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EDUCATIONAL PSYCHOLOGY

SECOND EDITION

REVISED AND ENLARGED

EDWARD L. THORNDIKE

PROFESSOR OF EDUCATIONAL PSYCHOLOGY IN TBACHERS COLLEGE
COLUMBIA UNIVERSITY

PUBLISHED BY

©ractj^ra (taiU^, OInlumbia Mniupraita

NEW YORK
1910

-1^

0^^

^^i^

CorYKlGllT, 1903, 1910

H\ RDWARD L. THORNDIKIC

TRUSS OF

FRANK II. UVORY S CO

ALUANY, N. Y.

©CI.AJi68683

PREFACE

This book is a revision of a book, Educational Psychology,
which appeared in 1903. Its primary purpose is, as was the case
with the first edition, to provide students in advanced courses in
educational psychology with material which they would otherwise
have to get from lectures at great cost of time.

The chapter on ' The Influence of Special Training upon More
General Abilities ' is not included in this edition. It was out of
place before since it treated facts of mental action in general
instead of facts of individual mental conditions and their causes.
It was put in the original book because of the great practical
importance of the facts concerned. The facts are now widely
known and are presented conveniently elsewhere.

This book attempts to apply to a number of educational
problems the methods of exact science. The problems chosen are
those of the mental natures of individual men, and the causes of
their differences. The problems concerned with the nature of
man as a species, — the general problems of instinct, habit,
learning, practice, memory, fatigue and the like, — will sometime
be treated in a separate volume. The two together will, I hope,
be a serviceable quantitative treatment of educational psychology.

CONTENTS

CHAPTER PAGE

I. Introduction ......... i

X^ II. 'Th^ Measurement of Individual Differences -.-- „ ... 3

^Llll. The Influence of Sex ........ 18

IV. The Influence of Remote Ancestry or Race . 51

y V. The Influence of Immediate Ancestry or Family ... 69

VI. The Influence of Maturity ....... 104

A VII. The Influence of the Environment .114

VIII. The Nature and Amount of Individual Differences in Single

Traits ......... 142

IX. The Relations between the Amounts of Different Traits in the

Same Individual . . . . . . .171

X. The Nature and Amount of Individual Differences in Com-
binations of Traits; Types of Intellect and Character 193

XI. Extreme Individual Differences; Exceptional Children . 207

APPENDIX

I. List of authors and titles referred to specifically in the text . 231

II. List and descriptions of measurements referred to cursorily

in the text ......... 236

III. List and definitions of statistical terms used in the text . 242

CHAPTER I

Introduction

The knowledge of human nature which psychology offers to
students of educational theory and practice may be roughly
divided into four parts. A body of general knowledge about
instincts, habits, memory, attention, interests, reasoning, etc., finds
place in the ordinary text-books. Detailed descriptions of the
thoughts, feelings and conduct of certain children at different
ages are available in the literature of child study. Particular
facts which bear upon this or that school subject or method of
teaching may be gleaned from researches upon perception,
association, practice, fatigue and other topics. Finally there is
an even more incoherent mass of facts about the differences
between one human being and another and the respective shares
which sex, age, ' race ' or remote ancestry, ' family ' or immediate
ancestry, and the circumstances of life have in the causation of
these differences. It is the aim of this volume to put this last
group of facts at the service of students.

Their significance for educational theory and practice is obvious.
What we think and what we do about education is certainly
influenced by our opinions about such matters as individual differ-
ences in children, inborn traits, heredity, sex differences, the
specialization of mental abilities, their interrelations, the relation
between them and physical endowments, normal mental growth,
its periodicities, and the method of action and relative importance
of various environmental influences. For instance, schemes for
individual instruction and for different rates of promotion are
undertaken largely because of certain beliefs concerning the
prevalence and amount of differences in mental capacity ; the con-
duct of at least two classes out of every three is determined in
great measure by the teachers' faith that mental abilities are so
little specialized that improvement in any one of them will help

(1)

2 Educational Psychology

all the rest; manual training is often introduced into schools on
the strength of somebody's confidence that skill in movement is
intimately connected with efficiency in thinking; the practical
action with regard to coeducation has been accompanied, and
doubtless influenced, by arguments about the identity or the
equality of the minds of men and women ; the American public
school system rests on a total disregard of hereditary mental differ-
ences between the classes and the masses ; curricula are planned
with some speculation concerning mental development as a guide.
It is thus easy to find cases where educational practice depends
upon opinions about our group of topics. It is still easier to note
a similar dependence in the case of educational theory. Abundant
illustrations will appear in the course of our study of the topics
themselves.

Effective description of the facts of individual differences and
of their causation must be quantitative. The questions are
questions of amount, or at least become such when carried beyond
a first survey. "Do boys and girls differ?" is itself a question
of amount, which soon becomes, " How much do boys and girls
differ ?" " In what do they differ ?" can be answered only by
comparing them quantitatively. "Are there distinct types of
children with respect to imagination?" can be properly answered
only by measuring children in respect to the various sorts of
imaginativeness or imagery in question. " What is the value of
the study of Latin?" means to even the student most averse to
quantitative thinking, "What changes in human nature are caused
by it?" But to prove the existence of any change one must
measure two conditions.

It is therefore necessary to understand certain elementary facts
about the means and methods of measuring the facts of individual
differences and their causation, in order to understand the facts
themselves. Portions of certain chapters will consequently be
given up to the essentials of the theory and practice of measuring
mental conditions, differences, changes and relationships.

CHAPTER II

The Measurement of Individual Differences

Exact knowledge of the nature and amount of individual differ-
ences in intellect, character and behavior is valuable to educational
theory and practice for two reasons. The first is the general need
of knowledge of what human beings are in order to choose the
best means of changing them for the better — a need which includes
knowledge of the divergences of individuals from the type of the
species as a whole, as well as knowledge of that type. Education
needs knowledge of men as well as of man. The second reason is
that by a study of the causes of these differences, — the causes
which make men good and bad, wise and foolish, skillful and
clumsy, efficient and futile, — education may hope to learn about
means of making all men more wise, skillful and efficient. The
causes of the differences between one man and another, as things
now are, will lead to knowledge of the causes whereby all men
may be made to differ from their former selves. It is of special
importance to know what differences amongst men are due to dif-
ferences in sex, race, immediate ancestry and maturity, which are
beyond control by ordinary educational endeavors, and what
differences, on the other hand, are due to training or education
itself.

Simple and Compound Differences

A difference in human nature may be (i) in the amount or
degree of the same thing* (as 'good — better,' 'quick — slow,'
^ imaginative — less imaginative — unimaginative ') ; or (2) in the
presence or absence of different things (as 'John knows Latin;
James knows German,' or, ' A is imaginative ; B is rational,' or,
^ C has an artistic temperament ; D has a scientific temperament').

*0r what is assumed to be the same thing.

(3)

4 Educational Psychology

The second case commonly reduces to an aggregate of
differences of the first sort if the statement of dift"erence is made
adequate. Thus, ' John knows x Latin ; James knows o Latin ;
James knows 3; German ; John knows 0 German' should properly
replace the former statement. Similarly we have, * A is imagin-
ative to 2 extent, B is imaginative to s—zv extent. B is rational
to V extent; A is rational to v — w extent,' and, 'C has r, y and s
amounts, respectively, of certain qualities, certain degrees of which
in combination we call the artistic temperament; D has small or
possibly zero amounts of these qualities.' A difference in human
nature then commonly is a difference in the amount of one thing
or an aggregate of differences each in the amount of one thing.

But conceivably there may be things which do not vary in
amount except from zero by a sudden jump to one positive
condition. The thing would then either be in one constant degree
or not at all. The literature of psychology and of education
abounds in cases of difference stated as if the difference were
that between 0 and k, without k - y^, or ^ - ^^, or k + }ik, etc.
But such statements are usually due to ignorance or vagueness.
' John is color blind ; James is not ' cannot really mean that there is
some one constant degree of color blindness which a man either
has just in that degree or does not have at all ; for there are
varying amounts of color blindness. In fact, it is doubtful if there
are any individual differences in human intellect or character of
this ' zero to k ' sort.

When, therefore, it is stated that John and James differ in
kind, the statement always, or almost always, means nothing more
than that one of the two individuals possesses a certain amount;
or degree of something of which the other possesses 0. When
it is stated that the difference between John and James in one
thing, say, knowledge, is qualitative whereas their difference in
another, say, motor skill, is quantitative, the statement always,
or almost always, means nothing more than that certain sorts of
knowledge, present in certain amounts in John, are absent in
James, and vice versa ; whereas, in motor skill, both have percep-
tible amounts of an identical set of things.

It is then not only permissible, but more scientific and more
useful, to think of human individuals as all measured upon the
same series of scales, each scale being for the amount of some
one thing, there being scales for every thing in human nature,.

The Measurement of Individual Differences 5

and each person being recorded as zero in the case of things not
appearing in his nature. And the only problem of method which
need concern us in this chapter is the problem of the nature and
use of a scale for measuring different amounts or degrees of the
same trait in different human beings.

Units and Scales for Measuring Mental Differences

The facts of importance about scales for mental and moral
traits can be best stated in connection with some concrete illus-
trations.

Consider the facts given in Table I concerning individuals
A, B and C, with reference to these questions : —

1. What are the differences between A and B, A and C,

and B and C in each of the traits ?

2. How many times as great is the difference between A and B

in trait I as that between B and C in trait I ? How many
times as great is the difference between B and C in trait
n as that between A and C in trait H, etc., etc.

What the difference is between A and B can be definitely deter-
mined in the case of stature (I), reaction-time (H), error in
drawing a line (HI), and age (XH) ; but all that one learns
about the differences in the case of ability in history (VH) and
interest in music (XI) is that one difference is that between
excellent and good on the arbitrary scale of some school and
that the other is that between little and moderate, in the mind
of some observer. The measures of I, H, UI and XH are by
objective or impersonal scales, that is, scales the identification and
similar use of which are possible for any competent observer.
The measures of VH and XI are by subjective or personal scales,
which another observer could not identify* or use in the way in
which the person giving the marks used them. Moreover, what-
ever the scales in VII and XI really are, they are certainly very
coarse ; a wide range of difference is expressed in them by a few
steps or marks or values. In short, any competent thinker knows
exactly what is meant by 160 cm. and by 160 cm. — 140 cm.,

*If, for example, the reader had heard the oral work and seen the
written work which in combination mean good in the school whence
A and B came, he would not know that they did mean good.

Educational Psychology

TABLE I.
Measurements op Three Individuals, A, B, and C

ABC

I. Stature 160 cm. 140 cm. 130 cm.

II. Simple reaction-time to sound 175 sec. .125 sec. .150 sec.

III. Average error in drawing a line to

equal a 100 mm. line 3.2 mm. 2.8 mm. 2.2 mm.

IV. Number of words (of a list of 12,

heard at a rate of i per second)
remembered long enough to write
them immediately after the last
word was read 6 words 9 words 7 words

V. Number of examples in addition
(each of 10 numbers, repeating no
number in any one example, taken
at random from the numbers 10
to 99) done correctly in 8 minutes 14 12 18

VI. Quality, or merit, or goodness of

handwriting See Fig. i See Fig. 2 See Fig. 3

VII. School marks in history Ex. Good Poor

VIII. School marks in spelling 82 62 93

IX. Efficiency in perception ; the number
of A's marked in 60 seconds on a
sheet containing 100 A's mixed

with 400 other capital letters ... . 48 A's 60 A's 82 A's
X. Criminality: number of times con-
victed of a penal offense 010

XI. Degree of interest in music little moderate a great deal

XII. Age in days 5080 d. 6150 d. 5615 d.

whereas he cannot be sure what is meant by excellent, or by the
difference between excellent and good.

Concerning the other measurements the following statements
are roughly true : —

A, B and C are measured objectively in the quality of hand-
writing. We know what is meant by the difference between
A and B. It is just the difference between the qualities of the
two samples presented. But they are not measured conveniently ;
the differences are not referred to any commonly known scale.

The measurement in addition is nearly objective. If the
conditions of the test are defined by a statement of how the
examples were presented (what type they were printed in, how
they were arranged, etc.), how the answers were given, at what

The Measurement of Individual Differences

•n

•a
n

W
pq

.<<

^ "3

8 Educational Psychology

time, under what distractions, with what incentives, etc., they
were done, and the Hke, they become still more fully objective.

In the case of memory, not only the conditions of the test, as
in addition, but also the exact words used need to be specified. A
differed from B by writing down three less words of a certain
list. The list needs to be known if all competent observers are
to think of the same thing by three zvords.

The measure of criminality is inferior to the measurement of
stature or age by using an ambiguous unit {convicted of a penal
oifense) and also by measuring only very coarse diflferences.
A and C are not differentiated by the measures, though A might
just fall short of crime and C be a very healthy-minded and
kind-hearted boy.

The measurement of ability in spelling might turn out to be,
were the conditions of the test and the system, of scoring results
in it known, as objective as that in addition, or, on the other
hand, may be only a record of the opinion of some teacher that
A was a good deal better than B and that C was somewhat
above A. As the record stands the A — B = 20 may mean no
more than 'A is good; B is unsatisfactory,' or 'A is soniezvhat
better than B in my opinion.'

The values ~^ > A — C ^"^ p_p ^^^ determinable m the

case of I, II, III and XII of Table I. In stature A — B = 20 cm.,

A B

A — C = 30 cm. and -r p^ = .667. When one says that A

differs from C in stature one and a half times as much as from B,
any competent person knows exactly what is meant. For VII

, A — B Excellent — Good ,. .

on the contrarv we have -r ^ = zz^ n — ;- which

A — C Excellent — Poor,

may be a true, but remains a mystical, answer, until excellent, good

and poor are defined on some scale.

In the case of the memory of words (A = 6, -B = 9, C = y)

B — A J B — C

Q A = 3 s"*i p ^ = 2 , if to remember any one word = to

remember any other one zvord. Suppose, however, that the series
of words was : * career, dilatory, opium, never, soap, numbers,
add, subtract, one, two, three, four,' and that A remembered the
last 6, C the last 7, and B these and the first two. It would

The Measurement of Individual Differences . g

be very risky to assume that the difference between A and B (re-
membering career, dilatory and numbers) was only three times
the difference between A and C (remembering numbers). And
it would be almost certain that a difference of lo — 4 in the test
would be really more than twice as great as a difference of 7 — 4.
Under the circumstances numbers, add and subtract are probably
much easier to remember than career, dilatory and opium.

In the case of centimeters or seconds every competent person
knows not only what fact is meant by any given number of the
units, but also that any one unit is equal to any other one, any two
to any other two, and so on. In the case of words remembered,
units called by the same name may not be really equal.

In the case of the addition, one example differed from another
in difficulty only by chance and only slightly ; for when 10 two-
place numbers are picked by chance and arranged in a chance
order, the chances are enormously against getting any very easy
examples like (a) or any very hard examples like (b).

(a) (b)

25 89

35 95

30 58

40 67

60 79

The chances are still more against getting two or three examples
in succession that are on the average more than a trifle harder
than any other succession of two or three. Reliance upon the truth

of 7:;^ — = — - would, however, be safer if 10, 20, 30, etc , and

C — B 6

II, 21, 31, etc., had been excluded from the numbers used in
the tests.

In the case of merit of handwriting, the differences between
A and B, B and C, and A and C do not even pretend to be put
in terms so as to allow comparison. As the records stand,
any one must get the differences transposed into terms of some

^ g

unit before he can calculate at all. Since the measures

A — C

of A, B and C are objective, this can be done. If, for example.

lo Educational Psychology

the measurer could show that the difference between A and C
was approximately five-twelfths of the difference between two
standard samples accessible to all competent persons, and that the
difference between A and B was approximately two-twelfths of
the difference between the same two standard samples, he could

then regard -r — ^ as, of course, ^— p or -, k being the difference

between the two standard samples. As a matter of fact the
difference between the sample of Fig. i (p. 7) and that of
Fig. 3 (p. 7) is in the combined opinion of some hundred judges
just about two and one-half times as great as the difference
between the sample of Fig. i and that of Fig. 2 (p. 7).

The sum and substance of the last four pages is that a measure-
ment of human nature to be useful for our purpose must identify
the amount in question for any competent thinker, just as a
useful description must identify the object in question. To do
this it must be objective, that is, free from individual caprice,
so that any competent person making the same measurement
would get the same result.*

It should also, if possible, so state the amount in question that
other amounts of the same thing may be compared with it as
so much greater or less, permitting differences between the
amounts to be expressed in ratios. In still briefer terms, the
measurements should be at defined points on an objective scale,
the distances of these points one from another being also defined.

The reason for the elaborate introduction to and illustrations
of this obvious principle is that in its application to particular

*Not, of course, exactly the same. There is a personal equation in

even the most objective measures, such as the length of this line .

If they measured it to thousandths of a millimeter, competent observers
would not get the same result, except by chance. Nor would the same
observer in several independent measurements. The ultimate distinction
between objective and subjective is simply that in the former sort of
measurements competent observers use very nearly the same criteria and,
tho independent, agree very closely, whereas in the latter they use very
different criteria and, if independent, agree only roughly. The reader may
safely postpone any subtle or thoroughgoing treatment of the distinction
until he can study the theory of mental measurements in detail. For the
purposes of this book, objective measures may be defined as measures
which competent observers could repeat and verify or reject, and subjective
measures as measures which they could not so repeat and verify.

The Measurement of Individual Differences ii

problems in the study of educational psychology it has not been
obvious to even the writers of treatises and investigators of
original data, much less to the rank and file of students of
psychology or of education. On the contrary this entire chapter
would not suffice to list and barely describe the quantitative con-
clusions that have been drawn from subjective opinions or from
the acceptance as equal of units which happened to be called by
the same name.

The reason for contrasting physical and mental measurements,
to the apparent disrepute of the latter, is not that I wish to dis-
courage the reader from trusting, or from making, measurements
of any feature whatever of intellect or character. It is to be
hoped, however, that he will be effectually discouraged from
trusting measurements which do not deserve trust. The lesson
to be drawn from the contrast is that a measurement can rightly
be trusted or rejected or criticized or, indeed, understood, only
if the concrete reality which it describes is known. Any numerical
statement has meaning only in reference to a concrete scale and
its units.

The Variability of a Mental Measurement

One cause of improper distrust of measurements of intellect
and character is so common that it demands special treatment.
This is the variability of the same measurement of apparently
the same fact.' For instance, individual A was tested by hearing
a series of 12 letters read at a rate of 2 per second, he being
required to write down as many as he could remember in theii:
proper order as soon as the reading was finished. His score
was 4 correct in one trial and 10 correct in another, the two
letter-series being, for people in general, of equal difficulty. What
assurance, it may be said, can be felt in a measurement
of now 4 and now 10 for the same fact? The defense is that
it is not the same fact. To measure A's memory for series of
letters is not to measure one constant thing, but a very variable
thing. A, as regards taking in and holding a series of letters,
is not the same from moment to moment. What is measured in
one trial is a sample of A's varying status in respect to this
ability. His first score in the measurement in question was 4.
This measurement is, so far, so good ; it is better to believe that

12 Educational Psychology

A's ability in that test is 4 than to guess at it. In a second test
the score was 10.

To say that A's ability is 4 or 10 or averages 7 is better than
to have taken the 4 as a measure. But further trials give
(including these two)

I record of 4

letters correct

4 records

" 5

4 "

" 6

7 "

" 7

13 "

" 8

3 "

4 "

"10

From all these scores we get, as an average, 7.44 letters
correctly written; as the most common record (the so-called
Mode), 8 letters correctly written. Since a record of 4 letters
correctly written means, perhaps, 4^/^ letters remembered, one
of 5 letters correctly written, 55^ letters remembered and so on,
we should perhaps call A's average memory letters 7.94 and his
mode or most frequent performance 8.5.*

Now the trustworthiness of any one of these is 6 times as great
as that of the first single score 4.t But we can not be sure
that the average of the 36 measurements is identical with A's
true average ability. In fact we can be almost sure that it is
not. Seventy-two measurements might give, and almost certainly
would give, a slightly different average. True average ability
in the case of variable measurements means the measure we
would get as an average from an infinite number of measure-
ments. Only by chance will the result from any finite number
of measurements be identical with it. All our measures represent

*If an individual writes 7 letters correctly, but does not write an eighth,
it means that he remembered at least 7 and not 8. The measurement is
comparable to one of length in which the observer notes that a stick is
over 62 inches, and is not 63 inches, long. And just as, in the long run,
sticks 62 inches or over but not 63 inches or over will average 62Y2 inches,
so the person remembering on many occasions at least 7 but not 8 letters
will average 7V2 letters. Some of his records of 7 mean 7 letters remem-
bered and one more letter almost, but not quite, remembered.

fit is found in variable measurements of the ordinary sort that the
reliability of an average increases as the square root of the number of
measurements taken.

The Measurement of Individual Differences

approximations, but the greater the number of measures the closer
the approximation will be.

The series of measures above is our knowledge of A's ability.
We can see the fact more clearly by expressing it in space rather
than in figures. If we let each quarter inch along a horizontal
line stand for one letter correctly written, and each eighth of
an inch of height above it stand for one manifestation by A
of the ability designated by that place, we have Fig. 4, by which
one can see at a glance A's ability, its variability and his general
tendency to keep nearer 8 than any other one ability.

4 5 6 7 8 9 10

Fig. 4. The ability of individual

5 6 7 8 9

Fig. 5. The ability of individual
A in memory of letters. B in memory of letters.

If we must for any reason abbreviate our description of A's
ability we may best take two measures, one of the ability about
which his various scores center most closely and the other of the
closeness of his grouping. We may term these the central tendency
and the variability. For the former the average or median* or
mode may be used, for the latter the average of the differences
between the individual records and their central tendency

*The Median has two meanings : the point on the scale above and below
which equal per cents of the individual scores lie, and the mid measure,

that is, the — — — th measure, counting in from either extreme, where
2

« = the total number of measures. These two definitions lead to sub-
stantially the same results, and for present purposes the reader may adopt
either one. Indeed it will do no harm if he can see no difference between
the two.

14 Educational Psychology

(Average Deviation or A.D.), or any one of a number of measures
of the closeness of clustering of the individual records about their
central tendency.

Let us suppose that, with the same test, individual B showed
the following ability:

2 records of 5 correct.

II " 7

17 " 8

3 " 9 "

This is shown graphically in Fig. 5. The average, median
and mode would be closely the same as for A, but the variability of
the measures would be less. The limits for A were 4 — 10. For
B they are 5 — 9. The average difference of the individual
measure from the mode for A was 1.17. For B it is 0.7. B's
ability has the sam,e central tendency as A's, but B is a more
constant performer.

It is obvious that an average from a set of measurements like
the second is less likely to deviate from the true status than an
average from a set like the first. And in general the less the
variability of the single measures the greater the reliability of the
result inferred from them.

In the case of A's memory we should say, using formulae the
derivation of which need not be described here: From what
knowledge we have, the most likely true average number of letters
correctly written for A is 7.44; the chances are

1 to I that the true average does not differ from 7.44 letters correctly

written by more than .171

2 to I that the true average does not differ from 7.44 letters correctly

written by more than .245

3 to I that the true average does not differ from 7.44 letters correctly

written by more than .291
99 to I that the true average does not differ from 7.44 letters correctly
written by more than .651
999 to I that the true average does not differ from 7.44 letters correctly
written by more than .835

The variability of mental measurements thus gives no reason
to distrust them, but, on the contrary, gives a means of knowing
just how trustworthy they are.

The Measurement of Individual Differences

Methods of Reporting Individual Differences Within Large

Groups

Suppose now that the average abiHty in remembering letters
in such a test as that described had been determined for every
human being six years old or older. From such records the
difference of any individual from any other could be computed,
but only by hunting out the records of the two individuals. The
frequency of any given degree of difference could be found a
very simple summary of such records, such as appears in Table 2.

TABLE 2

Supposed Distribution of Average Ability to Remember Letters in
THE Case of Human Individuals Six Years Old or Older

An average of o letters was remembered by

1 letter "

2 letters "

3 " "
4

6 "

<< "

9 " "

ID "

11 "

12 "

13 "

14 "

15 "

16 "

17 "

18 "

19 "

20 "

o individuals

2,000,000

30,000,000

60,000,000

190,000,000

280,000,000

360,000,000

310,000,000

190,000,000

40,000,000

6,000,000

400,000

100,000

40,000

20,000

4,000

500

100

5
o
o

A difference of 17 occurs only 10,000,00 times, between
each of the individuals of ability 18 and each of the 2,000,000
of ability i. A difference of 16 occurs 350,000,000 times
(5 times 30,000,000+100 times 2,000,000). A difference of 15
occurs 4,300,000,000 times (^ times 60,000,000+100 times
3,000,000 -J- 500 times 2,000,000) .

A distribution or table of the frequencies of the abilities of

Educational Psychology

individuals is then a convenient means of presenting the facts
from which the frequencies of the different differences amongst
them may be calculated. It serves many other purposes as well,
and so is commonly used in reporting the results of the measure-
ment of any one trait in a number of individuals. The main
features of such a table can be seen at once in their relations
one to another if it is presented in graphic form. Thus
Table 2 becomes Fig. 6, by letting the amounts of the trait be
represented along a horizontal line and the number of persons
possessing each amount be represented by the heights of a column

3S —
30-

iO-

0 1 2 8 4 5 6 7 8 9 10 11 12 13

Fig. 6. Relative frequencies of the different abilities in remembering
letters of human individuals six years old or older. The horizontal scale is
for the average number of words remembered. The vertical scale is for the
number of individuals, 10,000,000 being the unit.

erected at the place on the scale denoting that amount. Such a
graphic representation is called a surface of frequency or a surface
of distribution; the line which, with the base — or scale — line,
encloses this surface is called a frequency curve or distribution
curve.

No one has measured all human beings or even a small but
fair sampling of all human beings in even a single mental trait.
Nor, as we shall see, would that be a very useful undertaking.
If there were such measurements, — if, for example, Table 2 and
Fig. 6 represented actual facts, — they would emphasize the
problem, which should be emphatic enough without them, of
accounting for every difference existing. They would also make

The Measurement of Individual Differences 1 7

it easier to see, what is already clear enough, that accounting for
every difference is the same as accounting for each person's
position on the scale, — each person's amount of the trait. It is
this problem of the causes of individual differences or the causes
of each individual's amount of each trait that is to occupy our
attention in the next five chapters.

CHAPTER III
The Influence of Sex

Preliminary Cautions

By way of preface to an account of sex differences it is well
to note that their existence does not necessarily imply in any
case the advisability of differences in school and home training,
and, on the other hand, that even if the mental make-up of the
sexes were identical it might still be wisest to educate them
differently. It is true that a difference of two groups in a mental
trait will theoretically involve differences in treatment, but prac-
tical considerations apart from that of developing the highest
efficiency in that trait may outweigh the advantages of the differ-
ential treatment. For instance, consumptives theoretically need a
different mode of life from people with healthy lungs, but it
might in some cases be wiser to leave a consumptive to his
ordinary habits rather than to cause in him consciousness of his
disease and worry concerning it. On the other hand, two boys
might be identical in mental structure, yet their education might
best be very different if we wished to make one of them a
chemist and the other a psychologist.

Let us note in the second place that the existence of differences
need not imply the need of different training, because those
very differences may have been due to the different training
actually received and might never have appeared had training
been alike in the two classes. It is folly to argue from any
mental condition in an individual or class without ascertaining
whether it is due to original nature or to training.

The chapter should properly be devoted exclusively to the
differences necessarily produced by sex. Those produced by
virtue of the adventitiously different training which boy and girl
undergo belong in chapter VII. So far as may be, such a

(i8)

The Influence of Sex 19

separation of differences due to sex-nature from those due to
our traditional treatment of the sexes is in fact made. But in
many cases where the amount of the difference that is to be
credited to training- is doubtful, the difference will be described
in the present chapter, the discount to be made being left to the
reader's judgment.

A further caution is necessary before this description and
incomplete analysis begins. It is not to confuse differences in
behavior, achievement and mental activities indirectly caused by
physical traits with such differences directly caused by mental
traits. Lack of muscular strength and the phenomena intimately
associated with bearing children may serve as samples of such
physical traits. Even if women possessed mental capacities for
business identical with those of men, they still might not in active
work do as much.

In the fourth place the fallacy of unfair selection must not be
forgotten in our comparisons of men and women. For instance,
any inference from a comparison of yoimg men and women in
college or of working women with men in the same profession is
untrustworthy. College women and college men are two classes
selected by different agencies. The intellectual impulse has been
relatively a more powerful agent in sending girls to college,
while convention and the demand for a pleasant social and
athletic life have acted more powerfully on boys. In the case
of an industry, say laundering, women are selected by relative
ignorance, strength, widowhood, drunken husbands, etc., while
the men are selected largely by Chinese birth. Let not the
bizarre nature of this particular illustration blind us to the fact
that women and men physicians, lawyers, stenographers, teachers
or government clerks represent different samplings of the two
sexes. It is possible theoretically to make a discount for the
differential influence of selective agencies and thus permit a fair
comparison, but the amount of the discount is very hard to
determine.

The investigator of the direct share of sex in the production
of mental differences would like to compare individuals alike in
age, race, immediate ancestry and training, different in sex alone.
The nearest approach that he can make to this crucial comparison
is to compare a brother with his twin sister in the case of families

20 Educational Psychology

where the treatment of the two is most ahke.* What he has
done is to take such measurements as he can get, of boys and
girls or men and women as nearly alike in age and race and
training as practical exigencies allow, and to measure enough
individuals to make the average immediate ancestry of the one
group nearly like that of the other.

A Sample Study of the Influence of Sex

I shall report as a sample of such studies, that of Dr. Thompson.
[Thompson, H. B., '03] This report will be followed by a state-
ment of present knowledge concerning sex differences, first in
intellectual or semi-intellectual abilities, including sensory and
motor abilities, and then in those interests, tendencies and propen-
sities which constitute what we roughly call character and tem-
perament.

Dr. Thompson describes the essential arrangements made by
her to secure a just measurement of sex differences, as follows : —
['03 ; pp. 2-6, passim]

" In order to make a trustworthy investigation of the varia-
tions due to sex alone, therefore, it is essential to secure as
material for experimentation, individuals of both sexes who are
near the same age, who have the same social status, and who
have been subjected to like training and social surroundings. The
complete fulfilment of these conditions, even in the most demo-
cratic community, is impossible. The social atmosphere of the
sexes is different from the earliest childhood to maturity.
Probably the nearest approach among adults to the ideal require-
ment is afforded by the undergraduate students of a coeducational
university. For most of them the obtaining of an education has
been the one serious business of life. They have had at least
the similarity of training and surroundings incident to school life.

*I have made this comparison in the case of ten pairs of twins from
9 to 15 years old, in simple but fairly precise tests of efficiency in perceiving
small details (A test, a-t, r-e, and misspelled word tests) and of
efficiency in controlled associations of ideas (opposites test, addition and
multiplication). The difference between boy and girl of a pair of twins
varies greatly, but the general result is an absence of difference, the boys
doing worse by i per cent in the former and better by 2 per cent in the
latter tests. This general result might change if ten thousand instead of
ten pairs were studied, but the chances are over 9 out of 10 that there
would not be a difference of 15 per cent in favor of either sex.

The Influence of Sex 21

Most of those in a western university have received their education
in coeducational schools.

The individuals who furnished the basis for the present study
were students of the University of Chicago. They were all juniors,
seniors, or students in the first year of their graduate work. The
original intention was to limit the ages to the period from
twenty to twenty-five years. Owing to the difficulty of obtaining
a sufficient number of subjects within these limits, a few
individuals of nineteen years, and a few over twenty-five were
admitted. The subjects were obtained by requesting members
of the classes in introductory psychology and ethics to serve.
They were told nothing about the object of the tests except that
they were for the purpose of determining psychological norms.

The series of questions on age, health and nationality,

shows that in all these respects the m.en and women tested were
closely comparable

The series of tests employed in this investigation required
from fifteen to twenty hours of time from each subject. The
hours were arranged from one sitting to the next according to
the convenience of the subject. It was not possible to have the
hours for any one test constant for all subjects, since the schedules
varied so widely. No attempt was made to keep the order of
experiments rigidly the same for all. Convenience and economy
of time necessarily determined the order to a great extent. In
general, however, the simple sensory and motor tests were given
in the early part of the series, and the intellectual tests in the
latter part. The questions on personality usually came last.
The taste and smell experiments had to be scattered through
most of the periods, since only a few at a time could be performed
without fatigue. The entire series was applied to fifty subjects,
twenty-five men and twenty-five women.

The experiments fell into seven groups, dealing respectively
with motor ability, skin and muscle senses, taste and smell,
hearing, vision, intellectual faculties, and affective processes. . . .

A few words in general on the methods employed may not
be out of place, in spite of the fact that each is described in
full in connection with the test. The guiding principle in selecting
the method was the desire to make the directions to the subject
as clear and simple as possible and at the same time secure the
greatest possible accuracy of result."

Educational Psychology

The following quotations give an idea of details of method in
the case of two of the tests of " intellectual faculties " : —
[Thompson, '03, pp. 111-114]

Test I for Ingenuity

" Fifteen matches were laid on the table in such a way that
they formed five squares in the relative position shown in Fig. 7.
The subject was then asked if he had ever seen the figure before
or knew its purpose. One of the fifty — a woman — had seen it
before, but had forgotten its purpose. She found the solution in
ten seconds, but since she was doubtless assisted by her previous
acquaintance with the figure, her record is not included in the
curve. The others, upon stating that they had no previous

Fig. 7.

knowledge of the figure or its purpose, were told that the problem
was to remove three matches from it in such a way that three
perfect squares only remained ; in other words, to remove three
matches in such a way that every match remaining on the table
after the three were removed should be a part of a perfect square.
No rearranging of the remaining matches was allowed. The
subjects were all given exactly the same directions, and were
left entirely free to use any method they chose. Removing
matches on trial was permitted. Time was counted from the

moment the conditions were understood

The second ingenuity test was designed to call a pure process
of reasoning into play. It consisted of a puzzling mathematical
problem, perfectly simple in the computations involved but
demanding a somewhat complicated process of reasoning for its
solution — a problem in which it was easy to become confused
unless all the factors were sharply separated and clearly grasped.
The problem was handed written to the subject. He was told
that it involved no difficult computations. The process was

The Influence of Sex 23

g +
S •

H +
3 «•

III 1 1 nil 1 1 1 1 1 1 r

Oin45S7?ilO 15 20 2J id 35

3 • + + • •

2 + +

r'l I I I I I I I I I 1 1 1 1 I 1 1 f —

02 U glOI2l1IUno iS 30 35 10 IS 50 55 *

5 • •

3 . +

2 + * + +

]+ + + + • + -•

I 1 1 1 1 1 r 1 1 1 1 1 1 1 I

0 5 10 15 20 2S 30 35 10 W 50 55 60 ^5' 15 P

Figs. 8, 9 and 10. Comparison of men and women in respect to three tests

of ingenuity. The horizontal scales are for the time ( in minutes ) taken to

solve the problem. The vertical scales are for the number of individuals.

The height of a dot represents the number of men whose times fell within the

division of the scale above whose right limit the dot stands. The height of

a cross has the same meaning, but for women. Thus ( in the middle diagram )

4 men and i woman took from o to 2 minutes, 3 men and i woman from 2

to 4 minutes, 3 women and i man from 4 to 6 minutes, in the second test in

ingenuity.

Fig. 8 ( at the top ) records the results in the first test of ingenuity.
Fig. 9 (in the middle ) " " " " " second test of ingenuity.
Fig. 10 (at the bottom ) " " " " " third test of ingenuity.

24 Educational Psychology

timed from the moment the problem had been read through. A
failure was recorded only in cases in which the subject had
worked from forty-five minutes to an hour, and was completely
hopeless of getting any solution. The problem was the following :
' A man swimming in a river finds that he can swim three times
as fast down stream as up stream. The river flows at the rate
of a mile an hour. Find his rate of swimming in still water.'
Any solution which could he explained was accepted. A mere
stumbling upon the correct answer was not called a solution."

The third problem was to place eight counters on a checker-
board of 64 squares so that no two counters were on the same
horizontal, vertical or diagonal row of squares.

The results of these three tests are shown by Dr. Thompson in
the curves reproduced in Figures 8, 9 and 10.

Means of Measuring the Dirferences Between Two Groups

These distribution curves show fully the differences between
the men and the women, but they do not show them very con-
veniently. For convenience in comparing the difference in, say,
the second of these tests of ingenuity with the difference in the
third or in comparing the difference in any one of them with
the difference in memory or accuracy of movement or rate of
association, the difference in any one trait should be represented
by some one amount.

There are two ways of representing the difference between two
groups by one amount. The first is by stating the difference
between the two central tendencies. Thus in the second test
above the two tables of frequency are as in Table 3. The average
is not here a suitable measure of the central tendency since
' failed ' cannot be given a numerical value.* There is no clear
mode for either men or women. The median is however a useful
measure here. The median, in the sense of the point on the
scale which will have half of the men's records above it and half
below, is somewhere between 12 minutes and 14 minutes. Just
where it is for these 25 men cannot be stated since we do not
know the exact records of the three men who took from 12 to 14
minutes. It would be at the point of the quickest of these three
men. The most probable place for him is from 12 to I2f

*Also for other reasons.

The Influence of Sex

TABLE 3

Comparison of Men and Women in Ingenuity — Second Test
Frequencies of Different Times Taken in Solving the Problem

o to 2 minutes was required by

14
16
18
20

25
30

35
40

45
50

14
16
18
20

25
30

35
40

45
50
55

Women

4 and I

' I

I '

0 '

' I

0 '

' 0

0 '

' 2

I '

' I

I '

' 2

' I

0 '

' I

' 0

0 '

' 0

I '

' 0

Failed in 45 to 60 minutes

The median man required 12^ minutes; the median woman, i^H
minutes.

minutes. The midpoint of this place is 12^ minutes. The
median for women is the slowest of the 4 records in the 14-16
minute group. The most probable point for this is 15I minutes.
The median man is thus 3xV minutes quicker than the median
woman in this test and requires only 8 tenths as long as she. In
the third test of ingenuity the median man is the slowest one of
the three taking from 20 to 25 minutes, while the median woman is
the quicker one of the two taking from 60 to 65 minutes. The
most probable points for them are respectively 24.17 and 61.25. The
median man is thus 37.08 minutes quicker than the median woman
in test 3 and requires only 4 tenths as long.

The second method of representing the difference between two
groups by one amount is by stating the per cent of one group
that reaches or exceeds a given record made by some one of
the other group. Thus in the second test of ingenuity 60 per cent
of men reach or exceed (that is, are quicker than) 16 minutes,
which is reached or exceeded by 52% of women. 48% of men
reach or exceed 12 minutes, which is reached or exceeded by
36% of women. The particular comparison of this sort of

26 Educational Psychology

most service is the per cent of group i reaching or exceeding,
the median of group 2. In test 2, 60% of men reach or exceed
the mecHan for women. In the case of the third test 69% of
men reach or exceed the median for women.

The great advantage gained by comparing groups by the per
cent of one group reaching or cxceecUng the point on the scale
that is reached or exceeded by a given per cent of the other
group is that rcsuhs are mutually comparable whatever the traits
may be. In place of a list of differences now in time taken, now
in amount done, now in quality of this product, now in the amount
of that error made, etc., etc., the second method gives a simple
list of per cents of men who reach ihe median for women. Another
advantage lies in the fact that this percentile comparison reminds
one constantly of the overlapping of the two groups, when such
exists.

This second method should, therefore, be used in the statement
of sex dilTerences, and may be used exclusively for very small
dil'ferences and differences measured in ambiguous units such as
school and college marks.

Unfortunately, of the investigators who have made mental
measurements of men ami women, few have realized the need of
presenting the distribution of the trait in question for each sex,
and still fewer have calculated the per cent of one group passing
the point passed by half (or by any other assigned per cent) of
the other group. Many of the measurements of sex differences
thus remain incommensurate with the rest and are incapable of
inclusion in an exact general estimate.

Dr. Thompson does give the entire distributions so that we can
summarize the essential features of her results in the following
table (Table 4) :—

The Results of Measurements of Sex Differences

In examining Table 4 and similar results it will be Mistruc-
tive to have clearly in mind the significance of different per
cents of one sex reaching or exceeding the median of the other
sex. 50 means of course that the central tendencies of the two
sexes are identical.

45 o^ 55 nicans the amount of dift'erence shown in Fig. 11.

40 or 60 means the amount of dift'erence shown in Fig. 12.

25 or 75 means the amount of difference shown in Fig. 13.

The Influence of Sex 27

TABLE 4.
Differences between Young Men and Young Women in Various

Mental, Processes.

In the case of 50 students in the University of Chicago of approximately
equal age and academic status the per cent of men reaching or exceeding
the median of the women is as follows: —

In reaction time 68 •

Rate of tapping with finger for first 20 seconds 81

" " ' last 20 " of 120* 81

Sorting cards by color ; speed 14

" " " " accuracy 44

Accuracy in thrust from the shoulder at a target approx. 60

" " free arm drawing of a line within an angle 72

Lowness of threshold for sensations of impact 43

" pain 46

" taste (the presence of a taste) . . 34
(recognition of it as sweet,

salt, sour or bitter) 34

presence and recognition of

sweet and salt 45

of sour and bitter 22

" smell (cloves and violet) pres-
ence 43

recognition 41

* light 62

Range of sensitivity to pitch; upper limit 52

" " " " " lower limit 50

Delicacy of discrimination of differences in pressure 47

lifted weights 66

" (points on the forearm)

crosswise 43

lengthwise 18

" area on the skin 61

" " " " temperature (at 30 C.) 53

(at 5 C.) 36

(at 45 C.) 52

" " " taste (sweet 64, salt 35, sour

67, bitter 65) 58

" " " " " " smell (cloves 48, violet 51). 50

" " " " " " pitch 44

" brightness 78

" " " " " " color (as in tests for color-
blindness) 24

" area by the eye 56

*Six women of the twenty-five could not continue so long as the most
easily fatigued man. Two men and two women stopped after 100 seconds.
The others tapped for 120 seconds.

Educational Psychology

Memory of nonsense syllables; rate of learning, auditory 32

" " " " " " " visual 46

Retentiveness after one week ; auditory 5 ^

visual 43

{Quickness in solving ingenuity test i 46

" " " 2 60

" " " 2 69

" 4 68

" " " e 72

General information 5°

Information about English literature 31

" " physics 76

-...^a^rr^:

Fig. II. The amount of difiference between two groups when the per
cent of one group reaching ; or exceeding the median of the other group is
45 or 55.

Fig. 12. The amount of difference between two groups when the per
cent of one group reaching or exceeding the median of the other group is
40 or 60.

Fig. 13. The amount of difference between two groups when the per
cent of one group reaching or exceeding the median of the other group is
25 or 75.

The Influence of Sex

,g
•S

(L)
<U
U

<u
o

a
y

3 .
O O

bo M

o o

u o
a. bJ5
V

tn
O

. (U

y
it!

y
y

A per cent of 100 is ambiguous, meaning anything from the
amount of difference shown in Fig. 14 to an amount as great
as or greater than that shown in Fig. 15. So also a per cent of o

30 Educational Psychology

is ambiguous, meaning possibly a difference as little as that of
Fig. 14 (reversed), and possibly a difference as great as or
greater than that of Fig. 15 (reversed).

As a matter of fact there is no intellectual ability among those
so far measured in which the percentage of males reaching the
median for females is as low as o or as high as 100. The groups
always over-lap to the extent of half the range of one of them,
or, more exactly, to the extent of the distance on the scale from
the median to one extreme of one group.

Wissler ['01] found, in the case of young men and women
students in Columbia University, that in fatigue at pressing a
spring with thumb and forefinger, in the perception of weight,
and in discrimination of points on the skin, there was no appreci-
able superiority of either sex. Women responded with the
judgment of ' painful ' to a much less pressure than was required
in the case of men, but differences in the standard of ' painful '
probably played a large part in the effect. Only 18 per cent of
men judged painful as low a pressure as did the median woman.
Only 40 per cent of men were as accurate in judging pitch as
was the median woman, but in the case of size the figure was
75 per cent. In quickness of reaction time to sound it was 81,
but in quickness in marking out A's it was only 32 and in quick-
ness in naming colors it was only 18. In rate of movement
about 60 per cent of men equaled or surpassed the median woman,
and in rate of association (by a doubtful test) about 70. In
memory there was a trifling female superiority.

Gilbert ['94] measured 100 boys and 100 girls of each age from
6 to 17, chosen at random from those in school. He gives
simply the medians and the average variations of the individuals
therefrom, but it is possible to estimate from his data very closely
the percentages of boys reaching or exceeding the median for
girls in the case of the traits listed below. The facts are : In
the case of boys and girls 8-14 years old (inclusive), the per cent
of boys reaching or exceeding the median ability for girls of the
same age is: —

In delicacy of sense-discrimination for weight 48

In delicacy of sense-discrimination for color (shades of red) 39

In reaction time 57

In resistance to the size-weight illusion 55

In rate of tapping 64

The Influence of Sex 31

In the case of boys and girls 15-17 years old (inclusive), the
same per cent is : —

In delicacy of sense-discrimination for weight 58

In delicacy of sense-discrimination for color (shades of red) 58

In reaction time 76

In resistance to the size-weight illusion 68

In rate of tapping 73

I have compared the sexes in the case of various abilities, shown
in objective tests and in school marks, with the results shown below,
In the case of boys and girls from 8-14 years old (inclusive) the
per cent of boys reaching or exceeding the median ability for girls
of the same age is : —

In tests of the associative and conceptual processes, such as the
opposites test, alphabet test, word test, addition and multi-
plication 48

In speed and accuracy in noticing small details, as in the

A test, the r-e, o-n, a-t tests and the like 33

In memory of words for a few seconds (10-30) 40

In spelHng 33

In the case of boys and girls of the same classes in high
schools the same per cent is : —

In tests of the associative and conceptual processes 50 (approx.)

In English (Regents' examination and school mark) 41

In mathematics " " " " " 57

In Latin " " " " " 57

In history " " " " " 60

In the case of college students the same per cent is : —

In English 35 (approx.)

In mathematics 45 (approx.)

History and economics 56 (approx.)

Mental Science 5° (approx.)

Modern languages 40 (approx.)

In the case of college students the selection of women is
narrower, and probably a little better. The men probably devote
less time to their college studies. The students in question were
from two state universities in the north-central states.

The most important characteristic of these differences is their
small amount. The individual differences within one sex so
enormously outweigh the differences between the sexes in these
intellectual and semi-intellectual traits that for practical purposes

32 Educational Psychology

the sex difference may be disregarded. So far as ability goes, there
could hardly be a stupider way to get two groups alike within
each group but differing between the groups than to take the
two sexes. As is well known, the experiments of the past generation
in educating women have shown their equal competence in school
work of elementary, secondary and collegiate grade. The present
generation's experience is showing the same fact for professional
education and business service. The psychologists' measurements
lead to the conclusion that this equality of achievement comes
from an equality of natural gifts, not from an overstraining of
the lesser talents of women.

In detail the measurements show a slight inferiority of the male
sex in receptivity or impressibility and a slight superiority in
the control of movement and in thought about concrete mechanical
situations. Dr. Thompson would attribute the last difference
to differences in training and a charitable male psychologist
might so attribute the superior quickness of movement also. The
matter is not of great consequence, first because the differences
themselves are not, and second because the differences in training,
if they exist, are probably due largely to original differences
between the interests of the two sexes. If boys by training learn
more about the mechanical properties of objects, it is probably
because they by nature care more about such learning. It can
hardly be maintained seriously that forced differences in the
training of these 50 students in the University of Chicago or of
boys and girls in New Haven and New York, — differences in
training, that is, apart from the selection of certain training by
the children's natures, — favored either sex in such a matter as
solving an example in arithmetic or marking out A's or spelling
or giving the opposites of words,

A vast amount of time could be spent in analyses of the minor
differences reported and in argumentation about the reasons for
them, for their existence in original nature and for their relations
one with another. It would be largely profitless, however ; for
no one of these measurements is by itself very reliable and their
proper use is only to decide general questions about large differ-
ences and about the general extent to which sex is the cause
of the mental variations of mankind. They suffice to prove that
the sexes are closely alike and that sex can account for only
a very small fraction of human mental differences in the abilities

The Influence of Sex 33

listed. They do not suffice to prove the exact nature or amount
of the difference in each special trait.

The trivial difference between the central tendency of men and
that of women which is the common finding of psychological tests
and school experience may seem at variance with the patent
fact that, in the great achievements of the world in science, art,
invention and management, women have been far excelled by
men. One who accepts the equality of typical (i. e., modal)
representatives of the two sexes must assume the burden of
explaining this great difference in the high ranges of achievement.

The probably true explanation is to be sought in the greater
variability within the male sex.* The most gifted men may be
superior to the most gifted women even though the average
man is equal to or below the average woman, if men vary zvidely
enough from their central tendency. Thus in Fig. 16 the central
tendencies are the same for men and women, but there are two
men out of every hundred who are superior to all women. In
Fig. 17 only 45 per cent of men reach the median ability for
women, but i of the 45 is superior to all women.

Sex Differences in Variability

A difference between the sexes in variability may be of as
great significance as a difference in central tendency. This will
be clearest if its influence is observed first in one or two imagin-
ary cases. Suppose, for example, that the average position of
men on a scale for morality is the same as that for women,
and call this amount of morality 20 M. Suppose the average
deviation of individual men from 20 M to be 2 M, and the
average deviation of women from 20 M to be 3 M. Then the
two surfaces of frequency would probably be approximately as
in Fig. 18. The best man would be about twice as good as

*It should be obvious that the greater variability of males in the sense of
the divergence of individuals from the average or median or mode of their
sex implies nothing whatever about the variability of individual men in
the sense of the divergence of any man's different 'trials' from his own
general average, — in the sense, that is, of the inconstancy of performance
of an individual. Men might vary widely inter se, but each man might be
a very constant performer; women might vary very little from the modal
woman, yet each one might vary enormously on different occasions from
her average performance or central tendency.
3

Educational Psychology

the worst man, all men being between about 12 M and 28 M.
The limits required to include all the women would, on the
contrary, range from about 8 M to 32 M. The best woman would

Fig. 16. The continuous line encloses the surface of frequency for men;
theMotted line, that for women.

— 1 L

1
1

1
>

1
1

1
1 ,.,

Fig. 17. The continuous line is for men; the broken line, for women.

be four times as good as the worst. About two women out of
every hundred would be better than the best man ; about two
would be worse than the worst man.

The Influence of Sex 35

Thus, though the average moraUty would be the same, we
would have differences of tremendous practical moment. The
great acts of honor, philanthropy, nobility and sacrifice would
all be due to women. At the same time they would commit
all the basest of crimes and iniquities. They would lead in all
moral endeavor, but would also fill the jails and dens of wicked-
ness, while the men would present lives of equable, uninteresting
mediocrity of both vice and virtue. If the reader will contemplate
the practical importance of a similar difference in the variability
of the sexes in intelligence, originality, musical talent, piety and

IM. Sivl. IZM. 20 M. i8M- 32M.

