The  first  release 
box  had  glass  over  the  top  and  sides.  The  right  and  left  faces 
of  the  box  were  i2"xi5y'.  The  front  was  y^'xisi".  With 
this  release  box  the  distances  to  the  entrances  of  the  three  light 
boxes.  (L)  were  unequal.  Those  at  the  sides  were  each  19I",  while 
the  distance  straight  in  front  was  20^'.    These  various  inequal- 


FiGURE  1.     Ground  plan  of  Box  A 

ities  were  due  to  two  causes:  (i)  The  box  had  been  planned 
originally  for  a  different  type  of  test  and  was  only  later  arranged 
for  the  present  experiment.  (2)  The  release  box,  being  covered 
with  glass  would  have  been  too  heavy  to  handle  had  it  been 
made  larger.  During  the  course  of  the  experiments,  another 
release  was  made.  This  one  was  covered  with  wire  of  Y  mesh. 
Its  sides  were  m^'xisV;  and  its  front  was  Qi^xisi".  The 
distances  to  the  light  boxes  were  now  equal  and  of  the  dimen- 
sions indicated  in  Fig.   i. 

Sliding  doors  were  placed  at  the  points  marked   D  in  the 
figure.     They  were  controlled  by  strings  which  ran  from  them, 


24 


WALTER  S.  HUNTER 


through  screw-eyes  on  the  top  of  the  box,  to  the  experimenter 
at  E. 

A  1 6  c.p.  Hght  was  suspended  about  four  feet  from  the  floor 
over  the  center  of  the  apparatus.  Its  intensity  was  diminished 
approximately  by  two -thirds  by  wrapping  the  bulb  in  cloth. 
The  three  light  boxes  were  covered  in  order  to  prevent  light 
from  entering  them  from  above.  Part  of  the  entrance  box 
leading  to  the  release,  R,  was  covered  by  the  switch-board,  S, 
and  the  remainder  by  paste  board.  This  prevented  the  animals 
from  watching  the  experimenter. 


Figure  2.     Ground  plan  of  Box  C.     D,  exit  door. 


Box  B  was,  in  principle,  like  Box  A.  It  was  used  in  testing 
the  dogs.  Its  dimensions  differed  from  those  of  A.  Instead 
of  being  90  degrees,  the  extreme  lateral  angles  were  75  degrees. 
The  angles  on  each  side  of  the  middle  light  box  were  about 
145  degrees  as  opposed  to  127  for  Box  A.  Box  B  was  only 
2'  high,  and  the  length  of  its  entrance  box  was  \'  4".  The  re- 
lease box  was  covered  with  wire,  and  each  face  was  I'xio". 
The  distances  from  the  release  boxes  to  the  light  boxes  were 
each  \\' . 

Fig.  2  is  a  ground  plan  of  Box  C.  This  box  was  used  for 
rats.  In  addition  to  the  data  there  given,  the  following  points 
should  be  noted:    The  release  box,  R,  was  fastened  by  hinges 


DELAYED  REACTION  25 

SO  that  when  it  was  raised  the  three  faces  cleared  the  floor  prac- 
tically the  same  distance.  The  faces  and  the  front  half  of  the 
top  of  R  are  covered  with  glass ;  the  rest  is  of  wood.  The  doors 
leading  into  the  light  boxes  are  4"  x  3".  Those  leading  out  of 
the  light  boxes,  called  exit  doors  here,  are  3"  x  2  V.  The  switches 
at  S'  are  for  the  lights  which  are  of  the  same  intensity  and 
wiring  arrangement  as  those  in  the  two  preceding  boxes.  The 
switches  at  S  turn  the  current  into  any  or  all  cf  the  paths  from 
the  release  box  to  the  light  boxes.  This  current  is  obtained 
from  a  dry  cell  and  is  passed  through  the  primary  coil  of  a  Porter 
inductorium.    The  strength  of  the  current  passing  into  the  prob- 


FiGURE  3.     Box  C 

lem  box  was  regulated  so  that  the  animals  never  became  fright- 
ened by  severe  shocks.  The  current  was  never  strong  enough 
to  cause  the  animals  to  squeak  and  only  rarely  did  they  attempt 
to  jump  over  the  strips.  The  brass  strips  from  which  the  shocks 
were  obtained  (only  one  group,  marked  B,  is  shown  in  this 
figure),  were  very  thin  and  lay  flat  on  the  floor  of  the  box. 
Before  being  tacked  down,  they  were  given  an  acid  bath  which 
destroyed  their  lustre  but  left  their  conductivity  practically 
unaffected  for  my  puipose. 

Fig.  3  should  give  a  clear  presentation  of  the  essentials  of 
this  box  as  well  as  of  the  others  used  in  the  course  of  this 
research. 


26 


WALTER  S.  HUNTER 


Box  D,  also  used  for  rats,  is  similar  to  Box  C  in  all  save  two 
respects:  (i)  It  was  not  wired  for  punishment.  (2)  The  doors 
leading  from  the  light  boxes  could  be  closed  with  wooden  slides. 
The  use  of  these  slides  was  discontinued  shortly  after  the  ex- 
periments began.  Pieces  of  wire  mesh  were  then  used.  These 
admitted  the  light  and  thus  offered  less  opportunity  for  the 
animals  to  tell  which  box  was  open  and  which  was  closed. 

The  apparatus  (Fig.  4)  which  was  used  with  children  was 
constructed  on  the  same  principle  as  that  described  above  for 
the  other  problem  boxes.     Three  boards,  each  one  foot  square. 


L 


=!=■ 


Figure  4.     Ground  plan  of  apparatus  used  with  children.     D,  door;    W,  window 

were  placed  against  the  wall  of  a  room  12'  x  14'.  The  middle 
square  was  seven  feet  distant  from  the  release  box,  R.  On 
each  of  these  boards  was  mounted:  (i)  A  4  c.p.  miniature 
electric  light,  L;  and  (2)  just  below  the  light,  a  push  button. 
All  three  boards  were  painted  black  and  were  exact  duplicates 
the  one  of  the  other.  The  front.  A,  of  the  release  box  was  a 
lever  which  could  be  raised  by  a  handle  at  P.  The  experimenter 
usually  sat  at  E.  T  is  a  table  which  held:  (i)  The  candy  used 
as  a  reward  in  the  tests;  (2)  the  switches  regulating  the  lights 
and  the  buzzer;  and  (3)  the  buzzer.  C  is  a  curtain  which  hid 
the  experimenter  from  the  subject's  view^  w^hen  the  latter  had 


DELAYED  REACTION  27 

left  the  release  box.  At  first  this  curtain  was  also  continued 
between  R  and  T.  Subsequently,  this  was  found  to  be  both 
inconvenient  and  unnecessary  and  its  use  was  discontinued. 
The  apparatus  was  wired  so  that  any  light  could  be  turned  on 
at  will  and  so  that  any  push  button  could  be  connected  with 
the  buzzer.  Moving  the  switches  was  done  without  the  sub- 
ject's knowledge.  The  light  was  always  turned  on  over  the 
button  that  rang  the  buzzer.  The  child's  problem  was  to  find 
this  button  at  the  first  trial  when  the  light  was  on  (in  the 
learning  series)  and  then  (in  the  delayed  reactions)  after  the 
light  had  been  turned  off  for  a  certain  interval  of  time. 

The  general  method  of  experimentation  was  as  follows:  The 
animal  to  be  tested  was  put  in  the  release  box,  R,  of  problem 
Box  C,  for  example.  If,  now,  the  lighted  box  is  the  one  on  the 
left,  the  exit  doors  of  the  others  are  closed  and  the  switches  at 
S  are  so  set  that  if  the  experimenter  close  the  switch  at  S",  the 
animal  will  receive  a  shock  if  it  steps  on  either  the  strips  leading 
to  the  box  on  the  right  or  on  those  leading  to  the  one  in  front. 
The  light  is  then  turned  on  in  the  left  box.  The  animal  is  re- 
leased after  five  seconds,  the  time  being  taken  with  a  metro- 
nome. A  careful,  detailed  record  is  kept  of  the  direction  in 
which  the  animal  is  oriented*"  when  released  and  of  just  where 
it  goes  after  being  released.  In  the  case  of  the  animals  used  in 
Boxes  A,  B  and  C,  they  should  go  straight  to  the  lighted  box, 
out  through  the  exit  doors  and  back  to  the  entrance  of  the 
release  box  where  they  are  fed.  The  rats  used  in  Box  D  were 
fed  a  small- morsel  of  bread  and  milk  at  the  exit  doors  of  the 
lighted  boxes.  Theoretically  the  olfactory  control  was  not  so 
good  here  as  where  no  food  at  all  was  given  in  the  light  boxes. 
Practically,  there  was  no  difference.  The  rat  was  given  only 
a  bite,  so  almost  no  food  fell  on  the  floor;  all  the  boxes  were 
used  an  equal  number  of  times ;  and  all  were  frequently  washed 
out.  Whatever  odor  was  present  was  so  distributed  as  to  afford 
no  appreciable  basis  for  discrimination.  The  results  obtained 
with  these  rats,  when  compared  with  those  where  the  olfactory 
control   was   better,    support   this   statement.      In   any   event, 

*"  Orientations  are  spoken  of  as  right  and  wrong,  irrespective  of  whether  an 
animal  may  be  said  to  depend  on  them  as  cues  or  not.  When  the  orientation  is 
"right,"  the  animal  is  headed  toward  the  proper  box.  Any  other  orientation  is 
"wrong." 


28  WALTER  S.  HUNTER 

olfactory  inequalities  would  persist  after  the  light  was  turned 
out  and  would  aid  in  delayed  reactions  only  if  associated  with 
the  light.  More  attention  will  be  given  to  this  possibiHty  later 
in  the  discussion. 

After  the  animal  had  been  trained  until  it  chose  the  lighted 
box  almost  perfectly,  delays  were  begun.  The  light  was  turned 
off  just  as  the  animal  reached  the  box.  This  was  called  the 
first  stage  of  delay.  At  the  second  stage,  the  light  was  turned 
out  when  the  animal  was  half  way  to  the  box.  At  the  third 
stage,  the  light  was  turned  out  just  as  the  experimenter  started 
to  raise  the  release  box.  Here  there  was  a  genuine  delay,  al- 
though a  small  one.  The  first  two  stages  served  primarily  to 
adapt  the  animal  emotionally  to  the  sudden  change  from  light 
to  darkness.  The  rats  and  dogs  usually  ran  so  fast  that  their 
momentum  was  sufficient  to  carry  them  into  the  box  when  once 
they  were  started  toward  it.  In  any  case  they  only  needed  to 
continue  in  the  direction  in  which  they  were  going.  This,  how- 
ever, was  not  the  case  with  the  third  stage.  The  light  was  put 
out  before  the  animal  started.  Throughout  these  three  stages, 
the  animal  was  released  promptly  at  the  end  of  five  seconds. 
From  this  stage  on,  where  the  animal  was  detained  one  or  more 
seconds  after  the  Hght  was  out  before  being  released,  it  was 
obviously  necessary  to  let  the  animal  see  the  light  before  this 
was  turned  off.  Occasionally,  the  interval  thus  required  was 
more  than  five  seconds.  In  these  higher  stages  of  delay,  I 
always  waited  until  I  felt  sure  that  the  animal  had  seen  the 
light,  and  then  turned  off  the  current  while  the  animal  was 
still  oriented  toward  the  source  cf  light.  Record  was  kept  of 
any  change  in  the  orientation  w^hich  an  animal  made  after  the 
light  was  turned  oft'.  How  detailed  these  records  were  will  be 
seen  in  the  section  on  experimental  results. 

The  delays  were  gradually  increased  in  length  until  one  was 
found  at  which  the  animal  failed.  They  were  then  decreased 
until  the  animal  was  again  making  a  high  percentage  of  correct 
choices,  when  the  intervals  were  again  increased.  An  animal 
was  thus  tested  twice  for  the  limit  of  its  abihty  to  delay  with 
the  backgrounds  surrounding  the  entrances  to  the  light  boxes 
all  similar  the  one  to  the  other.  When  this  Hmit  was  found, 
the  wall  of  the  box  about  the  entrance  to  c  was  covered  with 
white  cardboard;   that  about  b,  with  a  black;  and  that  about 


DELAYED  REACTION  29 

a,*'  with  a  medium  gray.  If  the  animal's  limit  of  delay  was 
no  better  or  was  worse  with  this  arrangement  than  before,  the 
animal  was  dropped  from  the  experiment.  If  the  limit  were 
better,  the  different  backgrounds  were  removed  and  the  sim- 
ilar ones  used  again.  The  limit  of  delay  with  these  was  then 
re-determined.  If  this  third  limit  were  greater  than  the  second, 
the  effect  of  training  could  be  evoked  as  an  explanation  of  the 
fact.  But  if  it  were  markedly  less  than  the  second,  the  only 
cause  could  be  an  association  between  the  backgrounds  and  the 
lights.  The  significance  of  this  type  of  association  will  be  dwelt 
upon  in  detail  later  in  this  paper. 

One  more  point  in  general  method  remains  to  be  considered. 
This  is  the  question  of  what  percentage  of  correct  choices  shall 
be  taken  as  sufficient  to  justify  further  increase  in  the  interval 
of  delay.  With  three  discrimination  boxes,  pure  chance  would 
lead  the  animal  to  make  33^%oi  correct  reactions  out  of  a  long 
series  of  presentations.  But  series  used  in  experimentation  are 
very  rarely  long  enough  for  chance  to  operate  as  theory  de- 
mands. Besides  there  are  various  other  influences  which  enter 
in  to  determine  an  animal's  behavior  above  and  beyond  the 
influence  of  the  stimulus  proper  to  the  test.  One  such  influence 
is  the  position  factor.  Try  as  I  might  to  eliminate  this,  most 
of  the  animals  acquired  at  various  times  during  the  experi- 
ments more  or  less  pronounced  preferences  for  certain  boxes. 
And  these  preferences  varied  from  animal  to  animal.  Some- 
times they  were  so  strong  that  the  regular  tests  had  to  be 
stopped  until  the  habit  could  be  broken  up.  In  the  light  of 
this,  although  on  the  whole  each  box  was  presented  to  an 
animal  an  equal  number  of  times,  in  any  one  stage  of  the  tests 
such  an  equahty  might  not  be  present.  Thus  an  equality  of 
percentages  among  the  various  animals,  in  this  case,  would  not 
mean  that  they  knew  the  problem  equally  well.  Again  hesi- 
tancies and  waverings  must  be  noted  in  estimating  how  well 
the  animal  is  grounded  in  his  appointed  task.  Further  state- 
ments concerning  the  value  to  be  attached  to  the  percentages 
appear  later  in  the  paper  (pp.  44,  46  and  at  intervals  thereafter.) 
Considerations  such  as  these  render  it  highly  inadvisable  to  lay 
down  a  rigid  standard  as  to  the  number  of  trials  and  the  per- 

*i  a,  b,  and  c  will  be  used  in  this  paper  to  designate  the  right,  middle  and  left 
light  boxes  respectively. 


30  WALTER  S.  HUNTER 

centage  of  correct  reactions  to  be  required  of  all  animals.  As 
will  be  seen  in  the  following  experiments  some  animals  were 
advanced  from  stage  to  stage  when  but  70%  of  correct  reactions 
were  made.  Others  were  detained  on  one  stage  until  85%  or 
95%  were  made.  Sometimes  an  animal  was  given  5  or  10  trials, 
sometimes  150  or  200  trials  on  one  stage  of  delay.  One  general 
fact,  however,  should  be  noted:  The  first  set  of  rats,  Bob  and 
Betty  during  their  first  year's  work,  and  H,  L,  M,  and  Hd  of  the 
children  were  rushed  from  stage  to  stage  as  fast  as  was  at  all 
feasible.  The  emphasis  here  lay  upon  what  the  subjects  could 
do  with  their  native  equipment.  With  the  other  subjects  used 
and  with  Bob  and  Betty  during  the  second  year's  work,  a  larger 
number  of  trials  were  given  on  each  stage  of  delay  and  the 
advance  in  the  length  of  the  periods  was  more  gradual.  The 
emphasis  here  was  placed  on  what  the  subjects  could  learn  to  do. 

V.     EXPERIMENTAL  RESULTS 
1.     Tests  with  Animals 

A.  Learning  the  Association,  (a)  Rats. — The  method  of  ex- 
perimentation used  by  Hough  and  Reed  was  retested  with  the 
result  that  the  general  method  outlined  above  was  adopted. 
These  tests  were  made  upon  five  normal  adult  rats,  Nos.  18-22. 

The  regular  experiments  may  be  divided  into  two  sets:  (A) 
Those  in  which  reward  only  was  employed;  and  (B)  those  in 
which  both  punishment  and  reward  were  used.  Nine  rats, 
Nos.  1-9  were  tested  in  the  first  set  and  eight,  Nos.  10-17,  i'^ 
the  second  set.  Of  the  rats  in  A,  Nos.  i,  3  and  8  were  in  poor 
health,  and  their  records  will  not  be  considered. 

Table  I  gives  the  number  of  trials  required  by  the  rats  of 

Set  A  to  learn  the  association  between  the  light  and  getting 

food.     These  rats  were  given   5   trials  daily.     All  save  No.   6 

learned  the  association.     Of  the  last  50  trials  given  this  animal, 

only  40%  were  successful;    while  of  the  entire  800,  54%  were 

correct. 

TABLE  I 


No. 

of  trials 

Rat 

on 

learning 

No.  2 

176 

No.  4 

175 

No.  5 

505 

No.  6 

800 

No.  7 

361 

No.  9 

280 

DELAYED  REACTION  31 

The  rats  of  Set  B  were  tested  as  follows:  Nos.  lo,  ii,  14  and 
17  were  given  5  trials  daily.  Nos.  12,  13,  15  and  16  received  10 
trials.  All  of  these  animals  learned  the  association.  The  num- 
ber of  trials  required  for  this  learning  is  given  in  Table  II.    The 

TABLE  II 
Five  trials  Ten  trials 

No.  of  trials  No.  of  trials 

Rat  on  learning  Rat  on  learning 

No.  10  165  No.  12  440 

No.  11  160  No.  13  250 

No.  14  200  No.  15  220 

No.  17  175  No.  16  480 

results  here  indicate:  (i)  That  the  use  of  5  trials  favors  rapid 
learning  more  than  does  the  use  of  10  trials,  and  (2)  that  rats 
tested  with  5  trials  daily  under  conditions  of  reward  and  pun- 
ishment will  learn  the  association  more  nearly  in  the  same 
length  of  time  than  will  rats  given  the  same  number  of  trials 
but  tested  with  reward  only.  The  use  of  punishment,  while  it 
may  not  shorten  the  length  of  time  required  by  an  "intelligent" 
rat  to  learn  an  association  does  hasten  the  learning  in  the  case 
of  the  "dullards"  such  as  Nos.  5,  6,  7  and  9.  Rats  will  put 
forth  a  maximum  effort  under  punishment  when  they  would 
not  do  so  under  other  conditions.  These  results  are  in  harmony 
with  the  work  of  Hoge  and  Stocking." 

That  the  influences  on  time  of  learning  exercised  by  the 
number  of  trials  and  by  punishment  are  not  due  to  prefer- 
ences for  the  light  or  for  the  dark  room  boxes  is  indicated  by 
Table  III  which  gives  the  number  of  times  each  rat  chose  the 

TABLE  III 

Rat No.  2  No.  4  No.  5  No.  6       No.  7       No.  9 

No.  of  choices  of  light  box .  .  23            21  13             18            23            38 

Rat No.  10  No.  11  No.  14  No.  17 

No.  of  choices  of  light  box .  .  20            28  28            32 

Rat No.  16  No.  15  No.  13  No.  12 

No.  of  choices  of  light  box .  .  24            30  21             27 

*2  Hoge,  M.  A.  and  Stocking,  R.  J.  A  Note  on  the  Relative  Value  of  Punish- 
ment and  Reward  as  Motives.     Jour,  of  Animal  Behavior,  1912,  vol.  2. 


32  WALTER  S.  HUNTER 

lighted  box  during  the  first  50  trials.  The  data  given  for  the 
rats  of  each  group  were  obtained  under  similar  conditions  (for 
our  present  purpose)  and  are  strictly  comparable.  The  only 
cases  of  marked  preferences  occur  with  rats  Nos.  5  and  9.  No. 
5's  preferences  for  the  dark  boxes  will  help  to  account  for  his 
slow  learning;  but  it  would  seem  that  No.  9  should  have  learned 
very  rapidly  owing  to  its  marked  preference  for  the  light  box. 
With  the  exception  of  these  two  rats,  all  the  animals  were  on 
an  essential  par  as  to  preferences.  Hence  the  differences  noted 
in  their  learning  periods  must  have  been  due  to  the  different 
conditions  under  which  they  worked.  Accidental  individual 
variations  are  not  the  causes  of  these  differences  because  of 
the  number  of  rats  used. 