Fig. 18. The status of men and women, the two central tendencies being
identical, if the men vary only two-thirds as much as the women.

Other traits, he will see that its measurement is in no wise a
matter of merely abstract interest.

In particular, if men differ in intelligence and energy by wider
extremes than do women, eminence in and leadership of the
world's affairs of whatever sort will inevitably belong oftener
to men. They will oftener deserve it. But the greater male
variability should result also in a great preponderance of men
amongst the most idiotic idiots. Just this seems to be the case.
Cattell says ['03, p. 375] in the course of his report on the
thousand most noted individuals of the civilized world : —

" I have spoken throughout of eminent men as we lack in
English words including both men and women, but as a matter
of fact women do not have an important place on the list. They
have in all 32 representatives in the thousand. Of these eleven
are hereditary sovereigns and eight are eminent through mis-

36 Educational Psychology

fortunes, beauty or other circumstances. Belleslettres and fiction
— the only department in which woman has accompHshed much —
give ten names (of which three are in the first 500) as compared
with 72 men. Sappho and Joan d'Arc are the only other women
on the list. It is noticeable that with the exception of Sappho —
a name associated with certain fine fragments — women have not
excelled in poetry or art. Yet these are the departments least
dependent on environment and at the same time those in which
the environment has been perhaps as favorable for women as for
men. Women depart less from the normal than man — a fact that
usually holds for the female throughout the animal series ; in many
closely related species only the males can be readily distinguished.
The distribution of women is represented by a narrower bell-
shaped curve."

In a study restricted to British genius Ellis ['04, p. lo-ii] finds
a similar failure of women to reach the extreme of men.

"In the final result my selection yields 975 British men of a
high degree of intellectual eminence. The eminent women num-
ber 55, being in proportion to the men about i to 18.

A slightly lower standard of ability, it would appear, prevails
among the women than among the men. On account of the
greater rarity of intellectual ability in women, they have often
played a large part in the world on the strength of achievements
which would not have allowed a man to play a similarly large
part. It seemed, again, impossible to exclude various women of
powerful and influential personality, though their achievements
were not always considerable. I allude to such persons as
Hannah More and Mrs. Montague. Even Mrs. SomerviUe, the
only feminine representative of science in my list, could scarcely
be included were she not a woman, for she was little more than
the accomplished popularizer of scientific results. In one depart-
ment, and one only, the women seem to be little, if at all, inferior
to the men in ability, that is in acting."

It is well known that very marked intellectual weakness is
commoner amongst men than amongst women. Two times as
many men as women will be found in asylums for idiots and
imbeciles ; and one and a third times as many will be found by
a census including those cases (commonly somewhat less stupid)
cared for at home.

In the case of general ability both extremes of both sexes are

The Influence of Sex 37

thus fairly measured for us, but in more specialized traits care-
ful measurements are needed of the comparative variability of
men from the typical or ' modal ' man and of woman from the
' modal ' woman.

Methods of Comparing the Sexes in Respect to Variability

When the two groups are equal in respect to their central
tendencies it is easy to compare their variabilities. For instance,
in the case of the pressure required to cause a judgment of
"painful" the results in Dr. Thompson's investigation ['03]
were that the pressure required ranged from 800 to 3600 grams
for women and from 800 to 4000 for men. The average deviation
of the 25 pressures required for the 25 men from that required
for the average or median man was about 960 grams, while that
in the case of women was only about 530 grams. Twenty of
the twenty-five women are included within a range of 1600
grams, but a range of over 2800 grams is required to include
twenty of the twenty-five men. If the men and women were
alike in their central tendencies no objection could be raised to
comparing their variabilities by the above figures.

But if the men were markedly less sensitive to pain — if the
pressure required ranged, for them, from 4000 to 8000, but for
women from 800 to 3600 — if the median man required 6000
whereas the median woman required only 2200, — then the greater
range or greater average deviation of men might not mean a
greater real variability. For, an objector could properly say,
the average deviation of butterflies from their average in weight
is only a small fraction of an ounce whereas the average deviation
of men from their average is a hundred or more ounces, yet
butterflies really vary more in weight than men do. Only if one
man weighs twice as much as another and if one butterfly weighs
twice as much as another may the variations be called equal in
the two cases, the objector may continue. Equal variability should
mean equal ratios, not equal amounts.

There is obviously much force in this objection, and in the
recommendation that a variability around a C. T.* of 20 must be
two times as large as a variability around a C. T. of 10 to be
properly called equal to it. In certain cases, in fact, this method

*I shall use C. T. as an abbreviation for Central Tendency.

C. T.

38 Educational Psychology

is demonstrably just. The absolute or gross variation of sermons
in length would be much greater than the gross variation
in the length of the sentences composing them, but really the
latter are much more variable. Again, 22 individuals worked
addition examples, first for forty, then for eighty, then for one
hundred and twenty seconds. The scores were, respectively: —

A. D.* 2.18
A. D. 3.41
A. D. 5.18

Now the real variability of these 22 individuals in addition is

substantially the same thing in all three tests. They were not two

and a half times as much unlike among themselves in the third

test as in the first! An Average Deviation of 2.18 around a C. T.

of 9 measures the same fact as an Average Deviation of 5.18

around a C. T. of 24, If, instead of the gross variabilities

(2.18, 3.41 and 5.18), we use their ratios to the C.T.s (i. e.,

2.18 3.41 , 5.i8- J V ,, .

' --t- > and ' or .24, .21 and .22) this sameness

9 16 24

in reality is paralleled by the measures. If women tested in
addition for 80 seconds showed a C. T. of 16 and an A. D. of
3.4, while men tested for 120 seconds showed a C. T. of 24
and an A. D. of 5.1, it would certainly be absurd to claim there-
from that men were one and a half times as variable as women.

On the other hand, it would be folly to assume that the ratios
of the gross variabilities to the corresponding C. T.s are
infallibly fair bases for comparing the real variabilities of groups.
For instance, tall men vary actually less among themselves in
stature than do short men. So also men with long middle
fingers vary actually less in the length of their middle fingers
than do men with short middle fingers.

As a matter of theory the allowance to be made for a difference
in central tendency, when groups are compared in variability
in a mental trait, should be that obtained by dividing each gross
variability by the square root of the central tendency rather
than that obtained by dividing through by the central tendency
itself. In anatomical measurements empirical facts support this
theoretical expectation.

In measurements by scales with arbitrary units, such as school

* A. D. stands for Average, or Mean, Deviation.

The Influence of Sex

marks, any comparison of groups in respect to variability is
treacherous if the groups differ in central tendency. Thus suppose
men and women to receives grades in history as follows : —

Grades 40-44 were given to o men and to 4 women

45-49

50-54

55-59

60-64

65-69

70-74

75-79

80-84

85-89

90-94

<< <

(

95-99

The Average Deviation for men and that for women are equal.
The C. T.s are 62 (60-64) for women and yj (75-79) for men.
The best women get marks about twice as high as the worst
women, whereas the best men get marks about one and three-
fourths times as high as the worst men. But the variability
of men may be really greater than that of women. For the
difference called i from 85 to 99 may be very much greater than
the difference called i from 40 to 54. Moreover the fact that
the best woman gets marks two times as high as the worst woman
tells nothing about how many times as much she knows or how
many times as well she can do. The 'times ' statement is justifiable
only when the o of the scale means absolute nothingness of the trait
in question. 80 is twice 40, 84 is twice 42 only if it is twice as
far from the dividing point between nothing and just barely
something on the scale for the trait in question.

In any one mental trait the comparison of men and women
in variability may thus be ambiguous, but since the central
tendency for males is below about as often as above that fof
females, the possibility of error tends in the long run almost equally
toward exaggeration and toward unfair diminution of male vari-
ability. So in a score or more of traits taken at random in respect
to this question, any fundamental difference between the sexes in
variability should be fairly measured.

40 Educational Psychology

The Results of Measurements of Sex Diiferences in Variability

It is unfortunate that so little information is available for a
study of sex differences in the variability of mental traits in the
case of individuals over fifteen. Such statistics as I have been
able to secure give measures in 26 objective tests, with from
100 to 1,500 individuals, and in 25 records of school marks with
from 60 to 1,000 individuals.

The comparisons in the case of reaction time, reaction time
with discrimination and choice, and time memory are based on
the measurements given by Gilbert ['94]. For the data in
spelling, arithmetic and in the r-e and o-n tests I am indebted
in part to Messrs. E. L. Earle, W. A. Fox and L. W. Cole.

The nature of the material, which represents measurements
taken by different individuals and often with only small groups,
makes inferences from details unreliable. The data would be
slightly more accurate if all records had been reduced to a
common month age at least, but this could not be done with
the measurements taken by other observers than myself and
would involve an amount of labor out of proportion to the
increase in accuracy. The main facts that are relevant to our
present purpose are as follows : Variability being measured by
the per cent which the gross variability is of the central tendency,
the sexes differ as shown in Table 5.

If the gross variabilities themselves are used, the ratios for
the A test, a-t test, word test, memory of words and spelling are
somewhat higher, those for discrimination and reaction time are
somewhat lower, while those for the opposites test, time memory,
addition, multiplication, and scholarship remain practically the
same. The general eft'ect would be to raise the ratios somewhat
since in the particular tests given the central tendency for girls
is more often above than below that for boys.

These facts make it extremeh' probable that, except in the two
years nearest the age of puberty for girls,* the male sex is
slightly more variable. From the time of puberty for boys to
maturity this difference seems to increase rapidly, though the
records of marks which support this conclusion are not the best
of evidence.

The variability of girls with respect to the age at which any

*The greater variability of girls in these two years is probably a result
of sex difference in the rate of mental growth.

The Influence of Sex 41

TABLE 5-

Ratio of Female to Male Variability.

By ages. 9 10 11 12 13 14 15 16 17

A test 86 I. II 1.04 .94 1.08 1.03 1.07

A-t test 91 1.05 1.05 1.07 1.35 1-07 -73

Easy opposites test .97 .81 i.io 1.24 .89 1.15

Word test 1.05 .91 .85 .87

Memory (related words) .. . .77 .137 .93 .72

Memory (unrelated words) . .77 .46 .94 .66 .77 1.28

Discrimination of length. . . .7*5 .80 .81 .98 1.04 .70 .78
Simple and discriminative

reaction time 98 1.21 .98 .93 i.oo i.ii .83 1.14 1.22

Time memory 56 .75 1.21 .82 .85 1.27 1.26 .66 1.06

General ratio. Average... .92 1025 .97

Median .93 1.035 -95

The chances are i to i that the true result will not vary from the one
obtained by more than .023 (9-12 yrs.), .04 (13-14 yrs.), .055 (15 yrs.).

By grades. 4 5 6 7 8 ist high.

R-e and o-n tests 77 1.19 .97 .82 .85

Spelling 55 .69 .55 .68 .68

Addition i.oo .91 1.06 .85 .97

Multiplication .56 1.15

In a number of tests (six in all) the ratio of first-year high school girls
to boys in variability was .975.

In tests in arithmetic (six in all) the ratio of high school girls to boys
in variability was .96; in regents' examinations in Latin, English and in
history, it was .96; in school marks in eight subjects, it was on the average .86.

In college marks in fourteen different courses the ratios averaged .85.

given school grade is reached is less than that of boys. The
difference is not necessarily attributable in its entirety to an original
difference between the natures of boys and girls. The greater
variations of boys toward high ages in particular are probably
due in part to the slower maturing of boys, to the greater
frequency of temporary withdrawal and to other factors irrespec-
tive of an original greater variability. But in so far as boys
are found both younger and older than girls at entrance to a
grade, the evidence of their greater variability in the complex of
abilities that determines rate of progress in school is sound. A
careful estimate will probably show that in this complex girls
are not over 95 per cent as variable as boys.

For instance the combined figures for the census of the third-

42 Educational Psychology

year high school classes (1908) in Detroit, Fall River, Los
Angeles, Lowell and Worcester were : — *

Age 13 14 15 16 17 i8 19 20 and over. Total
Boys 3 18 113 237 274 154 69 25 893

Girls I 12 104 298 265 177 40 10 907

In Chicago (1908) the figures were (the numbers for the 1164
girls being reduced to a basis of 975) : —

Age 13 14 15 16 17 18 19 20 and over. Total

Boys I 34 165 306 291 127 34 17 975

Girls I 13 127 371 288 132 32 10 974

In Philadelphia (1908) the figures were (the numbers for the
872 boys being reduced to a basis of 750) : —

Age 13 14 15 16 17 18 19 20 and over. Total

Boys I 3 42 223 256 168 47 10 750

Girls 31 292 282 III 28 6 750

In New York (1905. Report of Superintendent of Schools,
p. 72) the figures were (the numbers for the 1939 girls being
reduced to a basis of 1356) : —
Age 13 14 15 16 17 18 19 20 21 and over. Total
Boys 2 37 274 480 382 123 43 12 3 1356

Girls 2 48 300 390 454 134 20 3 5 1356

On the whole boys are twice as frequent as girls in the youngest
and oldest age groups and about one and one-half times as
frequent at ages 14 and 19.

Dr. Thompson does not calculate the variability within either
sex, nor present the facts on sufficiently fine scales to allow anyone
else to do it exactly. I have calculated it as well as may be
from the measurements which she gives, with the result that
the variability among the 25 women seems on the whole only
93 per cent of that of the men. The difference is closely the
same whether the gross variabilities are used directly or are
first divided by the corresponding" central tendencies or by the
square roots of the latter. In reaction time, in the rate of
sorting colors, and in memory the 25 w^omen are more variable ;
in accuracy in hitting a target, in sensory discrimination and in

*For the statistics from which these measurements are computed I am
indebted to the U. S. Bureau of Education, through Prof. G. D. Straycr.

The Influence of Sex 43

the tests of ingenuity they are ahnost or quite as variable. But
in the majority of tests they are less variable. On the whole
the most probably true estimate is that women are one twentieth
less variable than men.

Wissler's results ['01] with college students show female vari-
ability to be in general about nine-tenths that of males. The
number of women measured was, however, only 42, and the
ratio of female to male variability differed greatly in the different
traits, so that the nine-tenths would, by itself alone, be of no
great reliability.

Sex Differences in Traits Not Measured Objectively

We have now to turn from fairly satisfactory studies of sex
differences in sensory, motor and intellectual capacities, to a looser
discussion of the life of feeling, action and general achievement.
Here objective and precise measurements will seldom be at our
service.

There are two studies which do report such differences
quantitatively, but the data given are subject, unfortunately, to
whatever errors of prejudice or custom teachers, physicians, and
German women of intellectual interests make in rating individuals,
and to possibly important errors due to the existence in their
minds of different standards for the two sexes.

Karl Pearson ['04], in securing data on the resemblances of
children of the same parents, had children rated by their teachers
for various qualities — as quiet or noisy, shy or self-assertive,
and the like. The results in the case where a boy and his sister
were both rated are given in Table 6. If taken at their face
value they show boys to be somewhat more athletic, noisier,
more self-assertive, more self-conscious, less popular, duller in
conscience, quicker-tempered, less sullen, a little duller intel-
lectually, and less efficient in penmanship, in the exact degrees
given by Table 6.

They cannot be thus taken unreservedly ; for, even in comparing
individuals, opinions about the sexes as total groups might be
influential and taint the estimates with some measure of current
irrational prejudices. This error Avould probably increase
differences beyond their real amounts. Such prejudices, if exist-
ing, would work still more insidiously in placing the dividing line
between say keenness and dullness of conscience at a different

44 Educational Psychology

point in the case of boys than was assigned to it in the case of
girls. A boy may not have to be really as conscientious or may
have to be really more athletic in order to be regarded by current
standards as equally conscientious or equally athletic in comparison
with his sister. This error would result in reducing differences
below their real amounts. However, these measurements are
much preferable to general announcements of opinion concerning
boys and girls, unless made by specially competent observers.

TABLE 6

Ratings by Teachers of Boys and their Sisters

IN Respect to Various

Traits.

Boys

Girls

Athletic

291

243

Betwixt

Non-athletic

131

182

Quiet

440

525

Noisy

313

228

Shy

312

355

Self-assertive

262

218

Self-conscious

380

337

Unself-conscious

277

321

Popular

474

487

Unpopular

Conscientiousness

Keen

427

490

Dull

260

197

Temper

Quick

142

116

Good-ntaured

490

501

Sullen

Ability

Quick-intelligent

131

129

Intelligent

271

302

Slow-intelligent

280

273

Slow

106

Slow-dull

Very dull

Handwriting

Very good

Good

249

313

Moderate

300

274

Poor

III

Bad

Very bad

The Influence of Sex 45

The greater variability found for males (see Table 6 under
Ability and Handwriting) is a sign of the trustworthiness of the
data ; and the direction of the differences in no case contradicts
what little objective evidence exists. So the amounts of differ-
ence are worthy of acceptance until a more adequate study is
made. They are slight ; there is much overlapping of one sex
by the other and a far greater range of difference within either
sex than between the averages of the two.

On calculating the probable percentages of boys reaching or
exceeding the degree of each trait that is reached or exceeded by
half of the girls, we have : —

61% 0

f boys are as athletic as or more athletic than the median girl.

62%

noisy

' noisy

42%

shy

57%

self-conscious

' self-conscious '

46%

popular

' popular '

40%

conscientious

' conscientious '

56%

quick-tempered

' quick-tempered '

47%

intelligent

' intelligent '

43%

write

as well as or better

than the median girl.

Heymans and Wiersma ['06, '07 and '08] studied mental differ-
ences of the sexes by means of estimates of individuals made
by other individuals who knew them more or less intimately. The
report covered 90 topics, some of which included several traits.
The individual was graded very coarsely — e. g., as emotional or
not emotional ; or as a drunkard, an habitual drinker, an occasional
drinker, or a total abstainer. Such reports are, as has been noted,
inferior evidence, since the person making them may use different
standards for men and for women. Thus the same degree of
emotionality might be called emotional in the case of a man and
not emotional in the case of a woman, or vice versa. Moreover
when, as often happens, no rating at all is given in a trait, it
may be because the condition of the individual to be rated was
not known in the case of that trait, or because he was on the
.dividing line between the two classes (or in the case of a single
judgment, like, "Has he mathematical talent?" lacked the specified
degree of the quality). Finally, general superstitions about sex
differences may affect the ratings of individuals. In the case of
the ratings given by women it seems probable that some of the
women knew that their ratings were to be used for a study of

46 Educational Psychology

sex differences. In the case of the ratings given by men this
was apparently not so often the case.

On the whole, the results of the ratings, though very inferior
to objective measurements, are probably superioi to the mere
opinions which one could give from reflection on the common
facts of life and his own narrow circle of acquaintances. They
may at least serve to make the reader critical of whatever such
opinions he has.

The authors do not pretend to distinguish, in the case of any of
these traits, the differences due to sex itself and the differences
due to the difference in the training given to girls. They do,
however, give interesting statements of the difference between
the present and the previous generation.

Their own conclusions are that the fundamental differences
shown by their studies are the greater (i) activity, (2) emotion-
ality, and (3) unselfishness of the female. They consider women
to be more impulsive, less efficient intellectually, and more fickle
than men as a result of the first two differences mentioned above ;
to be more gifted in music, acting, conversation and the invention
of stories as a result in part of the second difference ; and to
think well of people and be easily reconciled to them as a result
of the third ['07 p. 20].

These conclusions are vague and the tables of comparison of
the sexes which give rise to them are exceedingly long and
obscure. The latter take the form of 90 classifications such as : —

From the reports made From the reports made

almost exclusively by almost exclusively by

men, the per cents of women, the per cents

men and of women were : were :

Emotional

Not emotional

Men

Women

Men

Women

I have therefore calculated from them the probable per cent
of men reaching or exceeding the median woman in respect to
each trait, counting the ratings by men and those by women as
of equal weight. The differences so estimated I have arranged
roughly in the order of their magnitude. The largest difference is
that :—

Only 15 per cent of men are as much more interested in persons than in
things as the median woman is.

The Influence of Sex

The next largest differences are that : —

In accurate and orderly reten-
tion of what is read 73% of men equal or excel the median woman.

In industry 28%

In adroitness in manual work 28%

In love of sedentary games of
skill 71%

In emotionality 30%

In temperance in the use of
alcoholic drinks . . . 30% (or less)

In independence 70%

In zeal for money making . . . 69%

In desire for change 32%

In impulsiveness 34%

In quickness of recovery from
grief 66%" " " "

Then come the following :

In activity (of the aimless

sort) 36% of men equal or excel the median woman.

In dissatisfaction with oneself 36%

In religiousness 36%

In excitability 37%

In sympathy 38%

In patience 38%

In love of sports 62%

In humor 61%

In risibility 39%

In talkativeness 40%

In gaiety 40%

In vanity of person 40%

There are very slight differences as follows : men are a little
oftener reported as critical, attached to opinions once formed,
given to ambitious plans, given to contradiction, sensible, decisive,
gifted in mathematics, gifted in literature, specific, of good
memories, fond of eating and drinking, fond of distinction, strict,
and also easy-going, in discipline with children, kind to sub-
ordinates, widely read, and punctual. They are a little less
often reported as good-natured, anxious, easily reconciled after
anger, insistent on immediate results, good judges of human
nature, practically resourceful, narrow, gifted in languages,
gifted in music, good observers, thrifty, domineering, kind and
careful in discipline with children, active in philanthropic work,
demonstrative, honest about money, fond of intercourse with social

48 Educational Psychology

superiors, timid, well posted about the affairs of acquaintances,
polite, attentive, tidy, and courageous in sickness.

In the following traits there is still less difference reported or
no difference observable: Trustfulness, tolerance, inconstancy in
sympathies, devotion to old memories, quickness in comprehension,
superficiality, stupidity, ability in drawing, acting, mimicing, ear
for music, patriotism, naturalness, straightforwardness, truthful-
ness, kindness to animals, snobbishness, courage, and pleasure-
seeking.

It is not desirable to comment further on these results of
Heymans' and Wiersma's work, until further study by more
objective methods has been given to the topic.

It would be desirable in any such study that the sex differ-
ences in the instinctive acts, interests, aversions and emotional
responses should be studied apart from the differences in similar
traits that have been produced by circumstances. Two instincts
are worthy of special attention. The most striking difference in
instinctive equipment consists in the strength of the fighting
instinct in the male and of the nursing instinct in the female.
No one will doubt that men are more possessed by the instinct
to fight, to be the winner in games and serious contests, than
are women ; nor that women are more possessed than men by
the instinct to nurse, to care for and fuss over others, to relieve,
comfort and console. And probably no serious student of human
nature will doubt that these are matters of original nature. iThe
out and out physical fighting for the sake of combat is pre-
eminently a male instinct and the resentment at mastery, the
zeal to surpass and the general joy at activity in mental as well
as physical matters seem to be closely correlated with it. It has
been common to talk of women's "dependence." This is, I am
sure, only an awkward name for less resentment at mastery. The
actual nursing of the young seems likewise to involve equally
unreasoning tendencies to pet, coddle, and "do for" others. The
existence of these two instincts has been long recognized by
literature and common knowledge, but their importance in causing
dift'erences in the general activities of the sexes has not. The
fighting instinct is in fact the cause of a very large amount of
the world's intellectual endeavor. The financier does not think
merely for money nor the scientist for truth nor the theologian
to save souls. Their intellectual efforts are aimed in great

The Influence of Sex 49

measure to outdo the other man, to subdue nature, to conquer
assent. The maternal instinct in its turn is the chief source of
woman's superiorities in the moral life. The virtues in which
she excels are not so much due to either any general moral
superiority or any set of special moral talents as to her original
impulses to relieve, comfort and console. \

Training undoubtedly accentuates these inborn differences
since boys play more with boys and are trained more by men, the
opposite holding with girls. A reversal of training by which
girls would be surrounded by the social milieu now affecting
boys would, as we often see in isolated cases, lessen the sex
difference, i But we may be sure that if we should keep the
environment of boys and girls absolutely similar these instincts
would produce sure and important differences between the mental
and moral activities of boys and girls. \

Since these differences in instinctive equipment are true causes
it seems wise not to invoke other less probable traits to account
for any fact which these seem fairly adequate to explain. For
instance, if the intellectual achievement of men was found to be
superior to that of women we could explain it either by the
indirect effect of physical strength and bodily fitness or by an
actual difference in intellect or by the zeal and activity due to
the fighting instinct. Our rule would be to exhaust first the
influence of the known physical differences and second the
influence of the instinct in question. Only if these were
inadequate should we resort to the hypothetical cause of differ-
ences in purely intellectual caliber.

Havelock Ellis ['94, '04] chooses as general sex differences
the less variability and the greater affectability and primitiveness
of the female mind. The first point has been discussed fully. By
affectability he means not only greater impressibility by and
responsiveness to stimuli of all sorts, but also less inhibition of
the emotions and other instinctive reactions. The fact seems
indubitable though its exact amount can not be even roughly
estimated. Not only the superiority in tests of perceptual power
and the greater suggestibility which we have noted, but
also the relative frequency of dreams, trance states and emotional
outbreaks and the common differences between our treatment of
the men and of the women with whom we are associated, witness
to it. In his evidence for the discussions of the primitive nature

50 Educational Psychology

of vvomeii Mr. Ellis scoms to have physique in view primarily.
How far women resemble uncivilized races and children in mental
make-up is, to me at least, not at all clear.

The same author emphasizes, as so many others have done, the
fact of female dependence or lack of aggressiveness in intellect.
The ([ualilies that we call original, constructive, organizing and
critical are ill delnK-d and comparisons are hard to arrange
because men and women have devoted the active power of the
intellect to such different fields. Comparison of the most eminent
representatives from both sexes is obviously unfair in so far as
men are more variable.

If we are to believe the novelists and playwrights, women are
more concerned with their own feelings and personalities than
nun, are emotionally more subjective. This is not inconsistent
with the existence of greater sympathy of the motherly sort, nor
with the possibly superior gifts of men in the examination and
intellectual manipidation of subjective conditions. An interesting
bit of evidence supports the conventional view of fiction. Many
people carry on as a systematic day dream a continued story
in which they figure and which ])ossesses its interest from the
chance il gives to think pleasantly of oneself. According to
Learoyd | '96] three and a half times as many women as men
do this (46.7 per cent and 13.5 per cent).

On the whole the difl'erences reported in the case of the less
easily measurable features of intellect, character and behavior
are of the same order of magnitude as those found in objective
tests. They do not require any amendment of the general rule
that sex is the cause of only a small fraction of the differences
between individuals. The differences of men from men and of
women from women are nearly as great as the ditTereuces between
men and women.

CHAPTER IV
The Influence oe Remote Ancesiuy ou Race

The Possibility of Racial Mental Differences

Men are mentally like one another and unlike dogs or horses
because men spring from a presumably common remote ancestry
which was not the ancestry of dogs and horses. Men, dogs and
horses are more alike mentally than men, dogs, horses, earth-
worms and clams arc, because presumably men, dogs and horses
spring from a common ancestry which was not the ancestry of
earthworms or clams. Certain men, for example the American
Indians, springing from a common ancestry which was not the
ancestry of Europeans, may be expected to be mentally more
like one another than like Europeans, if their common ancestry
differed mentally from that of Europeans.

A distinct race is a group of men who to a considerable extent
have in common the same remote ancestry, its present descendants
being to a considerable extent confined to that group. The more
they all hark back to just the same ancestry, and the more
exclusively they represent the present product of this ancestry,
the more distinct a race they will be.

A race that is thus distinct in ancestry is commonly distinct
in some physical traits also. If its remote ancestry differed from
the remote ancestry of other races in mental traits, as it probably
did to at least some slight extent, the race has a probability of
differing from other races in these traits. So also if the race
has differed from other races in the nature or amount of selection,
natural or artificial, on the basis of mental traits. An individual
may thus, by original nature, possess certain racial mental
tendencies. His position on the scale for any mental trait may
be due in part to his membershii) in a certain race, — that is, to
his origin from a certain remote ancestry.

The influence of remote ancestry cannot however be isolated
for measurement at all perfectly. The pedigrees of human stocks,

(51)

52 Educational Psychology

at least of the modern civilized stocks, are not clear enough, and
the influence of similarity in remote ancestry is hard to distinguish
from that of similarity in training. Many of the mental similarities
of an Indian to Indians and of his differences from Anglo-Saxons
disappear if he happens to be adopted and brought up as an
Anglo-Saxon.

So, though the best way to think of the problem is to pictuife
the hereditary relations of all men and to measure the original like-
nesses within the same strains and the dilTorences between strains,
apart from all influences of training, the facts at hand do not so
group themselves. The facts are measurements of the differences
between groups which are distinct to an unknown degree in traits
which are influenced by training to an unknown degree. Any
conclusion will depend upon one's estimates of these two unknown
quantities.

I shall report one sample study of the topic in the case, of great
importance to American education, of differences between whites
and negroes in scholarship in the high school. I shall then sum-
marize the results of other measurements of racial mental differ-
ences ; and. lastly, describe the attitude which science recommends
toward the apparently original differences in intellect, character
and temperament which have not been measured.

A Sample Study of Racial Differences

Mr. Mayo [in a study as yet unprinted] secured the academic
records of 150 negroes* who entered the high schools of New
York City during the period from 1902 on. For each such
record he got a white pupil'sf record selected under the same
conditions. It is iiupossible to tell exactly whether and how far
the two groups of pupils thus taken represent dissimilar samplings
of the two total groups, negroes and whites in New York City.
In my opinion the samplings are closely similar. There are no
measurements of the extent to which residence in New York
selects the more scholarly of negroes from the country, or of the
extent to which entrance to high school selects differently from

*A negro being defined as an individual reported as a negro by school,
officers. MuUittoes arc of course frequent.

f A white pupil being defined as an individual reported as such by school
officers. There may in rare cases have been some slight mixture of negro
blood.

The Influence of Remote Ancestry or Race 53

the negroes in New York than from the whites. In general,
selection by entrance to the public high schools is narrow but
democratic ; and in Mr. Mayo's opinion and my own the high
school gets a somewhat, but not much, higher selection from the
colored than from the white youth. That is, in our opinion, the
superiority of the colored in high school to the colored outside is
greater, but not much greater, than the superiority of the whites in
high school to the whites outside.

Whatever be the difference in the selection of the two groups,
colored beginners in high schools in New York City differ from
whites in their careers there as follows :

( 1 ) On the average they are seven months older, only 36 per cent

of them being as young as the median white.

(2) They continue in the high school longer.

(3) In achievement in the different studies they are somewhat,

but not very much, inferior. The general tendency is for
only three-tenths of them to reach the median record for
whites.

(4) The difference is greatest in the case of English, in which

only 24 per cent of the colored pupils reach or exceed
the median for whites.

Table 7 gives a sample of Mr. Mayo's measurements of the
differences. Fig. 19 presents the facts graphically.

Mr. Mayo also measured the differences in variability, as far
as he could from the arbitrary measures afforded by school marks.
For the details the reader must turn to the full tables in his report
(which will be printed at an early date), one sample table and
the general drift of the results being all that can be presented
here. The records of colored pupils were perhaps a very little
less variable than the whites. Thus, in the score for total scholar-
ship (Table 7), 80 per cent of the colored pupils are included
within a range of 193^2 points on the scholarship scale, while to
include 80 per cent of the white pupils requires a range of 20
points. The corresponding figures for the inclusion of 60 per cent
are 143^ and 14 points. The figures for the inclusion of 50
per cent are 9 and lo^^. The figures for the inclusion of 90 per cent
(or, to be exact, 90.7 per cent) are 33 and 31. The comparison
in variability is, as in the case of the sexes, of great practical
importance. The ability of a hundred of its most gifted represent-
atives often counts more for a nation's or a race's welfare than

Educational Psychology

the ability of a million of its mediocrities. The fact that the
colored pupils, though clustered more closely at the center, range
to nearly or quite as high grades as do the white is thus noteworthy.

TABLE 7.
White and Colored Pupils Compared in Scholarship in New York

City High Schools.
Median of all marks

in the first trials (that

Number

is, excluding marks

for courses repeated

white

colored

after failure)

pupils

24—25

. .

26 — 27

. .

28 — 29

. .

30—31

32 33

34—35

36—37

. .

38—39

. .

40—41

42—43

. .

44—45

• .

46—47

. .

48 49

50—51

52—53

54—55

56—57

58—59

60 — 61

62—63

64—65

66—67

68—69

70—71

72—73

74—75

76—77

78—79

80—81

82—83

84—85

86—87

. ,

, ,

88—89

. .

90 91

92 93

Median

The Influence of Remote Ancestry or Race

The Results of Measurements of Racial Mental Differences

In summarizing the measurements of racial mental differences
I shall in the main quote the admirable account by Woodworth

['10].

The different races of men have been compared by objective
measurements in respect to the keenness of the senses, but in
few traits besides. The reports of travelers gave rise to the
doctrine that primitive races excelled modern Europeans in powers

I — I

.1/1..

Fig. 19. Comparison of white pupils (continuous line) and colored pupils
(dotted line) in respect to scholarship in the high school. The horizontal
scale is for the median of all marks obtained by an individual except those
obtained in courses repeated because of failure. The marks in these schools
are on a o - 100 scale.

of vision, hearing and smell. Skepticism concerning this doctrine
has led to many measurements by anthropologists.

"Ranke on testing natives of Brazil, a race notable for
its feats of vision, found that their ability to discern the position
of a letter or similar character at a distance, though good, was
not remarkable, but fell within the range of European powers.
The steppe-dwelling Kalmuks, also renowned for distant vision,
being able to detect the dust of a herd of cattle at a greater
distance with the naked eye than a European could with a
telescope, have also been examined ; and their acuity was indeed
found to be very high, averaging considerablv above that of

56 Educational Psychology

Europeans ; yet only one or two out of the forty individuals
tested exceeded the European record, while the great majority
fell within the range of good European eyes. Much the same
result has been obtained from Arabs, Egyptians and quite a
variety of peoples. Among the most reliable results are those
of Rivers on a wholly unselected Papuan population. He found
no very exceptional individual among 115 tested, yet the average
was somewhat better than that of Europeans. I had myself,
through the kindness of Dr. McGee, the opportunity of testing
individuals from quite a variety of races at the St. Louis Fair
in 1904, and my results agree closely with those already cited,
though I did not find any cases of very exceptional powers among
about 300 individuals. There were a number who exceeded the
best of the 200 whites whom I also tested under the same
conditions, but none who exceeded or equaled the record of a
few individuals who have been found in the German army.
Indians and Filipinos ranked highest, averaging about 10 per cent
better than whites, when all individuals of really defective vision
were excluded. The amount of overlapping is indicated by stating
that 65-75 P^'" cent of Indians and Filipinos exceeded the average
for whites." ['10, p. 175]

There are racial differences in hearing, as tested by the ticking
of a watch or a click artificially made. The Papuans were found
to be inferior to Europeans. Bruner ['08, p. 92] found that
only five per cent of Filipinos equalled or exceeded the median
white American, The per cent for Indians with more or less
school training was 38. Of the 18 Patagonians, Ainus and
reputed Pygmies, none equalled the median white American.
These differences are probably due in large measure and possibly
in toto to the greater cleanliness, freedom from injury to the ear,
and special training in hearing a click transmitted by a telephone

Of the sense of touch and the sense of pain Woodworth says :

"The sense of touch has been little examined. McDougall found
among the Papuans a number with extremely fine powers of dis-
crimination by the skin. The difference between two points and
one could be told by these individuals even when the two points
were brought very close together ; on the average, the Papuans
tested excelled Europeans considerably in this test. On the other
hand, Indians and Filipinos, and a few Africans and Ainu, tested
in the same manner, seem not to differ perceptibly from whites.

The Influence of Remote Ancestry or Race 57

The pain sense is a matter of some interest, because of the
fortitude or stoHdity displayed by some races towards physical
suffering. It may be, and has been conjectured, that the sense
for pain is blunt in these races, as it is known to be in some
individuals who have allowed themselves to be burned without
flinching, and performed other feats of fortitude. The pain
sense is tested by applying gradually increasing pressure to some
portion of the skin, and requiring the person tested to indicate
when he first begins to feel pain. Now as a matter of fact, the
results of McDougall on the Papuans, and those of Dr. Bruner
and myself on Indians, Filipinos, Africans and Ainu, are in close
agreement on this point. Greater pressure on the skin is needed
to produce pain in each of these races than in whites. This is
the average result, but in this test the distribution of the cases is
specially important. Though most whites feel pain at or about a
certain small pressure, there is quite a respectable minority who
give no sign till much higher pressures are reached, their results
corresponding very closely to those of the majority of Indians.
And similarly, a minority of Indians feel pain at much lower
pressures than the bulk of their fellows, falling into the ranks
of the white man. In each group, the distribution is bimodal, or
aggregated about two points instead of one ; but whites are prin-
cipally aggregated about the lower center, and Indians and other
races about the higher center. Introspection comes to our aid in
explaining this anomaly, for it shows that there is some difficulty
in telling just when the pressure becomes painful. If one is
satisfied with slight discomfort, a moderate pressure will be
enough ; but if a sharp twinge is demanded, the pressure must
be considerably increased. Most whites, under the conditions of
the test, are satisfied with slight discomfort, while my impression
in watching the Indians was that they were waiting to be really
hurt. The racial difference would accordingly be one in the
conception of pain, or in understanding the test, rather than in
the pain sense.

On the whole, the keenness of the senses seems to be about on
a par in the various races of mankind." ['10, pp. 176-177]

With respect to racial differences in speed of brain action and
in certain objective, though somewhat trivial, tests of intellect,
Woodworth says :

58 Educational Psychology

"Some interest attaches to tests of the speed of simple mental
and motor performances, since though the mental process is
very simple, some indication may be afforded of the speed of
brain action. The reaction time test has been measured on
representatives of a few races, with the general result
that the time consumed is about the same in widely different
groups. The familiar "tapping test," which measures the rate
at which the brain can at will discharge a series of impulses to
the same muscle, was tried at St. Louis on a wide variety of folk,
without disclosing marked differences between groups. The
differences were somewhat greater when the movement, besides
being rapid, had to be accurate in aim. The Eskimos excelled
all others in this latter test, while the poorest record was made
by the Patagonians and the Cocopa Indians — which groups were,
however, represented by only a few individuals. The Filipinos,
who were very fully represented, seemed undeniably superior to
whites in this test, though, of course, with plenty of over-
lapping

"Equitable tests of the distinctly intellectual processes are hard
to devise, since much depends on the familiarity of the material
used. Few tests of this nature have as yet been attempted on
different races.

"There are a number of illusions and constant errors of judgment
which are well known in the psychological laboratory, and which
seem to depend, not on peculiarities of the sense organs, but on
quirks and twists in the process of judgment. A few of these
have been made the matter of comparative tests, with the result
that peoples of widely different cultures are subject to the same
errors, and in about the same degree. There is an illusion which
occurs when an object, which looks heavier than it is, is lifted
by the hand ; it then feels, not only lighter than it looks, but even
lighter than it really is. The contrast between the look and the
feel of the thing plays havoc with the judgment. Women are,
on the average, more subject to this illusion than men. The
amount of this illusion has been measured in several peoples, and
found to be, with one or two exceptions, about the same in all.
Certain visual illusions, in which the apparent length or direction
of a line is greatly altered by the neighborhood of other lines,
have similarly been found present in all races tested, and to about
the same degree. As far as they go, these results tend to show

The InUiience of Remote Ancestry or Race 59

that simple sorts of judgment, being subject to the same disturb-
ances, proceed in the same manner among various peoples ; so
that the similarity of the races in mental processes extends at
least one step beyond sensation.

"The mere fact that members of the inferior races are suitable
subjects for psychological tests and experiments is of some value
in appraising their mentality. Rivers and his collaborators
approached the natives of Torres Straits with some misgivings,
fearing that they would not possess the necessary powers of sus-
tained concentration. Elaborate introspections, indeed, they did
not secure from these people, but, in any experiment that called
for straightforward observation, they found them admirable
subjects for the psychologist. Locating the blind spot, and
other observations with indirect vision, which are usually
accounted a strain on the attention, were successfully per-
formed. If tests are put in such form as to appeal to the
interests of the primitive man, he can be relied on for
sustained attention. Statements sometimes met with to the
effect that such and such a tribe is deficient in power of
attention, because, when the visitor began to quiz them on
matters of linguistics, etc., they complained of headache and ran
away, sound a bit naive. Much the same observations could be
reported by college professors, regarding the natives gathered in
their class rooms.

"A good test for intelligence would be much appreciated by the
comparative psychologist, since, in spite of equal standing in
such rudimentary matters as the senses and bodily movement,
attention and the simpler sorts of judgment, it might still be
that great differences in mental efficiency existed between different
groups of men. Probably no single test could do justice to so
complex a trait as intelligence. Two important features of
intelligent action are quickness in seizing the key to a novel
situation, and firmness in limiting activity to the right direction,
and suppressing acts which are obviously useless for the purpose
in hand. A simple test which calls for these qualities is the
so-called "form test," There are a number of blocks of different
shapes, and a board with holes to match the blocks. The blocks
and board are placed before a person, and he is told to put the
blocks in the holes in the shortest possible time. The key to
the situation is here the matching of blocks and holes by their

6o Educational Psychology

shape; and the part of intelligence is to hold firmly to this
obvious necessity, wasting no time in trying to force a round
block into a square hole. The demand on intelligence certainly
seems slight enough ; and the test would probably not differentiate
between a Newton and you or me; but it does suffice to catch
the feeble-minded, the young child, or the chimpanzee, as any of
these is likely to fail altogether, or at least to waste much time
in random moves and vain efforts. This test was tried on
representatives of several races and considerable differences
appeared. As between whites, Indians, Eskimos, Ainus, Filipinos
and Singhalese, the average differences were small, and much
overlapping occurred. As between these groups, however, and
the Igorot and Negrito from the Philippines and a few reputed
Pygmies from the Congo, the average differences were great, and
the overlapping was small. Another rather similar test for
intelligence, which was tried on some of these groups, gave them
the same relative rank. The results of the test agreed closely
with the general impression left on the minds of the experimenters
by considerable association with the people tested. And, finally,
the relative size of the cranium, as indicated, roughly, by the
product of its three external dimensions, agreed closely in these
groups with their appearance of intelligence, and with their
standing in the form test. If the results could be taken at their
face value, they would indicate differences of intelligence between
races, giving such groups as the Pygmy and Negrito a low
station as compared with most of mankind. The fairness of the
test is not, however, beyond question ; it may have been of a
more unfamiliar sort to these wild hunting folk than to more
settled groups. This crumb is, at any rate, about all the testing
psychologist has yet to offer on the question of racial differences
in intelligence." ['lo, pp. 179-181]

The difference between civilized whites and Negritos mentioned
by Professor Woodworth is shown graphically in Fig. 20 for
the first trial in placing the blocks and in Fig. 21 for the third
trial. In the first trial only gj4 per cent of the Negritos were
as quick as the median white ; in the third trial no one of them
was, the best individual of the twenty-twa just not reaching the
speed of the median w^hite. The Negritos also made many more
errors. The reputed Pygmies were still less capable than the
Negritos. The Pygmies apparently did not do so well in this

The Influence of Remote Ancestry or Race

test as the so-called 'feeble-minded' and 'higher grade imbeciles'
confined in state asylums in Massachusetts and Connecticut.

Havelock Ellis ['04] studied the relation of race to amount and
kind of achievement in the case of the 1030 most eminent British
careers from the 4th to the 19th century. He verifies the opinion
that the Scotch have a larger percentage of men of great intellect
than the English, Welsh or Irish. The most marked difference

1
I

! r

150

15 30 45 60 75 90 105

Fig. 20 (upper diagram). Comparison of whites (continuous lines) and
Negritos (dotted lines) in respect to time taken 'to put variously shaped
blocks in holes to match. The horizontal scale is for. time in seconds, first
trial.

Fig. 21 (lower diagram),
third trial were used.

As in Fig. 20, except that the records in the

which he finds is between the Scotch and Irish in the case of
ability in Science and in Acting. Of the 120 men of science, 21
were Scotch and only i Irish, while of the 42 actors 6 were Irish
and none were Scotch. He also finds signs of differences in the
character of the scientific work done by men from different sec-
tions representing somewhat different racial stocks. He writes :

62 Educational Psychology

'Tsychologically it is not difficult to detect a distinct character
in English scientific genius, according as it springs from the
Anglo-Danish district or the East-Anglian focus or the south-
western focus, although I am not aware that this has been pointed
out before. The Anglo-Danish district may here be fairly put
first, not only on account of the large number of scientific men it
has wholly or in part produced, but also on account of the very
high eminence of some among them. The Anglo-Dane appears
to possess an aptitude for mathematics which is not shared by the
native of any other English district as a whole, and it is in the
exact sciences that the Anglo-Dane triumphs.* Newton is the
supreme figure of Anglo-Danish science ; it will be noted that
he belongs to the East-Anglian border, and by his mother is
claimed by Rutland, a little county which, I am inclined to think,
really belongs psychologically and perhaps ethnologically to East
Anglia. The combination of the Anglo-Dane and the East
Anglian seems highly favorable to scientific aptitude ; the abstract-
ing tendency of the Anglo-Dane, and the exaggerated
independence of his character, with the difficulty he finds in taking
any other point of view than his own, are happily tempered by
the more cautious and flexible mind of the East Anglian. Darwin
(who also belonged to the Welsh Border) belonged in part, like
Newton, to the East Anglian border of the Anglo-Danish district,
and also (somewhat remotely) to Norfolk, a county which con-
tains many Danish elements. The science of the Anglo-Danish
district is not exclusively mathematical, and geology especially
owes much to the Anglo-Dane ; it will be remembered that geology
was one of the first sciences to attract Darwin.

" The East Anglian is in scientific matters drawn to the concrete,
and shows little or no mathematical aptitude. He is a natural
historian in the widest sense. He delights in the patient collection
of facts, and seeks to sift, describe, co-ordinate, and classify them.
In his hands science becomes almost an art. Gilbert illustrates
East Anglian scientific methods in the inorganic world, Ray in
the organic, and Francis Bacon, though he cannot himself be
classed among men of science, has in the Novum Organum and
elsewhere presented a picture of scientific method as it most
naturally appears to the East Anglian mind,

*The mathematical tendencies of Cambridge are due to the fact that
Cambridge drains the ability of nearly the whole Anglo-Danish district.

The Influence of Remote Ancestry or Race 63

"It is not easy to see anything- specific or definitely Brythonic
in the scientific activities of the Welsh Border. At most it may
be said that there is some tendency for science here to take on a
technological character and to become associated with the artistic
crafts. The scientific men found here often belong only in
part to the district, and many of them seem to possess the
psychological characters of the southwestern focus.

"The scientific characters of the southwestern focus are quite
clear, and definitely distinct from those of either the Anglo-
Danish district or the East Anglian focus. What we find here
is the mechanical impulse, and more especially the physiological
temper, the instinct to seek out the driving forces of vital
phenomena. It is on this account that Harvey, though of
Kentish family, may be said to belong psychologically to this
focus, as also Stephen Hales, though he belonged partly to
Kent and partly to East Anglia. The great scientific physicians
belong here (the surgeons are largely East Anglian), with
Sydenham at the head and Glisson. Huxley, again, is a typical
figure. Inventors are numerous, for the scientific men of this
region have frequently been enamoured of practical problems,
and just as they have been pioneers in the physical world, so
in science they have sought rather to make discoveries than
to formulate laws. Thus in astronomy we have Adams, and
one of the greatest and most typical scientific men of this region
was Thomas Young." ['04, pp. 68-71]

These last differences are not measured, but if they exist at
all they are surely very slight ; for even the most striking differ-
ence, that between the Scotch and Irish in science and in acting,
is really a very small difiference. Even supposing circumstances
of religion, education and the like to have had no part in it
and so attributing the whole of the difference found to race, the
facts found could be explained by supposing the two races to
differ in the capacity for science by much less than the amount
shown in Fig. 22. Similarly in the case of acting. A very slight
difference between two groups in central tendency may (and
will, except for contrary influences from differences in variability)
make an enormous difference between the percentages from the
two groups that possess a very high degree of the trait in question.
Indeed I have quoted Ellis's conjectures chiefly as a sample of
how, on the one hand, a striking difference between extreme

64 Educational Psychology

representatives may mislead one and of how, on the other hand,
a very small general difference between two races may by its
effect in producing many more men of very high ability, advance
the social condition of the favored race.

The Interpretation of the Differences Betzveen One Race and

Another in Achievement

The moderation of the findings by psychologists is in striking
contrast with the first and common impression made by the
history and present status of different races of men. The modern
European, who can kill a hundred of a race in an hour, or buy
up their entire property with the results from one day of his

Fig. 22.

labor, or get any of the results one of them desires in a tenth
of the time that they take, seems to be far more capable than
they. The Chinese, who resists all that we think he ought to
crave, seems obviously to have a temperament radically different
from ours. Large, glaring differences mark the achievements of
races and seem to need large differences in nature as their origins.
The most noticeable fact about the races of men seems to be
their great mental variety. Under the deliberate scrutiny of
actual measurements, however, what seemed to be large differ-
ences shrink to five or ten per cent, and what seemed to be wide
gaps are bridged. No two races have been measured which
do not overlap mentally whatever be the trait measured.

The first thing to note in respect to the apparent conflict
between common observation and precise experiments is that the
two have not measured the same traits. Common observation
of the African and the European, for example, decides that the
latter is superior in intellect, enterprise and self-reliance. Even

The Influence of Remote Ancestry or Race 65

when experiments show him to be approximately equal in sense
keenness, resistance to the size-weight illusion, or putting blocks
in holes that fit them, the claims of common observation are
not necessarily denied. The nature and amount of race differ-
ences in such traits as intellect, enterprise and self-reliance cannot
be inferred from the amount of difference found in sensory or
sensori-motor traits, but must be studied directly. We do not
know just what the symptoms of intellect are, but apparently
quickness and accuracy in making purely mental associations,
ability to respond to parts or elements of situations which cannot
be abstracted in reality but only in thought, the consequent power
to devise new responses to old situations, and a marked develop-
ment of the instinctive satisfaction in thought for its own sake
are leading ones. Measurements of these traits in different races
are much needed. In the second place, two races need not be
equally gifted because each is equally well adapted to its environ-
ment, if the second race has by superior enterprise sought out
or created a more exacting but also more remunerative
environment. The Bushman may count all that he needs to count,
but to put oneself in a position that needs algebra and the
calculus may itself be a symptom of superiority. So the complex
of qualities which is called enterprise remains largely untouched
by the psychologist's tests. The very fact that a certain test
seems to be unfair to the Bushman may be evidence of his
inferiority.

A third fact for consideration is that although the most rigorous
thinkers amongst anthropologists are skeptical concerning original
mental racial differences, the general body of scientific opinion
is by no means fully agreed with them. Francis Galton ['69, '92] in
a well known chapter on "The Comparative Worth of Different
Races" declares that, taking negroes on their own intellectual
ground, they still are inferior to Europeans by about one-
eighth of the difference between say Aristotle and the lowest
idiot. That is, he considers the two groups to differ approxi-
mately as shown in Fig. 23. His argument is:

"Thirdly, we may compare, but with much caution, the relative
position of negroes in their native country with that of the
travellers who visit them. The latter, no doubt, bring with them
the knowledge current in civilized lands, but that is an advantage
of less importance than we are apt to suppose. A native chief
5

66 Educational Psychology

has as good an education in the art of ruling men as can be
desired ; he is continually exercised in personal government, and
usually maintains his place by the ascendency of his character,
shown every day over his subjects and rivals. A traveller in
wild countries also fills, to a certain degree, the position of a
commander, and has to confront native chiefs at every inhabited
place. The result is familiar enough — the white traveller almost
invariably holds his own in their presence. It is seldom that
we hear of a white traveller meeting with a black chief whom
he feels to be the better man. I have often discussed this subject
with competent persons, and can only recall a few cases of the
inferiority of the white man, — certainly not more than might be
ascribed to an average actual difference of three grades, of which
one may be due to relative demerits of native education, and the
remaining two to a difference in natural gifts.

Fig. 23. The original difference between Europeans (continuous line) and
Negroes (dotted line) in intellectual ability, according to Galton.

"Fourthly, the number among the negroes of those whom we
should call half-witted men is very large. Every book alluding
to negro servants in America is full of instances. I was myself
much impressed by this fact during my travels in Africa. The
mistakes the negroes made in their own matters were so childish,
stupid, and simpleton-like, as frequently to make me ashamed
of my own species. I do not think it any exaggeration to say,
that their c is as low as our e, which would be a difference
of two grades, as before. I have no information as to actual
idiocy among the negroes — I mean, of course, of that class of
idiocy which is not due to disease." [Hereditary Genius, 2nd
Edition, '92, p. 327 f.]

On the other hand, common observation does not as a rule
observe mental traits, but only certain indirect consequences of
them which it is likely to misinterpret. It observes customs, not

The Influence of Remote Ancestry or Race 6y

moral capacity ; habits, not energy ; knowledge, not^ intellect.
But, obviously, the habits and knowledge possessed by a race
do not measure its present original nature. Its habits and knowl-
edge, its "civilization" or "culture" are in the main due to the
original nature of men long dead and have come to it by train-
ing. The origination of advances in civilization is a measure of
ability, but the abilities that have originated them have prob-
ably been confined to a very few men. A race that originated
none of them may now possess them all. Even if a race has
been completely isolated, its civilization has been originated by
only a few of its members ; and the chance of men of great gifts
being born is the result not only of the central tendency of a
race and its variability, but also of its size. Other things be-
ing equal, there is a far greater chance of the birth of a man
of great ability in a tribe of a million than in one of a thousand.
Since one such man may add to the knowledge and improve
the habits of the entire group regardless of its size, civilization
will progress more rapidly in large than in small groups, in a
condition of isolation.

The civilized races have not remained isolated and have got
most of their civilization from without. Of ten equally gifted
races in perfect intercourse each will originate only one tenth
of what it gets. The original nature of the Germans of to-day is not
much different from that of their ancestors in the time of Taci-
tus, and their progress in the meantime is not properly theirs,
but that of the European world and its American colony, each
of whose racial stocks has added something to a common fund.

Again the civilization, — the habits and customs, — of a race
need not be in a direct proportion to its intellect, even if entirely
caused by it. A very slight difference in intellect might give
one real supremacy over another, enable it to condemn the
other to servitude and so free its own intellect from uninstruct-
ive labor. It would thenceforth progress in civilization much
more rapidly than the other. What the mental ability of a race
actually achieves is due to the conditions under which it oper-
ates, and a race may put on or put off such conditions or have
them imposed or removed by other races, for all sorts of reasons.

From all these facts each student may make his own esti-
mate of the original mental differences of races, and learn at least
the need of more actual measurements of race differences and

68 Educational Psychology

of intelligence in interpreting them. My own estimate is that
greater differences will be found in the case of the so-called
"higher" traits, such as the capacity to associate and to
analyze, thinking with parts or elements, and originality, than
in the case of the sensory and sensori-motor traits, but that
there will still be very great overlapping. Calling the dif-
ference between the original capacity of the lowest congenital
idiot and that of the average modern European loo, I should
expect the average deviation of one pure race* from another
in original capacity to be below lo and above i, and the dif-
ference between the central tendencies of the most and the least
gifted races to be below 50 and above 10. I should consider 3
and 25 as reasonable guesses for the two differences.

Even if the differences were far larger than these, the prac-
tical precept for education would remain unchanged. It is, of
course, that selection by race of original natures to be educated
is nowhere nearly as effective as selection of the superior indi-
viduals regardless of race. There is much overlapping and the
differences in original nature within the same race are, except
in extreme cases, many times as great as the differences between
races as wholes.

*Defining a pure race arbitrarily as one whose ancestry has less than
I per cent of community with that of any other race for at least 20
generations back.

CHAPTER V
The Influence of Immediate Ancestry or Family

There is possibly even less agreement about the amount of
influence of immediate ancestry or ' family ' than about that of
remote ancestry or race. This is the more to be regretted because
all the social sciences and especially education need as a starting
point precise knowledge of the differences in original mental make-
up within the human species and of their relation to immediate
ancestry.

The problem naturally resolves itself into two, — the measure-
ment of the resemblance of individuals of like ancestry and the
subtraction of a proper allowance for their likeness in training.
Or, more exactly, we have to measure the amount by which the
likeness of individuals of like ancestry surpasses the likeness
of individuals of different ancestry, and subtract from it the
amount due to their greater likeness in training than that
found in the case of individuals of different ancestry. Measure-
ments of the greater differences of wwrelated individuals with an
allowance for the greater differences in their training would serve
the same end. But the effect of differences in ancestry in pro-
ducing differences in intellect and character is more easily meas-
ured by the effect of similarity or identity in ancestry in decreas-
ing such differences. The facts to be considered are then meas-
urements of resemblance and allowance for like training.

The Variability of Individuals of the Same Sex and Ancestry

Resemblance, not repetition, is to be measured. To say that
a man's original nature depends upon his ancestry does not mean
that it is an exact facsimile of any one or any combination of his
ancestors. There is no reason to believe that four sons of the
same parents and consequently of the same total ancestry will
have the same original natures. Indeed we know they will not,

(60^

70 Educational Psychology

save by chance. For twins who have presumably in some cases
identical or nearly identical antenatal influences and nurture may
vary widely in both physical and mental traits. What ancestry
does is to reduce the variability of the offspring and determine the
point about which they do vary.

Take, for instance,' the capacity to form intelligent habits or
associations amongst sense impressions, ideas and acts. The num-
ber of associations between situation and act, the number, that
is, of things an animal can do in response to the multitude of
conditions of life, varies tremendously throughout the animal
kingdom. The free swimming protozoa studied by Professor
Jennings had in addition to the common physiological functions
hardly more than a single habit. The sum of the life of Para-
Dioecium is to eat, breathe, digest, form tissues, excrete, reproduce,
move along in a steady way, and when passing from certain media
into others to stop, back, turn to the aboral side and move along
again as before. At the other extreme is a cultivated human being
whose toilet, table manners, games, speech, reading, business, etc.,
involve hundreds of thousands of associative habits.

If now we take a thousand descendants of human beings and
count up the number of associative habits displayed by each we
shall of course find a great variability. Some of our thousand
human offspring will learn fewer things than some dogs and
cats. Some of them may learn many more than any of the
parents from whom they sprang. But on the whole the offspring
of human beings will vary about the human average instead of
about the general animal average, and the average deviation of the
human group will be far less than that of the whole animal,
kingdom.

To illustrate again, the children of parents who are, say, 3
inches above the average of the general population in stature will
vary not about the general average, but about a point 2 inches
above it ; and will differ one from another only about ten seven-
teenths as much as one adult of the general population differs
from another.*

Immediate ancestry will then, when influential, cause children
to deviate from the general average toward the condition of their

* This illustration is based on the data reported by Galton in Natural
Inheritance.

The Influence of Immediate Ancestry or Family yi

parents and to vary less among themselves than would the same
number of unrelated individuals.

It might seem at first sight that two individuals of the same
sex, race and parentage, two brothers or two sisters, should, if
ancestry counted at all, have identical original natures and differ
only in as far as different environmental forces affect them.
Common observation shows this to be false, but common thinking
does not always or often understand that it is false just because
immediate ancestry does count. If ancestry did not count, either
all men would by original nature be identical, or the variations
among them would all be miracles. If ancestry did not count,
two brothers might well be identical in original nature, for all
human males might be. But if ancestry is a force, it is certainly,
a variable one, the germs produced by any one parent being some-
what different among themselves for the same reason that the
germs produced by all parents together vary still more. If the
germs differ at all, the differences are likely to be less amongst
the germs of any one human being than amongst an equal number
from all men, but the differences are not at all likely to be reduced
to zero.

In all thought of inheritance, physical or mental, one should
always remember that children spring, not from their parents'
bodies and minds, but from the germs of those parents. The
qualities of the germs of a man are what we should know in
order to prophesy directly the traits of his children. One quality
these germs surely possess. They are variable. Discarding syn-
tax and elegance for emphasis, we may say that the germs of a
six-foot man include some six-feet germs, some six-feet-one
germs, some six-feet-two, some five-feet-eleven, some five-feet-
ten, etc. Each human being gives to the future, not himself, but
a variable group of germs. This hypothesis of the variability of
the germs explains the fact that short parents may have tall sons ;
gifted parents, stupid sons ; the same parents, unlike sons.

Methods of Measuring Resemblance in Mental Traits

In order to understand the measurements of the resemblance
of related individuals which are to be reported in this chapter,
it will be helpful to consider one sample case in some detail.
Table 8 gives (in columns i and 2) the facts concerning the
cephalic index (width of head divided by length of head) in the

72 Educational PsycJwlogy

case of 78 individuals, comprising 39 pairs of twins. Columns 3
and 4 give the same facts expressed as deviations from .81, which
is the central tendency for cephalic index in the population from
which these children were chosen. That is. the first four columns
of the first line of the table read, — " Of two twins one had a
cephalic index of ./SS, the other of .790 ; one was .025 below*
the average of the population, the other was .023 below it."

Cohnnn 5 gives the difl"erence between the indices of the twins
in each of the 39 pairs. Column 6 gives the algebraic product of
the deviations of the indices of the twins from the average cephalic
index of the population.

Consider first column 5, in connection with this question. ** How
much smaller is the diflference between twin and twin of a pair
than that between two children in general ? " Colunm 5 gives the
former differences ; the latter can be got by getting all the dififer-
ences between each child and the other seventy-seven. Thus we
find individual 1 differing from loi, 2, 102, 5. 105, 6. 106, etc.,
by 2, 8, 15, 18, 24, 28, 38, 61, 49, etc. Individual loi differs
from 2, 102, 5, 105, 6, 106, etc., by 10, 13. 16, 22, 26, 36, 59, 47,
etc. Individual 2 dift"ers from 102, 5, 105, 6, 106. etc., by 7. 16,
32, 36, 40, etc. The differences between twin and twin range
from o to 57. averaging 18. If the reader should figure out the
difference between two children of the same age but not of the
same family, he would find it to range from o to 174 or more
and to average about 40. This is the simplest method of meas-
uring the degree to which individuals of like ancestry resemble
one another more than individuals of unlike ancestry do. But it
is for many reasons not the most convenient way and is rarely
used.

Consider now columns 3 and 4 in connection with the question,
" How much oftener are the twins both short-wide-headed or
both long-narrow-headed than are two children in general ? "
Both twins are thus alike (that is both deviate from the average
in the same direction) in 32 out of the 39 pairs, or in 82 per
cent of the cases. Two children taken at random will be thus
alike in 50 per cent of the cases. ' Greater th.an ^o f>cr cent fre-
quency of dcz'iation of related indk'iduals in the same direction
front the coitral tendency,' is another simple measure of their
greater resemblance than that of the non-related individuals.

* Below tneaning more long-narrow-headed, or "dolichocephalic."

The Influence of Immediate Ancestry or Family 73

TABLE 8.
Resemblances of Twins in Cephalic Index.

Pairs OF ^x °X t zl 2S l'^ g"?

Twins S S -sS 2| i^ ,5|-5 a

Bio Oio uiu tfli) " t", «

^I ^T §" . §" . ^ ^x-s->

o u Q P O fe

1 and loi 788 790 —25 — 23 2 575

2 " 102 780 773 —33 —40 7 1320

5 " 105 796 812 — 17 — I 16 17

6 " 106 816 826 3 13 10 39

7 " 107 849 837 36 24 8 864

8 " 108 853 859 40 46 6 1840

9 " 109 777 766 — 36 — 47 II 1692

10 " no 801 770 — 12 — 43 31 516

11 " III 745 738 —68 —75 7 5100

12 " 112 804 773 — 9 — 40 31 360

13 " "3 823 859 10 46 36 460

16 " 116 765 763 — 48 — 50 2 2400

17 " 117 778 788 —35 —25 10 875

18 " 118 836 836 23 23 o 529

19 " 119 839 797 26 — 16 42 .... — 416

20 " 120 761 768 — 52 — 45 7 2340

21 " 121 786 783 — 27 — 30 3 810

23 " 123 806 831 — 7 18 25 .... — 126

24 " 124 778 784 —35 —29 6 1015

25 " 125 826 850 13 37 24 481

26 " 126 802 793 — II — 20 9 220

27 " 127 834 839 21 26 5 546

28 " 128 763 817 — 50 4 54 .... — 200

29 " 129 827 843 13 30 17 390

30 " 130 814 827 I 14 13 14

31 " 131 789 773 —24 —40 16 960

32 " 132 819 828 6 15 9 90

34 " 134 758 725 —55 —88 33 4840

35 " 135 817 780 4 —33 37 —132

36 " 136 786 836 —27 23 50 —621

37 " 137 817 830 4 17 13 68

38 " 138 827 846 13 31 18 403

40 " 140 850 793 37 —20 57 —740

41 " 141 838 846 25 31 6 775

43 " 143 783 786 —30 —27 3 810

44 " 144 785 826 —28 13 41 —364

45 " 145 899 856 86 43 43 3698

47 " 147 832 828 18 14 4 252

50 " 150 836 838 23 25 2 575

74 Educational Psychology

Consider now columns 3 and 4 in connection with this ques-
tion, " What is the ratio of one twin's deviation from the C. T.*
to that of his mate ? " We find these 78 ratios, using the ratio
of I's deviation to loi's and also loi's to I's and so on, to be
If. If. fo. It. V. TT. A. -/. etc., fourteen of them being minus
quantities. The central tendency (Median) of these ratios is .87.
Now if twin and twin always possessed perfect resemblance, —
if the two indices of each pair were alike, — these ratios would
each be I. If we take the ratio of any person's deviation from
the C. T. to that of any other person regardless of blood rela-
tionship, there will be as many minus quantities as plus quantities
and the median of the ratios will be o. The median of the ratios,
each of the deviation of one member of a related pair from the
central tendency of the whole group to the similar deviation of
the other member, is an important measure of resemblance.
When it is o, it means no greater resemblance than one of the
group bears to another taken at random. When it is i.oo it
means perfect resemblance or identity. When it is .5 it means
a resemblance halfway between perfect identity and that found
between any two persons of the group taken at random. This
is for many reasons the most serviceable measure of resemblance
between individuals, and it, or a measure that may for the pur-
poses of this chapter be regarded as the same as it, will be used
in reporting the resemblances found by various students of hered-
ity. The figures, ranging from o to i.oo, called Coefficients of
Correlation, designated by the symbol R, and used to measure
resemblance, are to be thought of as expressing the central tend-
encies (medians) of series of ratios, such as the series of 78 ratios
afforded by the deviation-measures of Table 8.

The central tendency of a series of ratios may however be cal-
culated in another form, the so-called Pearson coefficient of cor-
relation or resemblance, which is somewhat less easy to describe.
Consider column 6 in connection with the question, "What would
these products be if the two twins were identical in the case of
every pair?" In the first pair the product is 575. If the twins
were identical it would be either 625 (25 times 25) or 529 (23
times 23) according as the second twin was to be identical with
the first or the first with the second. In the second pair the

*C. T. is used here and later as an abbreviation for central tendency.

The Influence of Immediate Ancestry or Family 75

product is 1320. With perfect resemblance it would be 1089 or
1600. In the third pair it is 17. With perfect resemblance it
would be 189 or i. In the fourth the corresponding products
are 39 and 9 or 169. In the fifth pair they are 864 and 1296 or

576.

Consider now the sum of the five products as it is (2815), and
as it would be with perfect resemblance (3208 or 2875). Con-
sider what the sum of the products would be with no greater
resemblance than that found between any one of the group and
any other one taken at random. A plus deviation would then go
with a minus deviation as often as with a plus ; in the long run
as many of the algebraic products would be negative as positive ;
and their sum would be o. The proportion which the sum of
the products of the related deviations is of what that sum would
be with perfect resemblance is thus a measure of the amount of
resemblance.

This proportions ^1 y^ + ^^7, + XaYs x„y„

2" X. y

V i'x2.i'y2

Xi, Xg, X3, etc. being the deviations of the first members of the
related pairs, and y 1,72,73, etc. being the corresponding deviations
of the second members of the related pairs. 2"= * sum of the
series of. '

Thus for the 5 pairs above

2815

1 3208.2875

^x y
When ' ^z- = 1, resemblance is perfect.

1/2x2. Jy^ ^

When — ^ -2 ^^ Q? there is no greater resemblance than

exists between the members of the group taken at random. A
resemblance calculated by this, the so-called product-moment
method, devised by Karl Pearson, may for our purposes be con-
sidered as meaning the same thing as the median of the series of
ratios previously described.

If the reader still feels a certain insecurity and unreality about
the values of R = o, R = .i, R = .2, R = .35, R=.75, R=-9.
and the like, he can make these coefficients of resemblance or

76 Educational Psychology

correlation living realities by artificially so pairing the following
series as to get from them various values of R, either as R= the

X V ^X V

median of the — -| — — ratios or as R —

y X V Ix\Iy^

Series i. (x) + 1 +1 + 1 + 1 +3+3+3 + 5 + 7 + n — i — i- i — i-

3-3-3-5-7-11
Series 2. (y) + i + i + i + i+3+3+3+5 + 7 + ii— i — i-i-i —

3-3-3-5-7-11
Thus, pairing them in order, R= i, while pairing them

( + 1+3) ( + 1-1) (+1 + 1) (+1-1) ( + 3+3) ( + 3 + 5) ( + 3-1)

( + 5 + 1) ( + 7 + 11) ( + 11 + 1) (-1+7) (-1-3) (-1-5) (-1+3)

(-3 + 1) (-3-1) (-3-7) (-5-11) (-7-3) (-ii-3),R = -54.
It will be specially useful to pair them so as to get R = — i, so

as to get R = o, so as to get R = about .2, and so as to get

R = about .8.

The Influence of Ancestry on Physical Traits

Before describing the similarities of closely related individuals
in mental traits I shall present the results of studies in the case
of some physical traits which will prove that heredity is a z'cra
causa, since, in them, similarity of training is out of the question
as a cause of the similarities found.

The coefficient of correlation between brothers in the color of
the eyes is, according to Pearson, .52. But parents could not, if
they would, exert any environmental influence upon the color of
•their children's eyes. The fraternal resemblance must be due to
the resemblance in ancestry.

In height Pearson finds the coefficient of correlation between
father and son to be .3, and that between brother and brother to
be .5. In other words, a son, on the average, deviates from the
general trend of the population by .3 the amount of his father's
deviation, a brother by .5 the amount of his brother's. Now no
one can imagine that tall fathers try especially to make their sons
tall. Nor will the class ' men two inches above the average
height ' feed their children any more than men one inch above it.

The coefficient of fraternal correlation in the case of the
cephalic index (ratio of width to length of head) is, according to
Pearson, .49. Here it is utterly incredible that fathers do any-

The Influence of Immediate Ancestry or Family yy

thing to their children that would tend to produce in them similar
indices.

Finally take color of hair. Fraternal correlation is, according
to Pearson, .55. Here again home influence could not cause one
whit of the resemblance.

Immediate ancestry can and does, apart from any other force,
cause in whole or in part the abmodality, or deviation from the C.
T. of his race, of an individual in the case of stature, cephalic
index and eye color. There is no reason to suppose that the brain
is less influenced by ancestry than are the tissues that cause
height, or the shape of the skull bones that causes cephalic index,
or the deposits of pigment that cause eye color. Immediate
ancestry is thus a probable cause for original mental nature. And
when there is doubt as to the choice between it and the environ-
ment as the cause of differences in mental traits of individuals
at any age, it must not be forgotten that the influence of the
latter is, after all, largely a matter of speculation, while the influ-
ence of ancestry is in physical traits a demonstrated fact.

Measurements of the Influence of Ancestry on Mental Traits

Deafness may be considered a physical trait because it is due
to physical causes, but so are all mental traits. The real dififer-
ence is that we know more about the causes in the one case than
in the others. The manifestation and results of deafness are cer-
tainly mental traits.

The brother or sister of a person born deaf is found to be
deaf in 245 cases out of 1,000, almost one case out of four. The
number of deaf persons amongst 1,000 brothers and sisters of
hearing individuals is not known exactly, but it is certainly less
than I, probably much less. That is, a person of the same ances-
try as a congenitally deaf person is at least 245 (probably many
more) times as likely to be deaf as a person of the same ancestry
as a hearing person. The child of two parents both of whom
were born deaf is at least 259 (probably many more) times as
likely to be deaf as the child of two hearing parents [Fay, '98,
p. 49]. In this case, as with the physical traits described, there
is no reason to impute any efficacy to training. Parents born
deaf would take pains to prevent deafness in their children.

Mr. E. L. Earle ['03] measured the spelling abilities of some

y8 Educational Psychology

600 children in the St. Xavier school in New York by careful
tests. As the children in this school commonly enter at a very
early age, and as the staff and methods of teaching remain very
constant, we have in the case of the 180 pairs of brothers and
sisters included in the 600 children closely similar school train-
ing. Mr. Earle measured the ability of any individual by his
deviation from the average for his grade and sex and found the
coefficient of correlation between children of the same family
to be .50. That is, any individual is on the average 50 per cent
as much above or below the average for his age and sex as his
brother or sister.

Similarities in home training might theoretically account for
this, but any one experienced in teaching will hesitate to attribute
much efficacy to such similarities. Bad spellers remain bad
spellers though their teachers change. Moreover, Dr. J. M. Rice
in his exhaustive study of spelling ability ['97] found little or
no relationship between good spelling and any one of the popular
methods, and little or none between poor spelling and foreign
parentage. Yet the training of a home where the parents do
not read or spell the language well must be a home of relatively
poor training for spelling. Cornman's more careful study of
spelling ['01] supports the view that ability to spell is little
influenced by such differences in school or home training as
commonly exist.

These facts make it almost certain that immediate ancestry does
count somewhat in producing the likenesses and differences found
amongst men in mental traits. In the measurements now to be
reported, the influence of family training enters as a more prob-
able alternative cause of the resemblance. I shall in each case
give the measurement of resemblance made and the allowance
for likeness in home training suggested by the author.

The first serious study of the inheritance of mental traits was
made in the 6o's by Francis Galton and reported in Hereditary
Genius ['69, '92]. He examined carefully the careers of the
relatives of 977 men each of whom would rank as one man in
four thousand for eminent intellectual gifts. They had relatives
of that degree of eminence as follows: — fathers 89, brothers 114,
sons 129, all three together 332 ; grandfathers 52, grandsons 37,
uncles 53, nephews 61, all four together 203. The probable
numbers of relatives of that degree of eminence for 977 average

The Influence of Immediate Ancestry or Family 79

men are as follows : — fathers, brothers, and sons together, i ;

grandfathers, grandsons, uncles and nephews all together, 3.
Galton argues that the training due to the possession of eminent

relatives can not have been the cause of this superior chance of
eminence in the relatives of gifted literary men and artists.

He says : "To recapitulate : I have endeavored to show in
respect to literary and artistic eminence —

1. That men who are gifted with high abilities — even men of
class E — easily rise through all the obstacles caused by inferiority
of social rank.

2. Countries where there are fewer hindrances than in England,
to a poor man rising in life, produce a much larger proportion of
persons of culture, but not of what I call eminent men. (England
and America are taken as illustration.)

3. Men who are largely aided by social advantages are unable to
achieve eminence, unless they are endowed with high natural gifts."

Galton demonstrates that the adopted sons of popes do not
approach equality in eminence with the real sons of gifted men.
He so orders his studies of men eminent in other fields as to leave
very slight basis for one who argues that training and opportunity
rather than birth caused the eminence attained. Finally, Gal-
ton's own opinion, that of an eminently fair scientific man based
upon an extensive study of individual biographies, may safely be
taken with a very slight discount. He says : — 'T feel convinced
that no man can achieve a very high reputation without being
gifted with very high abilities."

The historic importance of Galton's Hereditary Genius, the
originality and ingenuity of its author and its substantial results,
should make his book the first to be read by every student of
mental inheritance.

Loewenfeld ['03] confirms Galton's estimate of the resemblance
in intellect and energy amongst descendants from similar near
ancestry.

In 1889 Galton published his Natural Inheritance, the re-
sults of more precise studies * of resemblances amongst related
individuals in stature, eye color, the artistic faculty and diseases.
He found the resemblance between parents and their children
in the mental trait studied (artistic faculty) to be a little greater

*These studies were reported in various memoirs from 1871 to 1887.

8o Educational Psychology

than in the case of stature. The essential facts from which this
inference is drawn are that in 30 families where both parents
were artistic 64 per cent of the children were so, whereas in 150
families where neither parent was artistic only 21 per cent of the
children were so ['89, p. 218]. No attempt is made to divide the
causation of this resemblance between birth and training.

Pearson ['04] secured ratings by teachers of about 2,000 pairs
of siblings with respect to the following traits : — ability, vivacity,
conscientiousness, popularity, temper, introspection or self-con-
sciousness, assertiveness and handwriting. In ability and hand-
writing the measure was a grade from one to six according to
ability; in temper from one to three. In the other traits the
individual was put into an upper or a lower class. Such material
is not well suited for measuring resemblance, chiefly for two
reasons. First, the measurements are very coarsely made, and
so have a large chance inaccuracy. A slight prejudice or ignor-
ance in the teacher making the measurement may put a boy who
is really above the average in one of these traits below it. If
errors of judgment displace a boy on the scale at all, they will
alter his position by half the total scale in five of these traits, by
a third of the scale in one and by a sixth in the other. Such
chance errors are sure to occur. Their effect is to make the
resemblances obtained from the teachers' ratings lozver than the
real resemblances. Spearman ['04, p. 97 ff.] has estimated that
if these teachers' ratings suffer from such chance errors as he
himself finds in such ratings, the obtained resemblances (which
are about .5) are very much too low, the real resemblances
required to produce a measurement of R == .5 when ' attenuated '
by the teachers' chance errors, being over .8. Pearson denies that
the teachers' ratings were thus inaccurate, claiming that they
displaced a pupil from his proper class only rarely. Spearman
possibly overestimates the chance errors of a teacher's judgment
of the intellect or character of a boy well known to him, but
Pearson certainly underestimates them, when he makes no allow-
ance at all for them.

He measured them only in the case of ' ability,' which would
be the easiest of these traits for a teacher to grade accurately, and
which was graded by a six-step scale. Three teachers in a school
graded the same pupils for him * without consultation among

*This being done for some 150 boys and girls in all, distributed in six
schools.

The Influence of Immediate Ancestry or Family 8i

themselves, with the result, he writes, that ' the agreement in
classification was complete in more than 80 per cent of cases and
only differed by as much as two classes in about 5 per cent of
cases.' ['04, p. 161.] But such gradings are not really indepen-
dent, if the pupils are talked about by their teachers.

J»-

Js.

Fig. 24. The real un-
likeness of Jo. and Ja.

Fig. 25. The specious likeness of Jo. and Ja.
when they are rated by teachers who place'the
dividing-line between self-conscious and unself-
conscious too low or too high.

The second error acts in the reverse direction. Any teacher
has his own idea of ' quiet,' ' noisy,' ' keen' in conscientiousness
or ' dull ' in conscientiousness, and the like. Whether he shall
rate a boy as ' self-conscious ' or ' unself-conscious ' depends only
in part on what the boy's nature is. In part it depends on where
the teacher draws the line between being self-conscious and being
unself-conscious. Suppose, for instance, John and James to be
really at points lo and la on the scale for self-consciousness
represented in Fig. 24, and suppose the average self-consciousness

82 Educational Psychology

of English boys to be really at point Av. on this scale. Consider
now ten teachers each of whom is asked, " Is John self-conscious
or unself-conscious ? " Each of them is in total ignorance of the
position of the dividing point, every point above which should be
rated ' self-conscious ' and every point below which should be
rated ' unself-conscious.' Each of them makes his own dividing
point. These divisions will vary. How much they will vary is
not known. Fig. 25 gives an arbitrary estimate of ten as
an illustration. Now John and James, when rated by these ten
subjective scales, seem alike in four cases out of ten, though they
are really not in this sense alike, one being really above and the
other below the real dividing line. Now, in general, any differ-
ence in judges in making the subjective divisions of the scales
whereby they rate the boys will lead the judges to rate boys who
are really different as alike oftener than it will lead them to
rate boys who are really alike as different. For there are many
more boys near the dividing line than at the extremes, and the
brothers of a pair are usually rated by the same judge. Hence
the resemblances as calculated from these teachers' ratings are,
in so far forth, greater than the real resemblances. How much
greater is not known, since the amount of difference between the
subjective and the real dividing point is not known. The error
would probably be greater in the case of conscientiousness, self-
consciousness and shyness, where subjective standards prob-
ably vary very much, than in the case of intelligence or popularity.
The average resemblance of .52 obtained by Pearson would thus
be raised if one error had been avoided, and lowered if a second
error had been avoided. I judge that roughly on the whole the
two errors would somewhat nearly balance. Just what would
happen to each of the particular resemblances if accurate original
measurements had been secured, cannot be more than guessed.
Pearson's obtained measures were ['04, p. 155] : —

Brother and

Brothers

Sisters

Sister

Vivacity
Self-assertiveness

47
53

•43
•44

•49
•52

Introspection

Popularity

Conscientiousness

59
50
59

•47
•57
.64

•63
•49
.63

Temper

Ability

Handwriting

51
46

•49
•47
.56

•51
•44
.48

Average

.51

•52

The Influence of Immediate Ancestry or Family 83

A third criticism of Professor Pearson's measurements might
be that the teachers who reported cases of brothers tended to
select brothers whose Hkeness was notable and to grade them alike
oftener than the facts warranted. It is true that if you seek
information from people without special training in the field of
science concerned, the answers obtained are well-nigh sure to
be compounds of fact and prejudice, but there is apparently no
reason to believe that the teachers had, apart from the directions
sent to them, any prejudicial belief in fraternal similarity.

In two ways the directions for making the judgments may
have tended to suggest the existence of resemblances. The
directions read: — " i. The object of this investigation is two-
fold : ( I ) To ascertain the degree of resemblance, mental and

physical, between children of the same parents

2. The measurements and estimates are to be made on (I)
Pairs of brothers (white data paper). (II) Pairs of sisters (pink
data paper). (Ill) Pairs of brothers and sisters (blue data
paper)." ['04, p. 161.] It would have been far better to have
had all the children in the school rated each on a sheet by himself
and to have said nothing about the purpose for which the meas-
urements were to be used.

There is one more fact to be noted which must lessen con-
fidence in these measurements still further. Using just the same
method of securing the data as in the cases discussed. Professor
Pearson gets, from ratings of athletic or non-athletic , resemblances
of .72 for brothers, .75 for sisters and .49 for brother and sister
['04, p. 154]. Now we know that if these measurements are
free from error in all respects save the mere chance errors of
judgment of the teachers, the real resemblances must be even
higher than .72, .75 and .49. But so close resemblance as a result
of original nature alone is absurd. There is nothing like it else-
where in fraternal resemblances, save in twins. In the case of
athletic power Professor Pearson's figures surely measure the
differences of schools in devotion to athletics or the differences
of the judges as to where the dividing line is between athletic
and not athletic, as well as the resemblances of brothers and
sisters in original nature.

Professor Pearson thinks that no allowance is due for the
similarities of home training because the resemblances in health,
€ye-color, hair-color and five other physical traits average .54,

84 Educational Psychology

.53 and .51 for the three groups of pairs. The resemblances
in these physical traits cannot be due to the fact that the brothers
have the same home environment, he says, yet the resemblances
are as great as in mental traits. Professor Pearson lays great
stress on the exact equality of physical and mental resemblance,
but since his measures of the latter are subject to two important
sources of error, this exact correspondence is of doubtful
significance.

Unless one is a blind devotee to the irrepressibility and unmod-
ifiability of original mental nature, one cannot be contented with
the hypothesis that a boy's conscientiousness or self-consciousness
is absolutely uninfluenced by the family training given to him.
Of intelligence in the sense of ability to get knowledge, rather
than amount of knowledge got, this might be maintained. But
to prove that conscientiousness is irrespective of training is to
prove too much. One fears that Professor Pearson may next
produce coefficients of correlation to show that the political party
a man joins, the place where he lives, and the dialect he speaks
are matters of pure inheritance uninfluenced by family training!

The reader may at this stage be in some doubt as to precisely
what Professor Pearson's measurements give as a probable simi-
larity of brothers' original natures. I share this doubt, and from
estimating the different sources of error can do no more than
expect that adequate mental measurements with the effects of
similarity of training eliminated would leave resemblances of
from .3 to .5.

Dr. Frederick Adams Woods has reported in Mental and
Moral Heredity in Royalty ['06], a work which appeared first in
the Popular Science Monthly in 1902 and 1903, measurements
of the resemblances in intellect and in morals of many individuals
chosen from the royal families of Europe. Dr. Woods gave to
each person of the 671 studied a rating from i to 10 on a scale
for intellect — i representing feeble-mindedness or imbecility ; 10
such gifts as those of William the Silent, Frederick the Great
and Gustavus Adolphus ; and 2, 3, 4, 5, etc., steps at equal intervals
between, in his opinion. These ratings represented Dr. Woods*^
impressions from reading the statements of historians and biog-
raphers about these individuals. He gave similar ratings for
morality.

The ratings assigned by Dr. Woods are, of course, not accur-

The Influence of Immediate Ancestry or Family 85

ate. No one man's ratings of nearly seven hundred historical
personages could be. The effect of this chance inaccuracy would
be to make all his measurements of resemblance lower than the
real resemblance. He may also have erred from an unconscious
prejudice by rating as too much alike individuals who were closely
related. This error would tend obviously to make his estimate
of resemblance too high. His ratings are given in full and so far
nobody has proved or even suggested that they are thus biased.

There is still another chance for error. The reputation of a
prince may be a peculiarly unfair measure of his ability. A son
whose gifted father has brought the nation's affairs into a pros-
perous condition may thereby get, in histories and biographies, an
unduly high rating; whereas a son who must strive against the
unfavorable conditions produced by a stupid father, may thereby
incur an undeserved repute of inefficiency. This is, however, no
more plausible a supposition than the opposite one that a moder-
ately gifted son would be rated too low by contrast with a gifted
father and too high if his predecessor had been a marked failure.
On the whole Dr. Woods' ratings seem little subject to error
other than chance inaccuracy, so that the resemblances calculated
from them are probably too low rather than too high.

The bulk of this work is devoted to the concrete description
of particular stocks and the consequences of particular matings.
To Dr. Woods at least the likenesses and differences of these
men and women seem due in very large measure to their likeness
and difference in ancestry, not only in the case of the degree of
intellect and of morals but also in the direction of interests and
in minor features of temperament. The general results of the
measurements of resemblance are as follows : — "By taking the
records of each country separately and analyzing them minutely,
we have seen how almost perfectly established heredity appears
to be as a cause of decided mental and moral peculiarities,
wherever found. Instead of treating each country separately,
the entire number of interrelated persons will now be studied as
if they were arranged on a single chart, according to blood rela-
tionship. If such a great chart were constructed, we should see
the geniuses, or (9) and (10) grades, not scattered at random
over its entire surface, but isolated little groups of (9) and (10)
characters (the individuals within each group contiguous to each
other) would be found here and there. One such group would

86 Educational Psychology

be seen centering around Frederick the Great, another around
Queen Isabella, of Spain, another in the neighborhood of William
the Silent, and still a fourth with Gustavus Adolphus as a center
These would constitute the largest groups of closely related (9)
and (10) characters. There would also be a few other groups of
two or three geniuses each.

" Those in the lowest grades for intellect would also be found
close to others of the lowest type, and would fall especially in
Spain and Russia, in which countries we have seen an inherited
insanity. There would be certain regions composed almost
entirely of grades from (4) to (7). These would cover the
greater part of the chart and include the houses of Hanover,
Saxe-Coburg-Gotha, Reuss, Mecklenburg, Hapsburg in Austria,
Holstein, Denmark, Saxony, Savoy, Orleans and modern Portu-
gal." ['06, pp. 265-266.]

The general tendency to resemblance he finds to be : —
In intellect : —

Offspring and fathers, r = .30 ;

Offspring and grandfathers, r = .16;

Offspring and great grandfathers, r = .15
In morals : —

Offspring and fathers, r = .30

Offspring and grandfathers, r = .175
In the case of intellect there is a peculiarity in the resemblance.
Men of grades i to 4 have equally gifted fathers ; only from
then on is there a rise in paternal gifts in proportion to the gifts
of the offspring. In moral qualities it is not so.

Dr. Woods thinks that little or no allowance need be made for
greater similarity of environment for son and father or grand-
father than existed for sons of royal families in general. He
says that, while educational opportunities have been unequal, the
"advantages and hindrances must have always been of an acci-
dental character, depending on various causes, and their distri-
bution would occur largely at haphazard throughout the entire
number of collected persons (832) ; and could not account for
the great group of mediocrity and inferiority, like the houses of
Hanover, Denmark, Mecklenburg, and latter Spain, Portugal and
France." ['06, p. 284.]

So also the advantages of high military or political office have
been, in his opinion, distributed " at random throughout the entire

The Influence of Immediate Ancestry or Family 87

number and could not produce the grouping by close blood rela-
tionship found throughout this entire study." ['06, p. 285.]

He tests one environmental influence by the facts, namely, the
advantage of succession to the throne. " There is one peculiar
way in which a little more than half of all the males have had
a considerable advantage over the others in gaining distinction as
important historical characters. The eldest sons, or if not the
eldest, those sons to whom the succession has devolved, have
undoubtedly had greater opportunities to become illustrious than
those to whom the succession did not fall by right of primo-
geniture. I think every one must feel that perhaps much of the
greatness of Frederick II, of Prussia, Gustavus Adolphus, and
William the Silent, was due to their official position ; but an actual
mathematical count is entirely opposed to this view. The in-
heritors of the succession are no more plentiful in the higher
grades than in the lower. The figures below show the number in
each grade who came into power by inheriting the throne.

Grades i 23456789 10

Total number in each Grade .. . 7 21 41 49 71 70 68 43 18 7

Succession Inheritors 5 14 26 31 49 38 45 23 8 4

Percent 71 67 63 64 69 54 67 54 67 57

It is thus seen that from 54 to 71 per cent inherited the suc-
cession in the dififerent grades. The upper grades are in no way
composed of men whose opportunities were enhanced by virtue
of this high position. Thus we see that a certain very decided
difference in outward circumstances — namely, the right of suc-
cession— can be proved to have no effect on intellectual distinc-
tion, or at least so small as to be unmeasurable without much
greater data. The younger sons have made neither a poorer nor
a better showing." ['06, pp. 285-286.]

His conclusion is :— " The upshot of it all is, that as regards
intellectual life, environment is a totally inadequate explanation.
If it explains certain characters in certain instances, it always
fails to explain as many more ; while heredity not only explains
all (or at least 90 per cent) of the intellectual side of character
in practically every instance, but does so best when questions of
environment are left out of the discussion. Therefore, it would
seem that we are forced to the conclusion that all these rough
differences in intellectual activity which are susceptible of grad-

88 Educational Psychology

ing on a scale of ten are due lo predetermined differences in the
primary ,t;vrm-cells." ['o6, p. 286.]

In the case of the resemblances in morality Dr. Woods is less
emphatic in denying that any disconnt for similarity in training
is required. In fact his attitude is not clear. He says, " The
conclusion seems to be, therefore, that even in the moral side
of character, inherited tendencies outweigh the effects of sur-
roimdings, for the reason that, ai)plied to all the characters, hered-
ity is able to explain almost every one, — there being but a slight
error from the expected, — while environment will only explain
a relatively smaller number. I think we can conclude from this
that in each individual, inheritance plays, in the formation of
morality, a force greater than 50 per cent. Other considerations
enable us to go even farther than this. The comparison between
maternal and paternal grandsires is significant. Offspring
resemble their maternal grandfathers as much as their paternal,
llere we test the resemblances under diverse conditions of en-
vironment, the conditions of heredity remaining the same, yet
we find no weakening of the latter force. Such a result is sur-
prising, for it does seem improbable that environment has no
infiueuce in the determination of temperament, behavior, and
virtue in general ; anil there is, of course, an ingrained popular
belief that it has." ['o(>. p. 294.J

Rut only a i)age later he adds, " All I can say is, that I have
made several tests to find a measurable inthience of environment
apart from inheritance, and have failed to find it in this research."
I '06, p. 295. 1 In discussing the fact that the same stock shows
both very bad and very good men and women, he says, "It is
these strong contrasts, more than anything else, that must lead us
to the conclusion that what we have in Plate 2 [a chart showing
moral resemblance of offspring and parents, not reprinted here]
is truly the effect of blood relationship, for environment should
not cause this distribution. Spain, France, and Russia give us
most of the degenerates. In these countries the individuals are
closely associated in blood with insanity, epilepsy, or other psy-
choses. This is itself a coincidence to be explained by those who

iloubt that morality is much the result of inheritance

When strong contrasts are found among the children, we alwa}s
find strong contrasts among the ancestors." ['06, pp. 290-292.]

In 1905 the author published a report [Thorndike, 05] of

The Influence of Immediate Ancestry or Family 89

measurements of the resemblances of fifty pairs of twins in
marking A's on a printed page of capital letters (A test), mark-
ing words containing certain combinations of letters (a-t and r-e),
marking misspelled words on a sheet containing 100 words (mis-
spelled word test), addition, multiplication and writing the oppo-
sites of a set of words.* T quote or summarize the essential facts.
The resemblances of twins, resemblance meaning any greater
likeness than would be found in a pair of children of the same
age and sex picked at random from the school population of New
York City, are: —

In the A test R = .69

In the a-t and r-e tests R==.7i

In the misspelled word test R = .80 +

In addition R= .75

In multiplication R = .84

In the opposites test R = .90

There were two possible sources of error in the measurements : —
namely, (i) the possibly unfair selection of twins and (2) the
fact that the two members of a pair were commonly tested to-
gether. The method of discovering twins was as follows: —
Teachers in certain schools were asked to inquire of their pupils
whether any one had a twin brother or sister. All twins so
reported were tested. But also frequently some teachers would
report that in such and such a school there was a pair of twins.
These could then be found quickly and measured. These reported
cases were perhaps likely to have been noticed in the first case
because of their likeness and so to be an unfair selection. Again,
in the New York schools it is usual to separate the sexes after
three or four years of school life, and it is a frequent practice
to separate them from the start. Twins of like sex are therefore
more conveniently obtained and so more often tested than their
general frequency would recommend. The amount of the result-
ing constant error is not, however, great. f The tests were all
made by the same individual and in the same way except for

*Thcse tests are more exactly described in Appendix II.

fOf the fifty pairs of twins measured there were three more of the same
sex than would be expected in a random selection.

go Educational Psychology

unconscious changes. However, in respect to time of day, con-
ditions of weather and light, and such conditions as are deter-
mined by family life, e. g., the lack of breakfast, fatigue from a
party the previous night, and the like, two twins would, when
measured at the same time, be influenced alike. Thus the obtained
resemblance would be too large. I can evaluate the amount of the
resultant constant error only from general considerations. I be-
lieve it to be small. This constant error would also influence
the correction made from attenuation, but here would make the
obtained resemblance too small. An allowance was made for
these two sources of error to the best of the author's ability.

If now these resemblances are due to the fact that the two mem-
bers of any twin pair are treated alike at home, have the same
parental models, attend the same school and are subject in general
to closely similar environmental conditions, then ( i ) twins should,
up to the age of leaving home, grow more and more alike, and in
our measurements the twins 13 and 14 years old should be much
more alike than those 9 and 10 years old. Again, (2) if similarity
in training is the cause of similarity in mental traits, ordinary
fraternal pairs not over four or five years apart in age should show
a resemblance somewhat nearly as great as twin pairs, for the home
and school conditions of a pair of the former will not be much less
similar than those of a pair of the latter. Again, (3) if training
is the cause, twins should show greater resemblance in the case of
traits much subject to training, such as ability in addition or in
multiplication, than in traits less subject to training, such as quick-
ness in marking off the A's on a sheet of printed capitals, or in
writing the opposites of words.

On the other hand, (i) the nearer the resemblance of young
twins comes to equaling that of old, (2) the greater the superiority
of twin resemblance to ordinary fraternal resemblance is, and (3)
the nearer twin resemblance in relatively untrained capacities
comes to equaling that in capacities at which the home and school
direct their attention, the more must the resemblances found be
attributed to inborn traits.

The older twins show no closer resemblance than the younger
twins, and the chances are surely four to one that with an infinite
number of twins tested the 12-14-year-olds would not show a
resemblance .15 greater than the 9-1 1 -year-olds. The facts are: —

The Influence of Immediate Ancestry or Family 91

The resemblances of young and old twins compared

Twins 9-1 1 Twins 12-14

i) A test 66 73

2) a-t and r-e tests 81 62

3) Misspelled word test 76 74

4) Addition 90 54

5) Multiplication 91 69

6) Opposites 96 88

Averages 83 70

I have measured the resemblances between sibHngs (children
of the same parents) a few years apart in age only imperfectly,
and only in the A test, a-t test and opposites tests. The resem-
blances are between .3 and .4, or less than half the resemblance
found for twins.

The variations in the closeness of resemblance of the twins in
the different traits show little, and possibly no, direct correlation
with the amount of opportunity for environmental influences. The
traits most subject to training- (addition and multiplication) do
show closer resemblances than the traits least subject to training
(the A, a-t and r-e test) ; but on the other hand show less close
resemblances than the traits moderately subject to training (the
misspelled word test and opposites test). (See page 89.)

The facts then are easily, simply and completely explained by
one simple hypothesis : namely, that the natures of the germ
cells — the conditions of conception — cause whatever similarities
and differences exist in the original natures of men, that these
conditions influence body and mind equally, and that in life the
differences in modification of body and mind produced by such
differences as obtain between the environments of present-day
New York City public school children are slight.

We must be careful, however, not to confvise two totally dif-
ferent things : ( i ) the power of the environment, — for instance,
of schools, laws, books and social ideals, — to produce differences
in the relative achievements of men, and (2) the power of the
environment to produce differences in absolute achievement. It
has been shown that the relative differences in certain mental
traits which were found in these one hundred children are due
almost entirely to differences in ancestry, not in training ; but this
does not in the least deny that better methods of training might
improve all their achievements fifty per cent or that the absence

92 Educational Psychology

of training-, say, in spelling and arithmetic, might decrease the
corresponding achievements to zero.

Tlie argument is Hmited entirely to the causes which make one
person ditTer from another in mental achievements under tJie same
general conditions of life at the beginning of the tzventicth century
in Au-w ]'ork City as pupils in its scliool sysfon. If the
resemblance of twins had been measured in the case of a group
made up partly of New York City school children and partly of
children of equal capacity brought up in the wilds of Africa, the
variability of the group in addition and multiplication would have
increased and the correlation coefficients would rise. They would
then measure the influence of original nature plus the now much
increased influence of the environment.

Heymans and Wiersma ['06 and '07 J sought to measure the
influence of heredity by having the parents and children in a
family rated by some one who knew them well. Such reports
were obtained from physicians through a questionnaire. The
ratings were under ninety rubrics of which the following are
samples : —

1. Is the person in question active (gesticulating, jumping up
from the chair, going up and down the room) or passive and
quiet ?

2. Is the person in question, in his professional, business, school
or home life, always zealous at his work, or only sometimes
zealous, or outright lazy?

The resulting ratings suffer from the constant error toward too
great resemblance due to the fact that any one family is judged
with reference to the same dividing line for a trait, the line
being in a diflferent place along the scale for each judge. This
source of error is even more mischievous here than in Pearson's
study, since here apparently one judge commonly rated only one
family. They also suffer from the random inaccuracy of the
judgments which, as was shown on page So. would make the
obtained resemblances too low.

The authors do not measure the resemblances in the usual way
nor give data permitting anyone else to do so. In view of the
insecurity of their original data it seems best not to enter upon
an explanation of their somewhat awkward method of measuring
the force of heredity, and not to repeat the figures which are got by
this method. The authors do not attempt to estimate an allow-

The Influence of Immediate Ancestry or Family 93

aiice for the influence of similarity in home training, though they
state that some such allowance must be made.

They point out, however, that there is reason to believe that
the influence of heredity far outweighs the influence of home
training, since the resemblance is hardly any greater in traits
much subject to the latter influence than in traits little subject to it.
They instance industry, sympathy and patriotism on the one hand
and emotionality, consolability, and memory on the other.

The Speciali::ation of the Influence of Near Ancestry

In the facts so far given in this chapter, the emphasis has been
upon the amount of influence of near ancestry. The degree to
which it is specialized is also of importance. How far, for
example, do particular talents exist in a man's original nature as
a result of his ancestry? Is a man from the beginning organized
to be a novelist, or only to be a writer of fiction, or only to be an
artist of some sort, or perhaps even only to be a man of ability?
How far is this original specialization, if it exists, due to
ancestry? It is a plausible statement that individual minds are
dependent on heredity only in their rough outlines, the currents
of mental activity being fixed only in their general directions and
left to take what particular channels circumstances may decide.
But this or any other opposite statement must be put in terms
of ' how much ', ' how far ', ' in what cases ', to be theoretically
satisfying or practically useful.

Galton, who had this problem clearly in mind, notes a number
of relevant facts, some of which I quote. Concerning the judges
of England between 1660 and 1865 he says: "Do the judges
often have sons who succeed in the same career, where success
would have been impossible if they had not been gifted with the
special qualities of their fathers? . . .

" Out of the 286 judges, more than one in every nine of them
have been either father, son or brother to another judge, and
the other high legal relationships have been even more numerous.
There cannot, then, remain a doubt but that the peculiar type
of ability that is necessary to a judge is often transmitted by
descent." ['69, '92, pp. 61 and 62.]