(b)  Dogs. — The  two  dogs,  Blackie  and  Brownie,  were  given 
10  trials  daily  in  Box  B  under  conditions  of  reward  only.  The 
former  animal  was  given  560  trials  on  the  association.  Of 
these,  408  trials  or  72%  were  correct.  Brownie  was  given  650 
trials  on  learning  the  association.  Of  these,  396  trials  or  60% 
were  correct.  Ninety-five  per  cent  of  the  last  100  trials  were 
successful.  The  relatively  poor  showing  made  by  this  dog  was 
due  to  the  acquisition  of  habits  that  interfered  with  the  proper 
reaction.  Twice  during  the  learning  series,  extra  tests  had  to 
be  given  in  order  to  break  up  a  discrimination  now  against  the 
right  and  middle  boxes,  now  against  the  left  and  middle  boxes. 
In  general,  it  may  be  said  of  both  dogs  that  their  rate  of  learn- 
ing is  no  better  than  that  of  the  rats.  Indeed  it  is  much  worse 
than  any  of  the  rats  tested  w4th  reward  and  punishment  and 
10  trials  daily.  The  only  rat  that  learned  the  reaction  that 
did  not  do  much  better  than  the  dogs  was  No.  5.  I  would  sug- 
gest that  the  difference  is  due  to  the  dogs'  "helplessness"  when 
deprived  of  cues  from  the  experimenter.  The  following  para- 
graph elaborates  this  point. 

There  are  several  interesting  points  relative  to  the  dogs' 
behavior  in  the  learning  series  that  deserve  mention.  Indeed 
to  a  large  extent,  they  are  typical  of  their  behavior  throughout 
the  entire  experiment.  When  the  dogs  were  first  put  into  the 
problem  box,  instead  of  attempting  to  get  out,  they  merely  sat 
down  and  howled.  They  were  out  of  sight  of  the  experimenter, 
it  will  be  remembered,  and  when  placed  in  such  conditions 
seemed  quite  helpless.     They  gradually  overcame  this  timidity, 


DELAYED  REACTION  33 

helplessness  or  lonesomeness  but,  as  will  be  seen  in  the  delayed 
reaction  tests  to  be  described  below,  they  never  revealed  a 
high  order  of  resourcefulness.  We  shall  have  further  occasion 
to  see  that  their  behavior  was  almost,  if  not  entirely,  on  a  par 
with  that  of  the  rats.  In  learning  the  association,  e.g.,  the 
dogs  would  go  back  and  forth  between  some  two  boxes  for 
many  trials  before  investigating  the  third  box.  Often  they 
would  stop  and  look  around  in  an  apparent  attempt  to  find 
the  experimenter.  This  was  never  done  by  the  rats  and  rac- 
coons. Again,  the  brown  dog  fell  into  the  most  absurd  habit 
of  going  out  of  the  release  box,  turning  entirely  around  to  the 
left  and  then  going  to  one  of  the  boxes.  This  accomplished 
no  end  that  I  could  determine,  yet  it  was  persisted  in  for  some 
weeks. 

(c)  Raccoons. — Bob  and  Betty  were  each  given  lo  trials 
daily.  Jack  and  Jill  received  15.  Reward  only  was  used,  al- 
though running  into  the  wrong  box  and  having  to  back  out 
constituted  no  little  punishment  here  as  was  also  the  case  with 
the  dogs.  The  experimenter  was  practically  out  of  sight  of 
the  animals  all  of  the  time  and  absolutely  so  in  certain  control 
tests.  It  will  be  remembered  that  the  raccoon  tests  were  made 
in  a  room  illumined  by  a  single  light  suspfended  above  the  prob- 
lem box.  (See  p.  24).  This  left  the  remainder  of  the  room  dark 
and  thus  helped  conceal  the  experimenter. 

Bob  required  120  trials  to  learn  the  association.  Of  these, 
93  trials  or  77%  were  correct.  Of  the  last  50  trials,  96%  were 
successful.  Betty  was  given  340  trials  in  the  learning  series. 
The  work  was  not  properly  controlled  for  her  until  the  last  120 
of  these  trials.  She  formed  the  habit  early  of  looking  into  the 
light  boxes  and  seeing  whether  or  not  the  wooden  exit  doors 
were  closed.  This  difficulty  was  finally  obviated  by  using  coarse 
mesh  wire  for  the  doors.  These  could  not  be  sensed  until  the 
animal  practically  touched  them.  Of  Betty's  last  50  trials  on 
learning,  only  79%  were  correct.  These  tests  should  have  been' 
continued  longer.  Jack  was  given  540  trials  on  learning.  Of 
these,  428  trials  or  79%  were  correct.  Of  the  last  150  trials, 
98%  succeeded.  Jill  received  825  trials  during  the  learning 
period.  Of  these,  631  trials  or  76%  were  correct.  Of  the  last 
150  trials,  99%  succeeded.  (The  experiment  box  had  wire 
exit  doors  when  Jack  and  Jill  were  tested.) 


34  WALTER  S.  HUNTER 

Although  the  nature  of  the  learning  process  is  not  our  spe- 
cific problem,  the  differences  in  the  total  number  of  trials  re- 
quired for  learning  by  Bob  and  the  last  two  animals  are  so 
great  as  to  invite  comment.  The  conditions  under  which  the 
records  were  obtained  differ  in  the  following  points:  (i)  Jack 
and  Jill  were  younger  than  Bob  by  at  least  a  year.  (2)  Work 
was  begun  with  them  in  July  and  with  Bob  in  (the  preceding) 
October.  This  brought  him  nearer  the  period  of  hibernation 
when  his  appetite  would  begin  to  fail.  (3)  Jack  and  Jill  received 
more  trials  daily  and  also  were  tested  for  more  days.  Con- 
sidering the  fact  that  when  the  experiments  ceased  Jack  and 
Jill  were  younger  than  the  other  two  raccoons  were  when  the 
latter  started  and  yet  had  accompHshed  as  much,  I  do  not 
believe  that  age  was  an  important  factor  in  determining  the 
reactions.  However,  the  actual  fact  of  an  age  difference  re- 
mains. The  second  point  should  have  little  explanatory  force, 
since  the  animals  were  always  eager  to  work.  As  to  the  third 
point,  one  would  expect  this  factor  to  work  in  a  direction  oppo- 
site to  that  which  the  results  indicate.  However,  such  was  not 
true  with  the  rats,  and  it  may  be  that  here  also  the  lesser  num- 
ber of  trials  daily  is  more  favorable  to  rapid  learning.  The  fact 
of  a  possible  difference  of  preference  for  Hght  and  dark  remains 
to  be  considered.  Of  the  first  50  trials.  Bob  made  56%  correct. 
Of  the  first  45  trials,  Jill  made  22%  correct.  Jack  made  48% 
successful  responses  out  of  the  first  45  trials.  Age  differences, 
differences  of  brightness  preference  and  differences  in  the  num- 
ber of  daily  trials  are  possible  explanations  for  the  varying 
lengths  of  the  learning  records.  Innate  (?)  individual  abilities 
must  also  be  recognized.  (Betty's  results  are  not  considered 
because  of  their  unreliability  at  this  point  of  the  experiments.) 

Summary. — The  only  comparative  statement  w4th  reference 
to  the  learning  periods  of  the  different  groups  of  animals 
that  the  facts  warrant  is  this :  The  raccoons  Jack  and  Jill  and 
both  dogs  belong  together  in  the  class  that  learned  most  slowly. 
The  second  class  with  reference  to  speed  of  learning  is  com- 
posed of  the  rats.  Bob  is  in  a  class  by  himself.  He  learned 
more  rapidly  than  any  of  the  other  animals.  Further  comments 
upon  this  aspect  of  the  learning  process  will  be  deferred  to  the 
section  on  children. 


DELAYED  REACTION  35 

B.  Maximal  Intervals  of  Delay  Attained,  (a)  Group  differ- 
ences as  to  maximal  delay. — The  only  conditions  of  experimen- 
tation that  varied  from  animal  group  to  animal  group  were 
these:  (i)  Number  of  trials  daily.  Rats  2,  4,  5,  6,  7  and  9 
(Set  A)  and  rats  10,  11  ,14  and  17  (of  Set  B)  were  given  5  trials 
daily.  Rats  12,  13,  15  and  16  (of  Set  B)  received  10  trials. 
The  two  dogs  were  given  10  trials  daily.  Of  the  raccoons,  Jack 
and  Jill  were  each  given  15  trials  and  Bob  and  Betty  10  trials 
daily.  (2)  The  rats  of  Set  B  were  tested  with  reward  alone. 
As  was  mentioned  above,  the  dogs  and  raccoons  were  very 
much  discomfited  by  having  to  back  out  of  the  light  boxes 
when  a  wrong  choice  had  been  made.  This  was  even  more 
true  in  our  tests  than  in  most  discrimination  work  owing  to 
the  small  size  of  the  light  boxes. 

TABLE  IV 

Per  cent  of 
Rat  Maximal  delay  correct  response 


Set  A 

2 

1  sec. 

64 

4 

1  sec. 

52 

5 

3rd  stage 

52 

6 

did  not  learn  association 

7 

3  sees. 

56 

9 

10  sees. 

72 

SetB 

10 

1  sec. 

76 

11 

1  sec. 

64 

*12 

1  sec. 

72 

*13 

4  sees. 

88 

14 

3  sees. 

80 

*15 

1  sec. 

86 

*16 

1  sec. 

50 

17 

1  sec. 

37 

Set  A  tested  with  reward. 
Set  B  tested  with  reward  and  punishment. 

Those  rats  that  are  marked  with  a  *  received  10  trials  daily.  All  the  others  re- 
ceived 5. 

Table  IV  gives  the  maximal  delay  attained  by  the  rats.  The 
percentages  are  computed  on  a  basis  of  25  trials.  It  will  be 
seen  from  this  that  only  four  rats  of  the  fourteen  tested  reached 
intervals  greater  than  one  second.  The  percentage  of  correct 
behavior  for  one  of  these  (No.  7)  was  only  56.  Rats  Nos.  4, 
II,  15,  16  and  17  were  tested  with  a  choice  of  two  boxes  as 
opposed  to  three.     This  was  done  only  after  the  animals  had 


36  WALTER  S.  HUNTER 

more  or  less  completely  broken  down  in  their  reactions  to  one 
box.  Tests  with  two  boxes  were  never  made  on  any  subject, 
unless  the  animal  lost  the  cue  to  one  box.  It  was  this  box 
that  was  dropped  from  the  series.  The  maximum  delays  made 
by  the  rats  under  these  conditions  were  increased.  Nos.  ii, 
15  and  16  each  made  5  sees,  at  from  76  to  90%.  This  must 
mean  that  it  is  easier  to  use  two  cues  than  three.  Further 
comments  will  be  added  below  (see  p.  39). 

Of  the  dogs,  Blackie  made  10  sees,  at  76%  for  30  trials.  She 
then  lost  the  cue  to  one  of  the  boxes  and  was  unable  to  react 
successfully  to  that  one.  When  tested  with  two  boxes  she 
finally  made  a  delay  of  5  mins.  for  5  trials  at  80%;  86%  had 
been  made  at  3  mins.  for  30  trials.  Brownie  was  tested  only 
with  three  boxes.  She  made  a  delay  of  i  sec.  for  50  trials  at 
90%  and  2  sees,  for  70  trials  at  68%.  Both  dogs  were  tested 
for  eight  months.  The  results  should  be  representative  of  what 
dogs  can  do  under  the  present  conditions. 

Of  the  raccoons.  Jack  made  14  sees,  at  70%  for  30  trials. 
Tested  with  two  boxes,  he  finally  made  85%  at  20  sees,  for  40 
trials.  He  was  tested  for  eight  and  one-half  months.  Betty 
made  82%  at  7  sees,  for  50  trials.  Tested  with  two  boxes,  she 
reached  10  sees,  at  86%  for  30  trials.  She  was  tested  for  one 
year  and  three  weeks.  Jill  was  tested  only  with  three  boxes. 
She  made  3  sees,  for  45  trials  at  93%.  The  tests  extended 
over  a  period  of  seven  months.  Bob  made  90%  for  10  trials 
at  15  sees.  Tested  with  two  boxes,  he  reached  a  delay  of  25 
sees,  for  20  trials  at  90%.  Bob  was  tested  steadily  for  a 
year  and  five  months. 

For  fear  that  some  critic  would  urge  that  the  animals  could 
not  have  delayed  longer  than  they  did  even  though  the  light 
had  been  constantly  present,  control  tests  were  made  as  fol- 
lows: The  animals  were  taken  at  the  stage  when  they  had 
just  broken  down  at  some  (for  them)  long  interval  of  delay 
and  were  held  in  the  release  for  one  minute  with  the  light  on. 
When  they  were  released,  the  light  was  still  left  on.  The  results 
show  that  the  animals  made  a  very  high  percentage  of  correct 
behavior.  Their  failure  to  make  correct  long  delayed  reactions 
must  have  been  due,  then,  to  their  inability  to  use  some  cue 
by  which  to  guide  their  reactions  after  such  an  interval  and  not 
to  mere  restlessness  caused  by  the  long  confinement. 


DELAYED  REACTION  37 

Appendix  A  contains  tables  that  show  all  the  regular  tests 
given  to  the  raccoons  Bob  and  Jill  and  to  rats  4  and  16..  The 
data  are  there  given  in  the  order  in  which  they  were  obtained. 
They  are  typical  of  the  results  of  all  the  animals. 

There  is  so  much  individual  variation  within  the  three  groups 

of  animals  whose  results  have  just  been  given  that  any  exact 

correlation  between  length  of  delay  and  groups  of  animals  is 

unwise.     It  is  to  be  borne  in  mind  moreover  that  it  is  not  the 

length  of  delay  but  the  methods  of  reaction  after  delay  to  which 

the  greater  importance  attaches.     This  topic  will  be  discussed 

later.     To  give  some  further  idea,  however,  as  to  the  relation 

between  the  groups  Table  V  gives  the  longest  and  the  shortest 

delay  made  by  each  class  of  animals.     This  table  ignores  the 

different  conditions  under  which  the  delays  were  obtained.     It 

presents  the  maxima  and  minima  of  the  best  reactions  that  the 

individual  animals  of  a  group  were  able  to  make  under  the 

present  conditions. 

TABLE  V 

Subjects  Min.  delay  Max.  delay- 

Rats  Either  no  learning  or  3rd  stage  10  sees. 

Dogs  2  sees.  5  mins. 

Raccooris  3  sees.  25'secs. 

(b)  Effect  of  size  of  release  upon  interval  of  delay. — The 
experiments  so  far  described  were  all  made  with  the  small 
release  described  in  the  section  on  apparatus.  This  release  con- 
fined the  animal's  activities  to  a  small  part  of  the  apparatus. 
It  was  thought  if  a  release  was  used  which  would  give  the 
animal  the  freedom  of  the  whole  interior  of  the  box,  that  not 
only  might  the  maximal  interval  of  delay  be  increased,  but  the 
animal  might  reveal  more  clearly  its  method  of  solving  the 
problem, — ^indeed  it  might  even  develop  a  new  and  higher 
type  of  bqhavior  in  response  to  the  more  complex  situation. 
These  latter  possibilities,  we  shall  consider  below. 

The  new  release  that  was  used  fitted  just  inside  the  openings 
into  the  light  boxes.  It  was  made  of  a  continuous  piece  of  wire 
netting,  thus  making  possible  the  simultaneous  presentation  of* 
all  three  boxes.  It  was  now  possible  for  the  animal  to  go  over 
to  the  door  of  the  lighted  box  and  wait  there  during  the  interval 
of  delay.  The  light  was  always  left  on  until  the  animal  had 
reached  a  position  immediately  in  front  of  the   lighted  box. 


38  WALTER  S.  HUNTER 

Preliminary  tests  insured  an  absence  of  emotional  disturbances 
in  the  reactions. 

The  animals  tested  under  these  conditions  were:  Rats  13, 
15,  16  and  17  (No.  17  was  the  only  one  tested  with  a  choice  of 
three  boxes) ;  both  dogs  (Brownie  alone  was  tested  with  a 
choice  of  three  boxes) ;  raccoons  Jack,  Jill  and  Bob  (Jill  alone 
was  tested  with  three  boxes). 

Table  6  gives  a  comparative  statement  of  the  animals'  abil- 
ities with  large  and  small  release.  Both  records  for  each  animal 
are  for  discriminations  with  the  same  number  of  boxes.  It 
will  be  seen  from  this  that  rat  No.  13,  the  dog  Blackie  and  the 
raccoons  Jack  and  Bob  are  the  only  ones  that  failed  to  delay 
longer  with  the  large  release.  This  fact  can  be  readily  explained 
in  the  case  of  Jack  and  Blackie.  The  experimenter  was  prim- 
arily interested  in  discovering  whether  any  new  mode  of  be- 
havior would  appear  under  these  conditions.  When  this  ques- 
tion was  answered,  tests  were  discontinued  with  all  the  animals 
although  in  the  case  of  Jack  and  Blackie  the  interval  of  delay 
was  being  steadily  increased.  The  increase  in  delays  made  by 
the  other  animals  is  to  be  correlated  with  the  changed  condi- 
tions of  experimentation.  This  point  will  be  amplified  when 
the  detailed  behavior  of  the  animals  is  discussed. 

TABLE  VI 

Small  release  Large  release 


Per  cent  of  Per  cent  of 

Animal         Delay        correct  reactions  Delay        correct  reactions 

Rat  No.  13       4  sees.  88  3  sees.  95 

Rat  No.  15       1  sec.  86  6  sees.  86 

Rat  No.  16       1  sec.  50  9  sees.  82 

Rat  No.  17       7  sees.  68  1  sec.  37 

Blackie         5  mins.  80  1  min.  80 

Brownie         2  sees.  68  6  sees.  96 

Jill  3  sees.  93  7  sees.  80 

Jack  20  sees.  85  15  sees.  88 

Bob  25  sees.  90  20  sees.  76 

(c)  Effect  of  backgrounds  of  different  brightnesses  upon  the 
interval  of  delay. — When  the  apparatus  for  the  animals  was 
constructed,  every  effort  was  made  to  secure  qualitative  simi- 
larity in  the  three  light  boxes.  The  backgrounds  surrounding 
the  entrances  to  the  light  boxes  were  all  of  the  same  brightness. 
During  the  course  of  the  tests,  the  attempt  was  made  to  deter- 


DELAYED  REACTION  39 

mine  whether  the  animals  could  form  an  association  between  the 
lights  and  some  constant  marked  differences  in  the  external 
environment.  In  order  to  test  this,  three  backgrounds  of  widely 
differing  degrees  of  brightness  were  used  as  described  above  in 
the  section  on  method.  The  animals  tested  under  these  condi- 
tions were:  Rats  Nos.  2,  4,  5  and  7  of  Set  A  and  Nos.  10,  12 
and  16  of  Set  B;  the  dog  Brownie;  and  the  raccoon  Jill. 

The  results  of  this  test  were  entirely  negative.  No  case  was 
found  where  the  animal  made  use  of  the  different  backgrounds 
as  cues  for  guiding  its  reactions.  One  or  two  of  the  animals 
increased  their  interval  of  delay  under  the  new  conditions. 
However,  when  the  old  conditions  of  similar  backgrounds  were 
replaced,  the  long  intervals  of  delay  still  continued.  This  ind  - 
cated  that  the  improvement  was  due  to  practice. 

(d)  Effect  of  number  of  boxes  upon  delay. — As  stated  above 
in  section  (a),  whenever  an  animal's  reactions  broke  down  upon 
a  particular  box,  that  box  was  dropped  from  the  tests  and  the 
discrimination  confined  to  the  other  two.  The  following  ani- 
mals were  tested  under  these  changed  conditions:  Rats  4,  11, 
15  and  16;  the  dog  Blackie;  and  the  raccoons  Jack,  Bob  and 
Betty.  The  results  are  given  for  convenience  above  under 
section  (a).  Here  it  may  be  noted  that  all  the  animals  delayed 
longer  with  two  than  with  three  boxes.  This  can  be  readily 
explained  on  the  basis  of  the  complexity  of  the  problem.  The 
maximum  delay  for  any  animal  is  decided  by  the  accuracy  of 
its  response.  With  two  boxes,  this  accuracy  was  increased  and 
hence  the  maximum  delay  recorded  was  greater. 

(e)  Effect  of  other  conditions  upon  delay. — The  results  do  not 
indicate  certainly  any  effect  of  punishment  or  of  the  number 
of  trials  upon  the  length  of  the  interval  of  delay. 

The  results  of  this  section  indicate  that  the  following  factors 
influence  the  maximal  amount  of  delay:  (i)  Different  groups 
of  animals;  (2)  size  of  release,  and  (3)  the  number  of  light 
boxes  used.  The  following  factors  do  not  influence  the  amounts 
of  delay:  (i)  Punishment  and  reward;  (2)  number  of  trials 
daily,  and  (3)  backgrounds  of  different  brightnesses. 

C.  Methods  of  Reaction  After  Delay  Used  by  the  Animals. — 
There  are  three  different  methods  of  delay  which  might  have 
appeared  and  in  point  of  fact  did  appear  in  our  delayed  reac- 
tion experiments:     (i)  The  animal  may  maintain  an  orientation 


40  WALTER  S.  HUNTER 

of  all  or  part  of  its  body  during  the  interval  of  delay,  i.e.,  it 
may  keep  its  head  or  even  its  whole  body  pointing  toward  a 
certain  box.  (2)  There  would  be  the  negative  side  of  this, 
where  the  experimenter  could  detect  no  orientation  cues  used 
by  the  animal.  In  this  case,  no  observable  part  of  the  animal's 
body  would  remain  in  a  constant  position.  (3)  The  animals 
might  rely  upon  position  in  the  box  for  their  cues,  i.e.,  they 
might  actually  go  nearer  to  one  box  than  to  the  others  and 
then  wait  to  be  released.  (4)  Any  combination  of  these  three 
methods  might  occur.  The  discussion  of  methods  i  and  2 
(orientation  and  non-orientation  cues)  will  be  combined  and 
will  be  followed  by  a  consideration  of  method  3.  The  actual 
existence  of  method  4  will  be  considered  as  occasion  demands. 

(a)  Orientation  of  whole  or  part  of  body. — In  addition  to 
what  was  given  above  in  the  section  on  method  concerning 
orientation,  it  will  be  well  to  make  such  additional  comment 
here  as  will  indicate  clearly  the  nature  of  the  data  secured. 
Great  pains  were  taken  to  insure  accuracy  and  consistency  in 
the  recording  cf  orientations.  Needless  to  say  in  such  pro- 
longed tests  as  the  present  ones,  the  experimenter  soon  becomes 
expert  in  deciding  whether  an  animal's  movements  are  to  be 
interpreted  as  a  change  in  orientation.  Before  an  animal  has 
been  tested  long,  the  experimenter  can  pick  out  a  certain  range 
of  movement  and  call  this  the  orientation  toward  a  certain  box. 
The  animal  (dcgs  excepted)  was  in  constant  motion,  but  so 
long  as  its  activity  was  directed  toward  any  one  face  of  the  re- 
lease box,  the  orientation  was  recorded  as  unchanged.  There 
would  seem  to  be  some  chance  for  doubtful  cases  when  the 
animal  was  pointed  halfway  between  any  two  boxes.  These 
cases  were  never  counted  as  changes  in  orientation.  Record 
was  kept  not  only  of  the  body  position,  but  of  whether  any 
observable  part  of  the  animal  remained  in  a  constant  position 
during  the  delay.  Further  note  was  taken  of  the  gross  amount 
of  the  loss  of  orientation — i.e.,  whether  the  animal  turned  clear 
around  or  not ;  and  if  not,  then  how  far  around — ^and  of  just 
which  reactions  were  preceded  by  apparently  identical  orien- 
tations. The  data  were  recorded  quickly  and  easily  by  the  use 
of  symbols. 

Every  rat  at  the  moment  of  release,  went  in  the  direction  of 
his  bodily  orientation  in  99  cases  out  of  100.      (At  times  this 


DELAYED  REACTION  41 

was  not  true  because  of  position  habits  formed  by  the  animal.) 
(For  the  present  purposes,  it  makes  no  difference  whether  the 
reaction  was  correct  or  not.)  The  data  supporting  this  state- 
ment are  so  overwhelming  that  they  need  not  be  given  here  in 
detail.  The.  rat,  when  put  into  the  release  box  during  the  de- 
layed reactions,  oriented  immediately  to  the  light  with  its  entire 
body  and  began  a  series  of  attacks  on  that  side  of  the  box  in 
an  effort  to  get  out.  This  attempt  was  kept  up  until  the  animal 
was  released,  whereupon  it  went  to  the  box  that  was  straight 
in  front.  Experiment  served  only  to  lengthen  the  period  during 
which  they  would  attack  any  one  side  of  the  box.  These  state- 
ments hold  true  for  all  rats. 

Both  dogs  were  dependent  upon  orientation  for  the  guidance 
of  their  successful  reactions.  They  only  differed  from  one  an- 
other in  the  length  of  time  during  which  they  could  maintain 
a  certain  orientation.  The  dogs  differed  from  the  rats  in  that 
the  determining  cue  was  the  direction  of  the  head  rather  than 
of  the  body.  For  the  sake  of  concrete  material  illustrative  of 
this  type  of  reaction,  I  shall  give  a  summary  of.  typical  reac- 
tions made  by  Blackie.  Of  770  trials,  given  during  a  period  of 
two  months,  on  delays  less  than  3  sees,  long,  141  were  unsuc- 
cessful. On  116  of  the  141,  the  dog  had  the  wrong  orientation 
at  the  moment  of  release  and  followed  it.  On  the  remaining 
25  reactions,  the  dog  failed  to  follow  its  orientation  and  was 
wrong.  On  8  trials  the  dog  had  the  wrong  orientation  at  the 
moment  of  release,  i.e.,  was  not  headed  toward  the  proper  box, 
and  yet  reacted  correctly.  However,  only  3  of  these  trials 
were  with  a  2  sees,  delay  and  may  have  been  due  to  chance. 
The  remaining  5  trials  were  at  the  second  stage  of  delay  where 
the  light  was  on  until  the  animal  was  halfway  to  it.  Obviously, 
these  5  reactions  signify  no  great  ability.  These  results  indicate 
that  just  to  the  extent  that  the  dog  was  able  to  hold  the  proper 
orientation  during  the  delay,  just  to  that  extent  it  was  capable 
of  reacting  correctly. 

Let  us  take  another  typical  set  of  results  from  the  same  dog 
obtained  on  delays  from  15  sees,  to  5  mins.  extending  over  30 
days.  Two  hundred  and  eighty-five  trials  in  all  were  given  of 
which  37  were  incorrect.  In  all  37  trials,  the  dog  had  the  wrong 
orientation  and  followed  it.  Only  once  did  she  have  the  wrong 
orientation   and   react   correctly.      When    Blackie   entered   the 


42  WALTER  S.  HUNTER 

release  box,  she  would  turn  clear  around  and  then,  before  the 
final  breakdown  came,  would  lay  down  facing  the  light.  Occa- 
sionally she  would  be  distracted  by  some  accidental  noise  inside 
or  outside  the  laboratory.  In  the  great  majority  of  these  cases, 
she  only  turned  her  head.  A  few  times  she  got  up  and  turned 
clear  around.  But  in  any  event,  if  she  did  not'  recover  the 
proper  orientation,  the  reaction  failed.  If  she  could  have  lost 
,the  orientation  either  completely,  or  almost  so,  and  then  have 
returned  to  it  and  have  reacted  correctly,  the  fact  would  have 
been  strong  evidence  for  believing  that  the  dog  recognized  the 
proper  orientation  when  it  was  reinstated.  But  taking  the  last 
125  trials  as  typical,  and  classifying  the  instances  where  orien- 
tation was  lost,  reco\'ered  and  a  correct  reaction  made,  it  is 
found  that  33  times  the  orientation  was  changed  but  slightly 
and  three  times  completely  changed. — By  a  slight  change  is 
meant  that  the  dog  turned  her  head  and  not  her  body.  By  a 
complete  change  is  meant  that  the  animal  turned  completely 
around. — Of  the  three  cases  of  this  latter  behavior,  one  was 
very  probably  due  to  chance.  The  other  two  occurred  on  the 
second  day  of  the  5  min.  delays  when  the  final  breakdown 
was  beginning.  Moreover,  the  orientation  that  was  lost  and 
recovered, — ^in  one  case  at  the  end  of  36  sees. ;  in  the  other  at 
the  end  of  4^  mins., — was  the  orientation  toward  the  box  at 
the  right.  The  reaction  is  thus  not  significant  of  some  higher 
process,  for  on  the  following  day  the  box  at  the  right  was  the 
only  one  to  which  the  animal  responded.  The  recovered  orien- 
tation, therefore,  most  probably  indicates  solely  the  growth  of 
the  habit  that,  on  the  following  day,  resulted  in  the  complete 
disintegration  of  the  reaction. 

It  is  interesting  in  this  connection  to  trace  the  change  that 
occurred  in  Blackie's  behavior  from  the  beginning  to  the  end 
of  the  experiments.  It  has  already  been  noted  how  "helpless" 
and  inactive  both  dogs  were  when  the  tests  were  started.  After 
the  work  had  progressed  for  several  weeks  and  Blackie  had 
become  quiet  and  attentive,  she  would  stand  in  the  release 
box  on  all  four  feet  and  occasionally  paw  the  wire  in  the  direc- 
tion of  the  light.  A  little  later,  she  sat  on  her  haunches  during 
the  retention  in  the  release,  but  still  clawed  at  the  wire  in  a  very 
calm  manner.  Toward  the  last  of  the  tests  described  above, 
when  the  delays  were  growing  rapidly  longer,  she  lay  flat  down 


DELAYED  REACTION  43 

on  the  floor  with  her  head  pointed,  usually,  toward  the  light. 
But  she  did  not  lie  quietly.  The  long  delay  seemed  very  trying. 
Blackie  would  whine,  wiggle  her  body  and  pat  the  floor  with  her 
fore  paws  in  a  fever  of  impatience, — yet  never  change  the  align- 
ment of  her  body.  Many  times  the  dog  held  her  orientation 
almost  until  the  last  second  of  delay  and  then  if,  when  the 
release  came,  her  head  was  (apparently)  not  more  than  half 
an  inch  to  the  right  of  its  earlier  position,  she  went  in  that 
direction  and  consequently  went  to  the  wrong  box.  Surely  this 
is  weighty  evidence  against  the  functional  presence  of  any 
higher  processes.  Everything  points  to  the  conclusion  that 
Blackie 's  reactions  were  determined  by  the  orientation  of  her 
head  at  the  moment  of  release. 

It  has  just  been  indicated  that  the  maintenance  of  an  orien- 
ation  either  of  all  or  a  part  of  the  body  was  necessary  in  the 
case  of  the  rats  and  dogs,  if  their  reactions  were  to  succeed. 
Such  was  not  the  case  with  the  raccoons.  Each  of  these  ani- 
mals could  react  successfully  when  the  wrong  orientation  was 
held  at  the  moment  of  release  and  when,  so  far  as  the  experi- 
mienter  could  detect,  no  part  of  the  animal's  body  remained 
constant  during  the  interval  of  delay.  The  evidence  in  support 
of  this  generalization  is  perfectly  conclusive.  It  is  only  pos- 
sible— and  necessary — to  present  typical  cases  here.  I  use  Jack 
as  an  illustration,  although  he  did  not  delay  as  long  as  Bob. 

In  Jack's  first  800  trials  of  delays,  77  were  wrong.  In  7  of 
these  77,  the  raccoon  had  the  wrong  bodily  orientation,  but 
did  not  follow  it.  On  12  trials,  he  had  the  right  orientation, 
but  did  not  follow  it.  On  58  trials,  he  had  the  wrong  orienta- 
tion and  followed  it.  Of  the  723  correct  reactions,  167  were 
made  starting  with  wrong  orientations.  ^ 

In  the  following  1066  trials,  149  reactions  were  incorrect. 
This*  group  of  trials  extends  from  a  period  of  8  sec.  delays  at 
which  75%  was  made  through  a  series  at  11  sees,  where  91% 
was  made.  Forty-one  errors  were  made  when  the  wrong  orien- 
tation was  held  but  was  not  followed.  Thirty-seven  were  made 
when  the  right  orientation  was  held.  Seventy-one  were  made 
when  the  wrong  orientation  was  held  and  followed.  Out  of 
the  917  correct  trials,  Jack  reacted  309  times  correctly  when 
his  orientation  was  wrong. 

It  is  interesting  to  note  that  almost  one-fourth  of  the  last 


44  WALTER  S.  HUNTER 

mentioned  errors  were  made  despite  the  fact  that  the  proper 
orientation  was  being  held.  This  is  a  type  of  reaction  that 
almost  never  occurred  with  the  rats  and  the  -dogs.  It  would 
seem  to  indicate  that  this  raccoon  is  less  dependent  on  gross 
motor  attitudes  than  the  other  animals.  But  the  most  signifi- 
cant behavior  is  that  of  reacting  correctly  when  the  wrong 
orientation  was  held  at  the  moment  of  release.  From  the  first 
set  of  figures  above,  it  will  be  seen  that  of  232  trials  when  the 
wrong  orientation  was  held,  167  or  71%  were  correct.  The 
second  set  of  figures  shows  that  of  421  trials  when  the  wTong 
orientation  was  held,  309  or  73%  were  successfully  carried  out. 
Such  a  high  percentage  places  the  results  above  the  possibility 
of  explanation  by  chance.  Again,  the  fact  that  this  type  of 
behavior  dominated  for  several  days  at  a  time  indicates  that 
something  more  than  chance  was  manifesting  itself.  At  8  sees, 
delay,  e.g.,  Jack  made  10  correct  reactions  in  one  day,  starting 
with  wrong  orientations.  The  following  two  days  had  7  each; 
and  the  following  two,  4  each.  The  next  day  the  delay  was 
increased  to  9  sees,  and  8  correct  reactions  with  wrong  orienta- 
tions were  made.  Eight,  6,  4,  8  and  6  were  the  records  of  such 
reactions  for  the  following  days.  The  next  day  after  these,  10 
sees,  delay  was  given.  Here  9  correct  reactions  were  made 
starting  with  wrong  orientations.  These  are  fair  samples  of  the 
prevalence  of  this  type  of  reaction. 

In  order  to  emphasize  further  the  fact  that  Jack  did  not  need 
to  keep  any  observable  part  of  his  body  in  a  constant  position 
in  order  to  react  correctly,  I  shall  give  one  day's  record  in  detail 
(Table  X).  Often  only  the  raccoon's  hind  feet — or  one  of  them — 
remained  constant.  The  interval  of  delay  in  this  illustration  is 
10  sees.  N.c.  means  no  part  of  the  body  kept  constant.  H.f.c. 
means  hind-feet  constant.  Rt.h.f.c.  means  right  hind-foot  con- 
stant. If  the  letter  designating  the  orientation  held  at  the 
moment  of  release  is  in  italics,  the  animal  oscillated  between 
two  faces  of  the  release.  If  in  addition  the  letter  is  starred, 
the  animal  oscillated  from  one  to  another  of  all  three  faces  of 
the  release.  On  the  3rd  and  5th  trials,  Jack  was  distracted  by 
some  noise  during  the  delay.  A  concrete  statement  of  what 
these  symbols  mean  in  one  or  more  instances  should  make 
the  record  perfectly  clear.  On  the  first  trial,  the  light  was 
turned  on  in  the  right-hand  box.     It  was  turned  off  and  the 


DELAYED  REACTION 


45 


animal  held  for  lo  sees.  During  this  delay,  Jack  turned  toward 
all  three  boxes.  No  observable  part  of  his  body  remained  con- 
stant. At  the  instant  of  release,  he  was  headed  toward  the 
proper  box,  a,  and  reacted  correctly.  On  the  5th  trial.  Jack 
was  oriented  toward  the  middle  box,  b,  at  the  moment  of  release. 
He  went  to  a,  then  to  b,  then  to  c  and  back  to  the  experimenter 
for  food.  The  reaction  had  failed.  If  to  the  large  number  of 
correct  trials  made  with  wrong  orientations  be  added  the  correct 
trials  made  with  correct  orientations  that  had  been  completely 
lost  and  then  refound,  the  number  of  reactions  significantly 
different  from  those  of  the  rats  and  the  dogs  reaches  relatively 
huge  proportions. 

TABLE  X 


Orient. 

Raccoon 

when  released 

Light  box 

Behavior 

Jack 

*a 

a 

a 

n.c. 

*a 

a 

a 

h.f.c. 

*a 

a 

a 

h.f.c. 

*a 

b 

b 

rt.h.f.c. 

*b 

c 

abc 

n.c. 

*h 

c 

c 

rt.h.f.c. 

c 

b 

b 

n.c. 

*c 

a 

a 

n.c. 

h 

0 

c 

h.f.c. 

*a 

c 

c 

n.c. 

b 

c 

c 

h.f.c. 

a 

b 

b 

rt.h.f.c. 

*h 

a 

a 

h.f.c. 

b 

b 

b 

n.c. 

*a 

b 

ab 

rt.h.f.c. 

Two  other  types  of  reaction  remain  to  be  indicated  in  the 
above  table,  (X).  Orientation  b  was  held  6  times;  orientation 
a,  7  times,  and  c,  twice.  Yet  different  correct  reactions  followed 
from  the  same  orientations.  Jack  was  oriented  to  c  once  and 
went  to  b  correctly.  The  next  trial  he  had  the  same  orientation 
and  went  to  a  correctly.  In  neither  case  had  he  seemed  to 
keep  any  part  of  his  body  constant.  In  the  4  correct  responses 
to  the  light  box  b,  the  corresponding  orientations  were  as  differ- 
ent as  possible.  Twice  Jack  was  oriented  to  a  and  once  each 
to  b  and  c,  yet  each  time  the  correct  reaction  was  made.  In 
other  words,  the  same  orientation  did  lead  to  different  reactions 
and  different  orientations  to  the  same  reaction.  These,  again, - 
are  types  of  behavior  never  met  with  in  the  rats  and  dogs.  This 
behavior  occurred   so   frequently   with   Jack  and   with   Bob — 


46  WALTER  S.  HUNTER 

less  frequently,  however,  with  Jill  and  Betty — that  it  must  be 
described  as  a  genuinely  new  type  of  reaction  in  these  experi- 
ments and  not  as  the  result  of  chance  or  of  the  foreknowledge 
of  what  box  was  to  be  presented.  (This  latter  possibility  was 
adequately  ruled  out  by  controls.) 

Table  XI  gives  a  nuinerical  statement  of  the  importance  of 
orientation  for  the  rats,  dogs  and  raccoons.  As  far  as  this 
factor  is  concerned,  the  animals  within  each  class  were  on  a 
par  with  one  another.  For  this  reason,  I  give  the  results  for 
t57pical  subjects  and  not  an  average  for  all  members  of  a  group. 
The  data  given  for  each  animal  are  calculated  from  comparable 
groups  of  800  delayed  reactions  each. 


TABLE  XI 

Rat 
No.  14 

Dog 
Blackie 

Raccoon 
Jack 

No. 

of  reactions  in  accordance  with  orientation .  . 

698  trials 
or 

87% 

760  trials 

or 

95% 

614  trials 
or 

76% 

No. 

of  reactions  not  in  accordance  with  orienta- 
tion   

102  trials" 
or 
13% 

40  trials 
or 

5% 

186    trials 
or 

24% 

No. 

of  reactions  not  in  accordance  with  orienta- 
tion that  succeeded 

15  trials 
or 

14% 

5  trials 
or 

12% 

167  trials 
or 

89% 

This  table  indicates  plainly  the  similarity  of  the  behavior  of 
the  dogs  and  rats  as  well  as  the  wide  divergence  of  the  raccoons 
from  the  other  two  groups  of  animals.  The  rats  and  dogs 
almost  never  reacted  in  opposition  to  orientation.  When  they 
did  do  so,  the  number  of  their  successes  was  a  negligible  quan- 
tity. That  orientation  was  a  strong  factor  with  the  raccoons 
is  evidenced  by  the  76%  of  reactions  that  followed  it.  This 
fact  makes  the  89%  of  correct  reactions  starting  from  wrong 
orientations  of  great  significance.  The  reactions  succeeded  in 
opposition  to  strong  orientation  influence.  This  statement  is 
supported  by  the  facts  above  noted.  It  was  shown  there  that 
one  of  the  raccoons  (a  typical  one):  (i)  Made  different  correct 
reactions  from  the  same  orientation,  and  (2)  made  the  same 
correct   response  from  different   orientations.     Additional   evi- 

■^  The  large  percentage  of  reactions-  not  in  accordance  with  orientation  made 
by  the  rat,  when  compared  with  those  made  by  the  dog,  is  due  to  the  acquisition 
of  a  habit  of  holding  orientation  b  and  reacting  to  box  a,  i.e.,  to  a  position  habit. 


DELAYED  REACTION  47 

dence  will  be  presented  later  when  the  effect  of  the  size  of  the 
release  upon  the  methods  of  delay  is  considered. 

One  other  line  of  evidence  which  points  to  the  uniqueness 
of  the  raccoon's  behavior  should  be  noticed  here,  viz.,  the  growth 
of  the  methods  of  delay  during  the  course  of  the  experimenta- 
tion. Did  the  rats  and  dogs  rely  upon  orientation  from  the 
beginning  of  the  tests?  Was  the  non-orientation  cue  natural 
with  the  raccoons  or  acquired  under  the  stress  of  circumstances? 
An  examination  of  the  records  reveals  the  fact  that  from  the 
beginning  of  the  learning  tests  the  rats  and  dogs  reacted  in 
accordance  with  orientation.  There  was  no  development  of  a 
new  method  as  the  delays  were  increased  in  length.  There  was 
simply  an  improvement  in  the  facility  with  which  the  animal 
maintained  its  position  for  a  given  length  of  time.  When  the 
orientation  was  lost,  it  was  no  easier  to  react  correctly  at  the 
last  of  the  experimentation  than  at  its  beginning.  In  the  case 
of  the  raccoons  also  there  was  no  initiation  of  a  new  mode  of 
response.  There  were,  on  the  average,  as  many  reactions  per 
day  during  the  learning  period  that  did  not  follow  the  orien- 
tation as  there  were  per  day  during  the  delayed  reactions.  The 
improvement  that  took  place  as  the  experimentation  proceeded 
was  .in  the  accuracy  of  responses  not  in  accordance  with  orien- 
tation, when  these  responses  were  made  after  a  long  delay. 
"Non-orientation  reactions,"  therefore,  seem  to  be  natural  with 
raccoons  and  thus  seem  to  differentiate  their  behavior  from  that 
of  the  rats  and  dogs. 

(b)  Position  in  the  box. — The  data  considered  under  the 
above  title  are  those  indicating  the  effect  that  the  large  release 
box  had  upon  the  methods  of  delay  used  by  the  various  animals. 
It  will  be  remembered  that  the  large  release  gave  the  animals 
the  freedom  of  the  interior  of  the  box  and  thus  permitted  them 
to  take  up  a  certain  position  in  the  box  as  well  as  to  maintain 
a  certain  bodily  orientation.  , 

Four  rats,  both  dogs  and  all  of  the  raccoons  save  Betty  were 
tested  with  this  large  release.  Only  three  animals  had  their 
methods  of  behavior  essentially  modified:  Rats  17  and  16  and 
the  raccoon  Jack.  In  no  case,  however,  did  an  animal  that 
had  depended  upon  orientation  for  its  cue  begin  the  use  of  a 
non-orientation  factor.  What  the  modifications  were  will  come 
out  in  the  following  descriptive  summary. 