Concerning the eminent relatives of eminent statesmen he
says : " Thirdly, the statesman's type of ability is largely trans-
mitted or inherited. It would be tedious to count the instances

94 Educational Psychology

in favour. Those to the contrary are Disraeh, Sir P. Francis (who
was hardly a statesman, but rather a bitter controversiaUst) and
Horner. In all the other 35 or 36 cases in my appendix, one or
more statesmen will be found among their eminent relations. In
other words, the combination of high intellectual gifts, tact in
dealing with men, power of expression in debate, and ability to
endure exceedingly hard work, is hereditary." ['69, '92, pp. 103
and 104.]

Similar specialization of inheritance is shown to be the case
with the relatives of great commanders, literary men, poets and
divines. With men of science the fact is much more pronounced,
twenty-two out of the twenty-six eminent sons of eminent scientific
men having been eminent in science. This extreme specialization
of resemblance is in part due, Galton thinks, to training.

The eminent relatives of eminent painters seem to be well-
nigh universally gifted in the same special line. In Galton's list
all the relatives mentioned are painters save four. These were
gifted in sculpture (2), music (i) and embroidery (i). Finally,
" Mendelssohn and Meyerbeer are the only musicians in my list
whose eminent kinsmen have achieved their success in other
careers than that of music." ['69, '92, p. 231.]

Of course there is, in the case of all of Galton's facts, the
possibility that home surroundings decided the special direction
which genius took, that really original nature is organized only
along broad lines. Moreover, it is difficult to see just what in the
nervous system could correspond to a specialized original capacity,
say, to be a judge. Still the latter matter is a question of fact,
and of the former issue Galton's studies make him the best judge.
We should note also that it is precisely in the traits the least
amenable to environmental influence, such as musical ability, that
the specialization of family resemblance is most marked.

Ellis notes ' a clearly visible tendency for certain kinds of ability
to fall into certain [family] groups.' ['04, p. 83.] In his group
of 1030 eminent men he finds that, " Men of letters are yielded
by every class, perhaps especially by the clergy, but Shakespeare,
and it is probable Milton, belonged to the families of yeomen. The
sons of lawyers, one notes, even to a greater extent than the
eminent men of " upper class " birth, eventually find themselves
in the House of Lords, and not always as lawyers. The two
groups of Army and Medicine are numerically close together, but

The Influence of Immediate Ancestry or Family 95

in other respects very unlike. The sons of army men form a very
briUiant and versatile group, and include a large proportion of
great soldiers ; the sons of doctors do not show a single eminent
doctor, and if it were not for the presence of two men of the
very first rank — Darwin and Landor — they would constitute a
comparatively mediocre group.

"Painters and sculptors constitute a group which appears to be
of very distinct interest from the point of view of occupational
heredity. In social origin, it may be noted, the group differs
strikingly in constitution from the general body, in which the
upper class is almost or quite predominant. Of 63 painters and
sculptors of definitely known origin, only two can be placed in
the aristocratic division. Of the remainder 7 are the sons of
artists, 22 the sons of craftsmen, leaving only 32 for all other
occupations, which are mainly of lower middle class character,
and in many cases trades that are very closely allied to crafts.
Even, however, when we omit the trades as well as the cases in
which the fathers were artists, we find a very notable predominance
of craftsmen in the parentage of painters, to such an extent indeed
that while craftsmen only constitute 9.2 per cent among the
fathers of our eminent persons generally, they constitute nearly
35 per cent among the fathers of the painters and sculptors. It is
difficult to avoid the conclusion that there is a real connection
between the father's aptitude for craftsmanship and the son's
aptitude for art.

"To suppose that environment adequately accounts for this
relationship is an inadmissible theory. The association between
the craft of builder, carpenter, tanner, jeweller, watchmaker, wood-
carver, rope maker, etc., and the painter's art is small at the best,
and in most cases non-existent." ['04, pp. 84, 85.]

Ellis adds, " It may be noted that Arreat {Psychologic du
Peintre, 1892, ch. 11) in investigating the heredity of 200 eminent
European painters, reached results that are closely similar to
those I have reached in my smaller purely British group. He
found that very few were of upper class social rank, and those
not usually among the most important, while nearly two-thirds of
the whole number were found to be the sons either of painters
or of workers in some art or craft. He refers to the special
frequency of jewellers among the fathers. I may remark that in
my list, working jewellers and watchmakers occurred twice, a

96 Educational Psychology

small number, but relatively large considering that there are only
three fathers of this occupation in the total parentage of British
men of ability." ['04, p. 85.]

Pearson's measurements concern somewhat specialized traits
from the start. In so far as his results are trustworthy they
show equal resemblance in so specialized a trait as temper or hand-
writing with that found for ' ability.' Woods notes the inheritance
of literary ability, of common sense, of insanity and other some-
what specialized traits in the royal families. In the twins whom
I measured the resemblance is almost or quite as great in the case
of any one of the six tests (see p. 89) as in the average ability
in all of them.

From the work of Burris ['03], if his results are properly
corrected for the chance inaccuracies in the original measures, it
would appear that the ability to do well in some one high school
study is nearly or quite as much due to ancestry as is the ability
to do well in the course as a whole.

What knowledge we have thus supports the view that a man's
original nature is organized by inheritance in great detail,
particular traits and complexes of traits showing similarity be-
tween father and son or brother and brother.

Mental inheritance is specialized also in the further sense that
two individuals alike in one trait as a result of heredity need not
be equally alike in some other trait, though the latter be in general
equally subject to inheritance. For example, a pair of twins
may be indistinguishable in eye color and stature but notably
different in hair color and in tests of intellect.

To measure the extent of this specialization of resemblance,
exact measures of the resemblance of individual relatives are
needed. The procedure required to measure accurately the
resemblance between one individual and another in one trait is
somewhat intricate, and I shall not describe it here. The reader
may verify the accuracy of the measures which I give by examin-
ing Measurements of Twins, [Thorndike, '05] sections 16 to 18
and 21 to 23. Here I shall simply give the resemblances in
efficiency in the A test, a-t test, and misspelled word test of the
ten pairs of twins who showed the closest resemblance in efficiency
in addition, multiplication, and writing opposites. These show
(Table 9) that very close resemblance in efficiency in ' association '
may go with actual antagonism, or greater unlikeness than that

The Influence of Immediate Ancestry or Family 97

shown by children of the same age, taken at random, in efficiency
in tests of ' perception.'

TABLE 9.
Specialization op Resemblance in Twins.
Resemblance in association : Resemblance in perception :

Twin

pair

resemblance in efficiency

in add., mult, and oppos.

combined.

resemblance in A test,

word test and misspelled

word test combined.

102

1 .00 —

.28

117

•99

•83

120

1 .00 —

— .88

121

•99

— .86

126

■95

1 .00 —

127

.94—

1 .00 —

133

■95

1 .00 —

136

•94

— •73

146

1 .00 —

— .98

148

1 .00 —

•97

In the Measurements of Twins I have also shown in detail that
twins may be indistinguishable in any one physical trait without
being at all similar in certain others, or in certain mental traits.
For example, a pair of twins may show resemblance of .95 to i.oo
in bodily measurements other than head measurements and of o in
head measurements.

As a consequence of the specialization of resemblance the fact
of ' a child resembling his parents ' is seen to be in reality 'the
mental traits of a child resembling each the corresponding mental
trait in his parents.' Each trait or ' character ' may be inherited
in more or less independence of other traits or ' characters.'

The Analysis of Mental Inheritance

It has been noted that the fundamental fact in mental inheritance
is the relation between the germ making the parent and the germ
making the child, not between the parent and child themselves.
It has also been noted that inheritance is not merely of total
natures vaguely, but of particular details, traits of ' character '
each more or less independently of the rest. So far as mental
traits are thus inherited, we have to think of each amount of each
trait as possessing some determiner in the germs and of the deter-
miners of any one trait in different generations of germs as
standing in some relation.

98 Educational Psychology

What is called Mendelism or Mendelian inheritance (after its
discoverer, Gregor Mendel) offers an account of certain features
of these determiners and of the relations in which determiners
of the same trait in successive generations of a family stand.

In its clearest and most unlimited form* this account would
state that : —

First. — The determiner perpetuates itself with little or no vari-
ation. No such differences exist between the determiners of
trait A in germ generation i and the determiners of trait A in
germ generation 2, as are found between parents and children.

Second. — One fertilized ovum has either (i) no determiner for
trait A (when neither germ nor ovum had one), or (2) a single
determiner (when either the germ alone or the ovum alone had
one) or a double determiner (when both germ and ovum had one).

Third. — The germ cells later developing from one fertilized
ovum will in these three cases respectively be (i) all witliout the
determiner, or (2) half with it and half without it, or (3) all
with it.

Fourth. — Any difference between one man and another in
original nature is reducible to the presence or absence of such
determiners. Variation in them or blends of one with another are
not required.

Fifth. — A ' character ' or trait or feature of an individual may
be a unit character or a multiple character. A unit character is
one which is caused by the presence of one single or double deter-
miner in the fertilized ovum from which the individual developed
(positive unit character), or by the absence of one single or
double determiner (negative unit character). A multiple character
is one caused (i) by the presence of determiners of more than
one sort, or (2) by the absence of determiners of more than one
sort, or (3) by the presence of one or more and the absence of
one or more of a different sort.

These laws may be illustrated as follows : Call the condition
of a character, say A, in the individual which is produced by a
single determiner in the fertilized ovum from which he springs,
A simplex. Call the condition of the corresponding character in

*There are other possible views of the implications of the Mendelian
results with respect to the nature of the determiners, their behavior and
their relations to the ' characters ' that result from them. There are als^o
other views of the universality of the laws given here.

The Influence of Immediate Ancestry or Family 99

the individual which is produced by a double determiner in the
fertilized ovum, A duplex.

Suppose cooperativeness to be a positive unit character. Call
it C, and call its determiner c. Then the condition in the parents
may be: — (i) both with C duplex, (2) one with C duplex and one
with C simplex, (3) both with C simplex, (4) one with C duplex
and one without C, (5) one with C simplex and one without C,
(6) both without C. The results will be as follows :

(i) Ifsall ova have c and all \ / the unions will have \ / and the offspring
sperms have c J \ 2c / t will have C duplex.

(2) If all ova have c and half

of the sperms have c,

if half of the ova have c

and all sperms have c

(3) If half of the ova have c
and half of the sperms
have c

(4) If all ova have c and no

sperms have c
or
if all sperms have c and
no ova have c

(5) If half of the ova have c

and no sperms have c
or
if none of the ova have c
and half of the sperms
have c

(6) If no ova have c and no

sperms have c

half of the unions 1 / and the offspring
will have 2c J \ will have C duplex.

half of the unions \ / and the offspring
will have I c / \ will have C simplex.

one-fourth of the un- 1 / and the offspring
ions will have 2c J | will have C duplex.

one-half of the un-
ions will have ic

one-fourth of the un-
ions will have no c

■ the unions will have

half of the unions
will have ic

half of the unions
will have no c

none of the unions \
will have c J

/ and the offspring
\ will have C simplex.

/ and the offspring
\ will have no C.

/ and the offspring
\ will have C simplex.

r and the offspring
\ will have C simplex.

/ and the offspring
\ will have no C.

/ and none of the off-
\ spring will have C.

These results seem at first sight in sharp contrast with the so
common fact of blended inheritance. Blended inheritance denotes
the appearance, in offspring from parents possessing A and B

A -j- B

respectively, of conditions tending toward , these conditions

varying amongst the offspring around one central tendency and
not falling at all into two or three distinct groups. But the gross
facts of blended inheritance in a trait could perfectly well come
by the action of the strict Mendelian laws if the trait depended
on a sufficiently large number of different determiners.

It is interesting to see the resulting gradations if two, three,
four, and more determiners produce each an amount of the same

lOO

E ducatio nal Psy cho logy

mental trait. Suppose, for example, that a, b, and c are deter-
miners of intellect, aa, bb, and cc being the normal double
determiners. Suppose aa to produce in the individual an amount
of intellect represented by 2q, bb to produce an amount represented
by 4q, and cc to produce an amount represented by 8q. Suppose
a, b, and c to produce each approximately half as much as aa,
bb, and cc, respectively.

The union of a germ and ovum could have : —

o giving o degrees of intellect in the individual,

aab

aac

aab

or any one of many other combinations of the determiners, such
as aabbcc, aabbc, abbe, etc. The resulting degrees of intellect
would vary from o to I4q by steps of one.

The offspring of two individuals would then commonly show
with respect to intellect as a whole a great variety of degrees
as in blended inheritance, though the result with respect to the
effect of any one determiner followed pure Mendelian principles.
For example, suppose one individual to possess the character due
to a, duplex ; that due to c, simplex ; and to lack that due to b.
His intellect will be 6. Suppose another to possess the character
due to a, simplex ; that due to c, duplex ; and that due to b,
simplex. His intellect will be ii. On Mendelian principles the
germs of the first individual will comprise germs with a and c
and germs with a alone. The germs of the second individual
will comprise germs with a, c, and b, germs with a and c, and
germs with b and c. The unions will comprise ac + acb, ac + ac,
ac + be, a + acb, a + ac, and a + be. The resulting intellects will
comprise degrees 12, 10, 1 1, 8, 6, and 7. Mendelian principles applied.

The Influence of Immediate Ancestry or Family loi

to the elementary factors of heredity might then give, with respect
to the total traits compounded of these factors, a continuous
gradation and all the complexities of mental inheritance that
observation finds.

Many features of animals and plants have been more or less
perfectly analyzed into their unit characters, and the determiners
of these have been got under control in breeding, so that strains
with a desirable determiner present in all the germs have been
established. Undesired determiners have been weeded out of all
the germs of certain individuals, so that the offspring from any
two of these individuals are sure to be free of the undesired
character.

The Mendelian ideal is to represent all of each man's original
nature by a list of unit characters, to refer each of these to its
determiner, and to determine the future of the race by arranging
selection and elimination of the determiners. This ideal is, in
almost all ways, a great advance over the older plan of represent-
ing each man by a list of qualities chosen largely by historical
accidents, referring these vaguely to the germ plasm, and seeking
to determine the race's future by selection and elimination of
individuals.

In one respect, however, it may not be better. This concerns
its insistence on the invariability of the determiners from genera-
tion to generation, and within each fraternity of germs. If this
invariability is perfect, any unit character can appear in only
two forms or degrees, one corresponding to the presence of a
double determiner in the united sperm and ovum whence the
individual developed, and one corresponding to the presence of a
single determiner. But if this requirement is made strictly, it is
hard to find any unit characters. Curliness of hair and brownness
of eye, for instance, seem to be far from constant. The former
may be separated fairly clearly from straightness,* but within its
own range it varies from waviness to extreme kinkiness.

As a result of the difficulty of finding any traits appearing in
only two degrees each substantially invariable, many students of
heredity would frankly admit that the determiners did vary some-
what and that one determiner could blend with another similar
determiner.

*Though even this may be doubted.

102 Educational Psychology

Mendelian Inheritance in the Case of Intellectual and Moral Traits

The possibility of analyzing mental traits into unit characters
and controlling their appearance in the human species by breeding
so as to get the determiners of desired traits established in all
the germs, and to get all the germs freed from the determiners
of undesired ones, is very attractive. If bad temper in man is
as simple a compound of unit characters as hornedness in cattle or
color in mice, we may hope to raise a race of assuredly good-
tempered men!

It has been suggested [Davenport 'lo, p. I4f.] that imbecility
is a unit character, depending on the absence of a certain deter-
miner. " That imbecility is due to the absence of some definite
simple factor is indicated by the simplicity of its method of inherit-
ance. Two imbecile parents, whether related or not, have only
imbecile offspring. Barr gives us such data as the following from
his experience. A feeble-minded man of 38 has a delicate wife
who in 20 years has borne him 19 defective children. A feeble-
minded epileptic mother and an irresponsible father have 7 idiotic
and imbecile children. The L. family numbers 7 persons, both
parents and all 5 children imbecile. Among the " Family
Records " I have been collecting there occurs the R. family where
A (insane) marries in succession two mentally weak wives and

has 13 children, all mentally weak In a case

described by Bennett, a defective father and an imbecile mother
have 7 children all more or less mentally and morally defective.
There is, so far as I am aware, no case on record where two
imbecile parents have produced a normal child."

I fear, however, that the inheritance of imbecility will be found
by no means so simple as Dr. Davenport hopes. If it were due
to the absence of some definite simple factor, there should be
some clear division of intellects into those from germs totally
lacking this determiner, those from germs having a single deter-
miner, and those from germs having the normal double determiner.
There is certainly no such clear division and it is very doubtful
if there is any greater division between imbecile and not quite
imbecile, than between the latter and an intellect a trifle higher,
and so on up to and beyond individuals of average intellect. The
condition of the children in the families mentioned above should
certainly be made the subject of very careful measurements before

The Influence of Immediate Ancestry or Family 103

it is assumed that they are all sharply distinct from the offspring
of parents whose germs possess the ' intelligence ' determiner.
Rough estimates are very unsafe.

It seems probable that two imbecile parents produce widely
varying offspring including some more imbecile than they and
some far higher than they on the intellectual scale. Richardson
['02, p. 9] writes: "Imbeciles who have been impregnated by
imbeciles have produced normal children as a rule in the few
cases recorded, and in my experience I know of a case where a
feeble-minded boy of eighteen impregnated a feeble-minded girl
of sixteen, producing a perfectly normal child."

Mental traits are certainly not as a rule unit characters or the
results, each of two or three cooperating unit characters. On the
contrary, most of them seem to be the results of very manv unit
characters. It will be shown in Chapter VIII that no case is
known of a mental trait appearing in three sharply defined degrees,
— o, moderate, and full amount, — with clear gaps between,
as a unit character should. Almost, if not quite, all mental traits,
so far as they are due to original nature, appear in many different
degrees, each varying very slightly from the next. But this
gradation in a trait's amount necessitates the existence of many
determiners to produce it, if it is to be produced by determiners
that do not themselves vary greatly in force. So, for intellectual
and moral traits, the task of analysis into unit characters and
attribution to invariable determiners seems likely to be very, very
difficult.

It is not necessary to decide whether the facts of mental inherit-
ance can be explained by constant determiners or require variable
determiners ; nor whether, if the latter be the case, two variable
determiners of the same trait may blend. The question must be
left for investigation by students from both sides. The chief
present value of the Mendelian facts and hypotheses to students
of intellectual and moral traits is as an encouragement to the
more exact description and analysis of the original natures of
individual men, and to more exact measurements of individual
resemblances.

CHAPTER VI
The Influence of Maturity

No competent student doubts that in certain mental traits
maturity or inner mental growth causes one individual to dififer
year by year from his former self, irrespective of all training.
The same force necessarily accounts for some of the differences
found between children of different degrees of mental maturity.
If by a miracle a hundred children could be found who were alike
in sex, ancestry and training, but who were divided into two
groups by a difference in the extent to which the original impetus
to mental development had run its course, the groups would differ,
in at least certain traits, in accordance with this dift'erence in
stage of growth or maturity.

About the magnitude of the influence of maturity there is,
however, a wide range of opinion, from that which would expect
children in the same stage of growth to be all closely alike and
all very different from children in a later stage of growth, regard-
less of differences in their ancestry and training, to that which
would expect children of the same ancestry and training to be
all very much alike, regardless of differences in stage of growth.

The study of the facts is made difficult by the absence of any
exact measure of maturity, that is, of the extent to which the
original impetus to mental development has run its course. Length
of life is the measure which has been used, but chronological
age is not identical with physiological maturity and neither of
these two is identical with mental maturity. An individual's
degree of mental maturity cannot be inferred from his age. In
the long run, however, the central tendencies of children of the
ages 6, 7, 8, etc., will represent the central tendencies of
successive stages in mental growth. And in any case such
comparisons of children at different ages are the only measure-
ments available in support of conclusions about the influence of
maturity.

(104)

The Influence of Maturity 105

Changes in Mental Traits zvith Age

Some of the best known and most commended studies in
educational psychology deal with the differences in mental traits
between children of different ages. The most extensive and also
the most painstaking study of this sort is Dr. Gilbert's Researches
on the Physical and Mental Development of School Children
['94]. A fairly careful examination of its method and results
will be our best introduction to the general problems of the chapter.

Dr. Gilbert made a number of measurements of both physical
and mental traits in boys and girls from six to seventeen years old.
The mental traits were :

1. Delicacy of discrimination of weight ('Muscle-Sense').
(Ten weights, identical in shape and size, but weighing 84 grams,
86 grams, etc., were set before a child and he was asked to sort
out all those which seemed to him to be of exactly the same weight
as the 82-gram one (which was marked by a white dot). Delicacy
of discrimination was then measured inversely by the difference in
weight of the weights thought to be identical.)

2. Delicacy of discrimination of color. (A series of reds varying
progressively in darkness were used as the weights were in i.)

3. Force of suggestion. ( Measured by the amount a child over-
estimated a weight small in size compared with the same weight
made much larger.)

4. Voluntary motor ability. (The number of taps made with
the finger in 45 seconds.)

5. Fatigue. (Let T= the number of taps made in the first
5 seconds of a trial for 45 seconds. Let L = the number of taps

f L

made in the last 5 seconds. Let F = — wr~- F was the measure

of fatigue used.)

6. Reaction time. (Measured by the time taken to see a signal
and react by pressing down a key.)

7. Reaction with discrimination and choice. (Measured by the
time taken to see that the signal was blue and not red and to react
by pressing down a key.)

The essential results of Gilbert's study are given in Table 10.
It tells with fair accuracy the median ability of every such group
as ' girls from 9 years o months to 9 years 1 1 months inclusive,'
and the variability of every such group in four of the traits

io6 Educational Psychology

measured. In three traits the variability is given only for boys and
girls together.

TABLE lo.

The Central Tendencies and Variabilities of Children op Dif-
ferent Ages in Discrimination of Weight, Discrimination of Shades
OF Red, Resistance to the Size-Weight Illusion, etc.

M. V. = in all cases the average deviation of the individual children from
the median child of that year-age.

B = in all cases, boys.

G = in all cases, girls.

D wt. •= the number of grams difference required in order that the
median child should perceive the difference.

D col. = the smallest number of differences (not objectively defined)
required in order that the median child should perceive the difference.
For a statement of the nature of the differences see Gilbert, '93, p. 42 f.

H ~ the median difference in grams between the two weights (of equal
size) chosen as equal respectively to two blocks, each weighing 55 grams
and being 2.8 cm. thick, but being 2.2 cm. and 8.2 cm. in diameter.

T = the number of taps made in the first 5 seconds of 45 by the median
child.

T-L

F- /jK (L being tlic number of taps made in the last 5 seconds of

45 by the median child).

Rs = thc time, in thousandtlis of a second, between the movement of a
disc and the making of a contact by a child who is instructed to press
down the key as soon as he sees the disc move : the median child's time.

Rd = the time to see a lilue surface and react to it as for Rs. no
reaction being permissible if the surface shown was red instead of blue.

Muscle-Sense

Age.

Dwt.(B-\-G)

MV(,B+G)

Dwt.{B)

Dwi.(G)

14.8

5-2

130

16.8

13-6

4 4

132

13.2

II. 4

4.6

12.2

II .0

10. 0

4.4

10. 2

10. 0

8.8

4.4

8.6

9.2

8.6

3.8

10.2

7.6

.7-2

7.6

i.i

6.0

5.6

5-6

5-2

7.2

6.8

2 .2

6.2

7.2

6.6

2.4

6.0

6.8

5-8

2.6

6.0

6.4

The Influence of Maturity

107

Sensitiveness to Color-differences

Age.

Dcol.iB+G)

MV(B-\-G)

Dcol.{B)

Dcol.{G)

9.6

1.8

8.3

9.6

2.1

8.3

9.6

2.3

9.6

7.0

2.2

6.1

6.6

1-9

6.0

5-2

1-7

6.0

4-9

1-5

4.8

1-7

5-2

1-4

4.8

4.6

I.I

4.1

4.6

1-3

4-3

4.0

•9

1-4

4.0

4-9

Force of Suggestion

Age.

H(B+G)

MViB+G)

H{B)

H{(

42.0

17.0

43-5

42.5

155

43-5

13-5

450

10.5

50.0

12.5

40.0

"■5

38.5

9.0

38.0

9.0

370

9-5

310

10.5

330

lO.O

32.0

12 .0

25.0

Voluntary Motor Ability

T{D-^G) MV{B+G) T{B)

Age.

T{D + G

20.8

22.5

24.4

254

27.0

29.0

29.9

28.9

30.0

3i»

32.1

33-8

MV{B) T{G) MV{G)

2.4

21 .0

2.9

22.8

2.9

24.9

2.5

25.8

2.8

27.7

3-3

29.7

3-3

30.3

2.8

29.8

3.6

31-2

313

3-3

330

2.9

350

2-5

19.7

2.7

21.2

3-4

239

2.5

25.0

2.6

26.9

3-2

27.8

3-1

29.6

28.1

3-2

28.0

2.6

29.8

31-8

2.4

315

2.5

2-5
2 .2
2.9
2.8

30
30

3-3
3-4
3-2

3-4
2.3

io8

Educational Psychology

Fatigue

Age.

F(B+G)

Ml/(B+G)

F(i?)

MV{B)

F(G)

MV{G)

21.4

8.1

22.8

9-4

21.3

7.0

21 .O

20.2

6.7

24.0

233

21 .0

20.7

7.8

22.0

19.0

20.0

18.0

5-5

16.0

14.0

6.7

14 5

H-7

5-8

14.0

12 .0

6.1

12.7

II-5

5-7

147

II. 7

13.8

13-5

4-3

Reaction Time

Age.

RsiB-\-G)

MV{B-\-G)

Rs{B)

Ml/(5)

Rs{G)

MViG)

295

282

295

292

267

315

262

245

260

250

243

255

215

2IO

225

195

185

206

187

178

198

187

178

205

180

187

172

167

189

155

147

172

155

147

163

Reaction with Discrimination and Choice

Age.

Rd{B-\-G) MV{B+G)

Rd{B)

MV{B)

Rd{G)

MV{G)

525

535

510

530

490

528

478

480

475

450

445

460

410

400

415

385

387

388

370

385

370

395

360

415

365

367

355

335

311

345

325

315

350

312

305

315

The Influence of Maturity 109

Just what do these median abihties of Table 10 mean? Just
what do the differences between those for six and seven, seven
and eight, etc., tell us about the development of mental traits in
life? Just what do we learn about human nature from these
comparisons of the capacities of children of different ages ?

It is clear that an alteration in any mental trait in any individual
with age might be due to the mere maturing of some characteristic
of original nature or might be the creation of some environmental
force. The educational inferences would be exactly opposite in
the two cases. In the former we should say : This change comes
as a gift from nature which we may not be able to refuse without
damaging general growth. It is given as the partial basis and
starting point for education. We do not have to try to get it.
In the latter case we should say: This change comes as the
earnings of training. It is a product of education. With a
different training it might be absent. We may lack or possess it
as we choose.

Moreover, in the case of many measurements of mental traits,
for instance those quoted, the change due to an individual's age
would be possibly due not only to the maturing of the trait or
the influence of training upon it, but also to the influence of both
maturity and training upon the ability to understand and the wish
to follow instructions and the ambition to do well in tests. This
complex of traits we may call general ability in tests. It is even
conceivable that the last factor was the sole cause of all the
changes quoted above.

As a matter of fact all three of these factors are involved in
most of the changes of mental traits with age. Even if the changes
are due directly to outside forces, in the form of the experiences of
life and training, maturity may still count as a force cooperating
with these or furnishing the conditions in the individual which
permit their action on him to produce the mental changes in
question. On the other hand, mere inner growth, no matter how
potent, requires usually some stimuli from without. A child
grows mentally in some kind of a world of experience, forming
some habits. Only in thought can the contribution of his inner
impulsions be separated off from the contribution of the outside
stimuli by which the inner impulsions are roused to action. Further-
more, a mental test with children almost always measures some-

no Educational Psychology

what general powers of comprehension as well as the special power
of sensation, memory or the like that is its ostensible object.

Hence mere knowledge of age differences in a mental trait,
without knowledge of how their causation is distributed amongst
these three factors, does not allow us to estimate the amount of
influence of maturity in determining an individual's status in
respect to the trait. The total age change must at least be divided
between mere maturity and the added training which has accom-
panied maturity. Until this is done we cannot progress far
beyond the vague commonplaces of common observation.

The Difficulties in Inferring Changes in Individuals zvith Age
from Differe,nces Between Old and Young Indidivuals

So far upon the supposition that by changes in mental traits
with age, we mean changes in the same individuals measured at
different ages. The average change would then be the average
of the changes in all the individuals studied. But in the studies
that have been reported, the difference between the figures for,
say, ten and eleven years, is not the average of the changes of
all the individuals studied and need not in any real way describe
them.

For (i) the difference between the average of a group at ten
and of the same group at eleven years does not describe the real
individual changes; and (2) when we measure ten- and eleven-
year-olds as we find them in school or elsewhere, we can not be
sure that the eleven-year-olds represent what the ten-year-olds will
become.

The first point will be made clear by the following illustration.
Suppose that eighteen boys showed at the age of ten and a
half years the abilities in some mental trait denoted by the
measures in the first column and made the gains during the next
year shown by the figures in the second column, their consequent
records at eleven and a half years being given in the third column.
(Case I.)

If instead of this complete record we had simply the figures :
10I/2 years, Av. 5.94; nl/o years, Av. 8.16; Change in average
ability, 2.22, we should lack the essential features of our fact ;
viz., (i) the variability of the changes and (2) the antagonism
between ability at ten and a half years and growth during the

The Influence of Maturity in

Case I Case 2

Ability

at loK

Change

at 11^

at io>^

Change

at iiyi

Avg. 5.94 2.22 8.16 Avg. 5.94 2.22 8.16

next year. There is an almost inevitable tendency, when a single
figure is given to represent change, to fancy that all children show
exactly or nearly that amount of change. This is of course never
true. Rate of change as well as absolute ability is variable. And
it is precisely in relating the different degrees of progress found
in individuals to their original capacities and individual circum-
stances, that educational insight will accrue. The real individual
changes may often prove to be a partial function of the amount
of ability already acquired, as in our illustration. The mere
change in average ability given above could have come as well
from a condition, shown in Case 2, just opposite in this respect
to that of Case i.

In Case 2, the better a boy is at ten and a half years the more he
gains ; whereas in Case i, the better he was the less he gained. Case
2 would, I venture to prophesy, be the fact in the progress with
age of real mental efficiency, while with physical growth from
thirteen to eighteen we should have something like Case i, the
children who had matured early and so attained high stations in
stature growing little, while those who matured slowly would keep
on growing at a fair rate. In brief, the growth of averages does

112 Educational Psychology

not accurately describe, and may positively misrepresent, the real
growth of the individuals in the group.

Our second point was that the eleven-year-olds tested need not
represent what the ten-year-olds would become. The average
changes stated in the quotations at the beginning of this chapter
were obtained from facts like the following: Ten-year-olds
A, B, C, D, E, F, G, H, etc., give an average x ; eleven-
year-olds, L, M, N, O, P, etc., give an average y. The
change in average ability is 3/ - x. The individuals of the two
groups not being identical, the chance is given for the fallacy of
selection to run riot. The eleven-twelve-year-olds certainly
represent only those ten-eleven-year-olds who will live ; in any test
given in schools they represent only the ten-eleven-year-olds v/ho
will continue in that type of school. Now if one measures a mental
trait in elementary school children he gets for different ages some-
thing like the following figures: — 12 year-olds, 100; 13-year-olds,
90; 14-year-olds, 70; 15-year-olds, 30.

Nobody can imagine that the fifteen-year-olds here would give
anything like a fair sampling of what the twelve-year-olds would
become. The brightest twelve-year-olds pass out of the grammar
school before they are fifteen. Some mental defectives leave for
special institutions. Some moral defectives leave for reform
schools or the free life of thievery and trampdom. Some chil-
dren of very poor parents go to work. If we fill up our quota
of fifteen-year-olds by adding 70 from high school pupils we
jump from the frying pan into the fire, for these are a selection
of the brighter, the more ambitious, those whose parents are
fairly well off financially and are intellectually inclined.

I conclude, therefore, that the development of mental traits with
age has not been and can not be adequately measured by such
studies as those quoted. To measure it we must repeat measure-
ments upon the same individuals and for all purposes of infer-
ence preserve intact each of the individual changes. In connec-
tion with each of them account must be taken of the training
which the individual in question has undergone.

What measurements we do have may serve, however, to cor-
rect two errors of common opinion. The notion that the increases
in ability due to a given amount of progress toward maturity
are closely alike for all children save the so-called " abnormally
precocious " or "retarded " is false. The same fraction of the

The Influence of Maturity 113

total inner development, from zero to adult ability, will produce
very unequal results in different children. Inner growth acts
differentially according to the original nature that is growing.

The notion that maturity is the main factor in the differences
found amongst school children, so that grading and methods of
teaching should be fitted closely to 'stage of growth,' is also false.
It is by no means very hard to find seven-year-olds who can do
intellectual work at which one in twenty seventeen-year-olds would
fail. Although the influence of inner growth in causing individual
differences cannot be measured from the data at hand, an upper
limit for it can be set. Take discrimination of weight as a sample
case. Since early age differences are in part due to training and
since training acts here in the same direction as does maturity,
the average inner growth from, say, ten to seventeen must produce
less than the average difference found between ten-year-olds and
seventeen-year-olds. Since, in Gilbert's study, the seventeen-year-
olds and ten-year-olds both come from school pupils, including
pupils in the high school, the seventeen-year-olds represent at
least as high ranking pupils in mental respects as the ten-year-olds
would become. So the effect of average inner growth from ten
to seventeen is at the outside a reduction in the least noticeable
difference from 8.8 to 5.8 grams. But many ten-year-olds noticed
a difference of 5.8 grams or less. Gilbert's 4.4 (for the average
deviation of the individual ten-year-olds from their C. T.) would
put 30 per cent of them above the average seventeen-year-old
unless the distribution of individual differences among the ten-
year-olds is markedly eccentric. And within the ten-year-olds
there is a range of variation at least five times as great as that
between the average ten-year-old and the average seventeen-year-
old. The range cannot be less than four times 4.4 g. unless the
distribution (surface of frequency) is of a form never found in
measurements of discrimination of weight. Hence even the top-
most limit for the average effect of these seven years' maturity is
surely less than one sixth of the effect of the extreme differences
in ancestry and training upon children of the same age.

CHAPTER VII

The Influence of the Environment

Difficulties in Estimating the Amount of Influence of the

Environment

The questions suggested by the title of this chapter inchide
the effects on individuals of every environmental force, including
all the agencies for intellectual and moral education. Precise
quantitative answers can be given to hardly any of them.

Theoretically, there is no impossibility. Once we have esti-
mated the original nature of a man or group of men, we have
simply to note the mental changes consequent upon this or that
change in climate, food, school training, friendship, sermon, occu-
pation, etc. Practically, the complexity of the action of physical
and human influences upon intellect and character hampers scien-
tific study and favors guesswork. The environment includes a
practical infinitude of different causes ; these act differently upon
different types of original nature and at different ages and with
different cooperating circumstances ; in many cases their action
is very complex and must be observed over long intervals of
time. Indeed it has been common to deny even the possibility
of a science of the dynamics of human nature and to remain
content with the haphazard opinions of novelists, proverb makers
and village wise men.

Moreover, it is only by the utmost ingenuity and watchfulness
that studies of changes in human nature can be freed from a char-
acteristic fallacy — that of attributing to training facts which are
really due to original nature or to selection. For instance, col-
lege graduates are found to have a much greater likelihood of
being elected to Congress than other men have. Therefore it
is said that a college education causes to some extent political suc-
cess. But it is clear that even before they went to college the
group of youth who dW go were different from those who did not.

(114)

The Influence of the Environment 115

Their later election to Congress may as well have been due to
the mental traits which they possessed by birth or otherwise and
which caused their inclusion in the class ' boys who go to college '
as to any changes produced in them by the college training itself.
In other words, that they were the class selected by the college
is as important a fact as that they were the class trained by it.

Again it is said : " Who can doubt the enormous disciplinary
value of the study of Latin and Greek when we see the admirable
intellects of the men so trained in the English universities?"
But being born from the class whose children go to the university
of itself ensures to an individual uncommon mental ability.

To avoid this confusion of causes which train with those which
select is extremely hard. Any class of individuals studied because
they have been subjected to a certain training is almost sure to
be a class not only trained by but also selected by that training.
Suppose that one wishes to study the influence of a high-school
course, or that of the classical as opposed to the scientific course,
or that of training in independent research, or that of immoral
surroundings. High school graduates are but one fifth of gram-
mar school graduates ; and no one would claim that they repre-
sent an entirely random picking therefrom. They are surely
selected for better birth, better abilities and better ideals. Again,
in most high schools the graduate of the classical course represents
not only a different training, but also a different selection, com-
monly a superior selection.* So also scientific men are a class
resulting not only from the training given by research work, but
also from the selection of those eager to do and fitted to do that
work. Children brought up in a morally bad environment are
almost sure to be of morally inferior ancestry. The ordinary
arrangement of social and educational careers rarely presents
.us with convenient cases of similar natures, some with, some with-
out, the form of training under consideration.

The difficulty of eliminating the influence of selection is no
excuse for its neglect. Yet one may hunt through thousands of
pages of discussions of the influence of certain studies, school
systems, schemes of culture, religious beliefs, etc., without finding
a hint of its recognition.

Either because of the general complexity of environmental in-
fluences upon any mental trait and the mixture of selective

*This apparently is becoming less common every year.

ii6 Educational Psychology

with formative influences or because of the infrequency of scien-
tific habits and ideals in students of sociology and education,
there are few facts of sufficient security and precision to be
quoted. Only rarely has educational science progressed beyond
the reasoned opinions of more or less capable judges. We have
our beliefs about the causal relations between a hot climate and
indolence, necessity and invention, lack of parental control and
crime, religious training and morality, etc., but we can not be
said to know these influences with adequate surety or to have
any knowledge whatever of their precise amount.

A refusal to believe insecure opinions about the influence of
differences in training in producing differences in human indi-
viduals does not at all imply disbelief in their influence. Such
would be absurd. When the original natures are the same, every
difference that the individuals later show must be due to differ-
ences in the outside forces operating upon them. And any differ-
ence in outside forces always has its effect. No man is left un-
changed by even the very least of the environmental forces that
act upon him. Men are the creatures of circumstance. But they
are creations whose final patterns are determined in part by sex,
race, ancestry and conditions of origin. Circumstances alter
natures, but the alterations vary with the nature altered. It is
precisely because common opinions have thought verbally in terms
of 'man-training-product of training', instead of concretely in
terms of 'men-training-products, — each of an individual's nature
in interaction zvith his training ' , that a sound science of the in-
fluence of the environment has hardly been begun.

One of the best services such a science can render is to guard
its students against such verbal plausibilities. For example,
knowledge is not proportional to opportunity in the sense that an
individual's degree of knowledge can be foretold from his degree
of opportunity. Wealth does not create wealth in the sense that
what a man will have can be estimated from what he now has.
A good home does not make good children in the sense of doing
so always and in proportion to its goodness. Being treated like
slaves may not debase all and never debases all alike. The product
of the environment is always a result of two variables, it and the
man's nature.

Two of the corollaries of this axiom are of special significance.
The first is that the environmental stimulus adequate to arouse a.

The Influence of the Environment 117

certain power or ideal or habit in one man may be hopelessly
inadequate to do so in another. Washing bottles in a ding-shop
was, if a common story is true, adequate to decide Faraday's
career, and the voyage on the Beagle is reputed to have made
Darwin a naturalist for life. But if all the youth of the land were
put to work in drug-shops and later sent on scientific expeditions,
the result would not be a million Faradays and Darwins, or even
a million chemists and naturalists. All that one man may need
to be free is a vote ; but even a long education in self-direction
may be inadequate for another. Being told a few words suffices
to secure the habit of reading in one child, while the child beside
him remains illiterate after two years of careful tuition. The
amount of stimulus required in some cases is so infinitesimal
that the power seems to spring absolutely from the man himself.
In other men no agency is found potent enough to arouse a trace
of the desired result.

The second corollary is that each man in part selects his own
environment. The boy turns his eyes from the book. Even if
his eyes attend to it, his mind does not. Even if for the time he
lets it move him, it may be disregarded in memory. That connec-
tion which brings satisfaction to one man and is thereby given
power over him, may disgust another nature and so be repudiated
by it. As this world's nature selects for survival those animals
which are adapted to live in it, so any individual selects, by action,
attention, memory and satisfaction, the features of the environ-
ment which are to survive as determinants of his intellect and
character.

Common opinion and the older literature of sociology and edu-
cation neglected the differential action of the environment in
accord with the nature it acted on, but it would be possible for
a student, enamored of the simplicity of the explanation of all
men's differences by differences in their original make-up, to
neglect equally obvious facts of another sort. He might be
tempted to claim that, since the features of civilization, — the
acts, words, books, customs, and institutions of men, — have been
invented and perpetuated by human natures, and since conse-
quently the environment in all important respects is itself due to
original nature, — therefore original nature is at bottom the cause
of almost all of human destinies. " A people gets as good govern-
ment as it deserves ; a race has the environment its own nature

ii8 Educational Psychology

has found and chosen: a man in essential matters is treated as
his nature decides." So he might carelessly claim.

Many important features of the environment are thus due to
the original nature of the human race as a whole, but no one
man's nature and, under modern conditions, no one nation's or
race's is similarly responsible for the particular environment that
it meets. Forces set in motion by others play upon it. At the
best it can select only negatively by disregard, and at the worst
it may be molded directly against nature.

Even when it is known, and with some precision, that a given
difiference is due to some difference in training, there may be
doubt or total ignorance as to what difference in training caused
it. And even when it is known that a given difference in train-
ing has been operative and has produced an effect, there may be
doubt or ignorance about what the effect is.

Illustrations of the former case are abundant in history. His-
tory is in fact largely a record of unexplained changes in human
nature. Nearly all the intellectual and moral differences between
the modern English, French, or Germans and their barbarous
ancestors of two thousand years ago are due to differences
in environment. The original natures of the stocks may have
altered somewhat during that time, but surely not much. Our
thoughts and ways of thinking and our habits, customs and ideals
have been and are being made very unlike those of our ancestors
by some outside forces. But what the forces were and how each
contributed to the result is not known.

Illustrations of the latter case form a large proportion of the
facts studied under the vague rubric of education. Such and
such children have gone to school, they have been taught by such
and such teachers, using this and that method, at a cost of so
many dollars, with aid of a material plant worth so much ; but
what has come of it all, no cautious thinker would dare say.
What has been and is being done to children in schools is more
or less well described in official and private records, but what hap-
pens in children as its consequence is largely unknown.

So much for the attitude in which a student of human nature
must approach the problems of the effect of different environ-
ments on identical natures, of the effect of the same environment
on different natures, and of the effect of the endless different co-
operations of environments and natures.

The Influence of the Environment

119

Samples of Measurements of the Influence of the Environment

I shall report four samples of studies of the influence of the
environment upon intellect and character. The first is Galton's
History of Twins ['83], a study of the amount of its influence in
comparison with that of original nature. The second, from Cat-
tell's Statistical Study of American Men of Science ['06], is a
study of the effect of early opportunity upon scientific achieve-
ment. The third is Rice's study of the effect of different school
environments upon ability in spelling and arithmetic ['97 and
'02]. The fourth is a study of the effect of changing environment
upon the choice of a profession by scholarly youth.

Galton collected reports from parents concerning twins who
were closely similar in infancy but whose environments differed,
and twins who were in infancy notably unlike, but whose environ-
ments were in all important features identical. The increase of
differences in the former case and of resemblances in the latter
gives a measure of the influence of the environment. The per-
sistence of similarities in the former case and of differences in the
latter gives a measure of the influence of original nature.

This evidence in the first case consists of illustrations of iden-
tical mental habits, tastes, associations of ideas and suscepti-
bilities to mental diseases. The cases of unlikeness seem to him
to be due to such alterations in the amount of energy as could be
caused by illness or lowered nutrition rather than to fundamental
qualities of mind.

The evidence in the case of the twenty pairs in the second
group shows no exceptions to the rule that no weakening of
inborn differences by similarities of nurture is observable. The
following are representative parental observations : —

1. One parent says: — "They have had exactly the same nur-
ture from their birth up to the present time; they are both per-
fectly healthy and strong, yet they are otherwise as dissimilar as
two boys could be, physically, mentally, and in their emotional
nature."

2. " I can answer most decidedly that the twins have been
perfectly dissimilar in character, habits, and likeness from the
moment of their birth to the present time, though they were
nursed by the same woman, went to school together, and were
never separated till the age of fifteen."

120 Educational Psychology

3. " They have never been separated, never the least differently
treated in food, clothing, or education; both teethed at the same
time, both had measles, whooping-cough, and scarlatina at the
same time, and neither had any other serious illness. Both are
and have been exceedingly healthy and have good abilities, yet
they differ as much from each other in mental cast as any of my
family differ from another."

4. " Very dissimilar in body and mind ; the one is quite retir-
ing and slow but sure; good-tempered, but disposed to be sulky
when provoked ; — the other is quick, vivacious, forward, acquiring
easily and forgetting soon; quick-tempered and choleric, but
quickly forgetting and forgiving. They have been educated to-
gether and never separated."

5. " They were never alike either in body or mind and their
dissimilarity increases daily. The external influences have been
identical ; they have never been separated."

6. " The two sisters are very different in ability and dispo-
sition. The one is retiring but firm and determined ; she has no
taste for music or drawing. The other is of an active, excitable
temperament ; she displays an unusual amount of quickness and
talent, and is passionately fond of music and drawing. From
infancy, they have been rarely separated even at school, and as
children visiting their friends, they always went together."

7. " They have been treated exactly alike ; both were brought
up by hand ; they have been under the same nurse and governess
from their birth, and they are very fond of each other. Their
increasing dissimilarity must be ascribed to a natural difference
of mind and character, as there has been nothing in their treat-
ment to account for it."

8. '' They are as different as possible. [A minute and unspar-
ing analysis of the characters of the two twins is given by their
father, most instructive to read, but impossible to publish without
the certainty of wounding the feelings of one of the twins, if
these pages should chance to fall under his eyes.] They were
brought up entirely by hand, that is, on cow's milk, and treated
by one nurse in precisely the same manner."

9. " The home-training and influence were precisely the same,
and therefore I consider the dissimilarity to be accounted for
almost entirely by innate disposition and by causes over which we
have no control."

The Influence of the Environment 121

10. " This case is, I should think, somewhat remarkable for
dissimilarity in physique as well as for strong contrast in char-
acter. They have been unlike in body and mind throughout their
lives. Both were reared in a country house, and both were at
the same schools till act. 16."

The two lines of evidence taken together justify, in Gal ton's
opinion, the following general statements :

" We may, therefore, broadly conclude that the only circum-
stance, within the range of those by which persons of similar
conditions of life are affected, that is capable of producing a
marked effect on the character of adults, is illness or some acci-
dent that causes physical infirmity. . . . The impression that
all this leaves on the mind is one of some wonder whether nurture
can do anything at all, beyond giving instruction and professional
training. There is no escape from the conclusion that nature
prevails enormously over nurture when the differences of nurture
do not exceed what is commonly to be found among persons of
the same rank of society and in the same country."

Even in the hands of a master, the collection of data through
correspondence is inferior to direct observation and measure-
ment. Galton was misled to believe that twins fall naturally into
two groups, those much alike, and those little alike, in infancy.
They do not. His correspondents may have made careless re-
ports in other respects also. However, it will be remembered that
with respect to fifty pairs of twins, objectively measured, the
facts showed that the existing differences in home training had
very slight effects upon the six mental abilities tested.

The conditions of nurture of men of great achievement have
been studied by De Candolle ['73], Galton ['74], Jacoby ['81],
Odin ['95], Ellis ['04], Cattell ['06], and others. Within any
one nation such men are more likely than chance would allow to
be brought up in thickly settled districts, in particular in cities,
still more particularly, in the case of men of science or letters,
in cities containing universities ; by parents in comfortable or
more than comfortable financial circumstances ; and to have re-
ceived a good education.

Such facts are used in Odin, and by Lester F. Ward ['06]
following him, as evidence that the number of men of great achieve-
ment could be increased many times over if all men had in vouth
the stimulus of an intellectually active city, freedom from pro-

122

Educational Psychology

ductive labor, and good school training. But obviously the fea-
tures of the successful man's surroundings, enumerated above,
might all be the secondary results of superior parentage. If men
of high capacity go to live in cities, their sons will be born and
reared in cities ; if men of scientific and literary gifts are attracted
to university cities, such cities will, on grounds of heredity alone,
produce future scientific and literary men. If men of high achieve-
ment are born of men of over-average achievement, they will not
be brought up by day-laborers and without education as often
as chance would dictate. The parent's achievement leads for-
ward to these environmental conditions as truly as the son's
achievement leads back to them. So nothing is proved by them.
From Table ii [Cattell, '06], one can, according to his point of

TABLE II.

Distribution of 867 Men of Science Born in the United States.

Birthplace. Per

Million

I.-V* VI.-X.* Total. i860.

North Atlantic Division.

Maine 19 10 29 46. i

New Hampshire 7 8 15 46.0

Vermont 9 9 18 57-1

Massachusetts 60 74 134 108 . 8

Rhode Island 4 i 5 28.6

Connecticut 26 14 40 86.9

New York 99 84 183 47 . 2

New Jersey 9 19 28 41.6

Pennsylvania 32 34 66 23.7

South Atlantic Division.

Delaware o 2 2 17.8

Maryland 12 14 26 37-8

District of Columbia i 2 3 39-9

Virginia 5 8 13

West Virginia i o i 8.8

North Carolina i 4 5 5.0

South Carolina 2 3 5 7.1

Georgia i 2 3 2.8

South Central Division.

Kentucky 6 2 8 6.9

Tennessee 5 i 6 5.4

Alabama i i 2 2.1

* Column I -V. gives the facts for men of the highest ability; column
VI. -X. gives the facts for the 500 men of less ability.

The Influence of the Environment

123

I. -v.*

Mississippi 1

Louisiana i

Texas o

North Central Division.

Ohio 42

Indiana 17

Illinois 24

Michigan 12

Wisconsin 11

Minnesota i

Iowa 6

Missouri 4

North Dakota

South Dakota

Nebraska i

Kansas 5

Western Division.

Montana

Wyoming

Colorado o

New Mexico

Arizona

Washington i

California 5

Alaska

Hawaii i

Philippine Islands

Total 432

Birthplace.

Per

Million

VI.-X.*

Total.

i860.