48  WALTER  S.  HUNTER 

An  analysis  of  the  behavior  of  the  four  rats  when  tested  with 
the  large  release,  brings  to  light  the  following  facts:  Save  in 
four  cases,  No.  17  went  in  the  direction  in  which  his  body  was 
pointed  at  the  moment  of  release.  This  was  true  regardless  of 
his  position  in  the  box.  Nos.  13  and  15  always  went  in  the 
direction  of  body  orientation.  Hence  position  was  only  effec- 
tive as  an  aid  to  the  retention  of  body  orientation.  During 
the  last  week  of  the  tests  with  this  large  release.  No.  17  mani- 
fested an  exceedingly  interesting  type  of  behavior.  He  needed 
to  keep  neither  position  nor  orientation  constant  in  order  to  react 
correctly.  I  could  find  no  observable  body  cue  by  which  the 
problem  was  solved.  The  first  day  of  this  particular  week, 
3  of  the  10  trials  were  of  this  type,  but  for  several  days  no  more 
instances  were  noted  Then  they  were  again  in  evidence  until 
the  end  of  the  work.  The  correct  reactions  made  in  this  manner 
never  exceeded  3  per  day.  That  I  was  much  astonished  at  the 
sudden  appearance  of  this  type  of  behavior  in  the  rat  goes 
without  saying.  To  think  that  at  the  end  of  eight  months' 
steady  work,  the  animal  should  suddenly  adopt  a  new  mode 
of  behavior!  It  was  not  many  days,  however,  before  the  accu- 
mulated data  made  clear  the  explanation.  The  rat  always 
turned'  to  its  right  and  entered  the  first  box  that  was  encountered. 
Thus  the  animal  could  be  at  the  middle  box,  but  with  its  nose 
slightly  to  the  right  of  the  door  to  this  box,  and  when  released 
it  would  whirl  and  go  to  the  box  on  the  right.  In  the  same 
manner,  the  rat  might  have  its  nose  just  to  the  right  of  the 
door  to  the  left  box  when  the  release  was  raised  and  turn  and 
enter  the  middle  box.  The  behavior  of  rat  No.  16  differed  from 
this  only  in  the  direction  of  turning.  This  rat  always  turned  to 
the  left  and  entered  the  first  box  that  it  came  to.  From  these 
data,  it  is  obvious  that  the  animals  were  using  motor  cues  to 
guide  their  reactions.  Their  behavior  was  practically,  if  not 
entirely^  automatic. 

There  is  no  need  to  detail  the  results  obtained  with  the  dogs 
when  the  large  release  was  used.  Both  animals  always  went  up 
close  to  the  release  in  front  of  the  lighted  box  and  then  waited 
until  released.  Each  followed  the  orientation  of  his  head  re- 
gardless of  which  box  was  nearest. 

Among  the  raccoons,  Jack's  change  of  behavior  was  a  shift 
from  the  use  of  a  non -orientation  cue  to  a  position  cue.     The 


DELAYED  REACTION  49 

change  occurred  just  at  the  close  of  the  tests  with  the  large 
release.  His  usual  behavior  as  well  as  his  new  form  may  be 
set  forth  as  follows:  Before  the  new  release  was  used,  Jack 
was  being  tested  with  boxes  a  (the  right  one)  and  c  (the  left 
one)  only.  When  the  large  release  was  put  on,  the  tests  were 
still  confined  to  these  two  boxes.  This  was  necessary  in  order 
that  the  results  be  strictly  comparable.  Of  the  510  trials  given 
under  these  conditions,  56  were  made:  (i)  In  which  no  observ- 
able part  of  the  animal's  body  remained  in  a  constant  position ; 
and  (2)  in  which  the  animal's  position  in  the  box  was  wrong  at 
the  moment  of  release.  In  every  one  of  these  56  trials,  i.e.,  the 
animal  was  both  in  front  of  the  wrong  box  and  headed  away 
from  the  right  one  when  the  instant  of  release  arrived.  Twenty- 
six  of  the  56  were  reacted  to  correctly.  Chance  will  account  for 
this  number  of  reactions  as  far  as  the  mathematics  of  the  prob- 
lem are  concerned.  However,  from  the  point  of  view  of  the 
observer,  the  majority  of  the  reactions  looked  like  anything 
but  chance  behavior.  This  was  especially  true  when  Jack 
reacted  correctly  and  yet  was  pointed  directly  away  from  the 
proper  box.  There  was  a  directness  and  sureness  about  his 
reactions  that  hardly  savors  of  chance.  I  do  not  urge  these 
instances  on  the  reader  as  evidence  of  non-accidental  reactions. 
I  simply  note  the  fact  of  their  presence  and  the  impression  that 
they  made  upon  me.  It  is  well  to  remember  in  addition,  though, 
that  since  orientation  was  such  a  strong  factor  in  determining 
Jack's  reactions  (see  above,  Table  XI)  that  any  responses  in 
opposition  to  this  must  be  given  great  weight. 

Owing  to  the  fact  that  only  two  boxes  were  used  in  this  series 
and  that  they  were  located  far  apart,  the  raccoon  had  every 
incentive  to  rely  solely  upon  his  position  in  the  apparatus  for 
the  reaction  cue.  This  he  soon  did  to  a  large  extent.  In  every 
3ase  where  his  position  was  constant  (and  correct)  and  his  orien- 
tation changed,  he  reacted  successfully.  In  other  words,  posi- 
tion was  the  determining  factor.  When  this  became  evident, 
the  experiment  was  stopped.  The  raccoon  had  shifted  the  basis 
of  his  response  so  that  I  could  detect  its  nature  by  observation. 
Jack's  behavior  at  this  point  was  thus  on  a  par  with  the  dogs 
and  rats.  Had  the  tests  been  continued,  all  that  could  have 
been  expected  was  the  perfection  of  a  habit  of  staying  near 
the  proper  box.  This  did  not  appeal  to  me  as  a  profitable  goal 
of  endeavor. 


50  WALTER  S.  HUNTER 

For  further  confirmation  of  the  statements  made  above  con- 
cerning the  general  methods  of  delay,  I  shall  present  the  rac- 
coon Bob's  record  with  the  large  release  in  some  detail.  Three 
hundred  and  sixty  trials  were  given  on  two  boxes  with  this 
release.  Of  the  27  reactions  made  with  the  wrong  position  and 
correct  orientation,  19  were  correct.  Of  the  91  reactions  made 
with  the  right  position  and  wrong  orientation,  81  were  correct. 
Sixty-three  times  the  reactions  were  preceded  by  positions  and 
orientations  that  were  both  wrong.  There  are  two  possibilities 
here:  (i)  Orientation  and  position  may  favor  the  same  box; 
(2)  they  may  favor  different  boxes.  Forty  of  the  63  were  reac- 
tions of  class  I,  i.e.,  were  initiated  by  orientations  and  positions 
that  favored  the  same  wrong  box.  Fifteen  of  the  40  were  suc- 
cessful. In  other  words,  although  both  position  and  orientation 
favored  the  same  wrong  box,  Bob  was  able  to  overcome  the 
handicap  and  make  37%  correct  reactions.  The  remaining  23 
reactions  were  of  class  2.  Of  the  23,  16  were  successful.  Where 
position  and  orientation  were  both  wrong,  but  did  not  combine 
to  favor  the  same  box,  Bob  made  69%  correct  reactions.  Of 
the  7  reactions  of  class  2  that  failed,  5  were  in  accordance  with 
position  and  2  in  accordance  with  orientation,  i.e.,  5  times  the 
animal  went  to  the  box  favored  by  position  and  the  remaining 
times  to  the  one  favored  by  orientation. 

In  order  that  the  reader  may  have  a  perfectly  concrete  presen- 
tation of  the  reactions  with  the  large  release,  I  will  quote  a 
day's  record  from  the  diary.  The  reactions  were  made  at  8 
sees,  delay  and  with  the  exit  doors  from  the  light  boxes,  b  and 
c,  open.  In  the  records  obtained  with  the  large  release,  some 
new  symbols  were  used  in  describing  the  data  placed  in  the 

TABLE  XIV 

Eight  Seconds  Delay  with  Large  Release  ^ 

Animal         Orient.         Light  box  Beha\'ior 

Bob  ba-2  b  b        h.f.c. 

b 
b 

bc-2 
c 
b 
b 

cb-l 
b 
b 


c 
b 
b 

c 
b 
b 

D.C. 

h.f.c.  (walked  to  a  and  back) 
n.c. 

c 
c 
b 

c 

be 

b 

n.c. 

c 
b 

c 
b 

n.c. 
h.f.c. 

c 

c 

n.c. 

DELAYED  REACTION  51 

"orientation"  column.  The  first  reaction,  e.g.,  is  to  be  read 
as  follows:  The  light  was  turned  on  in  b,  the  middle  box.  Bob 
was  held  for  8  sees,  during  which  time  he  pivoted  on  his  hind 
feet,  swinging  his  body  along  in  front  of  b.  At  the  moment 
of  release  he  was  still  in  front  of  this  -box,  but  was  oriented  with 
his  nose  in  the  corner  halfway  to  a,  the  box  on  the  right.  Dur- 
ing the  delay  at  the  fourth  reaction,  no  part  of  the  raccoon's 
body  was  constant.  He  walked  over  in  front  of  a  and  when 
released  was  in  front  of  b,  but  his  body  was  pointed  to  the  corner 
half  way  to  c  at  the  moment  of  release.  At  the  instant  of  re- 
lease for  the  eighth  reaction,  Bob's  body  was  pointed  three- 
fourths  of  the  way  toward  c.  This  brought  his  nose  within  a 
few  inches  of  the  entrance  to  that  box,  yet  the  reaction  succeeded. 
In  the  tenth  trial,  as  in  the  second,  position  and  orientation  both 
favored  the  same  wrong  box.  In  each  case  the  reaction  was 
correct. 

The  net  result  of  the  data  presented  here  for  Bob  is  an  almost 
entirely  conclusive  proof  of  the  statement  that  he  does  not 
wholly  depend  either  upon  bodily  orientation  or  upon  position 
in  the  box  for  the  cues  determinant  of  the  subsequent  reaction. 
The  37%  made  with  the  reactions  of  class  i  is  very  significant 
when  one  does  not  lose  sight  of  the  fact  that  both  orientation 
and  position  were  here  combined  against  any  other  factor  lead- 
ing to  a  correct  response.  In  class  2  where  such  a  combination 
was  not  present,  the  percentage  is  conclusive  as  to  the  presence 
of  some  non-observable  cue.  This  is  but  further  data  confirma- 
tive of  that  already  presented  above  for  Jack  with  the  small 
and  large  release. 

In  view  of  the  generally  negative  results  obtained  with  the 
large  release,  as  far  as  developing  new  and  higher  types  of  be- 
havior is  concerned,  some  one  may  say;  (i)  That  if  all  of  the 
animals  had  been  started  with  the  large  release  instead  of  with 
the  small  one,  they  would  not  have  been  so  likely  to  develop 
gross  motor  cues  to  guide  their  reactions,  and  (2)  that  it  is  not 
surprising  that  no  new  type  of  behavior  appeared  after  the 
animals  were  firmly  in  the  grip  of  habits  developed  in  the  small 
release.  To  these  criticisms  I  can  only  reply  that  any  experi- 
ment must  exhaust  first  one  method  and  then  another.  Time 
did  not  permit  the  use  of  both  methods  here. 


52  WALTER  S.  HUNTER 

2.    Tests  with  Children 

A.  Method  of  Experimentation. — Details  of  the  method  of 
experimentation  here  used  may  be  presented  as  follows:  When 
the  subject  was  first  brought  into  the  room,  the  following  in- 
structions were  given:  We  have  a  little  game  in  here  which 
we  are  going  to  play.  You  will  stand  in  here,  (I  indicate  the 
release  box).  When  I  release  you  by  raising  the  gate,  (I  illus- 
trate raising  the  gate),  you  are  to  go  and  push  one  of  the  but- 
tons over  on  the  wall.  One  of  these  buttons  will  make  a  noise. 
If,  after  I  raise  the  gate,  you  push  the  noisy  button  first,  I  will 
give  you  some  candy  when  you  come  back  to  me.  But  if  you 
go  first  to  some  button  that  isn't  noisy,  then  you  must  try  again 
before  you  get  the  candy.  So,  you  see,  the  game  is  to  push 
the  noisy  button  first  and  so  get  candy.  Do  you  see  now  how 
we  are  to  play  the  game?  Run  over  there  and  push  on  some 
of  the  buttons.  See,  sometimes  they  make  a  noise  and  some- 
times they  don't.  (I  switch  the  buzzer  on  and  off  for  all  the 
buttons.  The  lights  are  not  on  yet,  nor  has  the  subject's  atten- 
tion been  called  to  them.)  Now  let's  try  the  game  and  see  if 
you  can  push  the  noisy  button  first.  (The  child  is  placed  in  the 
release  box.  The  light  is  switched  on  over  the  noisy  button. 
The  child  is  held  5  sees,  in  the  release  box  before  being  set  free.) 
These  instructions  were  memorized  by  the  experimenter;  and, 
although  parts  were  repeated  several  times  to  the  subject, 
nothing  that  is  not  given  above  was  told  to  the  child. 

It  was  found  that  with  all  save  F,  6  preliminary  trials  were 
sufficient  to  familiarize  the  children  with  the  apparatus  and  to 
overcome  their  timidity.  (H's  exception  will  be  noted  below.) 
F  was  given  35  trials  extending  over  three  days  on  the  prelim- 
inary work  of  learning  that  the  noisy  button  meant  candy. 
By  the  end  of  that  time  the  association  was  firmly  established. 

No  fixed  number  of  trials  per  day  was  given.  The  amount  of 
the  day's  work  was  adjusted  to  the  child's  disposition  and  to 
the  length  of  delays.  No  set  number  of  trials  was  given  at  any 
stage  of  delays.  In  other  words  much  the  same  method  was 
used  as  for  the  first  year's  work  with  the  raccoons.  Bob  and 
Betty.  Delays  were  increased  continuously  until  an  error  was 
made.  At  this  point,  they  were  either  decreased  at  once  or 
continued  at  their  existent  value  for  several  trials  before  further 
change  was  made.     The  experimenter  believes  that  so  flexible 


DELAYED  REACTION  53 

a  method,  when  properly  checked  by  careful  observation  of  the 
subject  so  that  the  task  is  changed  in  constant  sympathy  with 
the  subject's  apparent  needs,  is  excellently  fitted  to  bring  out 
what  the  subject  can  do  naturally  as  opposed  to  what  it  can 
be  trained  to  do.  Of  course  the  effects  of  training  cannot,  and 
need  not,  be  eliminated.  However,  they  are  not  so  great  in 
the  method  outlined  above  as  they  would  be  were  many  trials 
given  at  each  stage.  The  difficulty  here  is  the  same  as  that 
mentioned  when  discussing  the  records  for  the  raccoons  viz., 
where  only  a  few  trials  are  given,  the  critic  has  a  better  chance 
to  claim  that  the  results  are  due  to  chance.  Our  conclusions 
will  seek  to  avoid  this  criticism.  But  in  the  last  analysis,  the 
themselves  must  be  their  own  justification. 

B.  Are  the  Results  Obtained  from  Animals  and  Children  Com- 
parable?— In  the  light  of  the  foregoing  method  and  of  careful 
observation  of  the  children,  the  following  points  suggest  them- 
selves as  the  essential  considerations  in  a  relative  estimate  of 
the  conditions  under  which  the  children  and  the  other  animals 
worked:  (i)  Fear. — ^This  was  overcome  in  the  animals  by  the 
preliminary  training;  in  the  children,  by  kindliness  and  cheer- 
fulness on  the  part  of  the  experimenter  and  by  the  child's  ex- 
amination of  the  apparatus  as  described  above.  (2).  Motive. — 
Hunger  and  punishment  insured  a  maximum  of  effort  on  the 
part  of  the  animals.  Candy,  words  of  praise  from  the  experi- 
menter and  a  desire  to  excel  its  companions  incited  the  child 
to  do  its  best.  (3)  Knowledge  of  the  reaction  desired. — The 
rats,  dogs  and  raccoons  had  to  learn  everything  by  themselves. 

(a)  The  preliminary  series  acquainted  them  with  the  fact  that 
there  were  three  exits  to  the  problem  box  and  possibly  also 
with  the  fact  that  only  one  of  these  would  be  open  at  a  time. 

(b)  In  the  regular  learning  tests,  these  animals  had  to  associate 
the  light  and  the  open  box  in  such  a  manner  that  the  light 
became  the  sign  of  the  open  box.  (c)  In  the  delayed  reaction 
tests,  again,  they  had  to  learn  that  the  open  exit  was  always 
in  the  box  which  had  been  most  recently  lighted.  If  we  turn 
now  to  the  children,  we  find  the  following  situation:  (a)  They 
were  told  of  the  push  buttons  which  for  their  problem  corres- 
ponded to  the  exits  of  the  other  experiment  boxes.  Where  the 
animals  had  had  to  learn  the  fact  of  only  one  open  exit  by 
trial  and  error,  the  children  were  at  least  aided  'by  being  told 


54  WALTER  S.  HUNTER 

that  only  one  button  would  make  a  noise,  (b)  In  the  regular, 
learning  series,  the  children  had .  to  acquire  the  association 
between  noisy  button  and  light  on  their  own  initiation.  It 
must  be  remembered  that  the  experimenter  never  mentioned 
the  word  light  and  never  directed  the  subjects'  attention  to 
the  lights  as  long  as  the  experiments  continued,  (c)  In  the 
delayed  reaction,  also,  the  children  were  thrown  on  their  own 
resources  in  the  working  out  of  the  problem.  (4)  Treatment 
during  the  delay. — During  the  interval  of  delay  the  rats,,  dogs 
and  raccoons  were  usually  left  strictly  alone.  Only  in  a  few 
control  tests  was  any  effort  made  to  distract  them.  However, 
uncontrollable  noises  occasionally  intervened  and  disturbed  the 
dogs  and  the  raccoons.  During  the  period  of  delay,  the  children 
were  entertained  by  the  experimenter  by  means  of  stories,  the 
drawing  of  pictures  and,  in  a  few  of  the  long  delays,  by  gifts  of 
candy.  In  his  opinion,  these  distractions  made  the  experiment 
more  difficult,  although  it  is  true  that  impatience  and  fretting 
on  the  part  of  the  subject  were  largely  eliminated.  It  would 
thus  seem  that  the  only  objection  to  this  method  is  that  possibly 
the  distractions  served  to  urge  the  child  to  form  a  "purpose  to 
remember"  sooner  than  would  otherwise  have  been  the  case. 
I  cannot  deny  this  as  a  possibility.  It  may  have  occurred  with 
the  girl  M.  But  from  the  fact  that  the  others  remained  impa- 
tient and  complained  of  the  delay  until  late  in  the  experimenta- 
tion, I  do  not  believe  they  realized  before  that  time  that  the 
problem  was  to  see  how  long  they  could  remember.  Question- 
ing on  this  point  at  the  close  of  the  experimentation  confirmed 
this.  (5)  Possibility  of  the  problem  being  talked  over  by  the 
subjects. — This,  of  course,  has  no  bearing  on  the  case  of  the 
animals,  but  it  presents  a  fairly  serious  possibility  with  respect 
to  the  children.  The  possibility  is  all  the  greater  because  of 
the  fact  that  four  of  the  children  lived  in  the  same  neighbor- 
hood. Although  recognizing  this,  I  feel  that  it  played  very 
little  part  in  the  experiments ;  for  where  it  might  have  been 
effective,  the  tests  continued  but  ten  days.  j\I  was  old  enough 
to  do  as  she  was  told,  unless  severe  temptation  came  her  way. 
Such  a  possibility,  however,  was  prevented  by  cold  weather  and 
school  keeping  her  away  from  the  other  children.  As  will  be 
pointed  out  later,  talking  could  not  have  influenced  H's  con- 
duct because  she  knew  all  about  the  experiment.    F  was  under 


DELAYED  REACTION  55 

the  experimenter's  control  and  never  saw  the  other  children. 
Hd  and  L  differed  so  in  their  attitudes  toward  the  problem  and 
in  their  general  behavior,  that  I  cannot  well  believe  they  talked 
about  the  problem  when  together.  Further  evidence  why  it 
is  improbable  that  the  children  planned  with  one  another  how 
to  work  the  problem  is  that  there  was  a  very  keen  rivalry  as 
to  who  should  have  the  most  candy  beans  at  the  end  of  the 
day's  work.  When  the  work  was  finally  dropped,  the  children 
said  that  they  had  not  talked  the  problem  over  with  one  an- 
other. In  the  light  of  these  considerations,  I  believe  that  the 
children  and  the  animals  worked  essentially  on  a  par,  so  far  as 
extra-individual  influences  are  concerned,  throughout  both  the 
regular  learning  series  and  the  delayed  reaction  series.  I  say 
"essentially  on  a  par"  because  the  social  influence  due  to  the 
presence  of  another  member  of  the  same  species  was  operative 
in  the  case  of  the  children  while  it  did  not  appear  with  the 
animals. 

C.  Learning. — A  few  words  will  suffice  to  describe  the  trials 
given  on  learning  the  association  between  the  lights  and  the 
noisy  button.  With  all  subjects  save  F  the  light  was  first  turned 
on  at  a.  (For  F  it  was  put  on  at  h.)  On  this  first  trial  all  the 
subjects  failed.  F  went  to  a,  then  walked  past  h  to  c  and  thence 
back  to  h  and  rang  the  buzzer.  All  the  others  went  first  to  h 
and  then  to  a.  This  may  have  been  due  to  the  fact  that  h  was 
the  nearest  of  the  buttons.  F  was  the  only  one  that  made  an 
error  in  this  series  after  the  first  trial.  The  others  learned  the 
association  in  one  trial.  Out  of  the  i6  trials  on  the  first  day, 
F  failed  on  9.  The  first  test  was  missed  the  second  day  and 
none  the  third  day.  In  other  words,  no  errors  were  made  after 
the  17th  trial. 

D.  Differences  Between  the  Learning  of  Animals  and  Children. — 
Some  of  the  difference  between  the  above  data  and  that  for 
the  animals  is  undoubtedly  due  to  differences  in  attitude  toward 
the  problem,  although  the  conditions  were  so  arranged  that  this 
should  have  been  at  a  minimum.  Five  rats  learned  the  asso- 
ciation in  from  160  to  176  trials.  The  two  dogs,  it  will  be  re- 
called, required  more  than  500  trials.  Bob  received  only  120 
trials.  These  figures  present  the  number  of  tests  after  which 
no  errors  were  made.     Over  against  these  figures,   46  should, 


56  WALTER  S.  HUNTER 

stand  as  the  largest  number  of  trials  given  on  learning  to  any 
of  the  children,  and  this  to  F,  the  youngest. 

I  believe  that  the  main  factor  that  would  make  for  non- 
comparability  in  these  results  is  that  of  brightness  preference. 
It  is  not  known  what  the  value  of  this  factor  was  for  the  chil- 
dren. But  leaving  this  possibility  aside,  it  is  to  be  noted  that 
the  above  records  fall  into  two  well  defined  groups ;  those  for 
the  animals  and  those  for  the  children.  If  the  difference  here 
is  correlated  with  grades  of  intelligence,"  one  may  well  ask  why 
no  such  differences  appear  between  the  several  classes  of  animals. 
The  problem  is  all  the  more  interesting  when  it  is  pointed  out 
that  there  seems  no  certain  correlation  between  the  ability  to 
learn  the  association  and  the  ability  to  delay  when  one  considers 
the  various  groups  of  animals.  The  dogs  and  the  rats  used  the 
same  method  in  delay,  yet  Blackie  delayed  longer  than  any  rat. 
Jack  and  Bob  used  methods  of  behavior  in  delay  quite  different 
from  the  other  animals  and  their  delays  were  far  longer  than 
those  of  the  rats  and  of  Brownie.  Furthermore  two  of  these 
raccoons  delayed  about  the  same  period  of  time,  yet  varied 
greatly  in  their  times  for  learning  the  association.  Among  the 
children,  matters  would  seem  to  be  different.  They  learned 
raj)idly  and  in  delays  reached  relatively  long  periods  of  time 
by  what  seemed  the  same  method  used  by  the  raccoons.  The 
following  answers  suggest  themselves  with  reference  to  the 
question  put  just  above:  The  present  data  indicate:  (i)  Either 
that  the  different  grades  of  intelligence  among  the  animals  were 
not  great  enough  to  be  registered  in  the  learning  rates  although 
the  grades  between  an'mals  and  children  were  sufficient  to  mani- 
fest themselves ;  or  (2 )  that  the  association  can  be  learned  with 
a  t}^e  of  process  that  will  not  suffice  for  long  delays  where  the 
orientation  is  not  maintained.  If  this  latter  alternative  be 
correct,  it  would  seem  that  the  children  used  the  method  re- 
quired for  the  last  mentioned  type  of  delay  in  their  learning 
period.    The  raccoons,  on  the  other  hand,  used  the  same  method 

**  V.  C.  Hicks  and  H.  A.  Carr  **  find  no  such  correlation  of  the  number  of  trials 
taken  in  learning  a  maze  and  the  grade  of  intelligence  of  the  subjects.  The  time 
is  not  ripe  for  a  statement  of  the  type  of  learning  present  in  maze  problems  when 
compared  with  the  present  test.  However,  the  data  presented  by  the  above  writers 
and  by  myself  would  indicate  that  the  two  problems  do  not  involve  the  same  means 
of  solution,  at  least  to  the  same  extent. 

^'  Hicks,  V.  C.  and  Carr,  H.  A.  Human  Reactions  in  a  Maze.  Jour,  of  Animal 
Behavior,  1912,  vol.  2,  p.  101. 


DELAYED  REACTION  57 

in  learning  the  association  that  the  other  animals  did,  but  a 
different  method  when  it  came  to  delays.  There  may  thus  be 
a  difference  in  intelligence  due  to  varying  abilities  in  the  use  of 
some  one  instrument  of  adjustment  or  due  to  varying  abilities 
in  the  use  of  different  instruments  of  adjustment.  Blackie  and 
the  rats  would  illustrate  the  first  case ;  the  children  and  rac- 
coons in  comparison  with  the  other  animals  would  illustrate 
the  second.  So  much  for  the  possible  meaning  of  the  learning 
tirnes  of  the  different  animals  and  children 

E.  Delayed  Reactions. — M,  age  8  years,  was  given  38  trials 
on  delay.  The  first  2  only  were  at  intervals  less  than  i  sec. 
The  others  ranged  from  i  sec.  to  28  mins.  and  extended  over 
7  days.  Fifteen  trials  were  on  intervals  of  10  mins.  and  over. 
Only  two  errors  were  made,  one  at  5  mins.  and  one  at  20  mins. 
The  latter  was  probably  caused  by  ill-humor.  Longer  delays 
might  doubtlessly  have  been  secured  had  it  been  desired.  The 
only  attempt  was  as  follows:  On  four  days  (not  consecutive 
ones),  M  was  asked  which  button  she  pushed  last  the  day  before. 
Three  times  she  answered  correctly. 

M  did  not  need  to  keep  any  part  of  her  body  constant  during 
the  delay.  On  the  trials  involving  more  than  10  mins.  delay, 
she  was  sent  out  of  the  room  and  put  with  the  other  children. 
During  the  delays  she  conversed  freely  with  the  experimenter. 
Any  "•purpose  to  remember  "  that  the  subject  formed  was  formed 
on  her  own  initiative.  Great  care  was  taken — and  I  believe 
effectively  so — to  insure  that  no  suggestions  be  secured  from 
extraneous  sources.  As  early  as  the  15th  trial  on  delaysHM 
volunteered  the  information  that  she  remembered  where  the 
light  was  in  order  to  push  the  proper  button.  Several  times  she 
reacted  correctly  and  then  volunteered  that  she  had  guessed 
which  button  to  push. 

Several  extra  trials  were  given  in  which  the  problem  was 
changed.  The  light  was  now  placed  successively  over  two 
different  buttons,  the  last  button  being  the  noisy  one.  This 
problem  brought  out  a  type  of  reaction  very  often  seen  in  the 
animals.  M  would  start  toward  one  box  and  then  turn  and  go 
to  another.  In  the  regular  series,  hesitation  occasionally  oc- 
curred and  M  wavered  between  two  boxes. 

Hd,  aged  6  years,  was  given  47  trials  on  delays.  Only  the 
first  two  were  less  than  i  sec.  long.     The  others  ranged  from 


58.  WALTER  S.  HUNTER 

I  sec.  to  2^^  mins.  Fourteen  trials  involved  intervals  of  lo 
mins.  or  over.  A  total  of  15  trials  was  given  with  intervals  of 
4,  5  and  6  mins.  in  length.  In  the  47  trials,  10  errors  were  made. 
Two  of  these  came  in  each  of  the  delays  of  4,  5  and  6  mins.  One 
came  at  11  mins.;  i  at  12  mins.;  and  2  at  20  mins.  Hd,  there- 
fore, had  no  trouble  in  remembering  the  solution  of  the  problem 
until  the  intervals  of  delay  reached  4  to  6  mins.  Then  the 
difficulties  that  arose  were  mastered  and  did  not  reappear  until 
the  periods  11  to  12  mins.  and  20  mins.  were  reached. 

Hd  did  not  need  to  keep  any  part  of  his  body  constant  dur- 
ing delay.  He  and  the  experimenter  exchanged  stories  con- 
tinually. This  subject  differed  from  M  in  the  number  of  errors 
and  in  the  greater  frequency  with  which  information  was  offered. 
The  former  I  attribute  to  difference  in  ability;  the  latter,  to 
natural  garrulousness.  The  restraint  during  delay  was  a  great 
source  of  annoyance  to  Hd.  He  complained  a  great  deal  be- 
cause of  it.  My  diary  notes  contain  many  such  passages  as  the 
following:  When  light  was  turned  off,  he  said:  "Why  hold 
me  so  long,  I  may  forget  which  it  is."  The  subject  evidently 
realized  that  he  was  to  remember  where  the  light  had  been. 
Many  times  during  the  delay,  Hd  would  stop  conversing  and 
say  "O,  I  know  which  one  it  is"  and  would  then  point — not 
always  correctly — to  the  button  he  had  in  mind.  Instances  of 
wavering  and  hesitations  preceding  acts  of  choice  were  noticed 
with  this  subject. 

L,  age  6  years,  was  given  41  trials  on  delay.  Only  one  of 
these  involved  an  interval  less  than  i  sec.  long.  The  remainder 
were  from  i  sec.  to  25  mins.  in  length.  Twenty-one  trials  were 
on  delays  from  4  to  9  mins.  long.  Nine  were  on  delays  over 
10  mins.  in  length.  Seven  errors  were  made  in  the  total  41 
trials.  All  of  these  came  in  delays  of  4  mins.  or  over.  Two 
were  at  4  mins.  and  one  each  at  the  following  intervals:  5,  7, 
8,  15,  17  and  25  mins.  L,  as  Hd,  found  most  difficulty  in  the 
period  around  5  mins. 

L  did  not  find  it  necessary  to  keep  either  his  body  or  the 
direction  of  his  attention  constant  in  order  to  solve  the  problem. 
He,  too,  conversed  freely  with  the  experimenter  during  delays. 
L  would  often  watch  for  the  light  out  of  the  corner  of  his  eyes. 
After  it  appeared,  he  would  apparently  pay  no  further  atten- 
tion to  the  problem  until  released.     L  was  less  demonstrat  ve 


DELAYED  REACTION  59 

than  Hd  and  did  not  remark  so  often  during  the  delays  that 
he  still  knew  the  proper  button.  Like  Hd,  he  was  impatient 
during  the  short  delays  at  the  first  and  the  long  delays  at  the 
last  of  the  experiments.  At  times  he  wavered  and  hesitated  in 
his  reactions,  saying  that  he  had  forgotten  or  that  he  wasn't 
sure.  (In  such  cases,  of  course,  the  experimenter  gave  no  cue 
to  the  solution.) 

Each  of  the  three  subjects  whose  records  have  been  discussed 
formulated  his  own  "purpose  to  remember."  H  was  given  trials 
under  the  same  conditions  as  the  others,  save  that  she  was 
told  the  purpose  of  the  experiment.  She  was.  told  that  the 
light  would  be  over  the  noisy  button.  When  delays  were  begun, 
she  was  told  to  be  sure  and  remember  where  the  light  had  been. 

H,  age  6  years,  received  15  trials  on  delays.  Only  the  first 
two  involved  intervals  less  than  i  sec.  in  length.  The  others 
varied  from  10  sees,  to  35  mins.  One  error  was  made  at  21 
mins.  At  this  trial,  H  walked  half  way  to  b,  paused  for  5  sees., 
wavered  as  though  to  go  to  c,  but  finally  pushed  b.  She  then 
returned  to  the  release  and  was  told  to  try  again.  Again  she 
wavered  at  a  point  half  way  to  b,  but  this  time  she  went  to 
c.  The  light  had  only  been  turned  on  the  one  time.  I  did  not 
talk  to  H  during  the  first  12  delays.  She  was  always  told  before 
the  light  went  out  to  be  sure  and  remember,  but  this  was  alk 
In  the  subsequent  trials,  every  effort  was  made  to  distract  her 
during  the  periods  of  delay.  The  results  obtained  with  H,  when 
compared  with  those  for  Hd  and  L,  indicate  that  it  is  an  aid 
to  the  subject  to  have  the  "purpose  to  remember"  expressly 
formulated  for  him. 

F,  age  2^  years,  was  given  507  trials  on  delay.  Of  these,  30 
delays  were  less  than  i  sec.  long.  The  other  477  trials  ranged 
from  I  sec.  to  i  min.  Of  the  477,  143  were  wrong.  The  follow- 
ing table  (XV),  gives  the  relative  distribution  of  these  errors. 
It  does  not  give  the  delays  in  the  order  in  which  they  were 
given  to  F.  The  table  simply  summarizes  the  number  of  trials 
and  errors  at  each  stage.  An  advance  was  never  made  from 
one  stage  to  another  until  at  least  80%  correct  reactions  were 
made  for  at  least  5  successive  trials.  The  only  interval  that 
F  did  not  finally  master  was  i  rnin.  This  is  surprising  when 
such  a  high  percentage  of  correct  reactions  occurred  at  50  sees. 
On  each  of  the  two  days  when  F  was  tested  for  the  i  min.  delays, 


60 


WALTER  S.  HUNTER 
TABLE  XV 


Delay 

No.  of  trs. 

Errors 

Delay 

No;  of  trs. 

Errors 

1  sec. 

23 

4 

15  sees. 

65 

19 

2  sees. 

4 

0 

20     « 

40 

8 

3     " 

5 

0 

25     " 

22 

5 

5     " 

38 

10 

30     " 

22 

11 

6     " 

9 

0 

35     " 

18 

2 

7     " 

35 

9 

40     " 

23 

10 

8     " 

3 

0 

50     " 

19 

2 

10     " 

85 

37 

1  min. 

45 

26 

12     " 

10 

0 

the  first  one -third  of  the  trials  were  at  50  sees.  Reactions  were 
perfect.  The  last  two  thirds  of  the  day's  work  was  at  i  min. 
and  both  times  she  fell  below  50%.  There  were  no  known 
extraneous  factors  to  cause  this.  The  conditions  were  as  near 
ideal  as  possible.  The  method  adopted  with  F,  after  the  first 
three  days,  was  one  of  slow  advance  from  stage  to  stage.  At 
the  higher  delays,  each  day's  work  was  begun — as  just  illus- 
trated— with  the  longest  interval  that  had  been  mastered.  Some 
5  trials  were  given  here  and  only  if  the  reactions  were  perfect 
was  an  advance  made.  I  believe  that  entire  dependence  can 
be  placed  upon  the  results  obtained.  F  was  the  only  one  of 
the  children  that  did  not  reach  a  delay  of  at  least  20  mins. 

F  was  distracted  continually.  She  needed  to  keep  neither 
her  attention  nor  any  part  of  her  body  constant  in  order  to 
react  correctly  on  delays  up  through  50  sees.  She  often  hesi- 
tated and  wavered  in  making  the  choice  of  buttons.  It  is  inter- 
esting to  note  in  this  connection  that  this  wavering,  hesitant 
behavior  was  only  noted  in  the  case  of  the  raccoons  and  children. 
Every  individual  of  these  gave  many  examples  of  it.  This  is 
significant  when  it  is  borne  in  mind  that  these  subjects  used 
apparently  the  same  method  in  solving  the  problem.  If  that 
statement  is  too  broad,  at  least  it  may  be  said  that  they  agreed 
in  not  using  gross  motor  orientation  exclusively  as  did  the  rats 
and  dogs.  This  is  not  the  very  usual  type  of  behavior  described 
by  Yerkes  for  the  dancing  mouse.  He  says:  "I  have  at  times 
seen  a  mouse  run  from  one  entrance  to  the  other  twenty  times 
before  making  its  choice ;  now  and  then  it  would  start  to  enter 
one  and,  when  half  way  in,  draw  back  as  if  it  had  been  shocked. 
Possibly  merely  touching  the  wires  with  its  forepaws  was  re- 


DELAYED  REACTION  61 

Sponsible  for  this  simulation  of  a  reaction  to  the  shock."  *' 
The  above  reaction,  noted  by  Yerkes,  and  other  similar  cases 
in  the  literature  are  reactions  to  present  stimuli.  Where  the 
mouse  ran  to  the  entrance  of  the  box,  but  did  not  enter,  the 
explanation  undoubtedly  lies  in  the  inability  of  the  stimulus 
to  set  off  the  proper  reaction.  As  Yerkes  suggests,  the  stopping 
of  the  animals  half  way  to  the  box  was  probably  due  to  the 
contact  with  the  wires.  The  same  general  t3rpe  of  behavior 
described  above  for  the  raccoons  and  children  occurred  during 
certain  periods  of  time  with  my  own  rats  and  the  dogs.  In 
every  case,  however,  it  was  due  to  a  habit  of  turning  around 
when  released.  This  habit  was  executed  in  the  same  fashion 
no  matter  which  was  the  proper  box  to  choose.  As  opposed 
to  the  tests  where  either  present  objective  stimuli  or  habit  are 
involved,  the  reactions  of  the  children  and  raccoons  were,  as 
far  as  could  be  determined,  perfectly  spontaneous,  i.e.,  deter- 
mined by  intra-organic  conditions  that  varied  for  the  different 
boxes.  These  cases  belong  in  the  same  class  as  that  of  Miss 
Washburn's  cat  described  above  (p.  20). 

F's  father,  a  trained  psychologist,  informed  me  that  the 
child  was  just  reaching  the  stage  where  her  memory  for  objects 
and  events  had  begun  to  take  on  definite  form.  When  brought 
in  from  a  ride  in  the  park  or  a  visit  to  a  friend,  she  could  very 
seldom  remember  the  details  of  the  event,  indeed  not  more 
than  half  the  time  could  she  remember  the  gross  fact  of  having 
been  somewhere.  This  occurred  even  with  what  were  to  F 
very  interesting  experiences.  Sometimes,  it  is  true,  the  diffi- 
culty lay  with  the  lack  of  control  of  language ;  but  this  was 
not  always  the  case.  After  her  playmate  had  gone  for  some 
time,  if  F  was  asked  who  had  been  there,  not  only  could  she 
frequently  not  tell,  but  at  times  she  was  bewildered  even  by 
the  suggestion  that  anyone  had  been  to  see  her  at  all.  On  the 
other  hand,  some  cases  were  noted  where  F  remembered  an 
event  for  several  days.  Phrases,  also,  that  she  had  heard  but 
once  were  often  spontaneously  repeated  for  the  first  time  sev- 
eral days  later.  The  present  tests  thus  found  the  child  in  a 
very  important  stage  of  mental  development.  Definite  memo- 
ries, of  the  adult  human  kind,  were  still  hanging  in  the  balance 
with  the  chaos  of  the  preceding  period.    As  far  as  the  lengths 

*«  Yerkes,  R.  M.    The  Dancing  Mouse.     1907,  New  York,  p.  130. 


62  WALTER  S.  HUNTER 

of  delay  go,  F  ranks  approximately  half  way  between  the  other 
children  and  the  raccoons.  As  to  apparent  method  of  work 
she — and  the  other  children  too — is  superior  to  the  raccoons  in 
that  orientation  played  no  discernible  role  in  her  reactions. 

VI.     THEORETICAL  CONSIDERATIONS 
1.    The  Cues  Essential  for  Successful  Delayed  Reactions 

After  the  above  presentation  of  experimental  results,  there 
remains  the  important  task  of  determining  as  nearly  as  possible 
just  what  cues  the  subjects  used  in  their  reactions.  The  follow- 
ing paragraphs  of  this  section  will  set  forth  in  detail  the  various 
possibilities  of  interpretation  and  indicate  what  seem  to  me  to 
be 'their  relative  validities. 

Let  us  first  formulate  in  a  general  way  the  conditions  that  a 
reagent  will  have  to  meet  in  the  solution  of  the  present  problem. 
He  is  confronted  with  three  boxes  which  offer  as  many  known 
possible  points  of  egress.  One  of  the  boxes  is  Hghted.  In  the 
course  of  a  series  of  experiments,  the  reagent  has  learned  to  go 
through,  or  to  the  lighted  box  in  order  to  reach  food.  In  time 
the  stimulus  will  set  off  the  reaction  practically  automatically. 
Approximately  at  this  period,  I  begin  to  turn  off  the  light  before 
the  subject  reaches  the  box.  It  is  possible  that  for  several 
stages  of  delay  the  box  which  has  been  lighted  remains  light 
for  a  short  interval  of  time  due  to  the  presence  of  after-images 
in  the  subject's  eyes.  But  as  the  delays  increase  in  length,  there 
will  come  a  point  at  which  the  problem  shifts  from  "go  to  the 
lighted  box"  to  "go  to  the  one  of  three  dark  boxes  that  was 
most  recently  lighted."  If  this  shift  comes  before  the  i  sec. 
delay,  it  will  be  less  likely  to  involve  relearning.  If,  e.g.,  the 
change  comes  at. the  second  stage,  the  momentum  of  running 
will  make  it  easier  for  the  animal  to  continue  into  the  dark 
box  than  to  turn  and  seek  another.  With  some  rats,  the  results 
indicate  that  the  change  did  come  at  this  stage;  for  when  the 
light  was  turned  out,  the  animals  stopped  short  and  went  into 
another  box,  even  though  that  too  was  dark.  With  the  other 
animals  and  the  children,  it  was  impossible  to  tell  just  when 
the  shift  came.  The  problem  having  once  changed,  however, 
the  question  now  is  how  long  after  the  boxes  all  become  dark 
can  the  subject  pick  out  the  one  which  was  lighted  most  re- 
cently.    Our  special  problem  concerns  only  the  solution  of  this 


DELAYED  REACTION  63 

second  problem.  During  the  learning  series,  the  light  stimulus 
acquires  the  power  of  releasing  musdular  activity  applied  in  a 
certain  direction.  Just  what  direction  this  shall  be  is  deter- 
mined by  the  spatial  location  of  the  light.  A  significant  mean- 
ing here  attaches  to  the  object  ve  stimulus,  i.e.,  the  light  plus 
the  definite  location.  (By  the  term  meaning,  I  imply  nothing 
more  than  the  fact  that  a  certain  stimulus  evokes  a  certain 
reaction  under  conditions  that  are  not  usually  described  as 
involving  mere  habitual  or  reflex  activities.) 