1-3

1-4

4.9

32.1

20.7

24-5

36.0

45-1

23.2

29.6

II. 8

69 -3

65-3

o
6

I
II

87.2

86.2
28.9

435

867

27.6

view, get evidence that edticational opportunity counts enormously
or that it counts sHghtly in the relative production of scientific
men by the different states of this country.

For instance, the most striking fact is the high position of New
England and the low position of the southern states. The advo-
cate of great influence from opportunity may plausibly say that
from 1870 to 1885, the time when most of the men in question
were from 10 to 30 years of age, life in New England meant
cities, schools, books, lectures, the personal example of scholarly
men and freedom from poverty, whereas life in the south meant
the reverse. But the advocate of little influence may retort that
Maine, New Hampshire and Vermont should not, on these
grounds, have been so superior to Rhode Island ; or Louisiana so

124 Educational Psychology

inferior to Texas ; or Missouri so inferior to Wisconsin. He may
insist that the chief gift of Massachusetts parents to their sons was
the original nature which in earher days developed commerce
and manufactures, established the schools and libraries, and raised
life above a daily struggle for physical necessities, while the
southern planters and their servants were content to leave nature
unimproved.

Such a conflict of opinion is found between Professor Cattell,
who gathered the data of Table ii, and Professor Woods. Some
of the comments of the former are : — " The inequality in the
production of scientific men in different parts of the country
seems to be a forcible argument against the view of Dr. Galton
and Professor Pearson that scientific performance is almost ex-
clusively due to heredity. It is unlikely that there are such
differences in family stocks as would lead one part of the country
to produce a hundred times as many scientific men as other parts.
The negroes may have a racial disqualification, but even this
is not proved. The main factors in producing scientific and
other forms of intellectual performance seem to be density
of population, wealth, opportunity, institutions and social
traditions and ideals. All these may be ultimately due to race,
but, given the existing race, the scientific productivity of the
nation can be increased in quantity, though not in quality, almost
to the extent that we wish to increase it

" My general impression is that certain aptitudes, as for mathe-
matics and music, are mainly innate, and that kinds of character
and degrees of ability are mainly innate, but that the direction of
performance is mainly due to circumstances, and that the environ-
ment imposes a veto on any performance not congenial to it."
['06, pp. 734-735]

The cities in which five or more of the thousand men of science
were born, are given in Table 12. [Cattell, '06, p. 738] The
author of the study is cautious in estimating the beneficial results
of city life. He says simply, " Of the 866 men native to the
United States, 224 were born in the cities which in 1900 had a
population of more than 25,000. These places had in i860 a popu-
lation of about 4,500,000 as compared with a rural population of
about 27,000,000. The urban population was about one sixth of
the rural population and produced more than a quarter of the
scientific men. The urban birth rate was 50 and the rural birth

The, Influence of the Environment 125

rate was 23.8. The superior position of the towns is doubtless
due to a more favorable environment, but it may also be in part
due to the fact that the parents of these scientific men were the
abler clergymen and others of their generation who were drawn
to the cities. ['06, pp. 738-739]

TABLE 12.

Distribution in Different Places.

According to Birthplace Per

Million
I-V VI.-X. Total. i860.

New York, N. Y 33 25 58 71.2

Boston, Mass 24 19 43 241 . 8

Philadelphia, Pa 12 16 28 49 • 5

Baltimore, Md 9 11 20 94 -i

Cincinnati, 0 6 6 12 74-5

Brooklyn, N. Y 3 8 ii 39-4

Chicago, Ills 5 3 8 73.2

Buffalo, N. Y 3 4 7 86.2

St. Louis, Mo 2 5 7 43.5

Cambridge, Mass 4 2 6 230 . 2

Cleveland, 0 4 2 6 140 . 5

Salem, Mass i 5 6 269 . 6

Milwaukee, Wis i 4 5 no. 5

Newark, N.J 3 2 5 69 . 5

San Francisco, Cal 2 3 5 88 .0

Total 112 115 227

With respect to the circumstances of education " it appears
that those who attend the larger universities are not of higher
average performance than others

"There is no significant difference in rank between the 515 men
who attended the larger institutions and those who attended
smaller colleges or none. It might be supposed that abler stu-
dents would be attracted to a university such as Harvard, and
that they would have greater opportunities there, but this appears
not to be the case. So far as it goes, this favors the theory that
men of science are born such and are not dependent on the en-
vironment for the quality of their performance

" The conditions are similar in the case of the doctor's desfree."'
['06, pp. 740-741]

'&'

Dr. Rice's study is quoted at some length because it was the
first of a series of studies of the actual results of school work.

126

Educational Psychology

still few in number, but destined to increase rapidly with increasing
scientific interest in school administration.

Dr. Rice ['97] tested the spelling ability of some 33,000 children
in twenty-one schools representing a great variety in spirit,
methods, time given to spelling and in other respects. He then
compared the conditions in schools where the pupils did well in
spelling with those in schools where they did badly. He notes
first of all the slight dififerences between schools, only 6 out of
the 21 schools being outside the limits 73.3 and 77.9, and the
decrease in variation amongst schools as we pass from lower to
higher grades (see Table 13), facts which show that the dififer-
ences in spirit or method that characterize schools can not make
much difference in achievement. Of school systems where
mechanical methods are in use as compared with more progressive
systems he says :

" Indeed, in both the mechanical and the progressive schools
the results were variable ; so that while, in some instances, the
higher figures were secured by the former, in others they were
obtained by the latter ; and the same is true of the lower figures.
For example. School B, No. 11, in which the best average (79.4)
was obtained, belongs to a very progressive system ; while School
A, No. 12, which made only 73.9, belongs to one of our most
mechanical systems. And it is a peculiar incident that, in both
these cities, the results in the only other school examined are
exactly reversed, although the environment is about the same."

He eliminates the possibility that home reading or cultured
parents or English rather than foreign parentage is the cause of
the differences amongst schools by making the comparisons of
Table 14.

TABLE 14. (No. 3 of the original account)

Grade.

0
d

s
0

*.-■
0

PM
0

■2§

Children of

Foreign
Parentage.

6
1

No. of Children

Hearing Foreign

Language at

Home.

Children of
Unskilled
Laborers.

Sbntbncb
Test.

■ Fourth . .
Fifth....
Sixth... .
Seventh. .
Eighth. . .

4
4
4
4
4

27
29
22
18
19

821
829
778
566
528

64.7

76.

69.7

78.8

83.1

155

153

185

65.2

77-4
69.6

82.5
83.2

159

157

165

64.9
76.7
70.3
81.5
83.2

129
129
119

55
76

62.5

74 5
704
76.8
85.

The Influence of the Environment

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130 Educational Psychology

Dr. Rice further tabulated the results in accordance with the
methods of instruction used in the different schools, interviewing
some two hundred teachers for that purpose. He does not give
the detailed results, but assures us that there is no reason to be-
lieve that there is any clear choice between oral and written spell-
ing, writing isolated words and writing sentences, the sight or
flash method and its absence. Phonic reading does not make bad
spellers, nor do written language work and wide general reading
make good spellers. " In brief," says he, " there is no direct
relation between method and results. . . . The results varied
as much under the same as they did under different methods of
instruction."

That the amount of time given is not the cause of success in
teaching spelling is shown by the facts of Table 13. Schools
giving 15 or 20 minutes daily to spelling do as well as those
giving 40 or 50.

After this admirable array of " facts Dr. Rice jumps rather
hastily to this speculative conclusion : " The facts here presented,
in my opinion, will admit of only one conclusion, viz., that the
results are not determined by the methods employed, but by the
ability of those who use them. In other words, the first place
must be given to the personal equation of the teacher, while
methods and devices play a subordinate part."

This statement should have been based upon a demonstration
of a high coefficient of correlation between the measure of a class
in spelling and the measure of its teacher in ability, or of a great
increase in variability in spelling ability as we pass from the
children taught by one teacher to the children taught by 10 or
20 different teachers. I calculate that if the reliabilities of Dr.
Rice's eighth grade averages are what they would seem to be from
tests made in eighth grades by myself and my students,* the dif-
ferences amongst them are not much greater than we would ex-
pect by the law of chance if the teaching were in all cases equally
efficient. The average deviation from their mean of the 12 eighth
grade classes which were tested in the first half of the year is 1.9 ;
that of the 13 tested in the last half of the year is 2.6; the
average deviation by pure chance of 12 eighth grade classes of
40 students each would be 1.9, the variability of individuals

*These give a variability of 12.2 amongst the individuals of the grade.

The Influence of the Environment 131

being 12.2. So, in the case of the eighth grades, we may need no
cause at all for the differences amongst schools save the inaccur-
acy of the averages due to the small number of cases.

Dr. Rice measured the arithmetical ability of some 6,000 children
in 18 different schools in 7 different cities ['02]. The results
of these measurements are summarized in Table 15. This table
" gives two averages for each grade as well as for each school as
a whole. Thus, the school at the top shows averages of 80.3 and
83.5, and the one at the bottom, 25.2 and 31.8. The first repre-
sents the percentage of answers which were absolutely correct ; the
second shows what per cent, of the problems were correct in prin-
ciple, i. e., the average that would have been received if no me-
chanical errors had been made. The difference represents the
percentage of mechanical errors, which, I believe, in most in-
stances, makes a surprisingly small appearance."

From these results Dr. Rice seeks the causes of excellence in
arithmetical work, as in the case of spelling, by comparing the
conditions in the successful schools with those in the unsuccessful.
He deals seriatim with ( i ) the home environment of the pupils ;
(2) the size of the classes; (3) the age of the children; (4) the
time of day of the test; (5) the time devoted to arithmetic in
the school; (6) the amount of home work required; (7) the
methods of teaching; (8) teaching ability as represented by a
combination of education, training and the personality of the
teacher; (9) the course of study; (10) the superintendent's
training of teachers ; ( 1 1 ) the establishment of demands in regard
to results; (12) the testing for results (a) by teachers alone,
(b) by teachers and superintendents, (c) by principals, (d) by
principals and superintendents.

He finds that the work depends upon the method of testing
for results, that teachers and pupils do about what is demanded of
them, and that the best work appears when the superintendent, in
connection with principals of schools, tests and rates the work of
the classes.

The following are samples of the reasoning by which he
eliminates one after another of the possible causes :

Home Environment

" If the part that is played by the home environment should
be as important as it is generally supposed to be, we should, of

132 Educational Psychology

course, expect to find that the schools represented in the upper
part of the table had been attended by children from cultured
homes, while those in the lower part had been attended by those
whose home environment was very poor. However, if a line
should be drawn across the middle of the table, and the schools
above it compared with those below, such a condition would not
be found. Indeed, careful inspection would show that the odds
were certainly not in favor of the ' aristocratic ' districts. Of the
eighteen schools, three in particular are representative of the
latter, and the best of these secured the tenth place, while the
others ranked eleventh and sixteenth, respectively. The school
that ranked seventh was distinctively a school of the slums. That
is to say, the school laboring under the poorest conditions in
respect to home environment obtained a better standing than any
one of the so-called aristocratic schools. The building which
stands fifth is representative of conditions just a shade better
than those of the slums. And when I add that, from the stand-
point of environment, the schools of City I. did not average a
single degree better than those of Cities VI. and VII., I have
said enough to show that the poor results secured in the latter
cities can not be condoned on the ground of unfavorable environ-
ment. Thus, as in spelling, so in arithmetic, this mountain, upon
close inspection, dwindles down to the size of a molehill."

Si:::e of Classes

" Equally surprising, if indeed not more incredible, may appear
the statement that no allowance whatever is to be made for the
size of the class in judging the results of my test. I shall not
enter into the details in regard to this point, but will dismiss it
with the remark that the number of pupils per class was larger
in the highest six schools than it was in the schools of City VI.,
and that the classes were exceptionally small in the school that
stands at the lower end."

Age of Pupils

His argument is here too lengthy to quote and is rather awk-
ward, but sufficiently proves that the differences between schools
could have been due only in a very slight degree, if at all, to differ-
ences in the ages of the pupils. The obvious way to eliminate age
is to .compare a group from City VI. or VII. with a group iden-
tical in age and grade from City I. or III.

The Influence of the Enviromnent 133

Time of Day

This can not be the cause of much of the difference found, for
within any one city the time of day of the test makes Httle
difference.

The Time Devoted to Arithmetic in the School

" A glance at the figures will tell us at once that there is no
direct relation between time and result ; that special pressure
does not necessarily lead to success, and, conversely, that lack of
pressure does not necessarily mean failure.

"In the first place, it is interesting to note that the amoimt of
time devoted to arithmetic in the school that obtained the lowest
average — 25 per cent. — was practically the same as it was in the
one where the highest average — 80 per cent. — was obtained. In
the former the regular time for arithmetic in all the grades was
forty-five minutes a day, but some additional time was given.
In the latter the time varied in the different classes, but averaged
fifty-three minutes daily. This shows an extreme variation in
results under the same appropriation of time.

"Looking again toward the bottom of the list, we find three
schools with an average of 36 per cent. In one of these, insuffi-
cient pressure might be suggested as a reason for the unsatisfac-
tory results, only thirty minutes daily having been devoted to
arithmetic. The second school, however, gave forty-eight, while
the third gave seventy-five. This certainly seems to indicate that
a radical defect in the quality of instruction can not be offset by
an increase in quantity.

"If we now turn our attention from the three schools just men-
tioned and direct it to three near the top — Schools 2, 3, and 4,
City I. — we find the conditions reversed ; for while the two schools
that gave forty-five minutes made averages of 64 per cent, and
67 per cent., respectively, the school that gave only twenty-five
minutes succeeded in obtaining an average of 69 per cent. This
would appear to indicate that while, on the one hand, nothing is
gained by an increase of time where the instruction in arithmetic
is faulty, on the other hand, nothing is lost by a decrease of time, to
a certain point, where the schools are on the right path in teaching
the subject. Perhaps the most interesting feature of the table is
the fact that the school giving twenty-five minutes a day came
out within two of the top, while the school giving seventy-five
minutes daily came out practically within one of the bottom."

134 Educational Psychology

The Amount of Home Work Required

The greatest amount of home work was required in the lowest
ranking city while it had been practically abandoned in the first
five schools of the table.

In the other cases the facts are given more vaguely, and in his
presentation of positive evidence that differences in supervision
by tests are the leading causes of the differences in achievement
of the different schools, Dr. Rice seems to reach his conclusion
simply from observing (i) that all conditions in City VI. were
favorable save that examinations were given only by the teacher,
(2) that in City VII. the examinations were given by the teacher
and perfunctorily by the superintendent, while (3) in City I. the
superintendent, with the principals, took pains in setting the tests.
It seems probable that the cause he alleges is a real one, though
even his own facts show the cooperation of other causes. This
I take it he does not mean to deny.

The fourth sample of studies of the influence of the environ-
ment is not of major importance, but is distinctive in that its facts
cannot be accounted for by any force other than the environment.
The facts are the changes in the careers of scholarly college
graduates from the class of 1840 to that of 1895, comprising 5283
members of the honorary society, 0 B K, admission to which
was substantially a recognition of superior scholarship in college.

The four professions, law, medicine, teaching and the ministry,
have, together, attracted almost exactly the same proportion of
scholarly men in each decade. The per cent oi 0 B K gradu-
ates entering some one of these four professions was 65 in 1840-
59, 65!/^ in 1860-69, 65 in 1870-79, and 64 in 1880- 1894.

Among the professions, however, there have been marked
changes, as shown in Table 16. In twenty years the law doubled
its attractiveness to scholarly men and then, in half that time,
lost two-thirds of its gain. Medicine was, in the last decade of
the period, becoming more attractive. The table shows a very
rapid rise in the popularity of teaching from 1840 to i860 and
again from 1870 to 1895, The years from '60 to '65 show an
opposite tendency. The law was then gaining rapidly and the
ministry was holding its own. The most striking change was
the decrease in the proportion of scholarly men making the min-
istry their life work. The decrease would be even more marked
if those who entered the ministry but gave up its regular work

The Influence of the Environment 135

for that of teaching were included. The incomplete records avail-
able in the d) 5 Z" Catalogue of 1900 give only 53^ per cent of
clergymen amongst those graduating from '95-'99 ; and even with
later additions the per cent for 1900 is probably under 10.

Roughly, it may be said that three-fourths of the scholarly
young men who entered the ministry in 1850 would have gone into
teaching or the law if they had happened to be born a half century
later. The same original natures choose differently because the
social and intellectual environment has changed.

TABLE 16.
Percentages of Scholarly Youths Making Their Life Work That of : —

Law Medicine Teaching Ministry

1840 — 1844

■

37-5

1845—1849

■

1850 — 1854

9-3

36.5

1855—1859

34-5

i860 — 1864

5-5

275

1865 — 1869

28.5

1870 — 1874

5-5

22.5

1875—1879

1880—1884

4-5

195

1885—1889

7-5

1890 — 1894

The near future will doubtless see a rapid increase in the num-
ber and improvement in the quality of studies of the environmental
causes of individual differences in mental traits. Rice's investi-
gation of the differences due to different features of administra-
tion and teaching has been followed by similar studies by Corn-
man [02], Stone ['08], Courtis ['09], and Thorndike ['10].
Experts in education are becoming experimentalists and quanti-
tative thinkers and are seeking to verify or refute the established
beliefs concerning the effects of educational forces upon human
nature. Students of history, government, sociology-, economics,
ethics and religion are becoming, or will soon become, quantitative
thinkers concerning the shares of the various physical and social
forces in making individual men differ in politics, crime, wealth,
service, idealism, or whatever trait concerns man's welfare.

But for the present the exact answers to such questions are
lacking and all that can wisely be offered is a general statement
of how outside forces do act upon original natures so as to make
them more alike or more different than they would otherwise be.

136 Educational Psychology

The Method of Action of Differences in Environment

We may summarize the methods whereby diflferent environ-
ments act upon intellect and morals as : —

1. Furnishing- or withholding the physiological conditions for
the brain's growth and health.

2. Furnishing or withholding adequate stimuli to arouse the
action of which the brain is by original nature or previous action
capable.

3. Reinforcing some and eliminating others of these activi-
ties in consequence of the general law of selection in mental life.*

According to this description we should look upon the mental
life of an individual as developing in the same way that the
animal or plant kingdom has developed. As conditions of heat
and food-supply have everywhere been the first requisite to
and influence on animal life, so the physiological condiiions of
the brain's activities are the first modifiers of feeling and action.
As the stimuli of climate, food, unknown chemical and electrical
forces and the rest have been the means of creating variations in
the germs or of stimulating to action the inner tendency of the
germs to vary, and so have rendered possible the production of
millions of different animal types, so the sights and sounds and
smells of things, the words and looks and acts of men, the uten-
sils and machinery and buildings of civilization, its pictures and
music and books, awaken in the mind new mental varieties, new
species of thoughts and acts. In a score of years from birth the
human mind, like the animal world, originates its universe of mental
forms. And as, in the animal kingdom, many of these variations
fail to fit the conditions of physical nature and die after a genera-
tion or two, so in any one of us many of the mental forms pro-
duced are doomed to a speedy disappearance in consequence of
their failure to fit outside events. The elimination of one species
by others in the animal world is again paralleled by the death
of those thoughts or acts which are out of harmony with others.
Species of thoughts, like species of animals, prey upon one another
in a struggle in which survival is the victor's reward. Further,

*In all animals capable of profiting by training any act which in a given
situation brings satisfaction becomes thereby more closely associated with
that situation, so that when that situation recurs the act will recur also.
An act that brings discomfort becomes dissociated from the situation and
less likely to recur.

The Influence of the Environment 137

just as species of animals fitted to one environment perish or
become transformed when that environment changes, so mental
forms fitted to infancy perish or are transformed in school life ;
mental forms fitted to school life perish in the environment of
the workaday world ; and so throughout the incessant changes
of a mind's surroundings. In mental life resulting pain or dis-
comfort is the cause of the extinction of a species. The condi-
tion of a man's mind at any stage in its history is then, like the
condition of the animal kingdom at any stage in the history of
the world, the result not only of the new varieties that have ap-
peared, but also of a natural selection working upon them. The
tale of a human mind's progress is the tale of the extinction of
its failures. Possibility of existence, stimuli to variations, selec-
tion by elimination: these words that describe the action of the
environment on animal life are equally competent to tell the
record of a human life.

The influence of any environmental agency, physical or social,
varies with its avoidability. Oligarchies lose in influence if there
is a democracy to which men may emigrate. Customs do not
make men so infallibly if there is a radical party, however small,
which ofifers an alternative mode of life. Music's charms to
soothe obviously are not so universal if men can close their ears.
A creed loses authority as soon as one disbeliever seeks converts.
Social environments, institutions, beliefs and modes of behavior
are nearly omnipotent when undisputed ; for to be the first man to
revolt means either that one is a mere eccentric and so sure to
be a failure, or that one is a genius and so very rare. But once
a revolt is started and advertised, it may much more easily attract
those whose original natures it fits. And they may be the more
attracted by it for having been exposed to the opposite force. So
a given environmental force may even act as a stimulus toward
just the opinions, interests or acts that it is designed to thwart.

There are many differences in thought and conduct which are
nearly equally tolerated by all original natures. To wear a hat
or not to wear a hat, to express requests and opinions in English
or to express them in German, to learn astrology or to learn the
Ptolemaic astronomy or to learn the Copernican astronomy — to
all original natures these are nearly indifferent issues. Which is
done depends almost exclusively on environment. In general this
is true of all the ' whats ' of knowledge and technique. Hozv

138 Educational Psychology

many and how hard things a man can learn or do are largely de-
cided by original nature, but, within these limits, zvhat he learns
or does is largely a matter of what he is stimulated to do and
rewarded for doing. On the other hand, there are many features
of original nature each of which acts to produce nearly the same
efifect in spite of such differences in outside forces as different
men can meet in modern civilized countries. In such countries
it seems possible for any one to be a poet, or to be a political leader,
or to be a money-maker, if his nature so orders. Original nature
in general is not irrepressible, and no form of it is absolutely
irrepressible ; but some forms of original nature seem to be nearly
irrepressible by any of the environments a man in this country is
likely to have.

The Relative Importance of Original Nature and Environment

It is impossible at present to estimate with security the relative
shares of original nature, due to sex, race, ancestry and accidental
variation, and of the environment, physical and social, in causing
the differences found in men. One can only learn the facts, in-
terpret them with as little bias as possible, and try to secure more
facts. This interpretation is left to the student, but with certain
cautions in addition to or in amplification of those already
explained.

Many of the false inferences about nature versus nurture are
due to neglect of the obvious facts : — that if the environments are
alike with respect to a trait, the differences in respect to it are
due entirely to original nature ; that if the original natures are
alike with respect to a trait, the differences in respect to it are
due entirely to differences in training ; and that the problem of
relative shares, where both are effective, includes all the separate
problems of each kind of environment acting with each kind of
nature. Any one estimate for all cases would be absurd.

Many disagreements spring from a confusion of what may be
called absolute achievement with what may be called relative
achievement. A man may move up a long distance from zero
and nevertheless be lower down than before in comparison with
other men : absolute gain may be relative loss. One thinker may
attribute differences in achievement almost wholly to nurture
while another holds nature to be nearly supreme, though both

The Influence of the Environment 139

thinkers possess just the same data, if the former is thinking of
absokite and the latter of relative achievement. The commonest
error resulting is that of concluding from the importance of sex
and ancestral heredity that education and social control in general
are futile. On the contrary, as I have elsewhere said, such studies
as those of chapters III, IV, and V merely prove the existence of,
and measure certain determinants of, human intellect and charac-
ter and demonstrate that the influences of the environment are
differential, the product varying not only in accord with the en-
vironmental force itself but also in accord with the original nature
upon which it operates. We may even expect that education
will be doubly effective, once society recognizes the advantages
given to some and denied to others by heredity. That men have
different amounts of capacity does not imply any the less advan-
tage from or need of wise investment. If it be true, for example,
that the negro is by nature unintellectual and joyous, this does not
imply that he may not be made more intelligent by wiser training
or misanthropic and ugly-tempered by the treatment he now
receives. It does mean that we should be stupid to expect the
same results from him that we should from an especially intel-
lectual race like the Jews, and that he will stand with equanimity
a degree of disdain which a Celt would requite with dynamite and
arson.

To the real work of man for man, — the increase of achievement
through the improvement of the environment, — the influence of
heredity offers no barrier. But to the popular demands from edu-
cation and social reforms it does. For the common man does not
much appreciate absolute happiness or absolute betterment. He
does not rejoice that he and his children are healthier, happier and
more supplied with noble pleasures than were his ancestors of a
thousand years ago. His complaint is that he is not so well off
as some of those about him ; his pride is that he is above the com-
mon herd. The common man demands relative superiority, — to
be above those of his own time and locality. If his son leads
the community, he does not mind his real stupidity ; to be the
handsomest girl in the county is beauty enough. Social discon-
tent comes from the knowledge or fancy that one is below others
in welfare. The effort of children in school, of men in labor and
of women in the home is, except as guided by the wise instincts
of nature or more rarely by the wisdom of abstract thought, to

140 Educational Psychology

rise above some one who seems higher. Thus the prizes which
most men really seek are after all in large measure given or
withheld by original nature. In the actual race of Ufe, which is
not to get ahead, but to get ahead of somebody, the chief determin-
ing factor is heredity.

But the prizes which education ought to seek are all within
its power. The results for which a rational mankind would strive
are determined largely by mankind itself. For the common good
it is indifferent who is at the top, — zvhich men are achieving
most. The important thing for the common good, for all men,
is that the top should be high — that much should be achieved.
To the absolute welfare of all men together education is the
great contributor.

Another caution is not to make false inferences about moral
responsibility from the fact that individual differences are in large
measure due to nature ; nor to use such false inferences to discour-
age acceptance of evidence in support of this fact.

It is from time to time complained that a doctrine which re-
fers mental traits largely to original make-up, and consequently to
ancestry, discourages the ambitions of the well-intentioned and
relieves the world's failures from merited contempt. But every
one is agreed that a man's free will works only within limits, and
it will not much matter for our practical attitude whether those
limits are somewhat contracted. If the question is between orig-
inal nature and the circumstances of nurture it is rather more
encouraging to believe that success will depend on inherent quali-
ties than to refer it entirely to advantages possessed during life,
and contempt is merited more by him who has failed through
being the inferior person than by the one who has failed simply
from bad luck. Whether or not it is merited in either of the
two cases we shall decide in view of our general notions about
merit and blame, not of our psychological theories of the causes
of conduct.

On the whole it seems certain that prevalent opinions much
exaggerate the influence of differences in circumstances and train-
ing in producing the intellectual and moral differences found in
men of the same nation and epoch. Certain natures seem to have
been made by certain environments when really the nature already
made selected that environment. Certain environments seem to

The Influence of the Environment 141

eliminate certain traits from an individual when really they merely
expel the individual in toto.

Thinkers about the organized educational work of church,
library and school need especially to remember three facts.

First. — For the more primitive and fundamental traits in hu-
man nature such as energy, capability, persistence, leadership,
sympathy and nobility the whole world affords the stimulus, a
stimulus that is present well-nigh everywhere. If a man's origi-
nal nature will not respond to the need of these qualities and the
rewards always ready for them it is vain to expect much from
the paltry exercises of the schoolroom.

Second. — The channels in which human energy shall proceed,
the specific intellectual and moral activities that shall profit by
human capacities, are less determined by inborn traits. The
schools should invest in profitable enterprises the capital nature
provides. We can not create intellect, but we can prevent such a
lamentable waste of it as was caused by scholasticism. We can
not double the fund of human sympathy, but we can keep it
clear of sentimental charity.

Third. — Morality is more susceptible than intellect to environ-
mental influence. Moral traits are more often matters of the
direction of capacities and the creation of desires and aversions.
Over them then education has greater sway, though school educi-
tion, because of the peculiar narrowness of the life of the school-
room, has so far done little for any save the semi-intellectual
virtues.

The one thing that educational theorists of to-day seem to
place as the foremost duty of the schools — the development of
powers and capacities — is the one thing that the schools or any
other educational forces can do least. The one thing that they can
do best is to establish those particular connections with ideas which
we call knowledge and those particular connections with acts
which we call habits.

CHAPTER VIII

The Nature and Amount of Individual Differences in

Single Traits

For the purpose of the following discussion, let a ' single trait '
be defined as one whose varying conditions in men can be meas-
ured on one scale. A combmation of traits requires two or more
scales. For example, in so far as the difference between John
and James in reaction time to sound can be measured as so many
thousandths of a second on one scale, reaction time to sound is a
single trait. The difference between John and James in tempera-
ment, on the contrary, can be stated only in terms of several

scales, such as quick slow, intense superficial,

broad narrow, and the like. So temperament is to be re-
garded as a combination of traits.

Individuals may be compared with respect to one trait at a
time, or with respect to certain combinations of traits. We natur-
ally take up first the simpler case.

The most desirable description of the differences between in-
dividuals in a mental trait would be to give the facts for all hu-
man beings,* then for all of each sex,* then for all of each race
and of one sex,* and so on for each stock, degree of maturity, and
kind of training. That is, the condition of the individuals in each
of a great many groups, each defined by sex, ancestry, age and
training, would be described. By combining these one could de-
scribe the condition of the individuals in groups defined by sex
and age alone, or race and age alone, or race, age and training
alone, and the like.

For practical reasons, however, the individuals whose differ-
ences one from another have been measured often form groups
of a somewhat adventitious character. For example, the indi-
vidual differences between one student and another in university
classes in psychology have been measured, because such classes

*That is for a random sampling of them.

(142)

Individual Differences in Single Traits 143

are at the psychologist's service. So also " college freshmen ",
or " children of a certain school grade ", or " those who are will-
ing to reply to a series of questions sent out by mail " are groups
determined by convenience rather than by significance.

The group is often deliberately narrowed, as when the indi-
viduals are all insane, or all intellectually deficient, or all morally
delinquent, or all men of science.

Furthermore, many of the facts concerning individual differ-
ences came as by-products of investigations of general mental
laws or of group differences. For example, the early investigators
of the least noticeable difference, of the time required for a simple
reaction or for a reaction with discrimination, of the range of
consciousness and the like, often considered the divergences of
single men from the average of all men as " errors " due to chance
conditions. These investigators took no interest in these individ-
ual divergences save as annoying hindrances to the exact formu-
lation of constant laws of mental life. So also students primarily
interested in the differences of man from woman have, without
desire, got results concerning the differences of one man from
another.

Finally the experiments made for us by the general conditions
of life often provide data concerning the differences of individuals
within a group constituted by some very complex circumstances.
The differences of teachers in respect to salary, of college gradu-
ates in respect to general achievement in life, or of criminals in
respect to the number and nature of their convictions by courts
of law are samples.

As a result, there does not exist any study of the differences
of a random sampling of all human beings in a single mental
trait ; or of a random sampling of individuals of the same sex ; or
of individuals of the same sex and age. There are, however, stud-
ies of the differences of a random sampUng of individuals of the
same sex and approximately the same age and race. The boys
12 years o months to 13 years o months old found in the schools
of a German or English town would form such a group, and such
boys have been measured with respect to certain mental traits.
There are also studies of individuals of the same sex and of nearly
the same age, race, and training (in certain particulars). The
children just mentioned, if limited to a given grade or standard
in school, would be thus nearly alike in respect to school training.

144

Educational Psychology

In spite of the difficulties of interpretation that arise from the
mixture of unknown degrees of age, race and training, four gen-
eral facts about individual variations in traits taken one at a
time seem highly probable, (i) The variations are, in general,
greater in acquired than in original traits. (2) They are, in
general, greater in traits peculiar to man than in traits character-
istic of all mammals. (3) The variations are usually, perhaps al-
ways, continuous. One grade or degree or amount is not sepa-
rated from the next as ten men is separated from eleven men, but

TABLE 17.

The Abilities op 37 Adult Women Students in Adding, after One
Hour's Special Practice. Time Required (in Seconds) to Add 48
Single Columns Each op 10 Figures Taken at Random from the
Series 2-9. 50 Per Cent of the Time for One Column Was Added
FOR Each Wrong Sum.

3
>

4->

4-^

4-'

4-)

■i-t

.— <

•0
C

X3
<

•0
a
1— 1

a
>— 1

a
I— (

3
<

240

390

465

508

669

845

242

428

482

535

719

896

249

433

488

545

729

267

437

489

550

741

272

459

499

572

763

t
i

290

463

504

628

772

315

464

506

642

811

TABLE 18.

The Abilities op 37 Adult Women Students in Drawing Lines to Equal

100 MM. Lines: Average Error (in mm.) from the Stand.'vrd.

•— <

4-'

-a

■^-t

•d
>

J3
<

C
hH

•0
3

X!
<

■9

2.0

2.8

3-4

4-9

9-1

2.2

10. 2

2.3

2.4

2.6

2.7

Individual Differences in Single Traits 145

as ten pounds is separated from eleven pounds. (4) The varia-
tions usually cluster around one central tendency or " type."

Sample Surfaces of Frequency of Single Traits

As a preliminary to the discussion of these Laws of Mental
Variations I present in Tables 17 and 18 and Fig. 26 samples of
measurements of groups of individuals in traits taken singly.

From these tables one can calculate the amounts of difference
existing and the relative frequency of each. For example, in
Table 17 it appears that the two most unlike individual? of 37
chosen at random from women students of education differed
by 656 seconds (896-240) in adding 48 examples, or by 13^
seconds per example. Differences of 12 seconds or over per ex-
ample (576 seconds or over for 48 examples) occurred 11 times

I II Ml I II I III illil il III I ! I 11 III

800 m m m w m m

I I I I II III II Mini III |u II I \

I^A 10 W 1) Iq Sfl Hf} 3S IS )0.

Fig. 26. (Upper Diagram). The ability of each of 37 women in adding.
The scale gives the time in seconds required to add 48 single columns, each
of 10 figures, 50 per cent of the time for one column being added for each
wrong sum. Each vertical line represents one individual.

Fig. 26. (Lower Diagram). The ability of each of 37 women in draw-
ing lines to equal a 100 mm. line. The scale gives the average deviation in
millimeters from the standard. Each vertical line represents one individual.

(between each of individuals a, b, c, and d and each of individuals
J and K; also between each of individuals e, f and g and indi-
vidual K) ; etc., etc. The median of all the individual differences
will be found, by any patient reader who cares to compute it, to
be about 33^ seconds per example. The median of the deviations
of the 37 individuals each from 11 seconds per example, which is
the central tendency of adult women students of education in this
trait, is 2.2 seconds per example.
10

146 Educational Psychology

The Amounts of Difference in Different Traits

Any such measurements of the frequencies of different degrees
of difference between one individual and another or between indi-
viduals and some central tendency or type, are not, however, read-
ily commensurate except within the same trait. To the question,
" Do these women differ more in ability to add than in ability
to accurately equal a length of 100 mm?," the answer is: — The
range of difference is 13^ seconds in one case, (5 to i8f), 9.1
millimeters in the other ; the median difference is 3.5 seconds
(approx.) in one case and 1.8 millimeters (approx.) in the other;
the median deviation from the central tendency is 2.2 seconds
in one case and 1.2 millimeters in the other.

Now in common speech, and in books on psychology and edu-
cation as well, the differences between two individuals in two or
more mental traits are compared. Such statements as, " John
differs little from James in memory, and much in judgment," or
" Men are much more alike in sense powers than in imagery," are
made. If they are justifiable, the differences in different traits must
somehow have been made commensurate.

In particular, my statement concerning the variations in original
versus acquired traits, or in mammalian versus distinctively hu-
man traits, must depend upon some means of comparing the mag-
nitudes of variations in different traits.

In comparing the tallest and shortest of 100 adult men, we
can say, not only that they differ by, say, 20 inches, but also (sup-
posing them to be 76 and 56 inches) that the tallest is one and five
fourteenths times as tall. In comparing the wealth of the men
we can say not only that one has $10,000 more, but also that (sup-
posing them to possess $1,000 and $11,000) he is eleven times as
rich. In a certain real and useful, tho limited, sense, it can
be said that adult men differ more in wealth than they do in
weight, and more in weight than they do in stature. The ratio
of the difference of one man from absolute zero, or just not any
amount of the thing in question, to the difference of another man
from the same zero or just-not-ness is in a sense commensurate with
a similar ratio in the case of another thing. Nothingness is taken
to be the standard and ' just not any ' of one thing is treated as
equivalent to ' just not any ' of another thing.

If one wished to use the test in addition to place a person on a

Indhndual Differences in Single Traits 147

scale for " ability in addition " one would find no such clear and
sure way to make the judgment of " times as far from o
ability." It would be very hard to define " ability to add which
is just barely not no ability to add " in terms of any test's score.
It would be still harder, if not impossible, to define it in terms of
a score in this test. Should it be 100 sec. per example, or 1000,
or 10,000, or 100,000, or infinity?

If one wished to use the test in drawing lines to place a person
on a scale for ability to notice differences he would have not
quite so hard a task. For there would be some reason for taking,
as o ability, a divergence of 100 mm., — that is, failure to distin-
guish from the standard a line of zero length.

There is great absurdity in common opinions of what " just not
o " is in the case of a mental trait and of what the relative differ-
ences between this and that manifestation of the trait and o are.
Even gifted and well trained thinkers will assert, some that the
best handwriting is only one and a half times as " good " as a
nearly illegible scrawl, and some that it is eight or ten times as
good. They will declare, some that the average man knows twice
as much as the average dog, and some that he knows a thousand
times as much. Some of them will assert, on finding that one
boy spells 48 words correctly out of a list of 50 and another 6,
that the former was thereby proved to be eight times as good a
speller. Even if we should all study somewhat exhaustively the
logic of the " times " judgment in mental traits, there would still
be fairly wide disagreements concerning, say, how many times
as much curiosity the most curious man had than the average man
or than the least curious man ; or concerning how many times as
much mathematical knowledge the most learned mathematician had
than the stupidest idiot.

But by any rational and just decision as to what ' o ' or ' just
not anything ' was for each mental ability, we should find abun-
dant evidence of the truth of the two laws — that individual differ-
ences in single traits are greater in acquired than in original abili-
ties ; and that they are greater in abilities peculiar to man than in
abilities possessed by mammals in general.

For example, suppose that we regard as absolute zeros, the
following: just not any A's marked in a minute, just not any
sums correctly given in a minute, just not any dots placed in a
series of squares, and the like, using as the measure in every case

148 Educatiottal Psychology

the amount done of some task, some amount of which nearly all
adult Americans can do. The ' times as much ' then comes out
greater for thought than for movement, greater for memory of a
passage than for memory of unrelated words or numbers, greater
for responding to the meanings of words than for responding to
the differences of colors, greater for marking words containing
both a and t than for marking A's amongst other letters, greater
in solving problems in arithmetic, mechanical difficulties, or geo-
metrical puzzles than in sorting out colors.

For the reasons stated at the beginning of this chapter a survey
of the data bearing on the comparative variability of man in dif-
ferent traits would not be desirable, even apart from the difficulty
of choosing zero points. Moreover, the truth of the statement that
as a rule individuals differ more in acquired than in original traits
hardly needs statistical proof. The range of variations or the
average individual difference is obviously greater in the acquired
perceptions of words, music, geometrical forms and the like than
in the original sensitivities to colors, sounds or distances ; in the
acquired movements of writing, sewing, singing and the like than
in the original reflexes and instincts of winking, swallowing,
clasping, running or striking ; in knowledge, which is largely ac-
quired, than in movement, which is to a considerable extent orig-
inal ; in the interests in literature, science or politics than in the
interest in sex.

Within a narrow group, of course, uniformity of conditions may
occasionally act to reduce natural differences, for example in habits
of eating. But if men are taken over all the world and over a
number of centuries it is hard to find any trait where the modifi-
cations by training do not increase natural differences.

The second law, that variations are greater in traits peculiar to
man than in traits common to man and the mammals in general,
is evidenced by the comparison of variability in remembering
ideas with variability in remembering acts of skill, by the com-
parison of variability in marking A's with variability in marking
logically absurd sentences, by the comparison of variability in
drawing a line between two lines accurately with that in defining
a word accurately, and the like. As the superiority of the best to
the worst philosopher is greater than that of the best to the
worst rememberer of places or avoider of animal enemies,.

Individual Differences in Single Traits 149

so the variability in thinking with ideas in general is greater than
that in the simple sensori-motor processes.

The Continuity of Mental Variations

Continuity of variations means two things, — the absence of
regularly recurring gaps, such as those between 2 petals, 3 petals,
4 petals, and the like, and the absence of irregularly recurring gaps,
such as those between mice and rats, between rats and squirrels,
and the like.

That continuity* of variations in a mental trait taken singly is
the rule can best be realized by trying to find exceptions to it.
Such there may be, but I am not aware that any mental trait
varying in amount has been shown to vary by discrete steps. A
misleading appearance of regularly recurring gaps often arises
from inadequate measurements. In a test of memory, for example,
12 nonsense syllables being read, individuals may appear in the
scores as 5, 6, 7, 8 and 9 without any 5.5's, 6.75's and the like.
But if four such tests are made and the average is taken, there
will be 5.5's and 6.75's.

A misleading appearance of irregular discontinuity often arises
from the insufficient number of cases measured. If only a few
individuals are measured in a trait or if the scale is a fine one,
there will of course be divisions on the scale or amounts of the
trait unrepresented in any individuals. Thus in Fig. 26 (p. 145)
there are such gaps, which would all have been filled in, had the
number of individuals been very large. The 37 individuals whose
abilities were reported in Fig. 26 were, in fact, chosen at random
from 200. If all the 200 records had been used in constructing
Fig. 26, its gaps would have been largely filled in. For example,
the 37 cases show, between the abilities 500 and 700, a distribution
as in the upper surface of Fig. 27, whereas the 200 cases show,

*0f course continuity is not taken here in the sense of infinite
divisibility. There are doubtless ultimately unit-factors which either act
or do not act, and which consequently increase the amount of the trait
by either zero or a certain amount. But the discrete steps are exceedingly
small like the steps of increase of physical mass by atoms. Intelligence,
rate of movement, memory, quickness of association, accuracy of discrimina-
tion, leadership of men and so on are continuous in the sense that mass
amperage, heat, human stature and anemia are.

ISO

Educational Psychology

over the same extent of the scale, a distribution as in the lower
surface of Fig. 27.

It should be unnecessary to warn the reader against the
absurdity of deliberately changing continuous variations into a
few groups by coarse scaling ; next assuming that the central part
of one of these coarse divisions really measures all the individuals
therein ; and finally imagining that, because the continuous series,
varying from a to a + b, has been called, say, Poor, Medium, Good

600

500

.600

500

Fig. 27. The distribution of the cases falling between 500 and 700
seconds in adding 48 columns each of 10 one-place numbers, when, in all,
37 individuals were measured (upper diagram) ; and when, in all, 200
individuals were measured (lower diagram).

and Excellent, there are really gaps within it ! Unfortunately
even gifted thinkers are guilty of this error.

The Relative Frequencies of Different Amounts of Difference

The question of the clustering of variations around one central
tendency demands more elaborate treatment. Fig. 28 shows the
relative frequencies of the different amounts of the trait in the
case of six mental traits. These six distributions illustrate the
statement on page 145 that ' variations usually cluster around one

Individual Differences in Single Traits

151

C F

Fig. 28. Samples of the forms of distribution found in mental traits.

A. Reaction time : 252 college freshmen.

B. Memory of digits : 123 women students.

C. Efficiency in marking A's on a sheet of printed capitals : 312 boys from

12 years 0 months to 13 years 0 months.

D. Efficiency in giving the opposites of words : 239 boys from 12 years

0 months to 13 years 0 months.

E. Accuracy in drawing lines to equal a 100 mm line : 153 girls from

13 years 0 months to 16 years 0 months.

F. Efficiency in marking words containing each the two letters a and t :

312 boys from 12 years 0 months to 13 years o months.
In all six cases the left end of the scale represents the lowest abilities, —
that is, the longest times in A, the fewest digits in B, etc. The continu-
ous lines give the distributions. The broken lines are to be disregarded for
the present.

152

Educational Psychology

central tendency.' This statement is not, however, universally, or
even commonly, accepted. On the contrary the common opinion
is that the distribution of individuals with respect to the amount
of a single trait is multimodal, as in Fig. 29A, or even a compound
of entirely distinct species, as in Fig. 29B. There would then be
many small differences and many large differences with few cases
of medium differences. This may be called the ' multiple type '

Fig. 29. Multimodal distributions.

theory. For instance, in the case of intellect we find the terms
genius, normal, feeble-minded, imbecile and idiot used as if the
geniuses were separated by a clear gap from the normal
individuals, these again from the feeble-minded, and so on. So
also visualizers and non-visualizers, or men of normal color vision
and the color blind, are spoken of as if those in each group were
all almost identical and all much unlike all in the other growp.

Multimodality is to be expected in traits the amount of which
may be greatly increased or decreased by some one cause (or

Individual Differences in Single Traits 153

number of causes commonly acting together). If, for instance,
reading Aristotle added enormously to anyone's intellectual gifts,
we should expect to find men divided into two distinct surfaces
of frequency on a scale for intellect, the higher ranking species
being made up almost exclusively or even entirely of those who
had taken the Aristotelian dose. The action of ophthalmia in
causing blindness in the new-born is such a cause. By reason of
it and other diseases, the visual capacity is reduced enormously
in certain individuals, so that there are two modes, the seeing
and the blind. Fewer men are able just barely to see than are
totally blind. Injury to the head at birth or disease of the
thyroid gland may be such a cause, reducing certain individuals
all to an equal condition of intellect, so that possibly, by reason
of it and other accidents and diseases, the number of very idiotic
children may be greater than the number of those less idiotic

Fig. 30. A distribution showing a secondary type, of great inferiority.

over an equal length of the scale (see Fig. 30). This is doubtful,
however.

In certain traits, such as knowledge of a certain language, or
ability to play a certain game, there are two species. One includes
those who have had no opportunity to get the knowledge or
ability and whose knowledge or ability is consequently o ; the other
is made up of those who have had some opportunity to get the
knowledge or ability and who range in it from o or near o to a
large amount. Understanding of spoken English, or ability to
play chess or whist or golf, or ability to typewrite or to navigate
a ship by the compass, would, of course, give such groups, if
measured in adults the world over. Here the cause does not
produce a uniform amount of the trait, but the world is so
arranged that on many persons the cause does not act at all.

Many such causes may act in the case of particular habits.

154

Educational Psychology

knowledges and skills. Since, for example, some Germans are,
and some are not, subjected to the action of enforced military
service, there may well be two modes to the surface of frequency
of knowledge of the manual of arms, one group all knowing it very
well, the other group knowing hardly anything about it. Appren-
ticeship to a certain trade, or enrollment in a certain kind of school,
may thus lead to extreme and uniform amounts of knowledge of,
say, plastering or typewriting or medicine, so as to divide human
nature sharply into an ordinary and an expert class. How far this
happens is not known.

Fig. 31. Relative frequencies of different amounts of efficiency in mark-
ing A's on a printed sheet of capital letters, in the case of a group of
twelve-year-olds, boys and girls together.

If sex made a great enough difference in the amount of any
trait, there would be two modes in the surface of frequency for
the trait in question in the two sexes combined. But observable
bimodality as a result of mixture of the sexes does not in fact
appear, because the sex differences are so small. For example,
Fig. 31 shows the result of such mixture in one of the traits in
which the sexes differ most. Figs. 32 and 33 show the distribution
separately for each sex.

In traits in which race makes a great difference there will tend
to be a mode for each racial type if two extreme races are mixed.
Fig. 34 shows the results of so mixing civilized Europeans with
Negritos (Figs. 35 and 36 giving the separate distributions for
Europeans and Negritos). But if all races, or a random selection
of races, were mixed the resulting surface of frequency would not
show a distinct mode for each, or probably for any one. Even

Individual Differences in Single Traits

155

so great a difference as that between the whites and the colored
in scholarship in the high school is shown in the combined dis-
tribution only by a flattening of the surface of frequency as
compared with that of either race alone (see Fig. 37).

Fig. 32. Relative frequencies of different amounts of efficiency in mark-
ing A's on a printed sheet of capital letters, in the case of twelve-year-old
boys.

Fig. 33. Relative frequencies of different amounts of efficiency in mark-
ing A's on a sheet of printed capitals, in the case of twelve-year-old girls.

In traits in which age makes a great difference, there will be
a marked flattening of the surface of frequency. Thus, whereas
for any one age, say 10 years and 7 months, the variations with
respect to ' School Grade Reached ' will cluster closely around one
grade, the distribution for individuals of all ages from 8 years
through 14 years, shows three almost equally frequent degrees of

iS6

Educational Psychology

,. ... _ . _ 1

17 27 37

7 17 27 37

Figs. 34, 35 and 36. Relative frequencies of different times required to
insert variously shaped blocks in holes to match. The best abilities (that
is, the shortest times) are at the left end of the scale in each case. Fig. 34
gives the distribution for a group equally divided between vi^hites and
Negritos. Fig. 35 is for whites alone. Fig 36 is for Negritos alone.

Individual Differences in Single Traits

157

the trait. This fact is shown in the case of the boys of one large
city in Fig. 38.

The common opinion that there are distinct species of
individuals, with more or less pronounced gaps between, does not,
however, limit itself to presupposing such multimodalities as those
made by men and women, by Germans and Bushmen, by five-year-
olds and fifteen-year-olds, by the ordinary population and the blind
in respect to vision, by plumbers and non-plumbers in respect to

Fig. 37. The relative frequencies of different degrees of high-school
scholarship in a group composed of 150 whites and 150 negroes. The
lowest grade of scholarship is at the left, the highest grade at the right, end
of the scale.

skill in plumbing, by those who never tried to learn chess and
those who did, in respect to ability at playing chess, and the like.
It knows little or nothing of the effect of various combinations of
causes upon the form of distribution of a trait and it thinks of
men as divided off into sharp classes in mental traits chiefly
because it has not thought properly about the question at all. It
merely accepts the crude adjectives and nouns which express
primitive awareness of individual differences, as representatives of

158

Educational Psychology

1 2 3.4 6 «.7 8 9 10

Fig. 38. The relative frequencies of differ ent degrees of progress in
school in the case of boys 8 years o months to 14 years 11 months inclusive.
The horizontal scale at the bottom is for 'grade reached,' i, 2, 3, etc., mean-
ing first grade, second grade, third grade, etc. The surfaces of frequency
are, in order from the top down, for 8-year-olds, 9-year-olds, lo-year-olds,
ii-year-olds, 12-year-olds, 13-year-olds, 14-year-olds, and 8-14-year-olds
combined.