As  soon  as  the  problem  shifts  to  a  choice  of  one  of  three  sim- 
ilar boxes,  i.e.,  as  soon  as  a  stage  is  reached  where  the  deter- 
mining stimuli  are  absent  at  the  moment  of  reaction,  then  it  is 
necessary,  I  assume,  if  the  reactions  are  to  succeed,  that  the 
subject  develop  substitutes  which  shall  take  the  place  of  those 
stimuli  as  carriers  of  the  needed  meanings.  In  other  words,  the 
substitutes  must  fulfill  the  function  of  the  previous  stimuli  in 
arousing  the  three  appropriate  movements.  The  substitutes 
may  secure  this  power  either  through  association  with  the  light 
during  the  learning  series,  or  during  the  delayed  reaction  tests 
themselves  through  a  process  of  trial  and  error.  In  view  of  the 
fact  that  delayed  reactions  did  succeed  under  the  present  con- 
ditions, there  can  be  no  question  as  to  the  existence  of  the  sub- 
stitutes.    Our  next  problem  is  that  of  determining  their  nature. 

The  substitutes  or  cues  that  determined  the  subject's  reac- 
tions may  theoretically  have  arisen  either  within  or  without 
the  organism.     We  shall  consider  the  latter  first. 

A.  Substitutes  Derived  from  the  External  Environment. — Under 
this  heading,  we  shall  consider  two  possibilities:  (a)  Were 
there  three  simultaneously  present  objective  cues  that  may 
have  served  to  determine  the  subject's  reactions?  and  (b)  were 
there  three  objective  cues  that  varied  from  trial  to  trial  with 
the  position  of  the  light  which  may  have  determined  the  reac- 
tions after  the  light  was  turned  off?  In  any  case  there  must 
be  two  or  three  cues  each  determining  one  of  three  reactions. 
We  shall  consider  the  possibilities  in  the  above  order. 

(a)  Simultaneously  present  objective  cues. — Although  every 
effort  was  made  to  secure  uniformity  in  the  visual  appearance 
of  the  three  light  boxes,  they  differed  at  least  in  spatial  position 
and  in  the  nature  of  the  part  of  the  experimental  room  visible 
above  the  walls  of  the  apparatus.     In  addition  there  were  pos- 


64  WALTER  S.  HUNTER 

sibly  olfactory  differences  in  the  boxes  used  by  the  animals  due 
to  the  animal  odor  itself  and  (in  the  case  of  the  rats  and  rac 
coons)  to  a  food  odor  set  up  by  the  milk  that  was  on  the  fore- 
feet of  these  animals.  Suppose  now  that  these  simultaneously 
present  external  factors  be  treated  in  their  entirety  for  each  box 
and  be  represented  by  the  letters  x,  y  and  z.  It  may  be  assumed 
that  the  subjects  learned  to  react  not  to  the  lights — a,  b  and  c 
— ^alone,  but  to  the  complexes  ax,  by  and  cz.  Then  when  the 
delays  were  begun,  the  reactions  were  made  to  x,  y  and  z,  either 
immediately  or  after  a  period  of  learning.  Here  we  would  have 
three  cues  governing  as  many  reactions,  and  all  three  cues 
would  be  presented  simultaneously  at  the  moment  of  release 
whereupon  the  reaction  would  take  place. 

This  hypothesis  is  not  supported  by  t*he  experimental  facts. 
If  the  reactions  during  the  delay  were  determined  by  these 
stimuli  present  at  the  moment  of  release,  the  animals  should 
have  learned  to  delay  for  almost  any  interval  of  time.  It  should 
be  no  more  difficult  to  react  to  x,  y  and  z,  than  to  the  lights, 
since  the  reactions  during  delays  were  just  as  "precipitate" 
and  "headlong"  as  when  the  lights  were  present.  Now  it  was 
demonstrated  that  all  of  the  animals  could  react  perfectly  when 
held  in  the  release  i  min.  with  the  light  on.  Why  then  could 
they  not  delay  a  minute  with  the  factors  x,  y  and  z  which  were 
also  constantly  present?  Further,  if  the  subjects  succeeded  in 
reacting  to  x,  y  and  z  for  intervals  of  5  or  6  sees.,  why  should 
they  be  unable  to  reach  7  or  8  sees.?  In  other  words,  wh3% 
if  they  reached  one  stage  of  delay  on  this  basis,  should  the 
subjects  not  go  a  little  beyond  and  so  up  to  a  large  delay?  There 
is  no  answer  to  this,  if  one  assumes,  as  we  have  done,  that  the 
cues  are  simultaneously  present  at  the  moment  of  response. 

In  the  section  on  experimental  results,  tests  were  described 
where  the  entire  sides  of  the  problem  box  surrounding  the 
entrances  to  the  light  boxes  were  covered  with  cardboards  of 
widely  separated  grades  of  brightness.  This  device  accentuated 
(from  the  experimenter's  point  of  view)  the  constant  differences 
between  the  hypothetical  stimuli  x,  y  and  z,  yet  under  these 
conditions  neither  rats,  dogs  nor  raccoons  showed  improvement 
in  their  abilities  to  react.  This  series  does  not  prove  that  no 
objective  factors  x,  y  and  z  were  influential  in  initiating  behav- 
ior; but,  in  conjunction  with  the  immediately  following  theoret- 
ical discussion,  it  does  make  it  very  improbable  that  such  fac- 


DELAYED  REACTION  65 

tors  should  have  exercised  a  determining  influence  on  the 
reactions. 

Let  us  grant  for  the  moment  that  such  objective  factors 
were  present,  could  they  alone  control  successful  reactions,  i.e., 
could  they  be  the  determining  factors  in  initiating  correct  de- 
layed reactions?  Since  x,  y  and  z  are  present  simultaneously  at 
every  response,  they  per  se  cannot  be  the  bases  for  differential 
responses.  The  subject  must  select  one  of  the  boxes.  Hence 
the  hypothesis  would  need  to  assume  that  the  subjects  are  not 
reacting  merely  to  x,  but  to  x-where -the -light -has -just -been. 
Here  we  are  forced  face  to  face  with  the  problem  from  which 
we  started:  What  represents,  or  is  a  substitute  for,  the  light? 
What  is  the  element  attaching  to  x  that  is  equivalent  to  "where- 
the-light -has  just-been  "  ?  There  can  be  no  question  but  that 
X,  y  and  z  in  some  form  constituted  a  part  of  the  general  stim- 
ulus, for  the  subject  must  apprehend  the  different  spatial  loca- 
tions of  the  boxes  in  order  to  react  to  them.  The  objection 
may  be  offered  that  this  contention  as  to  the  effectiveness  of 
these  objective  stimuli  is  inconclusive,  inasmuch  as  the  animals 
may  have  been  reacting  entirely  in  terms  of  kinaesthesis,  i.e., 
had  learned  the  fixed  order  in  which  the  three  boxes  were  pre- 
sented. This  possibility  was  adequately  eliminated  by  control 
tests  whose  results  are  discussed  on  p.  67.  The  point  to  be 
established  here  is  that  x,  y  and  z  could  not  have  been  the 
crucial  substitutes  for  the  lights.  These  must  have  been  fac- 
tors which  were  not  all  simultaneously  present,  each  in  its 
entirety,  at  every  response,  i.e.,  they  must  have  alternated 
from  trial  to  trial,  depending  therefore  on  the  position  of  the 
light.  The  question  now  is:  Were  there  any  such  factors  in 
the  objective  environment? 

(b)  Alternating  objective  cues. — Controls  were  instituted: 
(i)  To  prove  that  during  the  learning  series  the  light  (an  alter- 
nating factor)  was  the  determining  cue  for  the  reactions;  and 
(2),  to  prove  that  in  the  absence  of  the  light  no  other  external 
factor  took  its  place  as  a  determinant  of  the  reactions. 

I.  The  reagents  did  not  derive  any  cues  from  the  experi- 
menter. Screens  were  so  arranged  that  the  operator  was  never 
visible  to  the  dogs.  Control  tests  were  also  made  under  these 
conditions  with  the  rats,  raccoons  and  children.  The  constant 
beating  of  a  metronome  covered  up  any  noises  due  to  the  ex- 


66  WALTER  S.  HUNTER 

perimenter's  breathing  that  the  subjects  might  have  utiHzed. 
The  dogs  and  raccoons  did  not  rely  upon  the  manner  of  being 
released.  This  was  proved  by  having  different  persons  operate 
the  release.  This  control  was  not  used  with  the  rats.  How- 
ever, it  is  extremely  improbable  that  these  animals  depended 
upon  cues  from  such  a  source.  Moreover  had  they  or  any  of 
the  reagents  done  so,  their  intervals  of  delay  should  have  been 
almost  indefinitely  great.  It  must  be  borne  in  mind  that  any 
cues  derived  from  the  experimenter,  in  order  to  afford  extra 
aid  in  the  reactions,  must  be  present  at  the  moment  of  release. 
This  would  make  it  possible  for  the  animal  to  avail  itself  of 
the  cue  after  a  delay  of  any  length.  If  the  cues  were  given  by 
the  experimenter  only  at  the  beginning  of  the  delay,  the  prob- 
lem confronting  the  animal  would  not  differ  from  that  of  delay- 
ing with  reference  to  the  light. 

2.  The  reagents  did  not  depend  upon  any  after-glow  of  the 
lights.  When  the  lights  were  left  on  for  one  minute — a  period 
much  greater  than  was  ever  used  in  the  experiments  proper — 
and  were  then  turned  off,  there  was  no  appreciable  after-glow 
of  the  carbon  filament  that  the  experimenter  could  detect. 
(In  any  event,  such  an  afterglow  would  not  persist  long  enough 
to  influence  the  longer  delays  of  the  reagents.)  Hence  any  con- 
tinued brightness  of  the  boxes  (considered  from  the  reagent's 
point  of  view)  after  the  current  was  switched  off  must  have 
been  due  to  the  reagent's  after-images.  The  possibility  of 
using  these  for  cues  will  be  considered  below. 

3.  The  reagents  did  not  depend  upon  variations  in  the  tem- 
perature of  the  boxes  in  making  their  reactions.  After  the 
lights  had  been  turned  on  for  one  minute  in  any  box,  the  tem- 
perature of  that  box  was  never  raised  more  than  a  degree  centi- 
grade. Indeed  only  occasionally  could  any  change  of  tempera- 
ture be  detected.  The  "headlong"  manner  in  which  the  ani- 
mals reacted  to  the  boxes,  together  with  the  fact  that  they 
oriented  toward  the  light  immediately  upon  its  appearance 
indicate  that  they  were  not  governed  in  their  reactions  by  the 
slight  variations  in  temperature.  Yoakum''  found  that  rats 
could  discriminate  differences  of  16°  C,  but  even  then  their 
behavior  was  the  result  of  long  special  training.     His  squirrels 

*'  Yoakum,  C.  S.     Some  Experiments  Upon  the  Beha\'ior  of  Squirrels.     Jour. 
Comp.  Neur.  and  Psych.,  1909,  vol.  19,  p.  565. 


DELAYED  REACTION  67 

— and  probably  the  rats  also,  although  he  does  not  say — ^were 
hesitant  about  entering  the  boxes  even  with  a  difference  of 
25°  C.  These  data  make  it  exceedingly  improbable  that  the 
animals  in  the  present  tests  were  influenced  by  temperature. 

4.  The  animals  did  not  derive  cues  from  the  doors  at  the 
exits  of  the  light  boxes.  Numerous  control  tests  were  made 
in  which  all  of  the  doors — and  they  were  of  large  wire  mesh, 
and  hence  hard  to  see — were  open.  Under  these  conditions, 
the  animals  reacted  as  though  only  one  door  had  been  open, 
as  was  usually  the  case. 

B.  Substitutes  Derived  from  within  the  Subject's  Body. — The  dis- 
cussion of  these  intraorganic  substitutes  will  be  divided  into  two 
parts:  (i)  What  were  the  internal  cues  used  by  the  various 
reagents?;  and  (2),  how  did  these  internal  cues  operate  in  order 
to  guide  behavior? 

(a)  The  type  of  internal  cue  used. — i.  Did  the  subject  antici- 
pate the  order  of  presentation  of  the  lights,  i.e.,  were  the  cues 
to  the  reactions  the  individual  responses  of  an  habitual  series? 
The  evidence  is  perfectly  unambiguous  in  support  of  the  fact 
that  the  reagents  did  not  rely  upon  the  presentation  order  of 
the  boxes  in  making  their  reactions.  The  order  for  each  group 
of  animals  (not  children)  followed  a  series  of  30  presentations 
so  arranged  that  each  box  recurred  an  equal  number  of  times. 
A  new  series  was  given  whenever  one  box  was  eliminated  from 
the  experiments.  Control  tests  in  which  the  regular  order  of 
presentation  was  varied  were  introduced  practically  once  every 
two  weeks  with  all  the  animals.  Controls  were  also  made  in 
which  the  lights  were  not  used. 

2.  Did  the  reagents  guide  their  reactions  by  after-images  of 
the  light?  Although  the  existence  of  after-images  in  animals 
has  not  been  demonstrated,  we  shall,  for  the  sake  of  the  argument, 
disregard  this  fact  and  admit  of  their  possibility.  In  order  to 
lead  to  correct  reactions  in  our  experimsnt,  these  after-images 
must  appear  in  the  proper  direction  for  each  response.  Their 
directional  position  is  a  function  of  the  orientation  of  the  head 
and  eyes,  and  as  a  consequence  the  hypothesis  can  not  explain 
those  correct  reactions  resulting  from  faulty  orientations.  After- 
images can  possess  a  possible  function  only  in  conjunction  with 
the  maintenance  of  a  constant  orientation,  and  the  hypothesis 
would  need  to  assume  that  these  overt  motor  attitudes  are  but 


68  WALTER  S.  HUNTER 

subsidiary  phenomena  serving  as  a  means  for  the  effective  func- 
tioning of  the  after-image  processes.  But  after-images  can 
hardly  persist  long  enough  to  account  for  the  maximum  periods 
of  delay  attained  by  this  method  of  solution.  Such  delays 
varied  from  lo  sees,  for  the  rats  to  25  sees.,  for  the  raccoons 
and  5  mins.  for  one  dog.  All  of  the  conditions  of  the  test  were 
distinctly  unfavorable  for  any  persistence  of  possible  after- 
images. The  light  was  weak  in  intensity  (3  c.p.).  Its  average 
duration  of  exposure  was  approximately  but  5  sees.  Any  ap- 
proximation to  steady  fixation  either  during  or  subsequent  to 
the  exposure  of  the  light  was  the  exception.  The  animals  as  a 
rule  were  continually  on  the  move,  nosing  and  clawing  at  the 
face  of  the  release  box  both  during  the  exposure  and  the  period 
of  delay.  Steadiness  of  fixation  after  the  perception  of  the 
stimulus  is  a  very  essential  condition  for  the  development  of 
after-images.  Movements  of  the  head  or  eyes  tends  not  only  to 
prevent  their  appearance  but  also  to  destroy  them  when  present. 
The  significance  of  these  conditions  is  more  apparent  by  re- 
calling the  fact  that  any  extended  duration  of  after-images  is 
an  exceedingly  rare  phenomenon  in  the  normal  perceptual  activ- 
ities of  humans.  Fixation  is  too  short  and  changeable  for  their 
development.  Since  we  are  forced  to  argue  from  analogy  with 
human  conditions,  one  must  also  distinguish  between  the  pos- 
sible presence  of  such  processes  and  the  ability  to  perceive 
them.  The  mind  tends  in  the  interest  of  clear  vision  to  over- 
look and  neglect  such  processes  as  it  does  in  the  case  of  entoptic 
phenomena.  With  many  people  the  ability  to  see  after-images 
involves  a  previous  knowledge  of  their  existence  and  some 
degree  of  training  and  practice  in  their  observation.  In  other 
w^ords,  after-images  as  persistent  objects  of  consciousness  are 
a  product  of  the  laboratory,  and  the  assumption  of  their  effec- 
tive existence  as  guides  to  conduct  in  the  normal  perceptual 
activity  of  an  animal  is  exceedingly  questionable.  After-images 
exhibit  the  phenomenon  of  intermittence.  No  high  percentage 
of  correctness  of  response  could  result  from  such  a  cue,  as  its 
presence  at  the  moment  of  response  would  be  a  chance  coinci- 
dence. The  theory  of  after-images,  moreover,  is  entirely  un- 
necessary, as  we  have  the  possibility  that  these  motor  attitudes 
of  orientation  may  themselves  serve  as  a   sufficient  guide  to 


DELAYED  REACTION  69 

conduct,  and  on  this  hypothesis  the  assumption  of  the  effective 
presence  of  after-images  is  an  explanatory  luxury. 

3.  Motor  attitudes  of  orientation  as  cues  of  response.  The 
data  of  the  preceding  section  conclusively  prove  that  main- 
tenance of  orientation  during  delay  was  an  essential  condition 
for  correct  response  with  the  rats  and  dogs,  and  that  such  motor 
attitudes  exerted  a  strong  influence  upon  the  behavior  of  the 
raccoons.  Either  these  attitudes  serve  as  the  substituted  cues 
and  control  conduct  directly,  or  they  function  indirectly  as  a 
means  of  support  to  some  such  cue  as  an  after-image.  The 
evidence  unambiguously  favors  the  first  supposition.  These 
orientation  attitudes,  like  any  sensory  process,  may  be  a  stim- 
ulus to  definite  movements.  This  tendency  of  the  animal  to 
run  in  the  direction  of  their  orientation  at  the  moment  of  re- 
lease was  natural  and  habitual.  The  tendency  was  present  in 
full  strength  at  the  beginning  of  the  experiment.  The  tests 
merely  developed  the  maintenance  of  orientation  for  longer  and 
longer  periods.  This  fact  indicates  that  the  motor  attitude 
functions  directly  upon  subsequent  conduct.  If  the  attitudes 
were  but  a  means  of  support  to  some  other  cue,  one  would 
expect  that  this  relationship  of  means  and  end  would  need  to 
be  acquired  gradually  during  the  experiment.  An  alternative 
theory  presents  many  theoretical  and  factual  objections.  Any 
such  roundabout  and  forced  type  of  explanation  is  entirely 
unnecessary  when  we  know  that  motor  attitudes  are  a  natural 
guide  to  the  direction  of  subsequent  responses.  The  mechanism 
of  such  a  cue  may  be  entirely  automatic  and  mechanical.  It 
requires  nothing  more  for  its  explanation  than  does  any  habit. 
A  stimulus  initiates  a  certain  act  whose  completion  is  prevented 
by  external  means.  This  initial  activity  persists  unchanged  so 
far  as  its  directional  aspect  is  concerned  until  the  raising  of  the 
release  permits  it  to  function  in  a  normal  and  habitual  manner. 

4.  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.  Our  proof 
of  this  statement  is  based  upon  the  method  of  exclusion  and 
the  nature  of  such  a  factor  must  necessarily  be  defined  at  pre- 
sent in  negative  terms.  We  have  exhausted  our  ingenuity  as 
to  objective  possibilities  of  explanation,  and  as  a  consequence 


70 


WALTER  S.  HUNTER 


are  forced  to  conclude  in  favor  of  an  intra-organic  factor.  The 
possibility  of  a  temporal  series  of  habits  was  eliminated  by 
control  tests.  Neither  orientation  nor  any  distinctive  motor 
attitude  could  be  detected  in  the  children  or  in  at  least  25%  of 
the  responses  of  the  raccoons.  The  after-image  hypothesis  is 
entirely  inadequate  when  orientation  is  faulty.  In  those  reac- 
tions of  the  raccoons  resulting  from  wrong  orientations,  the 
percentage  of  correctness  was  so  great  as  to  eliminate  the  possi- 
bilit}^  of  chance.  The  nature  and  mechanism  of  this  factor 
will  be  discussed  in  subsequent  sections. 

5.  The  following  table  (XIII)  summarizes  the  cues  used  by 
the  different  reagents.  P.C.  (possible  cue)  means  that  the 
reagents  so  listed  may  have  used  that  cue  at  times.  N.C. 
(necessary  cue)  means  that  the  reagents  so  listed  had  to  use 
that  cue  or  fail  in  a  significant  number  of  their  reactions.  R 
stands  for  rats ;  D,  for  dogs ;  RA,  for  raccoons ;  and  CH,  for 
children.     For  convenience  of  reference  a  classification  is  made 


TABLE  XIII 
Cues  Used  by  the  Re-agents 


Internal 

External 

After-image 

Orient.  At. 

Non-orient.  At. 

Idea 

P.C. 

N.C. 

P.C. 

N.C. 

P.C. 

N.C. 

P.C. 

N.C. 

Never  a 

determining 

cue 

R 

D 

RA 
CH 

RA 

R 
D 

RA 
CH 

RA 
CH 

in  this  table  of  those  reagents  that  may  have  guided  their  re- 
action by  ideas.  This  phase  of  the  table  will  not  be  clear  until 
the  final  section  on  the  Place  of  Ideas  in  the  Grades  of  Animal 
Learning  is  read. 