Individual Differences in Single Traits

159

corresponding divisions in reality ; neglects the existence of inter-
vening grades ; and does not even attempt to estimate the
frequencies grade by grade. How strong this tendency to verbal
thinking is can be beautifully illustrated by the firm conviction of
even long-trained men of science that people are either markedly
right- or markedly left-handed, are either ' normal ' in color vision
or far removed from the ' normal ' in color weakness or color

Fig. 39. The distortion of the form of distribution due to the presence
of too few cases. A is the distribution as found from several hundred
cases ; B is that found in the same trait from the first 28 of them.

blindness. Until recently the superstition that a great gulf separ-
ated children of normal intellect from the imbeciles and idiots was
also very strong in many scientific men. The multiple-type theory
does not refer to the separation of individuals into groups by the
presence or absence of some one cause, or closely interrelated
group of causes. It simply vaguely fancies that individuals, even
of the same sex, race, age and training, somehow naturally fall
into distinct classes or ' types.'

i6o Educational Psychology

In such a form it is surely almost always, if not always, wrong.
A group of such individuals does not, as a rule, show a separation
into two or more groups, all in one being much like each other
and little like any of those in the other group, or groups. Here
again the rule may be verified by searching for exceptions to it.
I know of no such. The misleading appearance of such may come
either (i) from inadequate measurements, as in the case of the
pseudo-discrete variations, or (2) from the examination of an
inadequate number of individuals. Thus ( i ) if men are rated, for
sensitiveness to red and green, as color blind, color weak and of
' normal ' color vision, there will appear to be three types, just as
there will appear to be three types of stature if all men are rated
as short, medium or tall. But in careful tests the color blind will
vary among themselves, the color weak likewise and the ' normal '
likewise ; the color blind will merge imperceptibly into the color
weak and these into the ' normal.' Thus (2) if only fifty
individuals are measured and if the scale is arranged so that these
are included by, say, twenty divisions of it, there is a fair
probability that, though the distribution of a thousand individuals
show a clustering around one type as in Fig. 39A, the fifty
may be clustered around two or more types as in Fig. 39B. The
absurdity of inferring the existence of two species of human
nature with respect to a trait from two apparent modes found
when only a few individuals are studied should be obvious.

The Chance or Probability Distribution in the Case of Single

Mental Traits

In sharp contrast to the common notion that human beings are
divided sharply into classes, is the theory that, for any one trait,
men, at least by original nature, form always only one class defined
by one single sort of distribution. This theory answers in the
affirmative the questions : " Do the distributions of mental traits
in groups of individuals follow any regular law? Are the differ-
ences between individuals in mental capacities and characteristics
amenable to any single type of description?" It supposes that,
in all original traits, human beings so differ as to make the
distribution that of a chance event, the surface of frequency being
that of the probability integral. The exact meaning of this sup-
position and the basis for it need not now be discussed. Our present

Individual Differences in Single Traits

i6i

interest is in discovering how far any one type of distribution does
characterize all original mental traits in human beings. By using
graphic representations rather than algebraic formulae, the answer
and the evidence for it can be made clear even to one who knows
nothing whatever of the mathematical properties of the surface
of frequency of a chance event or of any other.

Fig. 40 gives the distribution or surface of frequency of the
type to which by this theory the distributions of natural abilities

Figs. 40 and 41. The 'chance' or 'probability' form of distribution.

conform. Fig. 41 gives the same distribution as Fig. 40, but with
a coarser separation into grades.

Before comparing actual distributions with this theoretical form
of distribution it will be profitable to inquire somewhat more
systematically into the relation between the factors which deter-
mine the amounts of a trait in an individual and the relative
frequencies of its different amounts among men.

Suppose the amount of a trait to be determined by six causes or
factors — a, b, c, d, e, and f — each contributing i toward it; and
suppose that each individual's nature includes a chance drawing

i62 Educational Psychology

from these causes, any combination being equally likely to be
drawn.

The possible combinations are : —

None

a b c d e f

ab ac ad ae af be bd be bf cd ce cf de df ef

abc abd abe abf acd ace acf ade adf aef bed

bee bcf bde bdf bef cde cdf cef def

abed abce abcf abde abdf abef acde acdf acef

adef bcde bcdf beef bdef cdef

abcde abcdf abcef abdef acdef bcdef

abcdef

Consequently for every individual possessing o units of the
trait there will be 6 possessing 6 units of it, 15 possessing 2 units,
20 possessing 3 units, 15 possessing 4 units, 6 possessing 5 units,
and I possessing 6 units. The relative frequencies of the different
amounts of the traits will be : —

Amounts of

Relative frequencies

the trait.

of these amounts.

Fig. 42 shows the form of distribution graphically.

Suppose that instead of six such causes there were twenty. The
results of chance drawings from the possible combinations would
then be to give, for every individual possessing o units of the trait,
20 possessing i unit, 190 possessing 2 units, 1140 possessing 3
units and so on, as in Table 19 and Fig. 43.

Suppose the number of causes to be increased, the other condi-
tions remaining as before. The relative frequencies would assume
more and more closely the proportions shown in Fig. 40 (p. 161),
which is the surface of frequency of an event caused by a chance

Individual Differences in Single Traits 163

TABLE 19.

Form of Distribution Resulting from Random Combina-
tions OF 20 Causes of Equal Magnitude

Amounts of Relative frequencies

the trait.

of these amounts

190

1,140

4,845

15,504

38,760

77,520

125,970

167,960

184,756

167,960

125,970

77,520

38,760

15,504

4,845

1,140

190

selection from among the combinations of a large number of fac-
tors each of small and all of equal amount. This surface is
bounded by the probability curve. It is often called, or miscalled,
the ' Normal ' surface of frequency or ' Normal ' distribution

The distribution of individuals in certain anatomical traits is
much like that of Fig. 40. The close fit of individual variations
in stature and the like to the particular bell-shaped surface of the
probability integral naturally led to the expectation, or at least
the hope, that all variable facts in original human nature would
vary in this one way. In particular, individuals of the same sex,
age, race and training should form a true species and vary in
this one way.

164

Educational Psychology

As a matter of fact they do not, but they approximate it. No
one form of distribution fits them all, but the bell-shaped curve
given by the equation y=e-^^ fits them better than any other
simple curve. Fig. 28 (p. 151) gives fair samples of the closeness
of fit in mental traits.* The condition of an individual in a trait
is very often the result of something approximating a chance
selection of one out of many combinations of many factors, each
of small and nearly equal influence on the trait's amount. In so

Fig. 42. The 'chance' form of distribution from six equal and indepen-
dent causes.

Fig. 43. The 'chance' form of distribution from twenty equal and
independent causes,

far as it is so, the relative frequencies of the different conditions
of individuals in respect to the trait will be approximately those
of the so-called ' Normal ' surface of frequency. But just as
there cannot be two or more sharply defined types unless there
are certain large causes whose presence makes a great diflference
in the trait's amount, so there cannot be a very close approximation
to the ' Normal ' sort of distribution unless the causes are nearly-
independent, and of nearly equal influence.

*The broken lines in Fig. 28 give, in each case, the ' chance ' form of
distribution.

Individual Differences in Single Traits 165

Such a trait as stature shows approximately the probability dis-
tribution, because its amount in any individual is determined by
many only slightly correlated causes, such as the thickness of the
skull, height of various bones of the head, thickness of each
of the vertebrae, length of each of several bones in the leg, and
the like. Each of these causes is again determined by very many
imperfectly correlated causes. But such a trait as ' wealth pos-
sessed ' will not. For certain relatively very large causes are at
work, such as the discovery of a mine, or the death of rich rela-
tives; and there is a strong correlation between many of the
causes, for instance, between success in a business, directorship in
a bank, advanced knowledge of important actions, and power to
influence these actions.

" The form of distribution is then purely a secondary result of
a trait's causation. There is no typical form or true form. There
is nothing arbitrary or mysterious about variability which makes
the normal type of distribution a necessity, or any more rational
than any other sort or even any more to be expected on a priori
grounds. Nature does not abhor irregular distributions.

On a priori grounds, indeed, the probability curve distribution
would be exactly shown in any actual trait only by chance. For
only by chance would the necessary conditions as to causation be
fulfilled. And, in point of fact, as the reader has constantly been
told by the adjective ' approximate,' the exact probability curve
distribution does not appear in the facts or give signs of being
at the bottom of the facts of mental life. The common occurrence
of distributions approaching it is due, not to any wonderful tend-
ency of a group of cooperating causes to act so as to mimic the
combinations of mathematical quantities equal and equally prob-
able, but to the fact that many traits in human life are due to
certain constant causes plus many occasional causes largely un-
related, small in amount in comparison with the constant causes
and of the same order of magnitude among themselves." [Thorn-
dike, '04, p. 69 f.]

Distributions approximating it do occur very commonly in
mental traits of original nature. And one will probably never be
far misled by supposing that, in respect to the amount of original
endowments in any trait, individuals of the same sex, race and
age are distributed approximately according to the probability
surface. The evidence from measurements points toward such

i66

Educational Psychology

approximation. Moreover, what is known of the physical basis
of intellect and character leads to the expectation that many
somewhat nearly equal factors are at work to determine the
amount of any instinct or capacity possessed by men.

The meaning of some of the cases where the distribution of
mental traits does not approximate the chance distribution will
become clear if we examine, first, some cases of the distribution
of a trait in a group of individuals of two or more distinct degrees
of maturity or of training, and, second, cases where some selective

X ^

i-T_r-i

r£

46 47

Figs. 44-47. The effect upon the form of distribution due to combining
groups distinct in respect to age, training or some other cause affecting the
trait in question.

Fig. 44. The distribution of ability, in the A test, of children 8, 9, 14
and 15 years old.

Fig. 45. The distribution of abiHty, in the opposites test, of children
from grades 3 and 7.

Fig. 46. The distribution of ability, in muhiplication, of children from
grade 7 and high school.

Fig. 47. The distribution of ability, in the a-t test, of children 9 and IS
years old.

agency has been at work. Fig. 44 gives the distribution of ability
in the A test in a group of children 8, 9, 14 and 15 years old. Fig.
45 gives the distribution of ability in writing the opposites of

Individual Differences in Single Traits

167

te-

r^^-^

1 K

1 1

Figs 48-54. The effect upon the form of distribution due to the
selection of individuals in relation to causes affecting the amount of the
trait in question. The left end of the scale is for the lowest degree of the
trait in each case.

Fig. 48. The distribution of ability, in controlled association, of 12-year-
old boys in the 6A grade or higher.

Fig. 49. The distribution of ability, in controlled association, of 12-year-
old boys in the 6B grade or lower.

Fig. 50. The distribution of ability, in controlled association, of all
12-year-old boys in the school.

Fig. si. The distribution of ability, in mathematics, of candidates for
honors in mathematics at Cambridge University.

Fig. 52. The distribution of ability, in marking A's, of university teachers
and students.

Fig. 53. The distribution of ability, in memory, of university teachers
and students.

Fig. 54. The distribution of ability, in giving the opposites of words, of
inferior day-laborers.

i68 Educational Psychology

words in a group composed of about 140 girls in the third school
grade and about 180 girls in the seventh school grade. Fig. 46
gives the distribution of ability in multiplication in a group com-
posed of seventh grade pupils and high school pupils. Fig. 47
gives the distribution of ability in marking words, containing
each the two letters a and t, in a group comprising 9-year-olds and
15-year-olds. In general when the surface of frequency of a
mental trait departs from the probability curve toward a flatten-
ing and toward the appearance of two or more modes, one may
expect to find a mixture of sexes, races, ages or trainings.

Fig. 48 gives the distribution in a test of controlled association
of the 12-year-old boys in the 6A grade or higher. The lack of
symmetry in the surface is obviously due to the fact that we are
dealing with a selected group — that the duller and less mature
boys have been eliminated. The influence of the opposite sort of
elimination is seen in Fig. 49, which gives the distribution, in the
same trait, of 12-year-old boys in the grades lower than the 6A.
By combining the two we have Fig. 50, which approximates the
chance distribution. Fig. 51 gives a real case of a distribution dis-
torted by selection. It is the distribution of mathematical ability
in the candidates for honors in mathematics at Cambridge JJniver-
sity.* Of course such candidacy implies that the poorer grades
of mathematical ability are eliminated. Figs. 52 and 53 represent
the distribution of ability, in marking A's and in immediate memory
of lists of words respectively, in seventeen university teachers and
students, while Fig. 54 represents the distribution of ability in
the ' opposites ' test in the case of twenty day-laborers of inferior
sort. Any selective agency which works upon a species of indi-
viduals will alter the shape of the surface of frequency for any
mental trait, unless its selections are random with respect to dif-
ferent amounts of that trait. As the selective action is commonly
such as picks out the good or the bad, the result is commonly to
produce a ' skewness ' of the surface toward one extreme and a
blunted condition at the other. When a series of measurements
in a group of the same sex, age and training shows a deviation
from the probability surface toward conditions like those of Figs.
55 and 56, it is wise to ascertain whether some selective agency
has not been at work upon the group.

We have seen that the form of distribution of a single mental

*It is taken from Galton's Hereditary Genius, 26. ed. p. 16.

Individual Diiferences in Single Traits 169

trait is usually such that the individuals cluster around one cen-
tral tendency. We have seen also that, within a group of the
same sex, race and age, in original traits, the variations from
the central tendency occur in approximately the relative frequen-
cies described by the probability distribution. A deviation of any
degree plus is about as common as that of the same degree minus ;
or, more briefly, the distribution is approximately symmetrical.
The average, median and mode therefore nearly coincide. The
frequency decreases with the amount of deviation from the cen-
tral tendency, at first slowly, then rapidly and then slowly. The

Figs. 55 (above) and 56 (below).

average deviation from the central tendency is about 1.18 times
the median deviation. About 82 per cent of the individuals differ
from the C. T. by less than 2 times the median deviation ; about
96 per cent by less than 3 times the median deviation ; about 99/^
per cent by less than 4 times it.

The most important fact, however, is not the commonness of
this or that form of distribution, but the absolute law that the
form of distribution is a result of the nature of the factors at work
to produce the trait's amount. One large factor that is present
for some individuals and not for others will always act toward
the production of bimodality or distinct types. A multitude of
nearly equal factors from which each man's nature and training

170 Educational Psychology

is approximately a random selection will always act toward the
production of unimodality, symmetry, and slow-rapid-slow de-
crease in frequency around the central tendency. An interde-
pendence whereby the action of certain factors increasing the
amount of the trait is dependent upon the action of other factors
which of themselves bring the individual to a certain fairly high
station, will always act to disturb symmetry. For every peculiar-
ity in the causes determining a trait's amount in an individual
there will be an effect in the relative frequencies of the trait's
amounts in a group of individuals.

I should perhaps apologize to the reader for this long discus-
sion of a matter which may seem to be sufficiently obvious with-
out any discussion. I am glad if it does now seem obvious. The
excuse for the long discussion is that the usages of language have
persistently misled thinkers about human nature into supposing
that it was, in each trait, divided into sharply separated classes to
fit the adjectives and nouns by which primitive man roughly de-
noted different sections of a continuous scale, and that, on the
other hand, certain thinkers have carelessly extended the particu-
lar ' probability ' form of distribution to cases where it cannot
possibly fit the facts.

CHAPTER IX

The Relations Between the Amounts of Different Traits

IN THE Same Individual

One feels a bareness and paltriness in such piecemeal descrip-
tions of human beings and their differences one from another as
have been given in the last chapter. The actual varieties of hu-
man nature do not stand out when one trait at a time is measured.
Why, it may be asked, does psychology not take actual whole na-
tures and state how they differ? Why does psychology not de-
scribe human minds as zoology describes animal bodies, by classi-
fying them into families, genera and species, and by stating the
differences between the different sorts of minds found?

It is true that zoology does not measure all animals in length,
then in weight, then in color, then in number of organs, then in
number of bones, and so on through a list of particular traits. It
began with types or sorts apparent to common observation, such
as worms and fishes, and described their essential features and
the characteristic differences of one sort from another. And it is
true that psychology might try to do likewise. If there were types
or sorts of minds equally apparent to common observation, it
would surely be worth while to start a description of human na-
ture's varieties with them. But there are no sorts or types of
minds that stand out clearly as birds, fishes and worms do amongst
animal forms.* Psychology has first to find which the sorts or
types are.

There are two ways of discovering them. The first is by direct

*The men allied by common ancestry, men of the same race, would be
most likely to form a mental sort or type diflfering from other men, if not
as fishes differ from other animals, at least as much as salmon differ from
other fishes. But even between races there is no surety that such is the
case and no excuse for avoiding the slow and laborious comparison of
individuals from different races in one after another trait that seems
significant.

(171)

172 Educational Psychology

measurement of individuals in toto, and of their differences. To
measure the difference between one whole man and another
means to assign to each man his amount of each trait, and to
measure each difference. The difference between the two men
means just all those particular differences. To this method we
shall return in the next chapter, though it may be said at once
that no adequate total measurements exist of even a single indi-
vidual.

The second way of discovering the sorts or types into which
men as total natures are divided is by discovering what each
amount possessed of any one trait implies concerning the individ-
ual's condition in other traits.

A statement of the differences between one whole man and
another would be an almost interminable inventory of particular
differences, unless some traits were so related that knowledge of
the amount of one of them possessed by a man informed us of the
amount he possessed of the other also. Suppose, for instance, that
any given amount of error in judging one length with the eyes
always implied certain known amounts of error in judging all
lengths, whether by eye, by arm-movement or by pressure, all
weights, all colors, all pitches, all tastes, all smells, all bright-
nesses, all intensities of sound and all other sensory features of
objects. In such case, one measurement would inform us, once
for all, of a fairly large fraction of a man's nature and of his
differences from another man, similarly measured. The necessary
preliminary to the direct study of differences of total natures is
thus the study of the relations of single mental traits.

The Measurement of Relations between Mental Traits

It is necessary to be clear at the outset in respect to just what is
meant by the relation, or, as it is commonly called, the correlation,
between two mental traits. It means, of course, the relation of
some amount of one trait (A) to some amount of another trait
(B). It also means, for the present purpose, the relation between
an amount of A characteristic of a given individual to an amount
of B characteristic of that same individual. The amounts might
be the amount of A more than zero and the amount of B more
than zero; or they might be the amount of A more than, or less than,
some assigned amount and the amount of B more than, or less

Relations Between Mental Traits 173

than, some assigned amount. Let us call the first sort relations of
divergences from and the second part relations of divergences
from arbitrary standards, or arbitrary relations.

For example, suppose 5 eight-year-old girls, I, II, III, IV and V,
in tests of memory of German equivalents of English words, to
show the following abilities : —

Trait A Trait B

Median number of words Median number of words

remembered (after a given remembered (after a given

amount (K) of training) amount (K) of training)
' 2 minutes. at the end of 60 days.

3
5

In the first meaning, the relation of the divergence from zero
is, of course, expressed as |^, ^, yV, ^ and f , respectively
for these children. The central tendency of the relation is,
roughly, to remember half as much after two months as was
remembered after two minutes.

Suppose, now, that the relation sought is that between
divergence from the central tendency for eight-year-old girls in A
and divergence from the central tendency for eight-year-old girls in
B, and that this central tendency is 15 for A and 6 for B. The

w ^u +5+5+3-3 -I

relations are then -; — ^, - — 7, -; — , and

Individual

at the end of

II.

III.

IV.

4-8' +6' -hii' -4 -6*

Suppose that the relation sought is that between divergence from

the central tendency of all human beings in A and divergence from

the central tendency of all human beings in B, and that these central

tendencies are 24 for A and 10 for B. The relations are then

, — , — TT, and . It is clear that any relation

- I ' -3' -8' -13 -15 ^

varies according to the standards from which the related diverg-
ences are measured.

The relations to be considered in this chapter are arbitrary
relations. We shall always be concerned with the relation of an
individual's divergence from the central tendency of some defined
group in one trait to his divergence from the central tendency of
that same group in another trait.

174 Educational Psychology

The first fact to notice about such mental relations is that the
same relation varies greatly in different individuals. Such a case
as that of the last illustration, in which the relations were, for
five individuals, -i.oo, -.33, +.125, +.54, and +.33, is not at all
exceptional. The relations of traits differ in individuals as truly
as do the amounts of a trait. A single sample will suffice. Fig. 57
shows the relation of (A) divergence from the central tendency
of adult college women in drawing a line* to equal a 50 mm. line

-50 -30 -10 +10 +30 +60 +70 +170

-90 • , •

-70

-60 .

-80 ♦ .

-10

+ 10 . ,

+30 .: ' • .

+50

+^70 * ' .

Fig. 57. The relation between ability in equalling a 50 mm. line (average
of 30 trials) and ability in equalling a 100 mm. line (average of 30 trials),
in women students.

to (B) divergence from the central tendency of the same group
in drawing a line* to equal a lOO mm. line. Each dot represents
the relation in one individual by its location. Each dot is below
the point (on the scale for A) which is the individual's measure
in A and opposite the point (on the scale for B) which is the
individual's measure in B.

*Under certain specified conditions.

Relations Between Mental Traits 175

It is at once seen that superiority of an individual to the central
tendency of adult college women in A does in general imply
superiority to their central tendency in B, but that there is a
wide range in the relation in individual cases. If the relation had
been the same in all individuals, the dots would all be on one line,
since all the individuals under any one point of the horizontal
scale (that is, of the same ability in A) would all be opposite the
same point of the vertical scale.

Since the relation does vary with individuals, it is fully measured
or described only by such a list of all the individual relations as
Fig. 57 gives. But its main features can be summarized, for any
one degree of trait A, in two measures, one of the central tendency
of all these individual relations, and the other of their variability
around this central tendency.

Thus, suppose 10 individuals, all -8 in Trait A, to be, respec-
tively, - 12, - 7, - 5, - 5, - 4, - 4, - 2, - I, o and +6 in Trait

B. The median of the ratios 3^ , ^7^. ITe"' ^^^- i^ 3^' ^^

+ .5. The central tendency of the relation is for - 8A to imply - 4B.

The variability ranges from an implication of - 12 to one of + 6

The relation may also vary with different individuals according

to the amounts of A which they have. Thus, suppose that the

central tendency in the case of individuals all having +16A was

— 2
to the relation q^y^. The + .5 which restated the central tendency

of the relation for individuals of - 8A, is replaced by -.125.

Fig. 58 shows a case (hypothetical) of a relation varying much
with the amount of trait A, but with very little variation amongst
individuals of like ability in A.

Fig. 59 shows a case (also hypothetical) of a relation varying
little with the amount of trait A, but much amongst individuals
of like ability in trait A.

Fig. 60 shows a case (also hypothetical) of a relation varying
much in both respects.

In these figures the line formed by the points representing each
the central tendency of the relation in the case of one amount of A
may be called the relation line. In Figs. 58, 59 and 60, it is the
line formed by the large dots.

When a relation varies according to the amount of one of the
traits, — when, that is, the central tendency of the ratio A/^B

176

Educational Psychology

Amount of Tnit A -H >

«• » ■

• • •

• •.:•

• •

••• •• • •*

• ♦J

• . • -• i

Fig. 58. A relation varying much with different amounts of Trait A,
but varying little amongst individuals of like ability in A.

Amount ot Trait A -H >•

tad

Fig. 59. A relation varying little with different amounts of A, but much
amongst individuals of like ability in A.

is different for A=k, A=2k, A^3k, etc., — it may be called non-
rectilinear, because the relation line is curved or broken. When
a relation varies with individuals irrespective of their amounts of

Relations Between Mental Traits

177

Trait A, the central tendency of the A/B ratio being the same
for all values of A, it may be called rectilinear because the relation
line will be a straight line.

When only a few individuals are studied, so that the number at
any given point on the scale for A is not enough to give reliably
the central tendency of the relation at that point, the relation will

Amount of Trdit A

■>

V *

Fig. 60. A relation varying much in both respects.

Figs. 58-60. The variability of mental relations.
Trait A is scaled horizontally, the lowest degree being at the left.
Trait B is scaled vertically, the lowest degree being at the top.
Each dot represents the relation in one individual, the amount of A
possessed by the individual being that represented by the point on the
scale for A above the dot, and the amount of B possessed by the individual
being that represented by the point on the scale for B at the left of the dot.
The large dots represent, each by its position, the central tendencies
(medians) of those of each degree of ability in A.

appear non-rectilinear even though it may really be rectilinear.
For example, the relation between ability in the A test and ability
in the a-t test in 12-year-old boys (divergences from C. T.'s for
that age and sex being related) is really rectilinear or very nearly
so, but the relation line for any 100 boys will seem to be much
broken as in Fig. 61. Whatever be the real form of the relation
line, chance deviations from that form will appear unless the num-

178

Educational Psychology

ber of cases is infinitely large. But in reality sharply irregular
relations with zigzag relation lines, — such relations for instance as
.5for Arr=k, .7for A = k+l, .3for A = k+2, .5forA = k+3,
.4 for A = k + 4, .6 for A = k+5, .5 for A = k + 6, and so on
— probably do not exist between any mental traits.

Relationships with curvilinear relation lines deviating markedly
from straight lines, — such as that in Fig. 58 or those in Fig. 62, —
may exist, but no such relation has as yet been proved to exist.
It is therefore customary to treat relations between mental traits
as approximately rectilinear.

The relation of two traits in a given group of individuals being
expressed as the rectilinear relation which best fits them, their
relation can be compared with that of any other traits in the same
or any other group — provided one more simplification be made.

A-T
-6

-10 -8 -6 -4-2 0+2+4+6 +8 +10 +12 +14

Fig. 6i. The relation line in the case of the relation between ability in
marking A's (one trial of 6o seconds) and ability in marking words con-
taining both a and t (one trial of I20 seconds), in the case of girls of the
same school grade. (With more adequate tests the relation would be much
closer and the relation line somewhat straighter.)

This is that the divergences to be related be expressed each as a
fraction of the variability of the trait in question. For example,
suppose A, B, C and D to be series of divergences, in height,
weight, memory of words in a certain test, and ability in the A test,
from the condition of the modal twelve-year-old boy. Suppose
that the central tendencies of the ratios A/B, A/C and A/D
were respectively .5, .2 and .5. That would mean that a boy ten
centimeters above the central tendency would in the long run be
5 kilograms heavier, remember 2 words more, and mark 5 A's

Relations Between Mental Traits

179

more, than the modal twelve-year-old boy. This does not enable
one to tell whether A/B is really equal to the relation A/D,
though each is .5. Nor can one say with any useful meaning that
A/^B is two and one-half times as close a relation as A/C.

Fig. 62. Samples of curvilinear relation lines.

But if, instead of calculating the gross A/B, A/C and A/D
ratios (.5, .2 and .5), we calculate the values of these ratios after
every value of A is expressed as a multiple of the variability of
twelve-year-old boys in trait A, every value of B is expressed as

i8o Educational Psychology

a multiple of the variability of twelve-year-old boys in trait B and

so on, the ratios become commensurate.

Suppose the variabilities of twelve-year-old boys in the four

traits to be, respectively: — Var. A, 4.5 centimeters; var. B, 3.5

pounds ; var. C. 2.0 words ; var. D, 4.5 A's. Then the central

, , . A /var. A A/var. A , A/ var. A .„

tendencies of the ratios, =-—^ -, =r— ^ ^ and .pr =: , will

BXvar. B C/var. C D/ var. D

be .4, .09 and .5.* The .4, .09 and .5 will, in each case, mean the

same thing, if 'equal multiple of the variability' of any one trait

is regarded as always the same thing. They will mean, in each

case, the relation of (I.) an individual's divergence in one trait

measured as a multiple of the general tendency to diverge in that

trait, to (II.) his divergence in another trait, measured Hkewise

as a multiple of the general tendency to diverge in that trait.

It is with such a meaning that we compare the closeness of the
relation between, say, memory for numbers and memory for
words with the closeness of the relation between memory for the
same data over a short and over a long interval ; or compare either
of these with the relation between accuracy of discrimination of
length and accuracy of discrimination of weight.

If each divergence is expressed in terms of the variability of
its trait as a unit,we can think of an individual's condition in one
trait as resembling or differing from his condition in another
trait. The technique of measuring this resemblance between two
traits in one man is then the same as that m.ade familiar in Chap-
ter V in the case of the resemblance of two individuals in the
same trait. R, the coefficient of resemblance, then measures the
central tendency to resemblance or mutual implication found in
pairs of amounts or conditions in two traits, each pair being
characteristic of an individual. The amounts are divergences
from the central tendencies of some defined group. The relation
or resemblance or mutual implication is supposed to be constant
for all amounts of either trait. R is a figure so calculated from
the individual records as to give the one degree of relationship
between the two traits which will best account for all the sepa-
rate cases in the group. In other words it expresses the recti-
linear relation from which the actual cases might have arisen with

* A ^ var. A _ A var. B ^^ 3j „^ ^ Similarly for the .09

B -- var. B B ^ var. A ^ ^ 4.5 ^

and .5.

Relations Between Mental Traits i8i

least improbability. It has possible values from +1.00 through o
to — i.oo. 'R = +i.oo' means that the individual who is the
best in the group in one ability will be the best in the other, that
the worst man in the one will be the worst in the other, that if
the individuals are ranked in order of excellence in the second,
the two rankings will be identical, that anyone's divergence
in the one will be identical with his divergence in the other (both
being reduced to multiples of the variabilities of the abilities to
allow comparison). 'R = -i.oo' would, per contra, mean that
the best person in the one ability would be the worst in the
other, that any degree of superiority in the one would go with
an equal degree of inferiority in the other. ' R = + .62 ' would
mean that (the two series of divergences being reduced to mul-
tiples of the variabilities in question) any given divergence in the
one trait would imply, on the average, 62 hundredths as much di-
vergence in the other.

Samples of the Interrelations of Mental Traits

As samples of R's so calculated I give in Table 20 some of
those obtained by Burt ['09] in the case of 30 boys between 125^
and 13^ years of age in an Elementary School in Oxford, at-
tended by boys ' of the lower middle class ', whose parents paid
9d. a week tuition. The relations are all between divergences,
each from the central tendency of the group in the trait in ques-
tion. The traits were (in part) : —

Touch. — Delicacy of simultaneous discrimination of two points on the skin.

Weight. — Delicacy of discrimination of lifted weights.

Pitch. — Delicacy of discrimination of pitches (from 320 vibs.) .

Length. — Delicacy of discrimination of length; deviation from the
standard, 100 mm.

Tapping. — The number of holes made in 15 sec. in a sheet of paper over
cloth, a needle fastened in a holder being used.

Dealing. — The time required to deal 50 cards into 5 heaps in the ordinary
manner.

Sorting. — The time required to deal 50 cards into 5 heaps in accordance
with the color of the cards. An error was not corrected by
the boy, but was allowed for by an addition to his time- score.

1 82 Educational Psychology

Alphabet Sorting. — 52 cards, each 20 mm. square and printed with a letter,
each letter appearing twice in the series, were exposed in an
irregular order. The boy was required to find a, then to find
b, then c, etc., placing them in order in two rows. He then
repeated this selecting again. The time taken was the score.

Immediate Memory. — Of 90 words (30 concrete, 30 abstract, and 30 non-
sense) all of one syllable, each one seen and pronounced by
the boy, given in series of 4, 5, 6, 7, or 8. For method of
scoring see Burt, '09, p. 142.

TABLE 20.

Thb Interrelations op Nine Mental Traits in the Case of Thirty Boys

Each Entry Gives the Relation op the Trait Listed on the

Line to the Lept of the Entry to the Trait Listed

Above the Entry. Adapted from Burt ('09].

Decimal Points are Omitted.

4->

•a
•53

J3
PL.

a
a

1
P

a
<

Touch

Weight

—16

Pitch

— 01

—05

Length

—16

—05

Tapping

Dealing

Sorting

Alphabet

Memory

The figures of Table 20 show^ the traits measured by the tap-
ping, deahng and sorting tests to be so related that the amount
of any one possessed by a boy gives a fairly close prophecy of
the amounts that he w^ill possess of the others. The traits meas-
ured by the tests of discrimination of touches, weights, pitches
and lengths on the other hand are shown to be highly independent
one of another.

Mental relations have been measured by Wissler ['01], Spear-
man ['04a, '04b, '06], Thorndike ['03, '09], Pearson ['07],
Brown ['09], Burt ['09], Frost,* Simpson,* and others. The
results form a body of facts of great importance to psychology
and education, but a summary of them without elaborate discus-
sion of the methods used in each case, would be misleading. I

*In a study as yet unpublished.

Relations Between Mental Traits 183

shall, therefore, state only the general conclusions to which they
lead.

The Significance of the Relations Between the Amounts of
Different Traits in the Same Individual

The significance of the relations between mental traits which
have been measured in this way is seen most easily and clearly
by observing the doctrines about individual psychology which
they disprove.

First may be mentioned a series of beliefs in mental antago-
nisms or compensations. Such are : — that superiority to the cen-
tral tendency in vividness and fidelity of imagery of one sort
implies inferiority to the central tendency in vividness and fidelity
of imagery of other sorts; that superior ability to get impres-
sions through one sense is related to inferiority in getting im-
pressions through other senses ; that intensity of attention varies
amongst individuals in opposition to breadth of attention, so that
a high degree of power to attend to one thing at a time goes with
a low degree of power to attend to many things at once ; that the
quick learner is the poor rememberer ; that the man of great artis-
tic gifts, as in music, painting or literary creativeness, is weak
in scientific ability or matter-of-fact wisdom ; that divergence
above the mode in power of abstract thought goes with diver-
gence below the mode in thought about concrete things ; that
the man of superior intellect is likely to be of inferior mental
health ; that the rapid worker is inaccurate ; that an agile mind
goes with a clumsy body ; etc., etc.

Not all of these and other supposed antagonisms or inverse
relations have been specifically tested by the calculation of the
appropriate R's ; but those which have been so tested have been
found in gross error. Betts ['09] found the R's for any one sort
of non-verbal imagery with any other, in respect to vividness,
completeness and detail, to be not only positive but high. Peder-
sen's data ['05] show, though he apparently did not notice the
fact, a very close correlation between ability to grasp presenta-
tions through the eye and ability to grasp presentations through
the ear. Meumann ['07] somewhat grudgingly admits that his
contrast between " men with typically concentrative or intensive
attention " and " individuals with typically distributive atten-
tion" ['07, vol. I, p. 500], does not mean that the person who is

184 Educational Psychology

superior in the one is inferior in the other ; that, on the contrary,
he is more Hkely to be superior in the other also (" je grosser die
Konzentrationsfahigkeit eines Menschen, desto grosser seine
Distributionsfahigkeit " ['07, vol. I, p. 502 f.] ) The author
['08] has shown that the individuals who learn a thousand words,
as in a vocabulary, more quickly than the modal man, also, in a
majority of cases, remember more of them after 40 days. Cattell
['03] finds that eminence in artistic lines implies superiority in
politics or generalship or science more often than the reverse.
All relevant measurements witness to a positive correlation be-
tween efficiency in thought with abstract data and efficiency in
thought with concrete data ; also between the ability to work with
greater speed at a given accuracy, and the ability to work with
greater accuracy at a given speed. Indeed the individual who
works at higher speed often works more accurately at even that
higher rate than does the slower worker at his more favorable
rate.

The relations which do seem to be inverse are very instructive.
They are mostly cases of the relation of a desirable divergence
in one trait to an undesirable divergence in the other. Thus
general intellect seems to be antagonistic to sullenness. Intellectual
efficiency seems to be antagonistic to emotionality in the crude
sense.

It is very, very hard to find any case of a negative correlation
between desirable mental functions. Divergence toward what we
vaguely call better adaptation to the world in any respect seems
to be positively related to better adaptation in all or nearly all
respects. And this seems specially true of the relations between
original capacities.

The negative values in Burt's results, listed above, are probably
not exceptions to this rule, but are due to the chance variations
from truth which are to be expected from a small series of
measures. His -.16 for the relation of discrimination of length
to discrimination of weight, for instance, should be considered in
connection with the +.52 obtained by the author ['09] for the
same relation in the case of 37 young women, and the +.25
obtained in the case of 25 high school boys.

There may, however, be cases where some one large environ-
mental agency acts to bring all those individuals subject to it up in
one trait but down in another. The Roman Catholic Church

Relations Between Mental Traits 185

might thus, at least at certain periods of its history, make many
of its members more interested in theological argumentation, and
less interested in scientific verification, than the modal man. The
theory of asceticism might make all its adherents successful in
contemplation and inefficient in action. City life might so stimulate
adroitness in dealing with people and inhibit adroitness in dealing
with animals and plants, as to produce a negative relation.
Wherever some potent circumstances act to elevate one trait and
depress another in individuals subjected to them, whereas alterna-
tive circumstances act in the opposite direction, there is a chance
for individuals to show negative R's in the traits in question,
even though, in original nature, the traits are related positively.
Such negative relations might appear, if men were measured from
dififerent national cultures or over thousands of years so as to
include such contrasting environments, in cases where our present
measurements show even strong positive relations.

Little is known about the shares of original mental organization
and environmental influences in producing the relations of diver-
gence in one trait to divergence in others, and still less about the
special effect of what may be called irrational environments, those
which weaken or inhibit certain generally desirable mental traits.

Finally, there are the notable cases of apparent compensation
due to the special practice of one trait to make up for irremediable
weakness in some other. Keenness of touch in the blind, is, of
course, the clearest case. Of such cases it may be said that they are,
for the general relation, trifles, and are partly balanced by other
cases where special defect and special practice work to the opposite
eflfect upon the total relation. It should also be noted that in
original nature the rule is correlation, not compensation. Those
defective in vision are, by nature alone, more likely to be defective
in other senses than are those superior in vision.

On the whole, negative correlations between different 'efficiencies'
or ' adaptabilities ' or ' desirable traits ' are surely rare, seem almost
never to occur as a result of original mental nature, and require
as causes peculiar oppositions of influence upon the two traits from
the environment.

A second error in opinions about mental relations is in sharp
contrast to the one just described. It is the doctrine that some
one function is shared by all intellectual traits, and that whatever
resemblances or positive correlations the traits show are due to

i86 Educational Psychology

the presence in each of them of this function as a common factor.
In so far as they have it, they are identical. In so far as they
lack it, they are totally disparate. In the words of Spearman
['04 b, p. 84], who advocates such a view, "All branches of intellec-
tual activity have in common one fundamental function (or group
of functions) whereas the remaining or specific elements of the
activity seem in every case to be wholly different from that in
all the others."

This doctrine requires not only that all branches of intellectual
activity be positively correlated, which is substantially true, but
also that they be bound to each other in all cases by one common
factor, which is false. The latter would require that no two
intellectual abilities or branches of intellectual activity should be
more closely related to each other than to the fundamental func-
tion by which alone they are supposed to be related ; and, as a
corollary of this, that no four such abilities, A, B,C,andD, should
be more closely related in pairs, A to B, and C to D, than the
element common to A and B is related to the element common
to C and D. But unless one arbitrarily limits the meaning of ' all
branches of intellectual activity ' so as to exclude a majority of
those so far tested, one finds traits closely related to each other
but with, their common element only loosely related to the common
element of some other pair.

The next error may be roughly described as the supposition that
for any one operation that is the same in form, such as discrimina-
tion of differences, attention, observation, inference or the like,
the varieties produced by different data or content are perfectly
correlated.

It has been common in psychological and educational literature
to presuppose that the functions which we group under the same
name, e. g., attentiveness, somehow implied each other, that, for
instance, a high status in attentiveness to school work was closely
related to a high status in attentiveness to social duties, business
pursuits, mechanical appliances and all the other facts of the
individual's experience. Our rough and ready descriptive words,
such as accuracy, thoroughness, reasoning power and concentration,
have been used as if the quality must be present in approximately
equal amounts in all the different spheres of mental activity.
The notion of any special mental act, e. g., the discrimination of
100 millimeters from 104, has apparently been that some general

Relations Between Mental Traits 187

faculty or function, discrimination, was the main component, the
special circumstances of that particular act being very minor
accessories. Thus all the different acts in the case of discrimination
would be very closely related through the presence in them aU of
this same mental component.

On the contrary, measurements reveal a high degree of
independence of different mental functions even where to the
abstract psychological thinker they have seemed nearly identical.
There are no few elemental ' faculties ' or forms of mental activity
which work alike with any and every kind of content.

For instance, the correlation in adults between ( i ) memory for
figures and (2) memory for unrelated words (memory being
used to mean the power to keep a list in mind, after once hearing
it, long enough to write it down) is not over .8; the correlation in
pupils of the highest grammar grade between (i) quickness in
thinking of the opposites of words and of the letters preceding
given letters of the alphabet and (2) quickness in thinking of the
sums of figures is not over .7. Yet the first pair of tests would
commonly be used indiscriminately as tests of ' memory,' and the
second pair as tests of ' association.' upon the supposition that the
two members of each pair were practically identical traits. Even
so apparently trivial a difference as that between drawing a line
to equal a 100 mm. line and drawing a line to equal a 50 mm. line
causes a reduction from perfect correlation. The resemblance is,
for 37 young women students, only .yy.

A table of the known degrees of relationship would abundantly
confirm the statement that the mind must be regarded not as a
functional unit, nor even as a collection of a few general faculties
which work irrespective of particular material, but rather as a
multitude of functions each of which involves content as well as
form, and so is related closely to only a few of its fellows, to the
others with greater and greater degrees of remoteness.

The mental sciences should at once rid themselves of the con-
ception of the mind as a sort of machine, different parts of which
sense, perceive, discriminate, imagine, remember, conceive, asso-
ciate, reason about, desire, choose, form habits, attend to. Such
a conception was adapted to the uses of writers of books on gen-
eral method and arguments for formal discipline and barren de-
scriptive psychologies, but such a mind nowhere exists. There
is no one power of sense discrimination to be delicate or coarse.

i88 Educational Psychology

no capacity for uniform accuracy in judging the physical stimuli
of the outside world. There are only the connections between
sense-stimuli and our separate sensations and judgments thereof,
some resulting in delicate judgments of difference, some
resulting in coarse judgments. There is no one memory
to hold in a uniformly tight or loose grip all the experiences of the
past. There are only the particular connections between particu-
lar mental events and others, sometimes resulting in great surety
of revival, sometimes in little. And so on through the list. Good
reasoning power is but a general name for a host of particular
capacities and incapacities, the general average of which seems
to the namer to be above the general average in other individuals.
Modern psychology has sloughed off the faculty psychology in its
descriptions and analyses of mental life, but unfortunately reverts
customarily to it when dealing with dynamic or functional rela-
tionships.

But it is just in the questions of mental dynamics and of the
relationships of mental traits that we need to bear in mind the
singularity and relative independence of every mental process, the
thoroughgoing specialization of the mind. The mind is really
but the sum total of an individual's feelings and acts, of the con-
nections between outside events and his responses thereto, and of
the possibilities of having such feelings, acts and connections. It
is only for convenience that we call one man more learned than
another instead of giving concrete lists of the information pos-
sessed by each and striking averages from all the particulars ;
that we call one man more rational than another instead of com-
paring two series of rational performances. In any one field the
comparison may give a result widely different from the general
average. So also with inhibition, concentration, or any other of
the general names for forms of mental action.

It is easier to show that mental traits are not related in certain
ways than it is to show directly just how they are related. There
are three reasons for this. The first is that, until the work of
Spearman in 1904, it was not known that any relation, calculated
from other than complete measurements of the divergences to be
related, would be reduced from its true amount toward o. Wissler,
for example, found ['01] the relation between accuracy in
drawing a line to equal a 100 mm. line and accuracy in bisecting
it, to be only .38, because he had as measures of the two traits to

Relations Betzveen Mental Traits 189

be related only the results with a single line. If each individual
had been tested with hundreds of lines at different times so as
to get his real total abilities the result would have been an R of
.7 or .8. Since this fact of the ' attenuation ' of the R's obtained
from imperfect original data was not realized at all until 1904,
and is not realized by many students even now, the majority of
the R's that have been calculated are of doubtful meaning. For
only very rarely have the measurements of individuals in any
trait included many tests on many dates under many circum-
stances so as to give adequate measures. The true R's can only be
inferred from the obtained R's by a guess at the degree to which
the latter are attenuated. In the case just quoted the true R turns
out twice the obtained ; in other cases it turns out to be only a
trifle greater, depending of course on the chance deviations of
the original measures.

The second reason for our inability to give a clear, simple,
positive account of the relations of mental divergences is that the
divergences related have been measured in different groups and
from all sorts of different central tendencies. The result is that
many of the relations known are not directly comparable. For
example R for general scholarship with quality of handwriting is,
in children in the elementary school, being measured by their
divergences from the central tendencies of their age and sex,
about .3. R for general scholarship and desultory memory is,
certain educated adults being measured by their divergences from
the central tendencies of graduate students, also about .3. But
the two relations are really not equal.

The third reason is that the fact itself would, in any case, be
too complex for clear and simple positive description. The facts
which we do know prove that if we knew all the facts the inter-
relations of mental traits would be irreducible to any easy repre-
sentation. This is itself, however, an important fact about them.

Such a general positive description as can be given will be
best given in graphic form. Let the series of horizontal lines in
Fig 63 be each a scale for some mental trait ; let the right end
always represent superiority in the trait ; let the central tendency
of adult human beings be in each case at the point on the scale
where a vertical line down the center of the diagram would cut
the scale. The C. T.'s for all traits are then in a vertical line.
Let a constant distance always equal the variability of the trait.

igo Educational Psychology

Let any one individual be represented by a line joining all the
points denoting each his ability in one trait. Five individuals
are thus represented in Fig. 63, in ten traits. If now, instead of
ten horizontal scales for the traits, there were the thousands
necessary to inventory human faculty, and if, instead of five
cross-lines for five individuals, we had thousands representing a
fair sampling of all men, the picture would show a rough general
parallelism of the cross-lines corresponding to the general tend-
ency for efficiency in one trait to go with efficiency in others.
There would be very few cross-lines from the extreme left of

Fig. 63. Ten traits shown in their interrelations in the case of each
of five individuals. Three of the individuals are university teachers or
graduate students. The other two are inferior day-laborers.

one scale to the extreme right of the other. On the other hand
there would be few horizontal lines cut by the same man's cross-
lines at the same distances from the C. T. There would be many
cross-lines that departed from the general drift of the cross-lines
a little ; some that departed from it more ; and a few that departed
from it enormously.

The first impression would be of a general parallelism, i.e.,
perpendicularity, of the cross-lines disturbed at haphazard, some-
what as geological strata are distorted from their parallelisin in
a mountain region. If, however, one examined the relations, he
would find certain rough rules for prophesying others. Rela-
tions would in general be closer within the analytical or abstract-

Relations Betzveen Mental Traits 191

ing functions than between these and others. So also within the
purely mental associative functions like adding, completing words,
giving opposites, and naming objects, than between one of them and
one of the sensori-motor functions. The sensitivities would inter-
relate only loosely ; and any one of them would relate very loosely
to the associative or analytical functions, even when busied with
data from that sense. Sensitivity, association, and analysis would
justify their claims to the title of fundamental forms of mental
life, by showing closer intra- than inter-relations. The association
of sense impressions with movement, the association of percepts
and images as such with one another and with movement, and
the association of symbols or meaning-carriers such as percepts
and images of words, would be found to deserve recognition as
three ' levels ' of mental action for the same reason. Certain
functions quite diverse from the point of view of the fundamental
forms of mental life or the ' levels ' of the associative form would
be found to be related by reason of some instinctive tendency.
Different degrees of the instinctive interest in persons might thus
produce correlations between love of ceremonies, ability in sociol-
ogy and interest in literature. The variations in the love of mental
activity are one root of many of the correlations between all sorts
of efficiencies.

In more detail, the scale for any ability would be cut by a
cross-line at about the same point that this cross-line cut the scale
for the corresponding interest ; the scales for sensory and sensori-
motor powers would be cut by cross-lines in only a loose cor-
respondence with the scales for ideational controls ; a cross-Hne
would go far to the right or left as it passed from an ability to
analyze out intellectual elements to an ability to make a precise
movement. But the great majority of the details would be blurred
in the picture by our lack of knowledge.

Finally the circumstances of training would be seen to some-
times intensify and sometimes weaken original relations. Thus
the variations in the length of school training, by connecting a
long training in certain traits almost inevitably with a long train-
ing in certain other traits, make certain correlations more pro-
nounced. The world over, there is a close relation between knowl-
edge of Latin and knowledge of geometry, far beyond what nat-
ural interests would produce.

192 Educational Psychology

A case of the weakening of an original relation by training
might be furnished by ability in mathematics and ability in under-
standing human nature. The original relation is perhaps closer
than the actual relation in adults, the common forms of training
tending so often to develop one or the other.

Roughly the effect of the environment is to make closer the
relations due to content. A mother comes to observe, attend to,
and remember her children well ; the plumber ' develops all his
powers ', as the educational theorists were fond of saying, so far
as plumbing goes, and neglects them beyond that point ; the
classical student takes a high position in every formal operation
when Latin is the datum operated on.

Just what the original relations are will in the progress of re-
search be discovered. It is unlikely that the relations of original
capacities and instincts, including native interests, are so compli-
cated as the relations amongst adult achievements and abilities.
But present knowledge is insufficient to determine even the orig-
inal relations.

CHAPTER X

The Nature and Amount of Individual Differences in

Combinations of Traits : Types of Intellect

AND Character

Scientific studies of the natures of individual men in combina-
tions of traits by the direct method have been very few and
very inadequate in respect to both the number of individuals and
the number of traits studied. The measurements of mental rela-
tions described in the last chapter are the main means of improv-
ing upon common opinion concerning the varieties of human
nature in respect to total make-up, or to such large fractions of
it as are roughly denoted by temperament, mode of thought,
morals, mental health, manner of work, imagination, and the
like.

A Sample Problem: Individual Differences in Imagery

As a sample of the problems and their treatment we may take
the natures of individuals in respect to type of imagery, that is,
in respect to the combination of: — vividness of visual images,
fidelity of visual images, frequency of visual images, vividness
of auditory images, fidelity of auditory images, and so on, through
the list.

Early in the history of the scientific study of imagery it was
noted that certain individuals were able to recall in memory pres-
entations to one sense with a high degree of vividness and fidelity,
but lacked this power in the case of presentations to some other
sense. The existence of persons who, for instance, could get
before the mind's eye vividly and with full detail a mental photo-
graph, as it were, of a scene, but could not thus reproduce from
within a melody, an itching nose, or a blow, naturally gave rise
to the notion of the ' visualizing type.'

Such cases, of notable ability to get one sort of images and
notable inability to get other sorts, were then carelessly assumed
to be the rule. It was supposed that a high degree of vividness,

(193)
»3

194

Educational Psychology

fidelity and frequency in images from one sense tended to exclude
an equally high degree in images from other senses. People were
called visualizers, audiles, motiles, etc., with the meaning that
the visualizers had more vivid, faithful and frequent visual images
than other people and less vivid, faithful and frequent images
from other senses, and similarly for the audiles, or motiles. In
graphic form this view would give Fig. 64.

But the actual examination of individuals showed such ex-
clusiveness or predominance of one sort of imagery to be the
exception rather than the rule. To even superficial examination
it was evident that human natures did not fit into the scheme of
Fig. 64 at all well. Even those who believed unhesitatingly that
human natures must be distributed around fairly distinct types

V-

T —

Fig. 64. The interrelations of the degree of development of visual,
auditory, motor, and touch imagery according to the theory of pure types.
Imaginary horizontal lines at V, A, M and T are scales for the degree
of vividness, fidelity and frequency of visual, auditory, motor and touch
imagery respectively. The lowest degree is in each case at the left. 12
individuals are represented, each by a line crossing each of the scales at
the point representing the individual's ability.

in respect to imagery could not, try as they might, distribute in-
dividuals around these types. Meumann in fact admits that in
all his studies of children he never found one such pure type.
" How rare the pure types [of imagery] are amongst children
is witnessed by the fact that in our extensive investigations of
children at Zurich we have never found a perfectly pure type.
Also I know of no case in the entire literature of the subject in
which sure proof is given of the existence of a pure type in the
case of children." ['07, I, p. 494] So new intermediate types,
such as the auditory-motor, visual-motor, auditory-visual, or even
visual-auditory-motor-intellectual (!) [Segal, '08], were intro-

Individual Differences in Combinations of Traits 195

duced. There the matter remained until Betts ['09] actually
measured a sufficient number of individuals in respect to the
vividness and fidelity of non-verbal images from the different
sense-fields, so that the cross-lines of Fig. 64 could be located by
fact instead of by opinion.

The pillars of the doctrine were the separation of men into
types according to the predominance of images from one sense,
and the existence of inverse relations between the different
sense-spheres in respect to the extent and perfection of imagery.
Fact showed opinion to have been grossly in error as a result
of its assumption that distinct types of some sort there must be.
The contrary is true. Instead of distinct types, there is a con-
tinuous gradation. Instead of a few ' pure ' types or many
' mixed ' types, there is one type — mediocrity. Instead of antag-
onism between the development of imagery from one sense and
that from other senses there is a close correlation. Fig. 65 is a
fair sample of the facts found.

This case is instructive because the fate of many theories
concerning distinct types of human nature in combinations of
traits is likely to be the same as the fate of the doctrine of types
of imagery according to the sense involved, with inverse rela-
tions between the development of imagery from one sense-field
and that from other fields. In the case of temperament, for
example, we have the same history. Extreme cases are given
names and made into types. Verbal contrasts are supposed to
have real existence. Supplementary types are invented to help
out the discrepancies between the imagined types and the real
distribution of individuals. And it is highly probable that, when
actual measurements are made, mediocrity — a temperament
moderately sanguine, choleric, phlegmatic, and melancholy ; mod-
erately slow, quick, shallow, intense, narrow and broad ; moder-
ately slow-shallow, slow-intense-narrow ; moderately everything, —
will be found to be the one real type.

The Theory of Multiple Types and the Single Type Theory

The sample problem shows well two extreme views which may
be taken of the varieties of human natures, of the same sex, race
and degree of maturity, in respect to any combination of traits.
On the one hand is the theory of multiple types, a theory which
separates men more or less sharply into classes, and describes a

196

Educational Psychology

man by naming the class to which he belongs. On the other
hand is the theory of a single human type, a theory which joins
all men one to another in a continuity of variation and describes a

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Indkndual Differences in Combinations of Traits 197

man by stating the nature and amount of his divergences from
the single type.

By the theory of a single type, one make-up can be conceived
such that from it all individuals would differ less than they
would from any other one make-up, and such that, the greater
the divergences, the rarer they would be. By the theory of mul-
tiple types, no such single true central tendency would exist. By
the theory of multiple types, if a number, K, of ' typical ' natures
or make-ups are most favorably taken and if divergences of all
individuals are measured from, in each case, that nature which
the individual most resembles, the total sum of divergences is
enormously reduced below what it would be if they had been

Fig. 66. A graphic representation of the multiple-type theory in the case
of combinations of traits. The 11 horizontal dotted lines (drawn only at
the extremes) represent scales for 11 traits. Each cross-line represents,
by its location, the amounts of the 11 traits in one individual.

measured all from some one nature. By the theory of a single
type, this reduction in the sum of divergences due to measuring
each individual's divergence from any one of K natures, is much
less.

These two doctrines can be made clear by graphic illustrations.
Let the amount of each trait in the combination be scaled, as by
our custom, horizontally, the center always representing the mode.
Let the nature or make-up of each individual be represented by
the points where a cross-line denoting him cuts the scale lines.
The theory of multiple types then gives something like Fig. 66,

198

Educational Psychology

and that of one type something like Fig. 67. All the cross-lines
of Fig. 66 can be represented as minor divergences from five
typical cross-lines, far better than can all the cross-lines of Fig.
67. Those of Fig. 67 can be far better represented by one typical
cross-line than can those of Fig. 66.

A radically different scheme for graphic representation will
enable the reader to think of the meaning of the two theories for
a very large combination of traits, say total mental nature. Sup-
pose that each trait is scaled into 5 amounts, i, 2, 3, 4 and 5.
Suppose that there are 5 traits, a, b, c, d and e, concerned in the

Fig. 67. A graphic representation of the single-type theory in the case
of combinations of traits. The 11 horizontal lines represent scales for 11
traits. Each cross-line represents the amounts of the 11 traits in one
individual.

total complex. Suppose 3 to be the mode in each trait. Con-
sider every possible cross-line, every possible series of amounts
in the 5 traits that can be possessed by an individual (but without
fractionizing any scale farther than into fifths). There will be
3125 such series possible (5 to the 5th power). Now suppose
each of these 3125 series of amounts, — each of these 'natures,' —
to be represented by a spot of, say, .01 sq. in. on a surface.
Suppose further that the center spot of the map represents the
series 33333 (the traits being now and later always taken in
order a, b, c, d and e). Suppose that around this center spot
and adjoining it are placed all the spots or areas representing
those series diverging from the 33333 series by only one unit,
e-g- 23333, 43333. 32333. etc. Suppose that the next ring is

Individual Differences in Combinations of Traits 199

made up of the spots or areas representing those series diverging
from the modal series by two units, e.g. 22^2,2, 43433. 53333,
etc. Continue till, in the outermost ring, we have areas repre-
senting the series 55555, iiiii, 11555, 51 115, etc., which have
the greatest possible divergence from the modal series.

Now suppose that the relative frequencies with which these
series appear in men are represented each by the height of a
column erected with the appropriate area as base. Consider the
appearance of the resulting relief-map according to the two the-
ories. By the single type theory, it would be highest over some
one spot — in our illustration, over the center or 33333 spot.*
By the multiple type theory, it would have several maxima over
several spots. By the single type theory, the average height
would be less and less over each successively more distant con-
centric ring. The whole relief map would look like a mountain,
with, possibly, many radiating and cross ridges, casual valleys
and eminences, but with, always, a decreasing elevation, the
larger the radius of a circle drawn about the summit. By the
multiple type theory, the average elevation need bear no rela-
tion to the distance from the center spot ; the depressions would
be between the several peaks each representing a type. Tn pro-
portion as the types were held to be very sharply distinct and
widely separated, these intervalleys would be deep, even to the
original surface, and wide.

Extend now the process of construction of these models to
thousands of traits each scaled in fifty or a hundred amounts, and
one has the contrast of the multiple and single type theories applied
to men's total natures.

It is not necessary to try to decide between these two theories,
or to determine just what compromise is the true one. It is bet-
ter to accept frankly our ignorance of just how individuals do
differ in combinations of traits until they have been measured
in respect to all the traits involved.

But since, in general, writers about human nature openly or
tacitly assume the truth of the multiple type theory in a pro-
nounced form, and are governed by it in their methods of re-
search, of interpretation and of practical control, it will be useful

*This would be the case in the special form that the theory would almost
certainly take in the case of combinations of 5 traits, each unimodal, with
the mode at mediocrity.

200

Educational Psychology

to consider briefly some of the arguments in favor of the single
type theory.

The first is the fact that, in proportion as exact measurements
have been applied, evidence expected to favor the multiple type
theory has turned out in favor of the single type theory. It is
true that such cases are very rare, and that, until they are much
increased in number, little should be inferred from them. But
the fact remains that the single type theory arose from exact
measurements, while its opposite came from speculative pre-
possessions.

The second is the rarity of the inverse correlations between
desirable traits upon which so many of the supposed multiple

Fig. 68. A graphic representation of the condition of individuals in a
combination of two traits, if these are very antagonistic or inversely
correlated. The general scheme of the diagram is that used in Figs. 63 to 67.

Fig. 69. A graphic representation of the condition of individuals in a
combination of two traits, if these are closely and positively related.

types are based. We know that eye-minded and ear-minded,
quick and careful, broad and deep, sensorial and intellectual, men
of thought and men of action, and the like do not really repre-
sent human nature's varieties in the combinations referred to.
If two horizontal scales are drawn for ' ability to learn through
the eye ' and ' ability to learn through the ear,' and the cross-
lines are drawn for a thousand individuals, they will not go as
in Fig. 68 but as in Fig. 69. So also for scales for quantity of
work and quality of work, and so on through the list.

Individual Differences in Combinations of Traits 201

The third is the fact that the single traits involved are so often
distributed each approximately symmetrically around one mode
and that their intercorrelations are so often approximately recti-
linear. In so far as such is the case, no matter what the closeness
of the correlations may be, the distribution of the individuals in
respect to the combination of traits will be around one mode or
peak with less and less frequency the more they diverge from
that mode. The mode for the combination will be a nature
which is at the mode in all the single traits.

The fourth is the fact that investigators who are strongly in
favor of the multiple type theory and accustomed to interpret
facts in harmony with it, yet find so few actual cases of it.
Meumann for instance ['07, vol. I] clearly accepts the theory
in general and demands that educational practice should give
much attention to the classification of pupils under distinct types.
But in concrete particulars he rarely illustrates it.

He says ['07, vol. I, pp. 331-332] : " By establishing types we
orient ourselves in the endless possibilities of individual differ-
ences, and if we can place an individual under a type ....
in any respect we thereby have pointed out a group of universal
characters in his mental life, which he in general shares with
some individuals and by which he is in general distinguished
from others." But he does not establish such types. The majority
of the differences which he does report as ' typical ' are differences
between two extremes of the same trait. Intermediate conditions
are in some of these cases demonstrably, and in all cases probably,
more typical than the supposed types. And this, indeed, Meumann,
in some cases, admits.

Lastly, I may mention the fact that satisfactory proof of the
existence of a distribution of human individuals after the fashion
demanded by the multiple type theory has never been given in
a single case, and that the evidence offered by even the most
scientific of the theory's adherents is such as they would cer-
tainly themselves consider very weak if they were not already
certain that types of some sort there must be. Thus a fair-
minded perusal of Stern's Psychologie der Indizdduellen Differ-
enzen, designed to be a description of the types into which human
nature falls, is an almost sure means of stimulating a shrewd
student to the suspicion that intermediate conditions are more
frequent than the supposed types, and that there are far more

202 Educational Psychology

simply ordinary people than there are of all the ' types ' put
together. I report, to illustrate this point, the substance of all
that Stern says in favor of the multiple type theory in his five
chapters on Sensitivity, Perception, Memory, Association and
Apprehension ['oo, pp. 40-77].

On p. 43 f. he says, " We know the enormous gap which exists
between the unmusical and the musician in the discrimination of
pitch, between the perfumer and the ordinary person in the
recognition of odors, between the painter and the book-worm
in the delicacy of color perception." On the contrary,
between the keenest of the non-musical and the dullest of
musicians in the discrimination of pitch there is no enormous
gap, but an enormous overlapping (see Spearman, '04 b, pp. 90
and 92). Stern himself later points out that a little special prac-
tice bridges the ' enormous gap.'

Stern mentions (p. 46) " the types of the external observer
(the experimental scientist, possibly) and of the introspective
thinker (the mathematician or metaphysician, possibly)." But
these are not distinct, contrasting types. The experimental
scientist is far more likely to be a good mathematician than is the
ordinary man. Mathematical ability and interest are in no sense
confined to the metaphysicians. The good external observer may
be excellent at introspection, and the man with a strong interest
in his inner life of thought is much more likely than the average
man to have a strong interest in external facts.

Stern's next group of types are the 'Anschauungstypen.' In-
dividuals of the visual type, for instance, " imagine and dream
in the most vivid visual images ; they notice and retain colors,
forms, faces with especial ease ; they reproduce what is spoken
predominantly with the aid of images of the printed words ; in
fact they in general construct their world of ideas in great meas-
ure out of visual elements." The more such extreme develop-
ment of any one sense-sphere exists in a man, the more " the
others are restricted to their necessary, indispensable and irre-
placable functions." (p. 48) But here again the facts are in
opposition. Such cases as Stern describes are extreme and very
rare divergences from common mediocrity, not centers near which
most men are located.

Stern further divides men into a ' formal ' and a ' material ' or
* content ' type in their ' Anschauung ' or mental dealings with

Individual Differences in Combinations of Traits 203

concrete objects. The formal type gets the rhythm of a piece of
music easily, but the melody only with difficulty. The * content '
type gets the melody well, but the rhythm badly. "The former
type notices and retains above all the temporal grouping of the
sounds, whose qualitative nature and relations stay far in the
background. With the latter type, on the contrary, it is just the
material of the sensations, the succession of different pitches,
which is made the instrument of musical perception." (p. 55)
But no evidence is offered of this supposed inverse correlation,
and all that is known of the relation leads to the expectation that
it is positive, the individual best at getting rhythm being better
than the average at getting melody also.

Stern supposes these contrasting types to exist for spatial facts
also. Ability with position and outline denotes one type ; anility
with color, light and shade, another type (p. 57). But here
again the supposed inverse relation is really direct The supposed
types are two extreme and rare divergences from the real single
type, an individual who is mediocrely gifted with both the ' form '
and the ' material ', with both line and color.

In the case of memory. Stern reports, not multiple types, but
gradations from single types, with the single exception that he
quotes with modified approval, " Who learns easily, forgets eas-
ily also ; who learns with difficulty, retains better." This is, again,
contrary to the facts.

Under types of apprehension or apperception. Is given the
classification of individuals as describers, observers, emotional,
and scholarly, made by Binet ['97] on the basis of their written
descriptions of a single picture, and their classification as describ-
ers, observers, imaginative and poetic, and scholarly, made (also
by Binet) on the basis of written descriptions of a cigarette.
Stern points out that much more elaborate examinations of the
children are necessary. Leclere ['98] got, in a single experi-
ment, seven types, which, also, are not at all distinct. Of course,
many samples of each child's ' apprehensions ' or ' apperceptions '
of objects must be collected and classified independently by many
competent psychologists, and the exact rating of each person on
scales for scholarliness, imaginativeness, and so on must be given,
before one can tell whether the individuals are grouped around
one type or around several. The question is not whether Profes-

204 Educational Psychology

sor Binet can pick out certain papers that are distinctly different,
but whether the common judgment of experts will rank the indi-
viduals in classes that are distinctly different.

The above is all that is given as evidence for the multiple type
theory in the first 35 pages of Stern's inventory of types. The
balance of his discussion, devoted to Types of Attentiveness, of
Activity in Combining Facts, of Judgment, of Reaction, of Feel-
ing, of the Tempo of Mental Life and of Mental Work, would
give, if anything, less satisfactory evidence. The same lack would
be found in the writings of Kraepelin, Binet, Meumann and their
students.

In general the case is stronger for the single type theory in
combinations of original traits than in traits produced by train-
ing. One form of training — one environment — may possibly pro-
duce in every individual who is subjected to it certain large
increases in certain mental traits and certain large decreases in
others. All its subjects then tend thereby to differ much from
all other men, and to be much alike among themselves, that is, to
cluster around a type of their own. Such is not without reason
supposed to be the case with residence in a given nation, frontier
life, city versus country life, household industry versus factory
industry, slavery versus freedom, and the like. Just as, in any
one trait, the action of disproportionately large factors may cause
multimodality, so, in any combination of traits, the action of dis-
proportionately large factors may cause multitypality. And
doubtless there would appear many minor eminences upon our
relief-map of human nature due to the influence of ' nation lived
in,' ' language spoken,' ' occupation followed,' and the like. The
form of distribution of individuals in respect to combinations of
traits, as in respect to single traits, is a secondary result of the
nature and interrelations of the factors that produce the amounts
of the traits. There is no mysterious force of mental life herding
all individuals of the same sex, age and race around mediocrity.
Nor is there such a force separating them out into clusters
around distinct types. The former condition certainly occurs
in the case of many combinations of traits. The latter may very
well occur in the case of others. Knowledge of just what does
occur demands objective measurements of each of many individ-
uals in each of the traits in each of the combinations in question.

Individual Differences in Combinations of Traits 205

Individual Differences in the Average Amount of a
Combination of Traits

There are many combinations of traits which can be reduced to
single traits by abstraction from some of their particulars. Sup-
pose, for example, that A and B are measured in respect to
efificiency in marking A's, in marking words containing each the
two letters a and t, in marking hexagons on a sheet of various
simple geometrical forms, in marking grays of a certain intensity
on a sheet with 200 squares of grays of five intensities, and in
marking misspelled words on a sheet containing a passage with
100 out of 500 words misspelled. Suppose the results to be, in
terms of the variability for each trait : —

A B

Marking A's -i.i +1.0

a-t words -1.4 +7.

" hexagons -.6 +1.2

" grays .0 -.2

" misspelled words -1.7 +1.4

B-A equals 2.1, 2.1, 1.8, -.2 and 3.1 respectively.

If we abstract from the particular differences and ask only
concerning the condition of A and B, and their difference, in
average efficiency in marking these Hve sorts of visual objects,
the result is that A= -.96 (-4.8 divided by 5), B=+.82
(+4.1 divided by 5) and B- A= 1.78.

Such abstraction from certain particulars of each of a combi-
nation of traits can be, and is, in both ordinary and scientific
thinking, carried so far as to unite in a single trait very diverse
features of intellect and character. From the combination of all
the accuracies of discrimination with this and that length, color,
weight and the like, may be got the one trait, accuracy in sensory
discrimination. From the quickness of formation of each of a
thousand habits, is derived the single trait, rate of learning. Ac-
curacy, quickness, efficiency, permanence, amount of improve-
ment, rate of improvement, and acceleration or retardation in the
rate of improvement, are important cases of the measurement on
one scale of some feature of an individual's condition in a group
of traits. Originality, courage, timidity, suggestibility, scholar-
ship, judgment, interest and curiosity are samples from a long
list that could be made of terms, each used with comparatives to

2o6 Educational Psychology

denote, though very crudely, a man's position on a single scale.
This position or amount would, however, be the resultant of many
manifestations of what would have to be scored as a combination
of many traits, if represented in full, concrete detail.

For all such one-scale-representations of combinations of traits,
the entire theory of single traits given in Chapter VIII holds good.
In particular, the single type theory holds of them with fewer
exceptions. For some one large cause will much less often act
upon a man with the same effect in all the traits of a combination
than in some one of them. So, whereas, in discrimination of the
tastes of wines or teas or the like, men may be divided into an
ordinary and an expert class, they will not be, in respect to ac-
curacy of sensory discrimination in general. Similarly, though,
in knowledge of the Latin language, men may fall into two groups,
— an ignorant group and a group varying around some knowl-
edge,— in knowledge of languages in general, they do not.

CHAPTER XI
Extreme Individual Differences : Exceptional Children

From the discussion of the distribution of mental traits in
Chapter VIII it is evident that, unless peculiar causative or select-
ive agencies are at work, there will be a few individuals who will
possess so little of any given capacity or quality as to be obviously
' defectives ' in it, as well as a few who will possess so much
as to be obviously * prodigies.' There will be a larger number
who will possess so little as to merit the popular term ' weak '
in color vision, memory, self-control, moral sense, general intelli-
gence or whatever the trait may be. These, again, will be balanced
by an approximately equal number of ' remarkable ' or ' excep-
tionally gifted.'

If the mental trait in question is the compound of many traits
which we call intelligence, we shall find at the lower end of the
distribution curve children whom medical diagnosis would name
idiots, and next them a number who would be termed imbeciles,
and nearer still to the average the group to whom the name weak-
or feeble-minded would be applied. If the mental trait is the
compound called ' morality ', the individuals at the low extreme
will perhaps be diagnosed as cases of ' moral insanity ' or as
' moral degenerates.' If the trait be more specific, for instance
if it be ability to learn to spell, ability to learn to read, cruelty,
musical ability, memory, visualizing power or what not, we shall
find few, if any, special names for different degrees of its posses-
sion, though there will as truly be defectives in respect to any
such specific mental trait as in respect to general intelligence.

The means which educational endeavor will use and the re-
sults which may be expected therefrom will, in the case of any in-
dividual, depend upon his amount of the trait in question. No
one, unless he were himself an ' idiot ' in the trait of common
sense, would train a genius and an idiot alike or expect them to
develop alike. At present there is a widespread practice of

(207)

2o8 Educational Psychology

providing separate treatment at home or in institutions for idiots
and imbeciles, though some are to be found in the common
schools. And there is a growing demand for institutions and
separate classes for the feeble-minded. Notable moral defectives
are being cared for in separate classes in some cities. They also,
when the parents are wealthy, find refuge in private schools of a
certain type and in the somewhat mercenary ministrations of
private tutors. The children exceptional in their great superiority
to the average are not systematically given any special attention
except here and there by systems of rapid promotion.

For the proper treatment of exceptional children we need
knowledge of the exact distribution of all the mental traits which
we desire to develop or abolish, of the causes which determine
an individual's station in each, of the symptoms by which we may
conveniently find out any one's station in each, and of the agencies,
educational, hygienic and medicinal, which alleviate or in-
tensify the different conditions. The last involves the study of
the differential action of stimuli upon individuals of different
stations. For instance, the training of idiots should rest upon : —

1. A consideration of the distribution of intelligence which
will tell us what the frequencies of different degrees of low mental
capacity are.

2. A study of the extent to which original nature decides an
individual's station in intelligence, and of the displacements of
individuals from their original station to a lower station by acci-
dent, disease, unwise training, and the like.

3. A study of the physical and mental symptoms which enable
us to measure a person as very, very low in intelligence.

4. A study of the influences of climate, food, operative sur-
gery, medicines, manual work, school work, good and bad ex-
ample, etc., which make the mental condition better or worse.

In the case of idiocy, imbecility and pronounced feebleness
of mind, psychology, mental pathology and medicine could show
a respectable array of facts for the student, though precise quan-
titative studies fit to serve as models for study are very rare. We
know, at least roughly, the frequency of intellects so defective as
to disturb the home, resist school influence and excite popular
pity or derision (about i in 500). We know that, in all prob-
ability, by original nature human beings are distributed approxi-
mately according to the ' probability ' distribution, with some

Extreme Individual Differences 209

elimination at the low end, and that selection from the germs
produced by one's ancestry decides one's position ; that the ordi-
nary circumstances of life in which people differ do not much
alter one's position compared with his fellows, but that many
special influences, e.g., brain injuries, hydrocephalus, cretinism,
scarlet fever, and the like, may displace a person to a lower sta-
tion. Some of these influences probably act indifferently upon
individuals of all original stations, so that, so far as concerns
them, idiocy may be caused in one of the most intelligent ancestry.
On the other hand, many of them produce idiocy only upon the
fertile soil of originally weak mental structure. As regards
symptoms, we are not so well off as we may hope to be in the
future. Idiocy can not be recognized as early in life as it should
be. Nor can it always be distinguished from mere backward-
ness ; nor can its different degrees be measured with convenience
or with precision. As regards treatment for amelioration, we
have a great amount of information, though not all of the best
quality.

But if we look for similar information concerning other men-
tal defects we are doomed to disappointment. And exceptional
children at the high end of the distribution curve have been so
little studied that the very words, exceptional and abnormal, are
commonly used to refer only to those exceptionally defective. A
systematic treatment of the whole subject is thus out of the ques-
tion and we must be content with (i) a series of rather discon-
nected and ill-proportioned comments representing the present
state of knowledge and opinion on matters which concern edu-
cational theory and practice and (2) an outline which will sug-
gest what we ought to know but do not.

Exceptional Supe:riority

It is a corollary from the facts of the last three chapters that
exceptional superiority exists in the case of any mental trait or
combination of traits, and that the greater the degree of superior-
ity, the more exceptional it is. Some of the obvious and practi-
cally important cases are: — total intelligence, mental balance,
efficiency or capability, energy, quickness of mental processes,
breadth of mental processes, strength or intensity of mental pro-
cesses, abstract power, permanence of memories, mathematical

210 Educational Psychology

ability, musical ability, ability in drawing or painting, mechanical
insight, steadiness, courage, sociability, affection and enthusiasm.
The list might of course be indefinitely prolonged.

The cause of exceptional superiority is original nature plus
or minus a displacement, commonly slight, due to environmental
influence. The environment may displace a person downward to
a great extent, but upward much less easily. The forceps of
the physician, the strain of disease, the shock of brain concussion,
may reduce original superiority to pronounced defect ; but medi-
cine, favorable training and the impetus of zeal seldom elevate
a mediocre person to top rank. In the case of the combination of
gifts which we call intelligence they never do ; for it is only by
the concentration of much energy in a narrow line that an orig-
inally inferior person becomes superior. For him to do so in
all lines is impossible.

The symptoms of superiority in any trait are clear when the
trait itself can be directly measured. It is easy to tell an excep-
tionally good speller in school, or scientist in adult years, or sol-
dier in war, or orator in the pulpit. But when we have to infer
the future from present and past symptoms in young children,
or judge a general trait from a few particular manifestations,
our inferences lack surety and precision. Superior efficiency in
life's work, for instance, is not at all clearly shown by superiority
in school tasks ; success in formal grammar is not clearly symp-
tomatic of general abstract ability ; the best boy in a thousand in
discriminating length may not turn out much, if at all, above
the average in general keenness of sense discrimination. When
the relationships of a great many mental traits have been worked
out in the way shown in Chapter IX, any one measurement will
serve as a symptom to an extent now impossible. At present
a wise rule is never to infer from a symptom any condition
which moderate effort will enable you to measure directly, and
never to infer future conditions from present symptoms with-
out continuing observations into the future and modifying your
inference as they direct.

The development in individuals of a trait in which they are
exceptionally superior would undoubtedly be aided by training
different from that of those who approach the modal condition,
but experimental studies must be made before any safe decision
can be reached as to what sort that training should be.

Extreme Individual DilTerences 211

Exceptional Inferiority

The distribution of mental traits at the low end has not been
determined ; for the children accessible to the scientist in schools
probably do not include all of the children defective in any im-
portant particular. Most of those who are very deficient in
general intelligence are sure to be secluded at home or in institu-
tions. Some of the moral defectives will be in reform schools,
or will be habitual truants or the companions of thieves and
tramps, or will be in the care of private schools or tutors. To a
less extent those very deficient in memory or abstract power or
nervous control will tend to disappear for a longer or shorter
time from the schools. It is probable that the distribution in many
cases would deviate somewhat from the normal, taking a form
like Fig. 30 (p. 153). The increase of defectives over the prob-
able frequency would be due to the action of environmental
forces which may lower a person from almost any station but do
not raise him far. For instance, there seem to be many more
people totally blind than just able to see, the passage from good
eyesight to blindness being more frequent than the opposite.

Exceptional inferiority characterizes some members of the
human species in almost every mental trait or combination of
traits. The list given on page 2ogi. is appropriate here. Atten-
tion may also be called to defects of the senses ; defects of atten-
tion; defects of nervous action, e.g., chorea; to the cases where
a very great amount of a trait is a defect, e.g., cruelty or the
instinct to possess oneself of what one desires ; the minor automa-
tisms, such as biting the nails or counting groups of objects ;
morbid or useless impulses, such as touching every tree one
passes ; and fetichisms, e.g., great afifection for a red rag.

The causes of exceptional defects are the same as of excep-
tional superiority, but, as has just been said, environmental causes
play here a more important role. Their action has been carefully
studied only in the case of defects of sight, hearing and general in-
telligence, nervousness, choreic disturbance, and the psychological
defects with which medical practice deals. To the medical liter-
ature on these topics the reader is referred with the warning that
precise quantitative statements will, unfortunately, rarely be given.

What was said about symptoms in the case of exceptional su-
periorities may be applied equally here. In the case of general

212 Educational Psychology

lack of intelligence there will be some special facts to be noted.
Such additional iiiformation is also at hand in the case of those
other defects which have received the attention of medical science.
The reader is referred to text-books on sense defects, on children's
diseases and on idiocy and imbecility.

We know almost nothing about the remedial action of special
forms of training upon those mental defects which medical prac-
tice has disregarded. Leaving to one side such means as should
be prescribed and administered by a physician, we may make
the following recommendations : —

For nervousness : outdoor life, much absolute rest, free-
dom from competitive work and the exciting features of school
and social life, but not from participation in both physical and
mental work.

: For hysteria : outdoor life, removal from the home environ-
ment, calm but insistent training in good habits, the example of a
well-balanced, unemotional teacher, objective interests in nature,
industry and human affairs, freedom from the exciting features of
school and social life.

For general intellectual weakness : removal to a special insti-
tution, a stimulating physical and mental environment (though
not for the few cases complicated with great nervous irritability),
stirring physical play, outdoor life, systematic stimulation of
the senses and of curiosity, the arousal and direction of bodily
movements, systematic physical training.

The teacher or the consulting psychologist needs the cooperation
of the physician in almost all cases of mental defect. Their causes,
symptoms and relief are all connected with physical changes.
These are sometimes apparent to the ordinary practitioner, as in
defective school work due to indigestion or nasal or throat obstruc-
tions ; sometimes apparent to the specialist, as in defective ability to
read and spell due to retinal defects ; sometimes unrecognizable,
but yet doubtless existing, as in defective ability to form general
and abstract notions.

General Intellectual Defect

The psychology of those deficient in general intellect (idiots,
imbeciles and the feeble-minded) has been discussed at some
length by many students. The chief questions concern classification,
causation, symptoms and treatment. The aim of this section will

Extreme Individual Differences 213

not be to review the facts and opinions that have been stated, but
simply to help the reader to study the literature of the subject
intelligently.

English writers agree in using the terms idiots, imbeciles and
feeble-minded to refer in order to the three lowest conditions of
intellect. This common use makes the terms very convenient,
but it is certain from our knowledge of the distribution of mental
traits that any effort to separate sharply idiocy from imbecility,
and the latter from feebleness of mind, must fail. The words are
but names used roughly for sections of a continuous surface of
frequency. The obvious thing to do is to arrange a scale for
intellect and describe that of each individual by his precise station
on that scale, not by a vague name.

Numerous more detailed classifications have been proposed, some
on the basis of mental traits, e.g., the degree of capability in
attention, the capacity for feeling relationships, the efficiency of
the senses and motor apparatus ; some on the basis of the conditions
accompanying them, e.g., a classification into paralytic idiocy,
epileptic idiocy, syphilitic idiocy, etc. ; some on the basis of causa-
tion, e.g., a classification into congenital and acquired.

The fact is that the varieties of human nature referred to by
the words idiot, imbecile and feeble-minded, are numerous, that all
sorts of combinations of mental qualities, accompanying diseases,
causes and physical stigmata occur, and that no simple classifica-
tion can be adequate for all purposes. To grade idiots before
courts of law or for treatment in an asylum, a classification by
mental ability as measured by attentiveness or some other mental
traits may be best ; to provide for medical treatment their separa-
tion into groups according to concomitant diseased conditions may
be wise ; for medical science the pathological changes in the brain
correlated with the mental conditions may be the key to the useful
classification ; and so on through possible classifications for
prophecy of amelioration, for educational treatment, and for
psychological analysis.

I suggest as one of the most fundamental and useful classifica-
tions a division into : — ( i ) Those whose condition is due to original
nature, who hold the position in the scale of intelligence which
the make-up of their germs decreed, and (2) those who by accident
or disease have been displaced downward from their original
positions in the distribution scheme. The condition of members

214 Educational Psychology

of the first class should, as knowledge advances, be capable of
early diagnosis ; they should possess many characteristics in com-
mon and allow of further subclassification ; medical treatment
would be relatively inefficient, but from wise educational and
hygienic control we should expect much. The second class would
present fewer characteristics in common ; strictly medical or
surgical treatment would be of more importance than educational
training ; they should be studied in connection with mental diseases
in general. Roughly it would be fair to say that for the first class
we need psychologists and special schools, while for the second
we need physicians and hospitals.

It seems desirable further to separate children who are feeble-
minded, and are destined to remain so, from those who are simply
backward in mental growth and may eventually reach a fair
station. We know that in physical growth some children who
from six to twelve or thereabouts are far below average stature
for their age, in later years make up part or all of the deficiency,
and there are many reasons for believing the same to be the case
with mental growth. The essentially dull should never be con-
fused in theory or in actual treatment with those temporarily
deficient.

To the discussions of the causation of idiocy, imbecility and
feebleness of mind in the standard texts I have nothing to add
save that where so complex and so interrelated causes are studied,
great help will come from more precise measurements of amount
and from estimating the efficiency of partial causes by the coeffi-
cients of correlation between them and their supposed effects.

In the case of the symptoms of these conditions also, precise
measurements with objective tests would permit an advance in
knowledge which is impossible so long as cases are studied by an
undefined general examination and described by the loosest of
adjectives.

Amongst the recommendations for educational treatment those
which are in accord with the following facts should be given
especial weight : ( i ) Learning by the unconscious selection of
reactions which produce pleasure and the elimination of reactions
which produce pain, is widespread throughout the animal
kingdom and may be depended upon when learning from explana-
tion, insight and general principles is impossible. (2) The lower
the mental capacity of an individual, the closer in time must the

Extreme Individual Differences 215

pain or pleasure follow the reaction. (3) The connections between
impressions and obvious movements of the body are more easily
formed than between impressions and ideas or the more subtle
movements of the muscles of the face, throat and trunk which
perhaps always parallel ideas. The first type of connections may
be formed in individuals incapable of the second. The so-called
kindergarten and manual-training methods are therefore particu-
larly suited to defectives. (4) Mental defect often involves a
sluggishness of action on the part of the nervous system which
makes a rapid succession of stimuli interfere with each other and
result in mental confusion, and necessitates the continuation of the
same stimulus over a long interval or its repetition. (5) The
extreme narrowness of the field of attention and the inability to
control sudden alternations of attention from one topic to another
and back make it necessary for the teacher to take up but one small
issue at a time, to progress along one single line. (6) Knowledge
of relations, including appreciation of general and abstract
notions and the symbols for them, is practically beyond the
capacity of these inferior minds. It is therefore wisdom not to
pretend to give it and economy not to try. They need sense
training, object-lessons and concrete work throughout. (7) Sug-
gestion is potent here as elsewhere. By treating the feeble-minded
like normal children as far as is possible we help to make them
more normal. They should have their school, church, entertain-
ments, trades, excursions and the like. They should not be made
to appear peculiar in dress or encouraged in eccentric habits.

Exact Measurements of General Intellectual Defect

Measurements of various mental traits in intellectually deficient
children and adults have been made by Galton and Jacobs ['87],
Johnson ['95], Wylie ['00], Kelly ['03], Lobsien ['03], Kuhl-
mann ['04], Norsworthy ['06], Binet and Simon ['09], and
others. The main purpose of these measurements has been to
describe the defect more exactly and to analyze it into its factors.
Norsworthy attempted also to measure the effect of a year's
growth and institutional training.

Whatever intellectual function is tested, its efficiency is found
less than in the average man. The idiots, imbeciles and feeble-
minded are inferior in sense-discrimination, memory, the rapidity
and accuracy of sensori-motor habits, quickness of association,

2i6 Educational Psychology

span of attention and other traits. This was to be expected. But
they are not equally inferior in all functions. And it is the main
service of psychological tests to measure their relative inferiority
in different traits and so verify, refute or modify existing notions
as to the factors involved in idiocy, imbecility and feebleness of
mind.

The question of whether a child is more inferior in one trait,
say, memory of a list of simple words, than in another, say, ability
to select from ten dominoes the one like a sample shown, is some-
what subtle and cannot be answered by simply measuring his
abilities in the two cases. Suppose that, of ten words spoken once,
he remembers 5, and that in selecting a domino (the ten with the
fewest spots being used) he takes nine seconds, making no errors.
From these records alone we do not know whether he is inferior.
But even if it is known that the average person of his sex and
age remembers 7 such words in such a case and matches the
domino in 5 seconds, the question of the defective child's relative
inferiority in the two traits is still unanswered. Two words less
than seven and four seconds more than five are not commensurate.

They may be made commensurate by expressing each as a
multiple of the variability of men in general for the trait in ques-
tion. Thus if the median deviation of men in general from the
average of 7 words remembered is 1.2 words, the defective's
mferiority in memory is i§ times the median deviation in memory.
If the median deviation of men in general from the average
(5 seconds) in matching the domino is i second, the defective's
inferiority in matching dominoes is 4 times the median deviation.
In so far as the variability of men in general may be taken as the
standard by which inferiority is to be measured, he is 4/1.67,
or 2.4, times as inferior in the matching test as he is in memory.

Now the variability of men in general, though far from equal
in all traits, is a very useful standard for the present purpose.
The ratio of the defective's deviation from the central tendency of
his age and sex to that found in general is just what one needs
to know. ' Worse than all save 10 per cent in weight,' ' worse
than all save 10 per cent in height,' ' worse than all save 10 per cent
in memory,' ' worse than all save 10 per cent in attentiveness ' —
may very usefully be treated as ' equally inferior in weight, height,
memory and attentiveness.' If a defective is in height as far below
the central tendency as the 25 percentile (the median of all those

Extreme Individual Differences

217

men who are below the central tendency), in weight twice as far
below, in memory three times as far below, and in attentiveness five
times as far below, he may usefully be said to be five times as
inferior in attentiveness as in height, one and a half times as
inferior in memory as in weight, and so on.

Thus in Table 21 (arranged from data given by Norsworthy
['06, pp. 54-67]) the measures are all in terms of the median
deviation of the age and sex in question for the trait in question.
Each row gives the measures in the case of one individual. Each
column gives the measures in one trait. Each entry reads :
'Individual .... is .... times as far below* the central tendency
of American children in general of his age and sex as is the 25th
child from the bottom out of 100 children.'

TABLE 21.

Samples op Measurements op the Feeblb-Minded, Made Commensurate
One with Another by Being Transpormed Each into Multiples
OP THE Median Deviation op the Trait in Question
por the Age and Sex in Question.

Marking
A's and

Discrim- words Mem- Mem- Controlled association,

ination contain- ory of ory of

of ing a lists of sen- Part Genus Opposites.

weight, and t. words, tences. whole, species. I. II.

A. — .11 —1.94 —6.73 —3-42 X X X X

B. — 2.51 — 2.93 — 4.17 — 350 — 11.00 — 6.60 — 5.00 — 8.40
Q. X X X -5-00 X X X —3-82
D. —3-54 — 133 —2-49 —5-41 X —1300 —4.80 —6.00
E —4.01 —2.73 —8.57—13.00 —5.65 —8.75

F X X X X X X

G. — 1. 71 — 3.69 — 4. II — 3.33 — 10.00 — 16.60 — 5.65 — 8.15

H. +1.11 —409 —5.36 -3-39 t X —4-87

I. —6.54 —4.42 —5-98 —3-75 X X X

J —2.23 —5-30 X X t X

A group of defectives thus rated in commensurate units may
then be easily compared, with respect to their inferiority in diflPer-
ent traits, by a modification of the method used for comparing the
sexes and races. The modification necessary is to use in place of
'per cent of defectives equalling or exceeding the median ability

*Except for individual H in discrimination of weight.

JSignifies that the individual failed entirely in the test in question.

2i8 Educational Psychology

of people in general of that age and sex ' the ' per cent equalling or
exceeding some lower degree of ability ' of people in general, such
as the 25 percentile (or median of the half below the central
tendency) or the 12^ percentile (median of the lowest quarter of
people in general of the given age and sex. For instance, if: —
In height 61 per cent of defectives are above the 25 percentile,
In discrimination of weight 28 per cent of defectives are above the

25 percentile.
In memory of sentences 10 per cent of defectives are above the

25 percentile,
In giving opposites of words i per cent of defectives are above the

25 percentile,
it is clear that the inferiority is greater in giving opposites than
in memory of sentences, and so on.

Of the investigators of the psychology of the intellectually
deficient Norsworthy is the only one who has put the results in
such a form as to measure relative inferiority. Of the others some
have not even measured the variability of the defectives or of
people in general in the trait in question, so that only a very rough
estimate of relative inferiority can be got from their figures.

From the best estimates that I am able to make, the order of
inferiority of intellectual traits* in defectives confined in institu-
tions seems to be : — Sensitivity, in which, on the whole, 25 per cent
are above -i P. E. Speed and precision of sensori-motor connec-
tions, in which on the whole 20 per cent are above -i P. E. Speed
and precision of connections between idea and idea or between idea
and act, in which, on the whole, i to 10 per cent are above -i P. E.
Speed and precision of selective associations or of responses to
parts or elements of situations, in which, on the whole, o per cent
reach -i P. E.

The experimental data do not give a very clear picture and
universally true analysis of the condition which relegates
individuals to the class idiots, imbeciles and feeble-minded. But
they do show that such a clear picture and uniformly true
analysis is not to be expected, and that individuals thus classified
vary greatly among themselves in the nature of their defects. They
also show negatively that no single defect is an adequate explana-
tion of their condition. Seguin's notion that weakness in sensitiv-
ity and responsiveness is the cause of idiocy was certainly far from

*In height and weight about 60 per cent are above -i P. E.

Extreme Individual DiiTerences 219

true. On the contrary, power of connection is relatively much
weaker than power of reception or of action. Sollier's notion that
instability of thought, — lack of power to control attention, — is the
cause is also certainly wrong; for it leaves unexplained the
enormous slowness in their mental operations, including responses
to situations like the sight of food or the thought of candy, to
which attention is easily given. It also leaves unexplained their
relatively greater inferiority in all connections involving ideas than
in mere sensori-motor connections, like sorting colored beads or
marking a familiar letter.

If one is to hazard a description of a group which varies
enormously within itself, he may say of these exceptionally unin-
tellectual children : They are weak in the number, delicacy,
complexity, speed of formation, and permanence of associations of
whatever sort ; especially so when one or both of the members to
be connected is an idea. They are weaker in the analysis or
abstraction of elements out of gross total situations, and the deter-
mination of thought by the action of a part or element or aspect
of a situation. They are as a result weakest in those functions
which require the cooperation of many selected associations and
the partial activity of many relics of past experiences in the service
of some complex and ideal situation or problem. They are also
usually very weak in the instinct of mental activity, in the
satisfaction with mental life for its own sake. They represent the
extremes of the condition found in stupid people generally, the
opposite of the gifted person who connects rapidly, precisely and
permanently, analyzes facts into their elements easily and often,
thinks facts together, is guided by remote and ideal ends, and
enjoys thinking for its own sake.

They are inferior in sensitivity, but their appearance of being
very much so is due in part to their willingness to live in mental
torpor, their failure to connect the sense impressions with any-
thing further, and their more frequent failure to analyze out color,
size, shape, and the like from the gross total situations whose
partial aspects they are. They are inferior in movement, but
their appearance of very great inferiority in it is due in part to
their failure to connect movements with percepts and ideas or to
analyze out and get control over portions of movement-series and
recombine them anew. They are very inferior in attentiveness
from the point of view of one to whom attentiveness means power

220 Educational Psychology

of attention to elements rather than to gross totals, intellectually
fruitful things rather than the natural objects of the instincts
connected with food, fears, sex, and the like, or past and future
situations rather than present situations. But the words ' lack of
power of attention ' do not properly explain but only name this
fact. The facts given above are again the real explanation.

To this characterization there are numerous exceptions.
Sensory or motor defects (especially speech), if not overcome by
proper education, may simulate general intellectual defect. In
special lines a feeble-minded child may manifest a fair degree of
power of connection, analysis and even of selection. Learning
may be (though it usually is not) very slow but very permanent.
And so on with many other divergences. The experimental data
show abundantly that the idiots, imbeciles and feeble-minded are
subject to all the complexities of interrelations of mental traits
described in Chapter IX. They are not to be thought of apart
from the human species as a whole, but as certain very divergent
members of it, by no means alike save in great inferiority in the
complex of traits which we call intellect.

There is an ill-defined group of children separated roughly from
others of their age by the fact that they do not get on in school
work and still are capable enough in many matters to make unjusti-
fiable the title idiot, imbecile or feeble-minded, as commonly used.
Theoretically this group is composed of a number of different
species of individuals. Some fail in school work because of defects
of vision or hearing which their teachers fail to allow for. Some
are nervous, fretful and easily distracted. Some are extremely
unimpressionable and slow. Some lack only the capacity to deal
with abstract ideas and symbols and succeed well enough in con-
crete acquisition. Some may possibly possess full capacity and
lack only interest. Some are weak in intellect throughout, belonging
on the border line between the brighter of the feeble-minded and
the duller of the so-called normal children. Some are simply too
immature for the work. Practically the group possesses the unity
of a negative characteristic, inability to profit by the usual methods
of teaching the usual subjects. In any school of a thousand pupils
the principal can pick out from twenty to forty such children, who
are the despair of their teachers, a hindrance to their classmates,
and a source of worry to their parents. Even after sense defects
are corrected or allowed for, after adenoids have been removed,

Extreme Individual Differences 221

even when wise teaching prevents excitement and nervous worry
and arouses interest, a majority of these will be just as they were
before. The group thus left has not, until recently, attracted the
attention of medical science or of educational psychology to the
extent that its practical importance deserves.

Norsworthy ['06] gives data for the comparison of such a group
of 30 girls, 8-13 years old, picked out from about a thousand in a
city school on the ground of inability to profit by the regular
school work, with ordinary children of the same age who lived in
the same environment, attended the same school and were
measured by identical tests given by the same individual. In
giving instructions explanations were made very clearly and the
process required was also shown by samples put upon the board.
The measurements taken were as follows:

1. Height.

2. Weight.

3. Body temperature (taken at the mouth).

4. Pulse.

5. Rate of movement; tested, (a) by the number of crosses made in ten
seconds (two trials); (6) by the number of up-and-down movements made
in ten seconds (two trials).

6. Accuracy of movement; tested, (a) by the number of touches made
in drawing a line between the lines of a maze; {b) by the regularity and
evenness of the figures made in the tests for the rate of movement.

7. Efficiency of perception (rate and accuracy combined) ; tested by
the A test.

8. Efficiency of perception (rate and accuracy combined) ; tested by the
a-t test.

9. Delicacy of discrimination of length; tested by the variable error in
drawing a line equal to a lo-cm. line (ten trials).

ID. Efficiency in a test of perception and movement combined, viz., the
time taken to insert variously shaped blocks into a board made with depres-
sions to fit them.

11. Memory of unrelated words; number remembered out of ten after
a single hearing (two trials) — red, dog, day, tree, buy, never, sick, song,
boy, box, long, green, arm, inch, true, run, dress, break, friend.

12. Memory of related words; number remembered out of ten after a
single hearing (two trials) — school, teacher, book, desk, pen, read, write, add,
spell, word, river, water, broke, flow, ice, cold, winter, snow, sled, skate.

13. Semi-logical memory; memory of four simple dictations, viz., (i)
I have one head, two eyes, two hands and ten fingers. (2) I sit in my seat.
I read from a book. I write with a pencil. (3) One and two are three.
Three and four are seven. Five and six are more than ten. (4) In the
morning I go to school. After school I play. At night I go to bed.

14. Ability in the formation of abstract notions, the appreciation of

222

Educational Psychology

relationships and the control of associations; measured by the following
tests: (A) to write the opposites of a given Hst of words; (S) to mark those
words in a list which are names of things; (C) to write a word representing
some kind of the thing named by a given word; (£>) to write a word repre-
senting some thing of which the thing named by the given word is a part;
(E) to write the opposites of a list of words, the converse of the list used in
A, after the correct responses for A have been read to the class.

The detailed results of the comparison can not be given here.
Their general outcome is perfectly clear. In the physical traits
there is very little difference except in the rise of temperature at
the mouth in the course of twenty minutes of work at the tests.
This invariably occurred with ordinary children, but in only 60
per cent of the special cases. The pulse rate of the special cases

6 -4-3-2-1012346

-8 -7 -6 -5 -4 -3 -2,

Fig. 70. The relative frequencies of difTerent degrees of ability in respect
to trait 14 above, in the case of 73 mediocre nine-year-old girls (upper
diagram) and 19 girls from eight and a half to thirteen years old, m a
'special class' in a public school (lower diagram). The units of the scale
are multiples of the median deviation of nine-year-olds.

is a trifle lower. The difference increases as we pass from physical
traits to tests of movement, then to tests of verbal memory and
then to tests of perception, but even in the last case the special
cases rank about with the lower half of ordinary children. But
with tests 12, 13 and 14 the difference becomes increasingly greater,
until in the last the special cases come to rank as the extreme end
of the school population of their age (Fig. 70).

The one chief and essential characteristic of these children is

Extreme Individual Differences 223

thus their inability to think in symbols, or with relationships, or in
such a way as to let a number of processes combine to decide what
a given thought or reaction shall be. Concrete facts they can think
of and respond to one by one, but they can not think in symbols
that stand for groups of facts or elements in facts. Nor can they
think facts together in causal or other series, or respond correctly
to related groups. In short they are the weakest members of a
school population in thinking of the pure human type. Besides
this main defect there is a diminution of mental vigor, quickness
and tenacity along all lines. In no mental tests do they do as
well, and they give us some reason to believe that as they grow
older they will develop continually less and less rapidly than
ordinary children and so fall farther and farther behind in the
mechanical as well as rational capacities.

Moral Defectives

There are no general conclusions based upon exact measurements
of moral deficiency and its causes and accompaniments. There is
an abundance of ineffective detail stored up in medical comments
upon so-called moral insanity and morbid impulses, in prison
reports and in the minds of experienced schoolmasters. The
greater complexity of the phenomena will always make the
psychology of moral defectives more intricate than that of the
feeble-minded.

The one general truth which can be asserted is that all sorts of
moral defects exist, are far from perfectly correlated, and are due
to a multiplicity of causes. There are extremes of cruelty, deceit,
egotism, passion, knavery, destructiveness and of all immoralities
conceivable. There are boys and girls notably defective in only
a single respect and others in whom every meanness and vice seems
to thrive. We imagine, however, and probably with justice, that
the correlations between certain defects are particularly high,
so that certain combinations of traits are specially frequent.

Such are perhaps features of moral defect characterized by :
(i) Brutishness, extreme predominance of the animal instincts,
shown, for instance, by brutality and teasing, excessive sexual
appetites, fits of rage and sulking, unreasoning greed and
malice; (2) extreme egotism and lack of appreciation of
the feelings and rights of others; (3) extreme weakness
of control and moral instability, shown by susceptibility to

224 Educational Psychology

all temptations and petty vices, alternations of affection with
cruelty, anger with tears, peevishness, untrustworthiness, — an
hysterical and irresponsible mental type, bad more because
of the weakness of good habits than because of the
strength of evil impulses ; (4) the existence of one or more
morbid impulses of an immoral sort. Children may have intense
desires to cut or tear, without being generally extremely cruel ; to
run away from home and live a tramp life, without being generally
extremely disobedient ; to be kleptomaniacs but generally fairly
honest ; to be incendiaries without general destructiveness ; or to
be sexually disordered without being of excessive passions.