(b)  The  mechanism  by  which  internal  cues  guide  behavior. — As 
already  indicated  the  mechanism  of  orientation  attitudes  pre- 
sents no  dif!iculties.  The  light  stimulus  arouses  the  proper  act. 
This  inhibited  act  persists  unchanged  so  far  as  its  essentials 
are  concerned  during  the  delay.  At  the  moment  of  release  the 
animal  runs  in  the  direction  of  its  orientation.  This  tendency 
of   responding   in   conformity  with  orientation  is   natural   and 


DELAYED  REACTION  71 

habitual  with  the  animal.  The  whole  process  is  explicable  on 
the  basis  of  habit.  Maintenance  of  orientation  is  acquired 
gradually  by  the  trial  and  error  method  as  is  any  habit. 

The  case  of  the  non-orientation  cues  presents  more  difficulty. 
During  the  preliminary  learning  tests  there  was  established  by 
the  trial  and  error  method  an  association  between  the  lights 
and  the  three  acts  of  securing  food.  Between  the  two  terms 
of  each  of  these  three  primary  associations  there  was  interpolated 
probably  by  the  trial  and  error  method  an  intermediary  link. 
These  three  cues  were  associated  with  their  respective  lights  on 
the  one  hand  and  their  respective  acts  on  the  other.  Each  light 
will  now  awaken  its  coiTesponding  cue  and  this  cue  will  in  turn 
initiate  the  act  with  which  it  has  been  associated.  In  order  to 
insure  correctness  of  response,  the  proper  cue  must  be  present 
at  or  immediately  after  the  release.  As  the  interval  of  delay 
between  the  light  stimulus  and  the  response  is  increased  in 
length,  we  have  three  possibilities  as  to  the  behavior  of  the 
intermediary  link  or  cue.  (i)  After  being  aroused  by  the  light 
stimulus,  the  cue  may  persist,  or  be  constantly  maintained, 
during  the  interval  of  delay.  All  of  the  available  evidence  tends 
to  disprove  such  a  hypothesis.  The  raccoons  were  frequently 
distracted  during  the  delays  by  various  laboratory  noises,  such 
as  the  squealing  of  rats  and  the  rattling  of  windows.  Note  was 
made  of  these  occurrences  and  still  correct  responses  were  pos- 
sible in  spite  of  these  distractions.  The  raccoons  were  exceed- 
ingly active  during  the  delays,  pawing  and  clawing  and  running 
all  about  the  release  box.  I  often  distracted  the  animals  by 
bending  down  over  the  release  box  and  yelling  at  them  at  the 
top  of  my  voice.  A  typical  case  occurred  when  Bob  was  making 
a  delay  of  15  sees. — with  a  very  high  percentage  of  correct 
responses.  These  distractions  during  delay  lowered  his  per- 
centage approximately  eight  points.  His  behavior  indicated 
that  this  treatment  actually  diverted  his  "attention"  from  the 
problem  at  hand.  The  emotional  character  of  such  a  disturb- 
ance makes  the  high  percentage  of  correct  behavior  especially 
significant.  I  also  continually  distracted  the  children  during  the 
delays  by  engaging  their  attention  with  stories,  drawing  pictures, 
conversation,  etc.  In  fact  the  attention  and  interest  of  the 
children  were  often  engaged  to  the  point  of  absorption  by  these 
devices  with  no  effect  upon  the  correctness  of  their  reactions. 


72  WALTER  S.  HUNTER 

The  constant  maintenance  of  the  cue  under  these  conditions 
of  distraction  and  length  of  delay  is  highly  improbable.  Speak- 
ing in  conscious  terms,  it  would  require  great  concentration  and 
mental  ability  even  for  a  human  adult  to  keep  any  cue  con- 
stantly in  "mind"  during  such  conditions.  (2)  The  cue  might 
be  some  intrinsically  intermittent  process  such  as  an  after- 
image. Such  substitutes,  however,  could  not  suffice  to  guide 
reactions  under  the  conditions  of  the  experiment.  Their  pres- 
ence at  the  moment  of  release  would  be  purely  accidental  and 
hence  they  can  not  account  for  the  high  percentage  of  correct 
responses  obtained.  (3)  We  are  forced  to  adopt  the  third  hypo- 
thesis that  the  cue  disappears  after  being  aroused  by  the  light 
stimulus,  and  is  rearoused  in  some  manner  at  the  moment  of 
release.  To  explain  the  mechanism  of  this  revival,  we  shall 
assume  that  all  three  of  the  intra-organic  cues  have  become 
associated  during  the  course  of  the  experiment  with  some  sen- 
sory factor  connected  with  the  releasing  of  the  animal.  Hence 
the  release  is  a  stimulus  which  tends  to  arouse  all  three  intra- 
organic tendencies.  This  revival,  however,  must  be  selective 
and  adaptive  and  this  adaptiveness  can  be  explained  by  two 
additional  assumptions.  The  presence  of  each  light  stimulus 
at  the  beginning  of  delay  excites  its  corresponding  intra-organic 
factor,  and  this  excitement  subsides  after  the  disappearance  of 
the  light.  Although  the  release  stimulus  does  tend  to  revive 
all  three  factors,  yet  it  will  arouse  that  one  most  recently  active, 
viz.,  that  excited  by  the  Hght  at  the  beginning  of  the  delay. 
The  assumption  that  the  predisposition  of  a  tendency  to  response 
depends  upon  its  recency  of  functional  activity  is  a  recognized 
principle  of  human  psychology.'*  With  such  a  mechanism,  it 
would  seem  that  the  problem  of  delay  should  present  no  serious 
difficulties.  However,  the  time  interval  between  tests,  i.e.,  the 
differences  between  the  recency  of  excitation  of  the  three  fac- 
tors, is  small  in  many  cases.  Learning  to  enter  the  box  most 
recently  lighted  as  opposed  to  the  box  most  recently  entered  is 
also  no  easy  problem  to  master. 

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. 

■•*  Ladd  and  Woodworth.  Elements  of  Physiological  Psychologj'.  New  York, 
1911,  p.  285. 


DELAYED  REACTION  73 

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.  The  question  as  to  the  content  nature  of  these 
cues,  i.e.,  their  sensory  or  imaginal  character,  is  reserved  for 
the  succeeding  section. 

2.     The  Place  of  Ideas  in  the  Grades  of  Animal  Learning 

A  survey  of  animal  reactions  from  those  of  the  protozoa  to 
those  of  the  higher  vertebrates  leads  one  to  the  conclusion  that 
the  simplest  behavior,  from  a  genetic  point  of  view,  is  the  ad- 
justment of  a  certain  movement  to  a  certain  object  or  situa- 
tion. This  adjustment  may  be  either  native  or  acquired.  In 
the  former  case,  it  is  instinct ;  in  the  latter,  the  result  of  indi- 
vidual learning.  (As  such,  it  does  not  seem  to  be  present  in 
the  protozoa.)  The  remarks  in  what  is  to  follow  are  directed 
solely  to  the  latter  case.  In  the  literature  this  is  referred  to 
as  the  stage  of  learning  by  experience  on  a  sensori-motor  level. 
Over  against  this  genetically  simple  learning,  may  be  placed  a 
more  complex  form  of  behavior  which  involves  a  representative 
function.  This  ideational  or  representative  process  arises  out 
of  a  genetically  prior  sensori-motor  level  of  behavior.  The 
field  of  its  functioning  is  limited,  moreover,  to  the  representa- 
tion either  of  some  aspect  of  the  object  (or  sensory)  side  or  of 
some  part  of  the  movement  and  its  consequences.  In  other 
words,  the  representative  process  must  stand  for  either  the 
sensory  or  the  motor  aspect  presented  in  the  genetically  lower 
level  of  behavior.  According  to  the  law  of  parsimony,  the  only 
conclusive  evidence  in  favor  of  the  existence  of  such  a  repre- 
sentative element  is  the  case  where  successful  adaptations  occur 
when  that  part  of  the  sensori-motor  process  assumed  to  be 
represented  is  known  to  be  absent  at  the  moment  of  response. 
If  the  object  or  movement  to  be  represented  is  present,  why 
assume  a  representative  or  ideational  process?  The  adjustment 
can  be  explained  in  terms  of  sensory  stimulus  and  response. 


74  WALTER  S.  HUNTER 

This  is  the  defect  in  all  of  the  arguments  and  experiments  which 
we  have  examined  in  the  historical  section  above.  Ideas  may 
have  been  present,  but  since  all  of  the  beha^dor  can  bs  inter- 
preted in  terms  of  stimulus  and  response,  the  arguments  are 
inconclusive. 

From  this  point  of  view,  there  are  from  the  standpoint  of 
function  two  classes  of  ideas: — ^ideas  of  objects  or  those  repre- 
senting the  stimiilus  aspect  of  the  situation,  and  ideas  of  move- 
ment or  those  representing  some  aspect  of  the  movement  or 
its  sensory  consequences.  Theoretically,  the  problem  of  ideas 
can  be  attacked  from  either  point  of  view.  Many  discussions 
and  experiments  do  approach  the  topic  exclusively  from  the 
movement  side,  but  practically  such  a  procedure  involves 
almost  insuperable  difficulties.  Washburn,'"  e.g.,  makes  the 
number  of  ideas  of  movement  possessed  by  an  animal  more  or 
less  of  a  rough  index  of  that  animal's  place  in  the  scale  of  in- 
telligence. But  the  presence  of  such  ideas  is  as  yet  an  assump- 
tion of  very  uncertain  validity.  Furthermore,  an  experimental 
technique  that  would  isolate* and  control  the  movement  factor 
would  be  extremely  difficult,  if  not  impossible  to  devise.  When, 
e.g.,  an  animal  is  brought  along  a  path  in  a  maze  to  a  point 
where  two  possible  reactions  are  presented,  both  responses  are 
for  the  moment  inhibited.  But  the  two  movements  need  not 
be  represented,  they  may  be  actually  there,  although  in  an 
incipient  form  only,  i.e.,  the  conflict  may  be  between  the  motor 
impulses  themselves  and  the  conflict  may  be  resolved  on  this 
level  without  the  influence  of  any  f^-ctor  representative  of  the 
effects  of  the  movements.  I  doubt  whether  experimental  tech 
nique  can  ever  control  this  movement  factor.  Quite  the  reverse 
is  true  with  respect  to  controlling  the  presence  of  the  object, 
i.e.,  of  the  determining  stimulus.  This  latter  may  be  given  or 
withheld  at  the  investigator's  pleasure.  It  is  the  merit  of  the 
experiments  here  set  forth  to  have  followed  such  a  procedure. 
In  the  present  case,  there  seems  to  be  no  room  for  doubt  that 
the  object  reacted  to  was  the  light.  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  of  movement — 

5"  Washburn,  M.  F.     Op.  cit.,  pp.  279-284. 


DELAYED  REACTION  '  75 

was  constant  from  tr  al  to  trial,  whereas  a  selective  response 
must  needs  have  an  alternating  cue. 

In  the  light  of  the  evidence  in  the  present  monograph,  let 
us  grant  the  presence,  in  certain  reagents,  of  a  process  represen- 
tative of  objects.  The  question  now  arises,  Must  this  process 
be  imaginal  or  may  it  be  sensory?  We  may  treat  the  latter 
possibility  in  two  ways:  (i)  There  may  be  a  sensation  arising 
from  the  reagents  body — kinaesthetic,  e.g., — that  stands  for  a 
certain  reaction.  Or  (2),  the  substitute  may  simply  consist  of 
a  differential  meaning  attached  to  the  perception  of  the  par- 
ticular light  box.  In  this  case,  when  the  reagent  apprehended 
the  box,  he  would  simply  recognize  it  as  the  one  in  which  the 
light  had  been  most  recently.  This  would  be  perceptual  recog- 
nition as  the  term  is  understood  in  human  psychology. 

With  either  of  the  above  explanations,  it  must  be  remem- 
bered, the  question  that  we  are  now  raising  is  one  concerning 
the  content  of  the  representative  factor.  There  is  no  doubt  in 
my  mind  that  the  function  is  an  ideational  one.  Even  should 
some  critic  claim  that  all  of  the  present  behavior  is  but  per- 
ceptual recognition,  the  fundamental  difference  between  the 
behavior  of  the  class  containing  the  rats  and  dogs  and  that 
of  the  class  containing  the  raccoons  and  children  will  still  chal- 
lenge explanation.  If  the  behavior  of  both  the  above  classes 
of  reagents  is  to  be  termed  perceptual  recognition,  then  two- 
orders  of  this  must  be  admitted — one  on  a  level  with  habit, 
the  other  on  a  level  with  ideas. 

One  class  of  facts  suffices  to  disprove  the  possibility  of  ac- 
counting for  the  behavior  of  the  raccoons  and  children  on  the 
basis  of  perceptual  recognition.  These  reagents  did  not  stop 
and  search  for  the  proper  box.  They  started  their  reactions 
immediately  upon  being  released.  The  raccoons  Jack  and  Bob, 
e.g.,  might  be  headed  away  from  the  proper  box  at  the  moment 
of  release  and  yet  whirl  around  in  the  proper  direction  and 
react  immediately.  Bob,  in  particular,  might  go  half  way  to 
the  wrong  box  and  then  turn  suddenly  and  react  successfully. 
When  the  reagent  does  not  follow  his  orientation,  one  would 
expect  him  usually  to  look  toward  at  least  two  boxes  before 
reacting,  if  the  behavior  were  on  the  basis  of  perceptual  recog- 
nition. It  is  these  reactions  of  children  and  raccoons  that  were 
not  in  accordance  with  orientation  and  yet   that  were  "head- 


76  ■  WALTER  S.  HUNTER 

long"  and  "precipitate"  that  lead  me  to  regard  perceptual 
recognition  of  the  boxes  as  an  inadequate  explanation  of  the 
facts. 

The  objections  just  stated  do  not  apply  to  the  assumption 
that  the  representative  process  is  an  intra -organic  sensation. 
A  positive  justification  of  an  ideational  function  whose, content 
is  an  internal  sensation  may  now  be  elaborated.  There  is  no 
doubt  but  that  in  human  consciousness  a  sensation  may  carry 
a  meaning  that  is  woven  into  thought  sequences.  In  reading, 
e.g.,  all  of  the  actually  discernible  conscious  content  may  be 
kinaesthetic  sensations  from  the  muscles  of  the  throat  or  may 
be  auditory  sensations,  if  the  reading  be  aloud.  Whether  one 
say  that  the  sensation  is  the  meaning  or  that  sensation  is  there 
plus  a  meaning,  the  case  for  our  purpose  is  unaltered.  Each 
sensation  and  its  meaning  become  incorporated  in  a  train  of 
thought.  A  slightly  different  situation  is  presented  where  it 
becomes  necessary  for  the  sensation  to  represent  that  which  is 
not  there  and  then  stimulating  the  sense  organs.  The  following 
illustration  from  Titchener  is  a  case  in  point :  "I  had  to  carry 
across  the  room,  from  bookshelf  to  typewriter,  four  references — 
three  volume  numbers  of  a  magazine,  three  dates,  and  four  page 
numbers.  The  volumes  and  years  I  said  aloud,  and  ^then  con- 
signed to  the  care  of  the  preservative  tendencies.  Of  the  four 
page  numbers,  I  held  two  by  visual  images,  one  by  auditory, 
and  one  by  kinaesthesis.""  The  case  of  the  volumes  and  years 
and  that  of  the  page  numbers  remembered  by. means  of  kinaes- 
thesis  are  significant.  Each  is  an  instance  (so  far  as  we  can 
tell  from  the  account)  of  memory  without  the  revival  of  images. 
The  sensory  cues,  present  at  the  time  when  the  data  were  written 
on  the  machine,  elicited  the  proper  material.  It  is  a  dangerous 
procedure  to  complete  another  investigator's  introspections.  I 
do  not  intend  to  do  so  here.  I  simply  suggest  the  above  as 
a  possible  supplement  to  Titchener.'s  own  brief  statements. 
Whether  it  be  right  or  wrong  in  his  case,  the  experience  in 
which  a  single  sensory  process  represents  an  absent  object  is 
sufficiently  frequent  to  give  us  the  suggestion  for  which  we 
are  seeking.  The  suggestion  may  also  be  found  elsewhere. 
That  which  has  become  known  as  "conscious  attitude"  in  the 


"  Titchener,  E.  B.     Experimental  Psychology  of  the  Thought  Processes.     New 
York,  1909,  p.  202. 


DELAYED  REACTION  77 

literature  of  imageless  thought  is  identical  with  the  first  phe- 
nomenon that  we  have  had  under  discussion  in  this  paragraph. 
So  far  as  the  attitude  itself  is  concerned,  it  might  well  be  desig- 
nated sensory  thought  as  may  other  experiences  also,  such  as 
tjcie  reading  aloud  that  was  mentioned  above.  The  memory 
cases  also  may  go  into  the  same  category.  The  sensations,  both 
in  the  memory  instances  and  in  those  of  the  conscious  attitudes, 
differ,  if  at  all,  only  on  their  meaning  side  and  not  by  the  addi- 
tion of  any  overt  imagery.  Already  the  reader  may  have  sur- 
mised, and  rightly,  that  the  writer  is  introducing  the  theory 
that  the  representative  function  found  in  the  raccoons  and  in 
the  child,  F,  at  least,  who  was  most  nearly  comparable  with 
them,  is  likewise  sensory  thought  and  essentially  comparable  with 
the  cases  above  given. 

Let  us  come  to  closer  quarters  with  this  theory.  The  pro- 
posed hypothesis  is  equivalent  to  making  the  so-called  "image- 
less  thought"  genetically  prior  to  "thoughts  with  images"  and 
to  placing  the  point  of  origin  at  least  as  low  as  the  raccoon. 
As  opposed  to  this,  current  discussion  by  advocates  of  imageless 
thinking  would  seem  to  assume  the  opposite,  viz.,  that  "  thoughts 
with  images"  are  prior."  It  is  to  be  noted  that  the  assumption 
has  no  factual  basis,  but  that  it  seems  to  be  the  result  of  preju- 
dice or  of  temperamental  leaning.  My  usage  here  takes  for 
granted  that  imageless  thought  can  be  analyzed  into  either 
sensory  or  imaginal  content  which  carries  the  meaning.  It  is 
the  former  case  that  I  use  as  the  type  found  as  low  as  the  rac- 
coons. This  thought  is  imageless,  though  not  sensationless,  in 
the  strict  sense.  In  the  light  of  this,  I  can  see  no  intrinsic  objec- 
tion to  the  above  theory,  while  the  following  points  are  in  its 
:avor:  (i)  The  evidence  in  support  of  the  possession  of  sensa- 
tions by  animals  is  absolutely  convincing  to  any  save  one  who 
denies  all  consciousness  to  animals.  On  the  other  hand,  the 
evidence  for  images  is  very  meager  and  unsatisfactory.  In- 
deed, it  is  even  more  so  that  has  been  thought  if,  as  I  believe 
to  be  true,  the  present  theory  of  sensory  thought  will  account  for 
all  of  the  controlled  behavior  that  has  been  used  to  support  a 
theory  of  images  where  that  behavior  is  not  open  to  a  stimulus 
and  response  explanation.      (2)   Raccoons  and  yoimg  children 

^^  Biihler  is  an  illustration  of  this.     Referred  to  by  Jas.  R.  Angell,  Psych.  Rev., 
vol.  18,  p.  317. 


78  WALTER  S.  HUNTER 

are  capable  of  reactions  that  seem  explicable  only  on  the  assump- 
tion of  the  functional  efficiency  of  a  representative  factor.  If 
sensations  can  function  in  this  manner,  the  law  of  parsimony 
forbids  the  assumption  of  images.  (3)  That  sensations  can 
function  in  this  manner  is  indicated  by  the  illustrations  from 
human  psychology  noted  above.  It  is  a  different  matter,  I 
know,  to  say  that  the  sensations  of  animals  also  may  function 
in  this  manner.  But  in  order  to  explain  the  behavior  of  the 
raccoons,  it  is  necessary  to  assume  either  the  presence  of  images 
or  the  presence  of  sensations  that  function  in  this  manner.  The 
law  of  parsimony  favors  the  latter  type  of  process  because  sen- 
sations are  genetically  earlier  than  images. 

Inasmuch  as  the  rats  and  dogs,  as  well  as  the  raccoons,  used 
sensory  processes  in  the  solution  of  our  problem,  we  are  forced 
to  recognize  that  sensations  may  be  placed  in  two  classes  on  the 
basis  of  function:  (i)  There  are  sensations  that  can  initiate 
a  correct  reaction  from  at  least  three  possible  responses  only 
when  they  have  not  been  displaced,  during  the  interval  of  delay, 
by  other  sensations  of  the  same  modality.  Here  would  fall  those 
sensory  experiences  of  constant  orientation  possessed  by  the 
dogs  and  rats.  (Those  cases  where  these  animals  lost  their 
orientation  and  then  regained  it  were  few  enough  to  be  rated 
as  accidental.)  (2)  There  are  sensations  that  can  initiate  correct 
responses,  under  the  above  conditions,  even  though  they  have 
been  displaced  during  the  interval  of  delay  by  others  of  the 
same  modality.  Here  would  fall  the  sensory  experiences  of  the 
raccoons  and  children.  The  evidence  which  indicates  that  no 
sensory  process  need  be  constantly  maintained  in  order  that 
these  subjects  may  react  correctly  is  unambiguous.  It  is  this 
type  of  sensory  process  that  I  have  denominated  sensory  thought. 