Of course there is no rigid adherence to these types. Combi-
nations, intermediate conditions and children falling outside these
groups all exist. The extent to which such a grouping of cases
is allowable or useful can be told only after measurements of the
correlations between special immoral traits have been made.

Brutishness would seem likely to be due to original nature
accentuated or relieved by training ; egotism would seem to be an
original defect in sympathy coupled with lack of abstract intellec-
tual power and commonly made worse by the spoiling and selfish-
ness of parents ; moral instability seems to be due to original
nervous instability displayed in moral more than intellectual
matters as a consequence of feeble and vacillating parental inter-
ference. The morbid impulses of a special sort are probably more
ingrained in original nature and less influenced by environmental
conditions.

General moral defect commonly involves intellectual inferiority.
Woods ['06] and Pearson ['07] find the correlation between
intellect and character to be about .5. The brightness and
precocity that seem to characterize many cases of egotism and
moral instability are really glibness, pertness and lack of restraint.
It is therefore likely that general moral defect is due in part to
generally inferior nervous organization.

Exceptional Rates of Grozvth

Precocity, retarded development* and arrested development are
terms loosely used to refer to children who are exceptional in the

* The term retarded development is at times used not for an undefined
slowness of growth, but for a slowness in growth which will later be made
up. I shall therefore replace the two uses of the single term by the two
terms sloiv growth and delayed groivth.

Extreme Individual Differences 225

rate of mental growth. As we find them in books they hardly
mean anything more definite than very rapid growth, very slow
growth, and absence of growth. But they may be made exact
descriptive terms by the establishment of standards of change
with age from which exceptional rates may be measured.

By far the best arrangement would be to give stations above or
below the average in rate of growth in just the same way as is
done in the case of static conditions of a trait, and to speak in terms
of these numerical stations rather than in the vague terms super-
norm.al, normal, subnormal, and the like. If any individual's rate
belongs to a distinct species of mental growth the fact can easily
be made clear by giving the total distribution scheme as well as
his station therein.

As a matter of fact, precocity, retarded development, etc., are
rarely measured thus directly from the rate of change. Instead,
they are inferred from the fact that an individual is above or below
the condition usual at his age. The term retarded development,
for instance, is thus applied to a case which may be one of slow
rate of growth at the time of observation, or of a slow rate in
years long past, or of low initial station. This is unjustifiable.
Exceptional degrees of ability should be dealt with apart from
exceptional rates of change in ability.

Precocity

There is a popular opinion much encouraged by physicians that
children who in early life grow mentally very rapidly and so
attain high stations, are likely to come to grief, and be soon sur-
passed in health and mental ability by their less precocious fellows.
It is an illustration of the superficiality of human thinking that
so unhesitating an acceptance should be given to the paradox that
rapid mental improvement from birth to the age of ten should be
an evil, but from twenty to forty the greatest of blessings. For,
if we pass beyond a few striking examples which prove nothing,
it is hard to see any evidence for the first statement of the paradox.
On the contrary, bad physique and nervousness accompany dull-
ness oftener than brightness ; and early mental superiority is
prophetic of later.

Men and women of eminent achievements in life are far more
likely to be precocious in childhood than ordinary, dull or
inefficient men are. Havelock Ellis ['04, p. 136 fif.] writes: —

226 Educational Psychology

"The chief feature in the childhood of persons of eminent
intellectual ability brought out by the present data is their
precocity. This has indeed been emphasized by previous inquiries
into the psychology of genius, but its prevalence is very clearly
shown by the present investigation. It has certainly to be said that
the definition of ' precocity ' requires a little more careful con-
sideration than it sometimes receives at the hands of those who
have inquired into it, and that when we have carefully defined
what we mean by ' precocity ' it is its absence rather than its
presence which ought to astonish us in men of genius. Judging
from the data before us, there are at least three courses open to a
child who is destined eventually to display pre-eminent intellectual
ability. He may (i) show extraordinary aptitude for acquiring
the ordinary subjects of school study; he may (2), on the other
hand, show only average, and even much less than average, apti-
tude for ordinary school studies, but be at the same time engrossed
in following up his own preferred lines of study or thinking; he
may, once more, (3) be marked in early life solely by physical
energy, by his activity in games or mischief, or even by his
brutality, the physical energy being sooner or later transformed
into intellectual energy." ['04, pp. 136-137.]

" Although we have to make allowance for ignorance in a large
proportion of cases, and for neglect to mention the fact in many
more cases, the national biographers note that 292 of 1030 eminent
persons on our Hst may in one sense or another be termed preco-
cious, and only 44 are mentioned as not precocious. Many of the
latter belong to the second group, .... those who are already
absorbed in their own lines of mental activity, — and are really just
as ' precocious ' as the others ; thus Cardinal Wiseman as a boy
was ' dull and stupid, always reading and thinking ' ; Byron
showed no aptitude for school work, but was absorbed in romance,
and Landor, though not regarded as precocious, was already pre-
paring for his future literary career. In a small but interesting
group of cases, which must be mentioned separately, the mental
development is first retarded and then accelerated ; thus Chatterton
up to the age of six and a half was, said his mother, * little better
than an absolute fool,' then he fell in love with the illuminated
capitals of an old folio, at seven was remarkable for brightness,
and at ten was writing poems ; Goldsmith, again, was a stupid
child, but before he could write legibly he was fond of poetry and

Extreme Individual Differences 227

rhyming, and a little later he was regarded as a clever boy ; while
Fanny Burney did not know her letters at eight, but at ten was
writing stories and poems." ['04, pp. 140-141.]

" The very marked prevalence of an early bent towards those
lines of achievement in which success is eventually to be won is
indicated by the fact that in those fields in which such bent is
most easily perceived it is most frequently found. It is marked
among the musicians, and would doubtless be still more evident if
it were not that our knowledge concerning British composers is
very incomplete. It is specially notable in the case of artists. It
is reported of not less than 40 out of 64 that in art they were ' pre-
cocious ' ; only four are noted as not being specially precocious."
['04, p. 142.]*

In the case of 70 children chosen at random, for each of whom
I had records of ability in the school work of grade 4 and of
grade 7 or 8, that is at about the tenth and about the fourteenth
and fifteenth years, I find the relationship between the abil-
ity shown in the early and that shown in the later period to be
not at all one of antagonism but of resemblance. The Pearson
coefficients, uncorrected for attenuation, are :

r for 4-7 grade (40 cases) =+.i8

r for 4-8 grade (30 cases) =+.31

If corrected for attenuation they would probably be about .3 and .5.

The mistake current in educational literature seems to have
arisen from a number of fallacies. First, physicians meet with
cases of physical or mental breakdown in mentally superior chil-
dren. They still oftener meet similar cases in mentally inferior
children, but the former cases excite more pity and are more
interesting and dramatic. They tend, therefore, to remain in the
physician's mind while the others fade. Second, an interest in
and acquaintance with topics suitable for older people, such as
sex, theology or adult human social relations, is often taken to
be the sign of a precocious mind. Now these phenomena are often
morbid and may therefore well go with an unstable mental organi-
zation and so be somewhat prophetic of disaster. But they are
not per se indicative of superior mental growth. For the few
supernormal children who exercise their gifts on such questions,
there are many who are ahead in school, play, leadership and
accomplishments. One should not take the word precocious in the

*Loewenfeld ['03] corroborates the findings of Ellis. The same result
has been obtained by other writers also.

228 Educational Psychology

bad sense of unbalanced superior gifts and argue from premises
thus obtained to conclusions about precocity in the sense of gen-
erally supernormal mental growth. In the third place, physicians
often take the word of the parents for the children's precocity. It
then means probably mere forwardness, ready talk, so-called
' bright ' sayings and doings, and even impertinence. These all
witness to inferiority disguised by lack of inhibition. The quiet
child thinks of many much brighter things to say, but also has the
strength of mind not to say them. Lack of inhibition and im-
pertinence are prophetic of poor mental growth in the future be-
cause they are indicative of it in the past and present as well.
Finally it must be said that the average medical man in his ignor-
ance of the subtle hereditary and environmental causes of mental
breakdown grasps at any cause he can. If the child is dull, mental
weakness is to blame ; if he is bright, precocity !

Slozv Growth

In the absence of any quantitative studies of slowness of
growth, this section will be limited to brief comments upon the
question as to whether slowness of growth in one mental trait
implies equal slowness in the growth of others, and the question
of the desirability of a slow mental growth.

Slowness of mental growth is undoubtedly specialized, though
to just what extent is not known. An obvious illustration is
given by the sex instincts, which may mature far in advance of
or far behind the intellectual powers. So also with social facility
or musical talents. The resemblances between traits in an indi-
vidual in their rate of maturing are, however, probably much
greater than in their final condition.

Slowness of mental growth is in general an unfavorable sign.
It is correlated slightly with low original capacity and low ulti-
mate attainment. In some cases, of course, the growth is only
delayed and the individual who seems to be far behind may come
out well ahead. Moreover, as in height the boys who grow less
than the average from twelve to fourteen grow more than the
average from fourteen to sixteen, so in mental traits retardation
before puberty may mean acceleration after it.

The opposite view, a corollary to the superstition about pre-
cocity, has gained credence, I fancy, first because of the supposed
slowness of maturing of superior races, and secondly because of

Extreme Indimdual Differences 229

the supposed ill success at school of gifted men. But the ap-
parent mental attainments of children of inferior races may be
due to lack of inhibition and so witness precisely to a deficiency
in mental growth. Moreover, we can not argue from inferior
races to inferior members of one race. The failure at school work
of children destined to become eminent men is a myth. The per-
centage is far higher for thieves and paupers and lack-wits.

Inefficiency due to slow mental growth, especially in those
cases where the future will prove it to have been only delayed
mental growth, must not, however, be confused with inefficiency
due to inevitable incapacity. The correlation would have to be
1. 00 to permit the interchange of these terms as synonyms.

Accurate tests to differentiate inherent incapacity from im-
maturity would seem to be of great practical value. They would
prevent the injustice and discouragement due to mistaking the
second for the first and the false hopes inspired by mistaking the
first for the second. An approximation to such a differential
diagnosis can be made by using the following tests : —

A. Tests of Maturity Chiefly.

Motor control (rate of tapping, rate of making crosses, maze tests).
Memory of unrelated words, pictorial forms, etc.
Perception {A test, a-t test, geometrical forms test).
Delicacy of sense discrimination (of length and of weight).

B. Tests of Intelligence Chiefly.

Logical memory (memory of passages that involve connected and sys-
tematic exposition or argument).

Controlled association (alphabet and easy opposite tests or the like).

Preception of relations (filling up the blanks in passages like the fol-
lowing) :

In everything that we do . . . need ... be both qilick . . . careful . . .
we are . . . quick we do not get much done we care-
ful we do not do our work . . . well . . . others. It is better to be careful
. . . than to be quick . . . the best worker . . . the one . . . can do . . .

things . . . do . . . well we can not all be the best, we can . . .

improve.

Let US suppose a boy who does not get on well in school to be
tested and given stations in A and B with reference to the median
for his age and sex. The lower his station is in A and the higher
it is in B, the more chance there is that he will grow out of his
difficulty. Conversely, the higher his station is in A and the
lower it is in B, the greater is the probability that he is essentially
dull.

230 Educational Psychology

Arrested Development

The • phrase ' arrested development ' is used in medicine to
mean just what it says. Bodily organs, including the brain, may
remain stationary or nearly so in one individual at a period when
in the great majority they are growing. In the case of the brain
there may be no arrest apparent in gross structure, and yet the
neurones themselves may not have attained their full develop-
ment in complexity and delicacy. If we knew fully the history of
the growth (normal or pathological) of the neurones themselves,
we could probably extend the conception of arrested development
to the entire field of mental life and distinguish in post-mortem
examinations between the clodhopper who stagnates mentally after
a score of years, and the Gladstone or Virchow whom the allotted
span of life leaves still progressing, as we now distinguish be-
tween the brains of an amaurotic idiot and an average boy. It
seems, therefore, justifiable to use the phrase ' arrested develop-
ment ' from the psychological point of view in the case of any
mental trait in any individual which remains stationary or nearly
so at a period when it ordinarily is advancing. Medical men com-
monly apply the phrase to only those well-marked cases of general
mental weakness which are correlated with gross developmental
defects of the body or brain.

Arrest may be temporary or permanent. In the former case
sickness, low nutrition and disuse are the probable causes ; in the
latter, definite brain lesions or original lack of developmental
force. It may be general or specialized. In every trait perma-
nent arrest comes sooner or later to almost all of us. The dif-
ferences amongst men are not in its presence or absence, but in
its date. There is, of course, no absolute date for any trait
which is ' normal ' for it. The date is variable, and abnormality
here as elsewhere can mean only some arbitrarily chosen difference
from the average.

APPENDIX I

List of Authors and Titles Referred to Specifically in the Text

Betts, G. H '09, The Distribution and Functions of

Mental Imagery, Columbia Univer-
sity Contributions to Education,
Teachers College Series, No. 26.

Binet, A '97, Psychologic individuelle: La des-
cription d'un objet, L'annee psy-
chologique, vol. 3, pp. 296-332,
and. La description d'une cigarette,
Revue de Psychiatric, 1897, pp.
235-243-

Binet, A., and Simon, Th '09, L' intelligence des imbeciles, L'annde

psychologique, vol. 15, pp. 1-147.

Brown, W '09, Some Experimental Results in

Correlation.

Bruner, F. G '08, The Hearing of Primitive Peoples,

Archives of Psychology, No. 11.

Burris, W. P '03, The Correlations of the Abilities In-
volved in Secondary School Work,
Columbia Contributions to Phil.,
Psy. and Ed., vol. 11, No. 2, pp.
16-28.

Burt, C '09, Experimental Tests of General In-
telligence, British Journal of Psy-
chology, vol. 3, pp. 94-177-

Cattell, J. McK '03, A Statistical Study of Eminent Men,

Popular Science Monthly, vol. 62,
PP- 359-377-
06, A Statistical Study of American
Men of Science, III. The Distri-
bution of American Men of Science,
Science, Dec. 7, 1906.

Cornman, O. P '02, Spelling in the Elementary School;

An Experimental and Statistical
Investigation.

(23O

232 Educational Psychology

Courtis, S. A '09, Measurement of Growth and Effi-
ciency in Arithmetic, Elementary
School Teacher, vol. 10, pp. 58-
74. 177-199-

Davenport, C. B '10, Eugenics.

De Candolle, A '73, (Second edition, '85), Histoire des

sciences et des savants depuis deux
si^cles, etc.

Earle, E. L '03, The Inheritance of the Ability to

Learn to Spell, Columbia Contri-
butions to Phil., Psy. and Ed.,
vol. II, No. 2, pp. 41-44.

Ellis, H '94, '04, (Fourth edition, '04), Man and

Woman.

'04, A Study of British Genius.

Fay, E. A '98, Marriages of the Deaf in A merica.

Galton, F '69, '92, Hereditary Genius: An Inquiry

into its Laws and Consequences,
(first edition '69, second edition
'92). References are to second
edition.

'83, Inquiries into Human Faculty and
its Development.

'87, Supplementary Notes on Prehen-
sion in Idiots, Mind, vol. 12, pp.
79-82.

'89, Natural Inheritance.
Gilbert.rj. A '94, Researches on the Mental and Phy-
sical Development of School-Child-
ren; Studies from the Yale Psy-
chological Laboratory, vol. 2, pp.
40-100.
Heymans, G., and Wiersma, E., '06 (a), Beitrdge zur speziellen Psychologic

auf Grund einer Massenuntersuch-
ung, Zeitschrift iiir Psychologic,
vol. 42, pp. 81-127, 258-301.
'06 (b), Beitrdge zur speziellen Psychologic
auf Grund einer Massenuntersuch-
ung, Zeitschrift ftir Psychologic,
vol. 43, pp. 321-373-

'07, Beitrdge zur speziellen Psychologic
auf Grund einer Massenuntersuch-
ung, Zeitschrift ftir Psychologic,
vol. 45, pp. 1-42.

'08, Beitrdge zur speziellen Psychologic
auf Grund einer Massenuntersuch-
ung, Zeitschrift fiir Psychologic,
vol. 46, pp. 321-333.

Authors and Titles 233

Jacobs, J '87, Experiments on Prehension, Mind ,

vol. 12, pp. 75-79-

Jacoby, P '81, (Second edition, '04), Etudes sur

la selection dans ses rapports avec
I'heredite chez I'homme.

Johnson, G. E '95, Contribution to the Psychology and

Pedagogy of Feeble-Minded Child-
'95, ren, Pedagogical Seminary, vol. 3,
pp. 246-301.

Kelly, R. L '03, Psycho-physical Tests of Normal

and Abnormal Children — A Com-
parative Study, Psychological Re-
view, vol. 10, pp. 345-372.

Krueger, F., and Spearman, C '06, Die Korrelation zwischen verschie-

denen geistigen Leistungsfdhig-
keiten, Zeitschrift ftir Psychologic,
vol. 44, pp. 50-1 14-

Kuhlmann, F '04, Experimental Studies in Mental

Deficiency, American Journal of
Psychology, vol. 15, pp. 391-446.

Learoyd, M. W '96, The Continued Story, American

Journal of Psychology, vol. 7,
pp. 86-90.

Leclere, A '98, Description d'un objet, L'ann^e psy-

chologique, vol. 4, pp. 379-389-

Lobsien, M '03, Einige Untersuchungen iiber das

Geddchtniss bei Schwachbefdhigten,
Die Kinderfehler, vol. 8, pp. 157-
168 and 193-203.

Loewenfeld, R '03, Uber die Geniale Geistesthdtigkeit

Meumann, E '07, Vorlesungen zur Einfiihrung in die

Experimentelle Pddagogik und ihre
psychologischen Grundlagen.

Norsworthy, N '06, The Psychology of Mentally De-
ficient Children, Archives of Psy-
chology, No. 1 .

Odin, A '95, Genkse des grands hommes, gens de

letires fran(ais modernes.

Pearson, K '04, On tlie Laws of Inheritance in Man,

II. On the Inheritance of the Men-
tal and Moral Characters in Man,
etc., Biometrika, vol. 3, Part II,
pp. 131-190.

234 Educational Psychology

Pearson, K '07, On the Relationship of Intelligence

to Size and Shape of Head, and to
Other Physical and Mental Char-
acters, Biometrika, vol. 5, pp. 105-
146.

Pedersen, R. H '05, Experimentelle Untersuchungen der

visuellen und akustischen Er in-
ner ungshilder, angestellt an Schul-
kindern, Archiv fur die gesamte
Psychologic, vol. 4, pp. 520-534.

Rice, J. M '97, The Futility of the Spelling Grind,

The Forum, vol. 23, pp. 163-172
and 409-419.

'02, Educational Research: A Test in
Arithmetic, The Forum, vol. 34,
pp. 281-297; Causes of Success
and Failure in Arithmetic, The
Forum, vol. 34, pp. 437-452.

'03, Educational Research, The Results
of a Test in Language, The Forum,
vol. 35, pp. 269-293.

'04, English, Tlie Need of a New Basis
in Education, The Forum, vol.
35, PP- 440-457-

Richardson, H '02, The Etiology of Arrested Mental

Development, Journal of Psycho-
Asthenics, vol. 7, pp. 9-14.

Segal, J '08, ijber den Reproduktionstypus und

das Reproduzieren von Vorstel-
lungen, Archiv fur die gesamte
Psychologic, vol. 12, pp. 124-235.

Simon, Th '09, (See Binet and Simon.)

Spearman, C '04 (a). The Proof and Measurement of

Association between Two Things,
American Journal of Psychology,
vol. 15, pp. 72-101.
'04 (b), "General Intelligence" Objectively
Determined and Measured, Amer-
ican Journal of Psychology, vol.
15, pp. 201-292.

" (with F. Krueger), '06, Die Korrelation zwischen verschie-

denen geistigen Leistungsfdhigkeii-
en, Zeitschrift f{ir Psychologic, vol.

44, PP- 50-114-

Stern, L. W '00, Uber Psychologie der individuellen

Differemen.

Authors and Titles

235

Stone, C. W '08, Arithmetical Abilities and Some

Factors Determining Them, Colum-
bia University Contributions to
Education, Teachers College Series,
No. 19.

Thompson, H. B '03, Psychological Norms in Men and

Women, University of Chicago
Contributions to Philosophy, vol.

4, No. I.

Thorndike, E. L '03, Heredity, Correlation and Sex Dif-
ferences in School Abilities, Colum-
bia University Contributions to
Phil., Psy., and Ed., vol. 11, No. 2.
'04, An Introduction to the Theory of
Mental and Social Measurements.
'05, Measurements of Twins, Archives
of Philosophy, Psychology, and
Scientific Methods, No. i.
'08, Alemory for Paired Associates,
Psychological Review, vol. 15,
pp. 122-138.
'09, The Relation of Accuracy in Sen-
sory Discrimination to General In-
telligence, American Journal of
Psychology, vol. 20, pp. 364-369.
10, Handwriting, Teachers College
Record, vol. 11, No. 2.

Ward, L. F '06, Applied Sociology.

Wiersma, E (See Heymans and Wiersma.)

Wissler, C '01, The Correlation of Mental and

Physical Tests, Psychological Re-
vievF Monograph Supplement No.
16, June, 1 90 1.
'03, The Growth of Boys, American
Anthropologist, New Series, vol.

5, pp. 81-88.

Woods, F. A '06, Mental and Moral Heredity in

Royalty.

Woodworth, R. S '10, Racial Differences in Mental Traits,

Science, New Series, vol. 31, pp.
171-186.

Wylie, A. R. T '00, Taste and Reaction Time of the

Feeble-Minded, Journal of Psycho-
Asthenics, vol. 4, No. 3; A Study
of the Senses of the Feeble-Minded,
ibid., vol. 4, No. 4; Memory of the
Feeble-Minded, ibid., vol 5, No. i ;
Motor Ability and Control of the
Feeble-Minded, ibid., vol. 5, No. 2.

APPENDIX II

List and Descriptions of Measurements Referred to Cursorily in the

Text

A Test: Marking A 's.

A sheet printed with capital letters, as shown below, is used. The
individual who is being measured is instructed ' to mark as many A's
as he can,' or 'to mark as many and omit as few A's as he can,' or
'to mark all the A's.' The score used is the number marked in a given
time (or the time required for the entire sheet to be gone over) and
the number of omissions.

OYKFIUDBHTAGDAACDIXAMRPAGQZTAACVAOWLYX

WABBTHJJANEEFAAMEAACBSVSKALLPHANRNPKAZF

YRQAQEAXJUDFOIMWZSAUCGVAOABMAYDYAAZJDAL

JACINEVBGAOFHARPVEJCTQZAPJLEIQWNAHRBUIAS

SNZMWAAAWHACAXHXQAXTDPUTYGSKGRKVLGKIM

FUOFAAKYFGTMBLYZIJAAVAUAACXDTVDACJSIUFMO

TXWAMQEAKHAOPXZWCAIRBRZNSOQAQLMDGUSGB

AKNAAPIvPAAAHYOAEKLNVFARJAEHNPWIBAYAQRK

UPDSHAAQGGHTAMZAQGMTPNURQNXIJEOWYCREJD

UOLJCCAKSZAUAFERFAWAFZAWXBAAAVHAMBATAD

KVSTVNAPLIIvAOXYSJUOVYIVPAAPSDNLKRQAAOJLE

GAAQYEMPAZNTIBXGAIMRUSAWZAZWXAMXBDXAJZ

ECNABAHGDVSVFTCIvAYKUKCWAFRWHTQYAFAAAOH

a — t Test: Marking U^ords Containing, Each, Both a and t.

A sheet printed with text, as shown below, is used. The individual who
is being measured is instructed, and the score is kept, as in the A test.
The same sheet is used for marking words containing other combina-
tions of letters, such as r and e, or i and /.

Dire tengo antipatia senores; esto seria necedad, porque hombre vale
siempre tanto corao otro hombre. Todas clases hombres merito;
resumidas cuentas, sulpa suya vizconde; pero dire sobrina puede
contar dote veinte cinco duros menos, tengo apartado ; pardiez tamado

(236)

Descriptions of Measurements 237

trabajo atesorar-los para enriquecer estrano. Vizconde rico. Mios,
quiero ganado sudor f rente saiga familia; suyo, pertenence, tendran.
Conozco marido pueda convenirle Isabel: Carlos, sobrino. Donde
muchacho honrado, mejor indole, juicioso, valiente? Quieres sobrino.
Esposo parece natural, pero. Pero, pero, diablos objeciones hacer.
Posible quedandonow solos siempre hacer oposicion. Solo delante
hentes eres ministerial. Pues, sidens siempre plan, dicho antes, porque
hace tierapo notade cose aflige cierto. Sabes cuante quiero Carlos;
consuelo apoyo; despues persona quiero mundo. Como eres buena
amable, quieres porque, darme gusto, pero quisiera. Palabra cuesta
trabajo; parece sino teines miedo agasajarle, manifestarle carino.
Veces tratas cumplimiento veces senor. Probare; ejemplo pudiendo
abandonar case negocios, deseaba hubiese acompanado viaje; pre-
feriste sola sobrina doncella. Quise contradecir, pero para sen-
timiento, para tambien. Voto gasta palabra, dice frases, dice; pero
alia adentros quiere. Mientras estado malo, puesto dirigir casa;
pardiez aunque carrera, hacia mejor; cabo tiene sobre ventaja poca
edad, actividad zelo, pues para contigo digo. Siempre ordenes; dejaria
matar alcanzarte billete para opera para baile . Necsitamos para felices ;
algo estrano, desconocido. Esta resuelto; supuesto hemos hablado
esto, mismo preciso empieces darle conocer nuestros planes. Quien
mejor. Opone nunca deseos, sera facil nadie persuadirle. Probare
menos, preciso sino creere tienes interes decidido proteger vizconde.
Pudieras creer siempre inclinado senores cabra tira monte. Pero tengo
nada ellos esposo tienes siempre pensativo siempre trists. Diablos
tiene Carlos acercate, tiene hablarte. Hola parece sacado letargo tengo
algunas instrucciones cajero marcha dentro poco. Para empresa piesna
usted establecer Habana. Precisamente bonita especulacion bien
manejada sobro todo. Espero pero tengo entre manos etro proyecto
interesa aqui estabamos ocupando pienso. Eres porque quieres

B.
porque e tregas defensa peligro lugar huir mujer, harto debil duda pero
algun desgracia tuviese luchar sentimientos semejantes tuyos, lejos
ceder ellos cobardemente moriria pero triunfaria. Tendras menos
valor tendre darte lecciones valor energia. Vamos, Carlos, amigo
creeme sentimiento, profundo razon pueda subyugar, desgracia grande
pueda soportar veneer nuestro corazon. Ofrezco apoyo eres creo sequiras
consejos. Bien, hable usted. Quiere casarte Isabel. Isabel, prima
imposible; quiere otro, vizconde amigo. Preciso persuadirselo hare
otros partidos habra jamas para jurado nada espero pero conservare
siempre entero este amor ella ignora unos juramentos recibido. En-
horabuena otro medio asequarara tranquilidad, uya destino ofrecido
aleja Madrid, preciso aceptarle. Privarme presencia felicidad hecho
usted para consejo especie embargo preciso seguirle solo puedes con-
servar amistad elige. Jamas caballero crei usted digno consejos dejo
usted abandonado mismo nada tango decirle Carlos aleja, echa mirade
salir Dona mira; suspira sale. Porque inquieta partida desterremos
para siempre memoria quiero puedo presente terao; ausente, echo

238 Rducational Psychology

menos, verle sonrojo, nombre hace temblar. Embargo nunca dicho
debiera ignorarlo Dios Dame fuerzas para resistir.

Alphabet Test.

A sheet printed with/, k, s, p, u, I, e, r, d, 0, v, j, n, t and h in a cokimn
is used. Instructions are: — 'to write after each letter, the letter that
comes immediately before it in the alphabet.' The score records
time required (or number written in a given time), errors and omissions.

Genus-Species Test.

A sheet printed with hook, tree, room, toy, name, dish, boat, game, plant
and Jish in a column is used. Instructions are: — 'to write, after each
word, a word which means some kind of the thing named by the printed
word.' The score is kept as in the Alphabet test. The words may
be given to the subject, and the replies made by him orally. A harder
list is used for older children.

Geometrical Forms Test: Marking Circles, Hexagons, etc.

A sheet printed with Fig. 71 is used. Instructions and scoring are as
in the A or a — t test.

Maze Tests. Drawing a Line between Two Given Lines.

Sheets printed with Fig. 72, or similar mazes, are used. The instructions
are to draw a line along the pathway as quickly as possible without
touching the sides. The score includes amount done (or time taken),
and number of touches.

Memory of Related Words.

Memory of such series as: — school, teacher, book, desk, pen, read, write,
add, spell, word.

Memory of Unrelated Words.

Memory of such series as: — red, dog, buy, day, never, sing, boy, sick, tree,
can.

Misspelled Word Test: Marking Misspelled Words.

Sheets printed with passages like that below are used. Instructions and
scoring are as in the A test.

1. On the 3d of September, 1832, inlcligence was broght to the collecter
of Tinnevelly that soni wildd eliphants had appeared in the neighbor-
hod. A hunting party was imediately formed, and a large number of
nattive hunters were engaged. We left the tents, on horsback, at
half-past sevin o'clock in the morrning and rode thre miles to an open
spote, Hanked on one sid bye Rice-fields, and on the other by a jungle.

2. After waiting som time, Captain B and myself walked acros the

rice-fields to the shad of a tree. There we herd the trunipett of an
elephant; we reshed acros the rice-fields up to our knes in mud, but
all in vain, thogh we came upon the trak of one of the animels, and
then ran five or six hundredd yards iutoo the jungle.

Descriptions of Measurements

239

r\^'

<]vgAoa^i:^

pRny anySHMn^Poo

iRo^p°^°

1^7

H<\a

n<i0o

LJ>iA^nC

e3HRB

DPsOQ

ooDdD[5d dooc

oC^

240

Educational Psychology

Descriptions of Measurements 241

3. After varius false allarms, aud vane endevors to discuvor the obgects

of our chace, the colector went into the jungle, and Captin B

and myself into bed of the stream' where we had sen the traks; and
here it was evedent the elaphents had passed to and fro. Disapointed
and impasient, we allmost determined to giv up the chace and go
home; but shots fird just before us reanimated us, aud we proceded,
and found the collecter had just firred twicce.

4. Of we went throuh foerst, over ravin, and through strems, till att
last, at the top of the ravine, the elephants were seen. This was a
momant of excitment! We wer all scatered. The collector had

taken the midle path ; Captain B , some huntsmen, and myself

took to the feft; and the other hunters scrabled down that to the
rite. At this momunt I did not see enything but after advanceing a
few yards, the hugh hed ef an elephunt shaking abuve the jungle,
withen ten yards of us, burst sudenly upon my view.

5. Captain B ande a hunter justt befor me: we al fired at the

same moment, and in so dirrect a line thet the percussion cap of my
gun hitt the hunter, whome I thougt at first I had shoot. This accident,
thogh it pruved slight, troubled me a litle. The grate excitement
ocasioned by seeing, for the first tim, a wild best at liberty and in a
state of natur, product a sensation of hop and fear that was intens.

Opposites Tests.

Sheets printed with words in a column are used, one list being: — good,
outside, quick, tall, big, loud, white, light, happy, false, like, rich, sick,
glad, thin, empty, war, many, above and friend. Another list is: — bad,
inside, slow, short, little, soft, black, dark, sod, true, dislike, poor, well
sorry, thick, full, peace, few, below and enemy.

Harder lists, used for older children and adults, are:— serious, grand,
clumsy, to win, to respect, frequently, apart, stormy, motion, forcible,
to float, straight, to hold, after, unless, rough, to bless, to take; and bar-
barous, simple, rude, obscure, gentle, to expand, elation, adroit, loquacious,
to degrade, to hinder, precise, permanent, repulsion, to respect, genuine,
separate, deceitful.

Instructions are to write (or, if the test is given orally, to say) the word
which means the opposite of the given word, 'just what that word
does not mean.' The score is kept as in the Alphabet test.

Part-Whole Test.

To give the name of that whole thing of which the printed or spoken
word is a part. The list used for young children and for mentally
deficient individuals is: — door, pillow, letter, leaf, button, nose, cover
page, engine, and glass.

Word Test.

To write words conforming to certain requirements, such as: — 'to contain
six letters,' or 'to contain a and g.'
16

APPENDIX III

List and Definitions of Statistical Terms

Measures of Central Tendency.

The Average = (the sum of the individual measures) -=- (their number).
The Median = the middle measure, the measure so chosen that the
number of measures greater than it equals the number less than it.
The Mode = the most frequent of the individual measures.

Measures of Variability.

The Average Deviation (A. D. dis.) = the average of the deviations

(regardless of signs) of the individual measures from their central

tendency.
The Median Deviation (P. E. dis.) or Probable Error (when used as a

measure of variability) = the median of the deviations (regardless

of signs) of the individual measures from their central tendency.
The Mean Square Deviation (S. D. dis.) = the square root of the average

of the squares of the deviations of the individual measures from their

central tendency.

Measures of Reliability.

The average deviation of the true central tendency from that obtained

A D dis
from a random selection of n measures (A. D. ^j_ ^^ q x^~ ~ — "

l/n
Similarly,

P P _ P. E. dis. ^, ^ J. S. D. dis.

P-E- tr.-ob.C.T.= 7=- and S. D. j^_^^ (,^ =

yn V ^

For measures of the reliability of measures of variability and of relations
see Thorndike, Mental and Social Measurements, Chapter X.

Measures of Relations.

Let xi, X2, X3, X4, etc., be the first series of divergences.
Let yi, y2, ys, yi, " " " second " "

Let ^ x.y be the sum of the products xiyi, X2y2, xsya, X4y4, etc.
Let i' x2 " " " " " squares xi^, x^, x^, Xi\ etc.
Let y y2 " " " " " " yi2, y22, y^, yi\ etc.

I x.y

Then the Pearson Coefficient of Correlation, R, =

For other measures of relations see the author's Mental and Social
Measurements, Chapter IX, and Empirical Studies in the Theory of
Measurement, §§ 5 to 9, inclusive.

(242)

INDEX OF NAMES

Barr, M. W., 102.
Betts, G. H., 183, 195.
Binet, A., 203, 215.
Brown, W., 182.
Bruner, F. G., 56, 57-
Burris, W. P., 96.
Burt, C, 181, 182, 184.

Cattell, J. McK., 35 f., 119, 121 ff., 184.
Cole, L. W., 40.
Cornman, O. P., 78, 135.
Courtis, S. A., 135.

Davenport, C. B., 102.
DeCandolle, A., 121.

McDougall, W., 56, 57-
Mayo, M. J., 52 ff.
Mendel, G., 98.
Meumann, E., 183, 194, 201.

Norsworthy, N., 215, 217, 221.

Odin, A., 121.

Pearson, K., 43 f., 80, 81, 82, 83, 84,

96, 182, 224.
Pedersen, R. H., 183.

Ranke, J., 55.

Rice, J. M., 78, 119, 125 ff.

Richardson, H., 103.

Earle, E. L., 40, T] f.

Ellis, H., 36. 49 f.. 61 ff., 94 f., 121, ^'^"'■'' ^- ^- ^•' 56. 59.

225 ff. C 1 T

Segal, J., 194.

Seguin, E., 218.

Simon, Th., 215.

Simpson, B. R., 182.
Galton, P., 65 f., 70, 78, 79, 93, 94, Sollier, P., 219.

119 ff., 121, 215. Spearman, C, 80, 182, 185, 188.

Gilbert, J. A., 30 f., 40, 105 ff-, Ii3- Stern, L. W., 201 ff.

Stone, C. W., 135.
Heymans, G., 45, 46, 48, 9'2; 93 Strayer, G. D., 42.

Fay, E. A., TJ.
Fox, W. A., 40.

Jacobs, J., 215.
Jacoby, P., 121.
Johnson, G. E., 215.

Kelly, R. L., 215.
Kraepelin, E., 204.
Kuhlmann, F., 215.

Learoyd, M. W., 5°.
Leclere, A., 203.
Lobsien, M., 215.
Loewenfeld, R., 79, 227.

Thompson, H. B., 20 ff., 32, 37, 42.
Thorndike, E. L., 89, 96, I3S, 165,
182, 184.

Ward, L. F., 121.
Wiersma, E., 45, 46, 48, 92, 93.
Wissler, C, 30, 43. 182, 188.
Woods, F. A., 84 ff., 124, 224.
Woodworth, R. S., 55 ff-
Wylie, A. R. T., 215.

(243)

INDEX OF SUBJECTS

Ability, inheritance of, 80 flf.

Abnormal. See Exceptional.

Achievement, relative versus absolute,
138 ff.

Activities, sex differences in, 46 ff.

Addition, individual differences in,
144 f.

Age, changes in mental traits with,
105 ff.

Ancestry. See Inheritance.

Arithmetic, differences of school
classes in, 129; the causes of ability
in, 129, 131 ff.

Arrested development, 228 ff.

Artistic faculty, inheritance of, 80.

Assertiveness, inheritance of, 80 ff. ;
sex differences in, 44 f.

Association, sex differences in, 30 f. ;
the inferiority of intellectually defi-
cient individuals in, 218; the in-
heritance of speed and control in,
89 ff.

Athleticism, inheritance of, 83 ; sex
differences in, 44 f.

Attenuation of resemblances, 80 f.

Average Deviation. 13 f. See also
Measurement.

Averages. See Measurement.

Brightness. See Senses.
British genius, racial differences in,
61 ff.

Central Tendency, 12.
Cephalic index, inheritance of, 72, 76.
Chance form of distribution, 160 ff.
Character, sex differences in, 44 ff. ;
types of, 193 ff.

Characters, unit and multiple, 98 ff.

Classification, of individuals, 142-206
passim; of individuals exceptionally
inferior in intellect, 213 f. ; of in-
dividuals exceptionally inferior in
morals, 223 f.

Color. See Senses.

Combinations of traits, 3 f., 193 ff.

Compensations in mental relations,
183 ff.

Conscientiousness, inheritance of,
80 ff. ; sex differences in, 44 f.

Continuity of variations, 149 f.

Correlations See Relations.

Curve of frequency, 16. See also Dis-
tribution and Distributions.

Dealing, relations of ability in, 181 f.
Defectives. See Exceptional.
Determiners of traits in the adult,

97 ff.

Deviations. See Individual Differ-
ences, Distributions, Distribution of
Amounts of a Trait, and Varia-
bility.

Dilation of resemblances by variations
in the scales used, 81 f., 83.

Discrimination. See Sensory Dis-
crimination and Senses.

Distribution of amounts of mental
traits, IS f., 142 ff. ; as affected by
mixture of species, 166; as affected
by selection, 167 ff. ; as affected by
the number of cases, 159; multi-
modality of, 152 ff. ; the probability
type of, 160 ff. See also Individual
Differences and Variability.

Distributions, corresponding to stated

(244)

Index of Subjects

245

group differences, 28 f., 33, 64,
66; of adult women, in add-
ing, 144 f., 150, in discrimination of
length, 144, in memory of digits,
151 ; of boys, in giving opposites,
151, in marking A's, 151, in mark-
ing words containing a and /, 151 ;
of boys and girls, in age at reach-
ing a given grade, 42, 158, in mark-
ing A's, 154 f. ; of individuals, in
combinations of traits, 194 ff. ; of
men, in reaction-time, 151 ; of men
and women, in ingenuity, 23, 25 ; of
relationships, 174 ff. ; of whites and
Negritos, in the block test, 61, 156;
of whites and negroes, in scholar-
ship, 54 f., 157.

Economics, sex differences in scholar-
ship in, 31.

Emotions, sex differences in, 44 ff.

English, sex differences in scholar-
ship in, 31.

Environment, and maturity, the co-
operation of, 109 f. ; and original
nature, the cooperation of, 138 ff. ;
as a cause of multimodality or dis-
tinct types, 153 f., 154 f. ; as a cause
of sex differences, 38, 42; differ-
ences in as causes of individual
differences in ability in arithmetic,
129, 131 ff., in ability in spelling,
• 126 ff., in scientific achievement,
122 f., in the choice of a profession,
134 f. ; is, in part, selected by an
individual's nature, 117; resem-
blances in, as causes of individual
resemblances in ability to learn to
spell, 78, in genius, 79, in various
mental traits, 83-93 passim; the
action of is differential, 116 f . ; the
influence of in the case of twins,
119 ff.

Exceptional inferiority, 211 ff. ; in
intellect, 213 ff. ; in morals, 223 f.

Exceptionally defective individuals
intellectually, 213 ff. ; classification

of, 213 f. ; general description of,
219 f. ; measurements of, 215 ff.,
221 f. ; relative inferiority of in dif-
ferent traits, 216 f. ; symptoms of,
214; treatment of, 214 f.

Exceptional rates of growth, 224 ff. ;
rapid growth, 225 ff. ; slow growth,
228 f.

Exceptional superiority, 209 f.

Extreme individual differences, 207 ff.

Eye-color, inheritance of, 76.

Fallacy of unfair selection, 112, 114 f.

Family. See Inheritance.

Fatigue, age differences in, 105 ff. ;
sex differences in, 27.

Feeble-mindedness. See Exception-
ally Defective Individuals.

Frequency. See Distribution, Dis-
tributions, and Variability.

Genius, inheritance of, 78 f. ; racial
differences in, 61 ff. ; sex differ-
ences in, 35 f.

Groups, measurement of differences
between, 24 ff., 37 ff.

Growth. See Maturity.

Habits, effect of on relations, 191 f. ;
formation of in individuals excep-
tionally defective in intellect, 214 f.;
indifference of certain habits to all
natures, 137 f. ; not measures of
capacity, 67 ; relation to multimodal-
ity, 153 f. ; susceptibility of to
environmental influence, 141.

Hair-color, inheritance of, 77.

Handwriting, inheritance of, 80 ff. ;
sex differences in, 44 f.

Heredity. See Inheritance.

History, sex differences in scholar-
ship in, 31.

Idiocy. See Exceptionally Defective

Individuals.
Illusions, sex differences in, 30 f.

246

Educational Psychology

Imagery, individual differences in,

193 ff.

Imbecility, and Mendelian inherit-
ance, 102 f. See also Exceptionally
Defective Individuals.

Immaturity, tests of, 229.

Individual differences, environment as
a cause of, 114 ff. ; extreme, 207 ff. ;
immediate ancestry as a cause of,
6g ff. ; in combinations of traits,
193 ff. ; in single traits, 142 ff. ;
maturity as a cause of, 104 ff. ;
measurement of, 3 ff. ; remote
ancestry as a cause of, 51 ff. ; sex
as a cause of, 18 ff.

Information, sex differences in
amount of, 28.

Ingenuity, sex differences in, 28.

Inheritance, analysis of, 97 ff. ; and
education, 138 ff. ; and responsibil-
ity, 140; blended versus Mendelian,
99 ff. ; from near ancestry, 69 ff. ;
from remote ancestry, 51 ff. ; Men-
delian, 98 ff. ; of ability, 80 ff. ; of
ability to learn to spell, yy i. ; of
artistic faculty, 80; of assertiveness,
80 ff. ; of athletic ability, 83; of
cephalic index, 72, 76; of conscien-
tiousness, 80 ff. ; of deafness, yy ;
of eye-color, 76 ; of genius, 78 f. ;
of hair-color, yy; of handwrriting,
80 ff. ; of imbecility, 102 f. ; of in-
tellect, 84 ff. ; of morals, 84 ff. ; of
popularity, 80 ff. ; of self-conscious-
ness, 80 ff . ; of stature, y6 ; of tem-
per, 80 ff. ; of vivacity, 80 ff. ;
specialization of, 93 ff.

Instincts, sex differences in, 48 f.

Intellect, defects of, 207 ff. ; inherit-
ance of, 78, 80 ff. ; racial differences
in, 58 ff. ; sex differences in, 44 ff. ;
types of, 193 ff.

Interests, sex differences in, 46 ff.

Inverse correlations, 200.

Languages, sex differences in scholar-
ship in, 31.

Mathematics, sex differences in
scholarship in, 31.

Maturity, and environment, the co-
operation of, 109 f. ; exceptional
individuals in the rate of 224 ff. ;
the influence of upon individual
mental differences, 104 ff. ; the in-
fluence of upon multimodality, 155;
the measurement of the influence
of, 104, iioff.

Measurement, of changes with age,
1 10 ff. ; of group differences in
amount, 24 ff. ; of group differences
in variability, 27 ff- J of individual
differences, 3 ff. ; of mental rela-
tions, 172 ff. ; of relative inferiority
in different traits, 216 f. ; of resem-
blance, 71 ff. ; of variability, 15 ff.

Measurements. See the references
given under the subject concerned.

Median, 13.

Median ratio, 74.

Memory, in individuals exceptionally
deficient in intellect, 219, 221 f. ; of
digits, distribution of, 151; relations
of, 182 ; sex differences in, 28, 30 f.

Mental science, sex differences in
scholarship in. 31.

Mode, 12.

Moral traits, exceptional inferiority in,
223 f. ; inheritance of, 80 ff., 86 ff.,
92 f. ; sex differences in, 44 ff.

Motor ability, differences in, due to
age, 105 ff. ; differences in, due to
sex, 2y, 30 f. ; in individuals excep-
tionally deficient in intellect, 218 f.,
221 f.

Multimodality, 152 ff.

Multiple type theory, 152 ff., 195 ff.

Negritos, ability of in matching
forms, 60 f.

Negroes, and whites compared in
scholarship, 52 ff. ; intellectual
powers of, according to Galton, O5 f.

Nurture. See Environment.

Index of Subjects

247

Objective measurements, 5 f.
Opposition of traits. See Relations,
inverse.

Pain. See Senses.

Pearson coefficient of correlation,
74 fif., 180 f.

Perception, distribution of individuals
in, 151 ; inheritance of ability in,
89 ff. ; racial differences in, 58; sex
differences in, 27, 30 f., 41 ; special-
ized in inheritance, 97 f.

Pitch. See Senses.

Popularity, inheritance of, 80 ff. ; sex
differences in, 44 f.

Precocity, 225 f.

Pressure. See Senses.

Primitive races, mental traits of 55 ff.

Probability form of distribution, 160 ff.

Profession, causes of an individual's
choice of a, 134 f.

Qualitative differences, reducible to
quantitative, 4.

Race, as a cause of individual differ-
ences, 51 ff. ; as a cause of multi-
modality, 154 f.

Races, the interpretation of the dif-
ferences of, in achievement, 64 ff.

Range of sensitivitjf. See Senses.

Rates of growth, exceptional, 224 ff.

Reaction time, age differences in,
IDS ff. ; distribution of ability in,
151 ; sex differences in, 27, 30 f.

Relations between amounts of differ-
ent traits in the same individual,
171 ff. ; common factor in, 185 f . ;
comparison of, 179 f . ; curvilinear,
178 f. ; general features of, 189 ff. ;
inverse, 183 ff., 200; measurement
of, 172 ff. ; rectilinear, 177 ff. ; signi-
ficance of, 183 ff. ; through identity
of form, 186 ff. ; variability of,
174 ff. See also Resemblances.

Reliability of mental measurements,
II ff.

Resemblances, attenuation of, 80 f. ;

dilation of, 81 f., 83 ; measurement

of, 71 ff.
Royal families, hereditary resemblance

in, 84 ff.

Scales, for mental traits, 5 ff.
Scholarship, of whites and negroes
compared, 52 ff., sex differences in,

31-

School progress, sex difference in
variability in, 41 f.

School work, individuals failing in,
220 f.

Science, the causes of achievement in,
122 ff.

Selection, fallacies due to unfair, 112,
114 f . ; influence of on the form of
distribution, 167 ff.

Selective thinking, inferiority of in-
tellectually deficient individuals in,
218, 222 f. ; sex differences in, 31.

Self-consciousness, inheritance of,
80 ff. ; sex differences in, 44 f.

Senses, age differences in the, 105 ff. ;
racial differences in the, 55 ff. ; sex
differences in the, 27 ff.

Sensory discrimination, individual dif-
ferences in, 144 f., 151 ; inferiority
of intellectually deficient individuals
in, 218 f. ; relations of, 181 f. See
also Senses.

Sex, as a cause of individual differ-
ences, 18 ff. ; as a cause of multi-
modality, 154.

Sex differences, 18 ff. ; in abilities,
20 ff. ; in character and interests,
43 ff. ; in variability, 34 ff.

Sexes, differences in the training of
the, 18, 32.

Shyness, sex differences in, 44 f. ;
the inheritance of, 80 ff.

Simple and compound differences, 3 f.

Single type theory, 145, 168 ff., 195 ff.

Skewness of distribution, 167 ff.

Slow growth, 228 ff.

Sorting, relations of abilities in, 181 f. ;
sex differences in, 27.

248

Educational Psychology

Specialization, of heredity, 93 ff. ; of
mental traits, 186 flf.

Speed of mental and motor processes,
racial differences in, 58.

Spelling, differences of different
school classes in, 127 f. ; sex differ-
ences in, 31 ; the causes of ability
in, 126 ff. ; the inheritance of the
ability to learn, yy f.

Stature, inheritance of, 76; of mental
defectives, 218.

Subjectivity, of measures, 5 ff . ; sex
differences in, 50.

Suggestibility, differences in due to
age, 105 ff.

Surface of frequency. See Distribu-
tion.

Tapping, relations of ability in, 181 f. ;
sex differences in, 27.

Taste. See Senses.

Temper, inheritance of, 80 ff. ; sex
differences in, 44 f.

Temperament, individual differences
in, 19s ; sex differences in, 44 ff.

Temperature, of individuals exception-
ally inferior in intellect, 221 f. See
also Senses.

Tests. See the references under the
subjects concerned. See also
Appendix II.

Threshold. See Senses.

Touch. See Senses.

Training. See Environment.

Twins, resemblances of, 72 ff., 89 ff. ;
specialization of inheritance in,
96 ff. ; the action of likenesses and
differences in the environment upon,
119 ff.

Types of intellect and character,
171 ff., 193 ff.

Variability, allowance for in the com-
parison of defects in different traits,
266 f. ; allowances for in the com-
parison of relations, 178 ff. ; compari-
son of groups in respect to, 37 ff. ;
methods of measuring, 15 ff. ; of
determiners, loi ; of different
measures of ostensibly the same
mental fact, 11 ff. ; of germs from
the same parents, 71 ; of individuals
of the same sex and ancestry, 69 ff. ;
of races, 53 ; of the same groups in
different traits, 144 ff. ; of the sexes,
ZZ ff- ," reduction of in individuals of
similar ancestry, y2. See also
Individual Differences and Distribu-
tion.

Vivacity, inheritance of, 80 ff. ; sex
differences in, 44 f.

Weight, of mental defectives, 218.
Zero-points for mental scales, 146 flF.

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