On  the  basis  of  human  introspection,  there  is  another  grade  or 
kind  of  learning,  viz.,  the  stage  of  the  functional  efficiency  of 
images  or  centrally  aroused  conscious  processes.  Why  there 
should  be  both  sensory  and  imaginal  thought  in  human  ex- 
perience is  very  difficult  to  say.  The  most  obvious  suggestion 
w^ould  be  that  imaginal  thought,  since  it  is  genetically  later, 
could  accomplish  tasks  which  sensory  thought  could  not.  I 
shall  hazard  no  guesses  as  to  what  such  tasks  might  be.  At 
the  present  stage  of  psychological  theory,  there  seems  to  be  no 
question  but  that  the  distinction  of  sensory  and  imaginal  thought 


DELAYED  REACTION  79 

itself  is  valid.     Future  work  must  attempt  the  formulation  of 
the  functional  differences  between  them. 

The  result  of  the  above  theoretical  considerations  is  a 
classification  of  the  grades  of  animal  learning  different  from 
those  hitherto  advanced.  Washburn,"  e.g.,  has  presented 
three  classes:  "First,  there  is  the  condition  where,  so  far  as 
we  can  see,  the  animal  does  not  learn  by  individual  experience. 
*  *  *  In  the  next  place,  we  have  the  grade  where  the  ani- 
mal learns  by  experience,  without  having  the  power  to  recall 
an  image  of  its  experience.  *  *  *  Finally,  *  *  *  ^g 
have  the  possibility  of  an  image."  I  would  modify  this  scheme 
by  the  insertion  of  a  stage  called  sensory  thought  between  the 
second  and  third  stages.  The  table  would  then  read:  (i)  The 
animal  shows  an  absence  of  learning  by  experience.  (2)  The 
animal  is  able  to  profit  by  experience,  but  has  no  higher  capacity 
than  "trial  and  error"  or  the  "stimulus  and  response"  behavior 
would  indicate.  The  rats  and  dogs  of  the  present  tests  come 
here.  (3)  The  animal  can  learn  by  the  "  trial  and  error  "  method. 
Indeed,  probably  most  of  its  reactions  are  on  this  basis,  being 
ruled  by  stimulus  and  response.  But  a  new  element  now  makes 
its  appearance,  viz.,  sensory  thought,  which  is  a  representative 
function  of  strictly  sensory  content.  The  raccoons  that  I  used 
are  in  this  class.  Of  the  children,  F  is  the  most  likely  to  belong 
to  this  class.  (4)  The  fourth  grade  reveals  the  presence  both 
of  "stimulus  and  response"  behavior  and  of  sensory  thought, 
but  added  to  these  is  the  possibility  of  directing  reactions  by 
images.  The  older  children  of  the  present  tests  very  probably 
belong  here  rather  than  in  the  third  class. 

r '  '  VII.     SUMMARY  AND  CONCLUSIONS 

The  following  is  a  statement  of  the  results  and  conclusions 
that  have  been  reached  as  a  result  of  the  foregoing  experiments 
and  analyses: 

I.  The  rats  (one  excepted),  dogs,  raccoons  and  children  made 
successful  reactions  in  situations  where  the  customary  deter- 
mining stimulus  was  absent  at  the  moment  of  response.  The 
stimulus  might  appear  in  any  one  of  three  boxes.  These  boxes 
were    qualitatively   alike,    but   situated   in    different   directions 

53  Op.  cit.,  p.  276. 


80  WALTER  S.  HUNTER 

from  the  release  box.  At  every  trial,  three  possibilities  of  reac- 
tion confronted  the  subject.  A  selection  had  to  be  made  and 
that  box  chosen  in  which  the  stimulus  had  appeared  most 
recently. 

2.  The  conditions  under  which  the  maximal  delay  was  tested 
and  the  results  obtained  are  indicated  as  follows: 

(a)  Different  classes  of  subjects  were  used.  Table  XIV  gives 
the  maximum  and  minimum  delays  that  were  obtained  from 
the  different  classes. 

TABLE  XIV 

Subjects  Min.  delay  Max.  delay- 

Rats  either  no  learning  or  3rd  stage  of  delay         10  sees. 

Dogs  2  sees.  5  mins. 

Raccoons  3  sees.  25  sees. 

Children  50  sees.  25  mins. 

(b)  Backgrounds  of  widely  different  grades  of  brightness  did 
not  affect  the  intervals  of  delay. 

(c)  The  use  of  a  large  release  which  gave  the  animals  the 
freedom  of  the  interior  of  the  box  lengthened  the  intervals  of 
delay  in  the  case  of  some  subjects. 

(d)  The  use  of  two  boxes  as  opposed  to  three  lengthened  the 
intervals  of  delay  by  increasing  the  accuracy  of  response. 

(e)  Neither  punishment  nor  the  particular  number  of  trials 
per  day  appear  to  have  aft'ected  the  interval  of  delay. 

3.  An  analysis  of  the  possible  cues  that  may  have  been  used 
by  the  subjects  in  the  solution  of  the  present  problem  gave  the 
following  results:  (a)  Overt  orienting  attitudes  were  the  prob- 
able cues  for  many  reactions  of  the  raccoons.  These  attitudes 
must  be  assumed  as  cues  for  the  rats  and  dogs  in  order  to  explain 
their  reactions,  (b)  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,  (c)  All  of  the  re- 
agents were  influenced  by  external  stimuli  that  were  constantly 
present  from  trial  to  trial,  e.g.,  those  given  by  the  box  itself. 
However,  these  could  not  be  used  as  a  basis  for  selective  re- 
sponses inasmuch  as  they  were  constant  from  trial  to  trial  and 
hence  could  not  furnish  varying,  or  alternating,  cues. 


DELAYED  REACTION  81 

4.  No  animal  that  had  used  overt  motor  attitudes  in  solving 
the  problem  when  the  small  release  and  similar  backgrounds 
were  used  adopted  another  type  of  cue  either  when  a  large 
release  or  when  backgrounds  of  d  fferent  brightnesses  were  used. 

5.  The  method  used  in  the  present  tests  for  attacking  the 
question  of  the  functional  presence  of  a  representative  factor 
in  an'mal  behavior  is  superior  to  that  of  imitation,  use  of  tools 
and  others  that  have  been  used  in  the  past,  because  here  it  is 
possible  to  determine  what  stimulus  controls  the  behavior.  It 
is  therefore  possible  to  insure  the  absence  of  the  stimulus  at 
the  moment  of  response. 

6.  The  representative  factor  for  which  search  has  been  insti- 
tuted in  this  monograph  stands  primarily  for  "objects"  and 
not  movements.  A  technique  that  would  make  certain  a  con- 
trol of  the  latter  factor  so  as  to  insure  its  presence  or  absence 
at  the  will  of  the  experimenter  has  not  as  yet  been  perfected. 

7.  From  a  consideration  of  the  theoretical  advantages  to  be 
derived  from  interpreting  this  representative  factor  as  sensory 
rather  than  as  imaginal,  a  decision  was  reached  in'  favor  of  the 
former  alternative  for  all  reagents  save  possibly  the  older  chil- 
dren, H,  Hd,  M  and  L.  Illustrations  were  given  from  human 
consciousness  where  a  sensation  performed  a  memory  function 
or  served  as  a  link  in  a  train  of  thought.  Such  cases  have  been 
termed  "conscious  attitudes"  or  "imageless  thought."  This 
function,  as  considered  in  this  paper,  was  designated  sensory 
thought. 

8.  The  theory  was  advanced  that  such  a  function  as  sensory 
thought  represents  the  highest  grade  of  behavior  in  raccoons 
and  probably  also  in  children  of  some  two  and  one-half  years 
of  age.  This  theory  is  supported  by  the  hardly-to-be-doubted 
presence  of  sensations  in  animal  consciousness  and  by  the 
assumption  that  these  sensations  can  function  as  the  illus- 
trations indicate  that  such  processes  do  in  human  behavior. 
Such  a  theory  seems  more  in  accordance  with  the  law  of  parsi- 
mony than  would  a  theory  which  made  images  perform  the 
representative  function  found  in  the  raccoons  and  the  child  F. 

9.  From  this,  theory,  it  follows  that  subjects  may  be  put  into 
at  least  four  classes  on  the  basis  of  the  highest  type  of  learning 
present  in  their  behavior:  (a)  Absence  of  learning;  (b)  trial 
and  error;    (c)  sensory  thought,  and  (d)  imaginal  thought. 


82 


WALTER  S.  HUNTER 


VIII.     APPENDIX 

A.  Detailed  Records  of  Two  Rats  and  Two  Raccoons. — The 
data  given  in  the  following  two  tables  are  self-explanatory. 
They  give  the  course  of  the  delayed  reaction  tests  as  these 
were  presented  to  the  animals. 


rABLE  XV 

Raccoons 

Bob 

Jill 

Delays 

Trials 

% 

Delays 

Trials 

% 

1st  i 

stage 

10 

100 

1st  stage 

15 

100 

2nd 

» 

10 

100 

2nd      " 

75 

97 

3rd 

u 

179 

67 

3rd      " 

75 

97 

Controls  were 

not  perfected  until 

1  sec. 

150 

77 

the 

last    100  trials. 

Of  these 

3rd  stage 

150 

92 

72%  were 

correct. 

Of  last 

50 

1  sec. 

150 

84 

trials,  80% 

were  correct. 

2    " 

75 

50 

3  1 

sec. 

20 

80 

1    " 

30 

40 

3rd! 

stage 

5 

100 

3rd  stage 

120 

87 

1  I 

sec. 

7 

28 

1  sec. 

155 

83 

3rd  i 

stage 

4 

50 

2    " 

105 

86 

1  1 

sec. 

10 

30 

3    " 

45 

57 

learning 

17 

52 

2    " 

105 

79 

3rd  stage 

50 

88 

3    " 

75 

56 

1  1 

sec. 

11 

72 

Backgrounds 

were  used  now: 

3 

tt 

50 

56 

2  sec. 

90 

58 

1 

u 

80 

70  • 

1    " 

45 

71 

2 

u 

50 

78 

3rd  stage 

150 

97 

3 

u 

20 

90 

1  sec. 

75 

93 

4 

u 

62 

69 

2    " 

105 

96 

5 

a 

56 

82 

3    " 

90 

66 

8 

u 

20 

55 

2    " 

45 

55 

6 

u 

40 

75 

1    " 

45 

71 

7 

u 

10 

100 

3rd  stage' 

60 

96 

8 

11 

189 

55 

1  sec. 

45 

97 

last 

48 

79 

2    " 

60 

98 

10 

a 

25 

76 

(backgrounds 

off  for  30 

100) 

12 

u 

29 

68 

3  sec. 

45 

93 

15 

It 

30 

73 

4    " 

45 

62 

5 

" 

1 

100 

Learning  with  light  on  5  sec. 

5-15 

" 

10 

50 

30 

100 

15 

(( 

10 

60 

Learning  with  light  on  1  min. 

20 

11 

18 

44 

25 

80 

2 

u 

3 

■      33 

Wire  release  now,  10  trials  daily: 

20 

u 

10 

20 

Learning 

80 

95 

2 

u 

3 

33 

2  sec. 

50 

98 

5 

a 

9 

55 

4    " 

50 

60 

10 

u 

13 

46 

2    " 

100 

89 

5 

a 

4 

50 

last     50 

96 

7 

u 

10 

33 

4    " 

50 

88 

A—      5 

a 

49 

75 

5    " 

50 

70 

7 

u 

20 

75 

last     30 

90 

8 

a 

36 

80 

6    " 

40 

90 

10 

11 

50 

72 

7    " 

50 

84 

12 

tt 

10 

90 

last     30 

70 

15 

tt 

10 

90 

6    " 

30 

86 

20 

a 

96 

64 

Small  release 

again: 

lasl 

;    46 

71 

6  sec. 

30 
(dropped) 

56 

DELAYED  REACTION 


83 


TABLE  XV— Continued 
Raccooxs 


Bob 

Bob 

Delays          Trials             % 

Delays 

Trials 

% 

Two  boxes,  a  and  e,  from  now  on: 

2nd 

stage 

10 

100 

20  sec.             20                 95 

3rd 

" 

50 

100 

25    "                20                 90 

1 

sec. 

30 

100 

30    "                10                 90 

2 

" 

40 

97 

35    "                70                 64 

3 

u 

20 

100 

25    "                10                40 

.     4 

a 

50 

80 

B—     15    "                10                 60 

5 

a 

100 

85 

•  5    "                10                33 

6 

a 

50 

88 

Boxes  a  and  b  now  used  to  break 

7 

a 

100 

83 

up  position  habit. 

8 

a 

100 

70 

5  sec.             60                 30 

7 

a 

100 

81 

3rd  stage          10                 40 

8 

a 

110 

89 

Learning         295                97 

9 

a 

80 

81 

2nd  stage        240                 86 

10 

" 

50 

86 

last     51                 93 

11 

" 

80 

73 

1  sec.             51                 94 

10 

" 

50 

66 

2    "                50                96 

Boxes  b 

and  c 

;  from  now  on 

3    «                51                 60 

10 

sec. 

40 

100 

2    "                50                 66 

12 

" 

30 

100 

1    "                10                40 

15 

" 

50 

96 

3rd  stage          51                 86 

20 

« 

30 

90 

Learning  c  alone 

25 

« 

50 

86 

21                 14 

30 

(I 

71 

80 

Learning  all  three 

35 

" 

101 

70  or  less 

C—                          120                 80 

4 

" 

30 

96 

last  100               100 

5 

u 

30 

100 

Learning  with  light  on  5  sec, 

8 

" 

10 

100 

boxes  b  and  c 

15 

" 

20 

55 

30                 86 

8 

" 

50 

86 

last     20               100 

12 

" 

90 

84 

Learning  with  light  on  1  min. 

20 

" 

80 

70 

30                90 

first     50 

76 

Wire  release,  3  boxes: 

(dropped) 

Learning           50               100 

2  sec.             50                48 

Two  boxes,  b  and  c: 

2  sec.             50                94 

84 


WALTER  S.  HUNTER 


TABLE  XVI 

Rats 

Rat  No.  4 

Rat  No.  16 

Delays             Trials 

% 

Delays 

Trials 

% 

1st  stage                5 

100 

1st  stage 

50 

96 

2nd      "                  10 

80 

2nd      " 

100 

98 

3rd      "                 30 

50 

3rd      " 

110 

83 

2nd      "                    5 

100 

last     50 

.76 

3rd      "                  15 

40 

2nd      " 

100 

99 

2nd      "                  75 

70 

3rd      " 

50 

100 

3rd      "                  50 

60 

1  sec. 

40 

50 

2nd      "                  75 

85 

3rd  stage 

20 

et) 

3rd      "                 25 

92 

2nd  stage 

100 

99 

1  sec.                 30 

60 

3rd    •" 

50 

96 

3rd  stage              25 

88 

1  sec. 

30 

36 

1  sec.                 25 

52 

Different  backgrounds  now: 

Different  backgrounds  now: 

3rd  stage 

20 

30 

3rd  stage              25 

60 

2nd      " 

90 

96 

2nd      "                 60 

80 

3rd      " 

50 

58 

3rd      "                  50 

80 

2nd      " 

100 

99 

1  sec.                25 

64 

3rd      " 

50 

48 

H "                   25 

48 

2nd      " 

70 

100 

1  sec.                 35 

68 

3rd      " 

50 

68 

1* "                   50 

62 

Two  boxes  now,  b  and  c. 

r  «                   25 

64 

3rd  stage 

50 

92   / 

3rd  stage              50 

64 

1  sec. 

100 

87 

Old  backgrounds  now: 

2    " 

40 

97 

3rd  stage              65 

61 

3    " 

50 

98 

2nd      "                  75 

94 

5    "* 

50 

90 

3rd      "                  60 

66 

7    " 

35 

60 

Two  boxes  now,  a  and  c : 

Series  with  wire  release: 

3rd  stage              25 

100 

Learning 

80 

80 

1  sec.                 20 

75 

2  sec. 

70 

78 

(dead) 

3    " 

50 

88 

4    " 

40 

92 

5    " 

80 

78 

6    " 

60 

76 

7    " 

50 

90 

9    " 

40 

.  82 

10    " 

30 
(dropped) 

50 

DELAYED  REACTION  85 

B.  Notes  on  Raccoons. — Davis''  and  Cole"  have  given  an 
excellent  description  of  the  habits  of  raccoons  in  captivity. 
In  the  main  my  observations  substantiate  theirs.  A  few  differ- 
ences, however,  may  be  noted.  Davis  lays  particular  stress 
upon  one  habit  which  his  raccoons  formed,  viz.,  that  of  covering 
their  excrement.  As  well  known  this  is  contrary  to  their  be- 
havior in  the  natural  state.  My  four  animals  were  confined  in 
one  cage,  10x10x14  feet,  the  floor  of  which  was  covered  an 
inch  or  more  deep  in  shavings.  Yet  in  all  the  long  months 
during  which  the  animals  lived  there,  they  never  formed  the 
habit  of  covering  their  faeces.  These  were  always  voided  along 
the  walls  of  the  cage,  and  not  once  have  I  found  evidence  of 
an  attempt  to  cover  them.  Moreover  both  Mr.  DeVry  of  the 
Lincoln  Park  Zoological  Garden,  Chicago,  and  Dr.  Homaday  of 
the  New  York  Zoological  Garden  give  an  unqualified  "no"  in 
answer  to  the  following  question:  Will  the  tame  raccoon  bury 
or  cover  his  excrement,  if  given  the  opportunity? 

No  trouble  was  found  in  adapting  the  animals  to  a  rather 
monotonous  diet  of  bread  and  milk,  varied  occasionally  with 
raw  meat.  But  the  amount  of  the  rations  to  be  given  was  more 
difficult  to  determine.  Throughout  the  spring,  summer  and 
into  the  winter,  the  raccoon  will  eat  voraciously.  But  by  the 
middle  of  January,  unless  strict "  precautions  be  taken,  the  ani- 
mals will  be  so  fat  that  they  will  refuse  to  work  and  will  sleep 
almost  continually.  My  animals  were  kept  on-  a  back  porch 
which  was  not  artificially  heated,  and  which  w^as  but  slightly, 
if  any,  warmer  than  out  of  doors.  Whether  they  would  have 
gone  into  a  genuine  state  of  hibernation  had  I  not  cut  down  their 
rations  in  the  fall,  I  cannot  say.  However,  in  view  particularly 
of  Betty's  behavior,  I  am  inclined  to  think  that  this  would  have 
happened.  From  about  the  middle  of  January  until  late  in 
April,  my  notebook  indicates  that  Betty  lacked  a  motive  for 
working.  Tests  were  made  during  this  period  in  order:  (i)  To 
prevent  forgetting  of  the  problem,  and  (2)  to  give  the  animal 
food  in  order  that  it  might  not  become  too  weak  from  a  long 
fast.  The  cases  of  the  three  other  raccoons  are  not  so  extreme 
as  this  one, — yet  all  become  less  eager  for  food  during  the  last 

"Davis,  H.  B.  The  Raccoon:  A  Study  in  Animal  Intelligence.  Amer.  Jour. 
Psych,  vol.  18,  1907. 

°*  Cole,  L.  W.  Observations  of  the  Senses  and  Instincts  of  the  Raccoon.  Jour, 
of  Animal  Behavior,  vol.  2,  1912. 


86  WALTER  S.  HUNTER 

two  months  of  the  winter.  Davis  found  that  all  of  his  raccoons 
hibernated  during  the  first  winter  when  they  were  kept  out 
doors.  But  during  the  second  winter  when  they  were  kept 
within  doors,  although  unsupplied  with  artificial  heat,  they  did 
not  hibernate.  How  he  regulated  the  food  supply  at  this  period, 
and  whether  the  animals  became  sluggish,  he  does  not  state. 
Further  observations  should  be  put  on  record  before  the  con- 
clusion is  reached  that  the  raccoon  will  change  so  fundamental 
an  instinct  upon  so  slight  a  change 'of  habitat.  Both  Mr.  DeVry 
and  Dr.  Homaday  inform  me  that  their  raccoons  do  not  hiber- 
nate in  the  winter,  although  the  living  quarters  are  no  warmer 
than  outdoors.  In  addition.  Dr.  Homaday  replies  as  follows  in 
answer  to  the  question  of  how  to  prevent  hibernation:  "By 
constant  feeding.  Bears  and  raccoons  hibernate  because  they 
cannot  find  food  in  the  deep  snow.  Our  bears  never  hibernate 
because  they  are  constantly  fed."  I,  too,  fed  my  animals  regu- 
larly, although  sparingly,  in  the  fall,  yet  indications  of  a  desire 
to  hibernate  were  observed.  The  subject  of  hibernation  is 
very  poorly  understood  at  the  present  time,  even  among  the 
biologists  proper. 

Both  of  the  authorities  above  quoted  inform  me  that  raccoons 
reach  maturity  at  three  years  of  age.  I  note  this  fact  because 
Cole's  statement  that  "The  year-old  raccoons  apparently  are 
not  quite  full  grown  "^'  may  be  as  misleading  to  some  as  it 
was  to  me. 

Two  other  observations  may  be  noted  in  passing:  (i)  The 
raccoon  appears  to  have  a  very  acute  vision.  I  have  seen  sev- 
eral individuals  chase  flies  that  were  crawling  upon  the  floor 
of  the  experimental  room  whose  illumination  was  extremely  low. 
(2)  The  price  of  keeping  tame  raccoons  is  eternal  vigilance.  In 
the  spring  when  the  "wanderlust"  strikes  them,  they  will  gnaw 
wood  and  tear  wire, — anything  to  escape.  And  the  usual  reward 
for  attempting  to  catchy  loose  raccoon  is  a  severe  bite. 
^Op.  cit.,  p.  213.