Sex Differences

The question as to the relative intelligence of the

sexes is one of perennial interest and great social importance. The

ancient hypothesis, the one which dates from the time when only men

concerned themselves with scientific hypotheses, took for granted the

superiority of the male. With the development of individual psychology,

however, it was soon found that as far as the evidence of mental tests

can be trusted the _a
erage_ intelligence of women and girls is as high

as that of men and boys.

If we accept this result we are then confronted with the difficult

problem of finding an explanation for the fact that so few of those who

have acquired eminence in the various intellectual fields have been

women. Two explanations have been proposed: (1) That women become

eminent less often than men simply for lack of opportunity and stimulus;

and (2) that while the average intelligence of the sexes is the same,

extreme variations may be more common in males. It is pointed out that

not only are there more eminent men than eminent women, but that

statistics also show a preponderance of males in institutions for the

mentally defective. Accordingly it is often said that women are grouped

closely about the average, while men show a wider range of distribution.

Many hundreds of articles and books of popular or quasi-scientific

nature have been written on one aspect or another of this question of

sex difference in intelligence; but all such theoretical discussions

taken together are worth less than the results of one good experiment.

Let us see what our 1000 I Q's have to offer toward a solution of the


1. When the I Q's of the boys and girls were treated separately there

was found a small but fairly constant superiority of the girls up to the

age of 13 years. At 14, however, the curve for the girls dropped below

that for boys. This is shown in Figure 3.

The supplementary data, including the teachers' estimates of

intelligence on a scale of five, the teachers' judgments in regard to

the quality of the school work, and records showing the age-grade

distribution of the sexes, were all sifted for evidence as to the

genuineness of the apparent superiority of the girls age for age. The

results of all these lines of inquiry support the tests in suggesting

that the superiority of the girls is probably real even up to and

including age 14, the apparent superiority of the boys at this age being

fully accounted for by the more frequent elimination of 14-year-old

girls from the grades by promotion to the high school.

2. However, the superiority of girls over boys is so slight (amounting

at most ages to only 2 to 3 points in terms of I Q) that for practical

purposes it would seem negligible. This offers no support to the opinion

expressed by Yerkes and Bridges that "at certain ages serious injustice

will be done individuals by evaluating their scores in the light of

norms which do not take account of sex differences."

3. Apart from the small superiority of girls, the distribution of

intelligence in the two sexes is not different. The supposed wider

variation of boys is not found. Girls do not group themselves about the

median more closely than do boys. The range of I Q including the middle

fifty per cent is approximately the same for the two sexes.

4. When the results for the individual tests were examined, it was found

that not many showed very extreme differences as to the per cent of boys

and girls passing. In a few cases, however, the difference was rather


The boys were decidedly better in arithmetical reasoning, giving

differences between a president and a king, solving the form board,

making change, reversing hands of clock, finding similarities, and

solving the "induction test." The girls were superior in drawing designs

from memory, aesthetic comparison, comparing objects from memory,

answering the "comprehension questions," repeating digits and sentences,

tying a bow-knot, and finding rhymes.

Accordingly, our data, which for the most part agree with the results of

others, justify the conclusion that the intelligence of girls, at least

up to 14 years, does not differ materially from that of boys either as

regards the average level or the range of distribution. It may still be

argued that the mental development of boys beyond the age of 14 years

lasts longer and extends farther than in the case of girls, but as a

matter of fact this opinion receives little support from such tests as

have been made on men and women college students.

The fact that so few women have attained eminence may be due to wholly

extraneous factors, the most important of which are the following: (1)

The occupations in which it is possible to achieve eminence are for the

most part only now beginning to open their doors to women. Women's

career has been largely that of home-making, an occupation in which

eminence, in the strict sense of the word, is impossible. (2) Even of

the small number of women who embark upon a professional career, a

majority marry and thereafter devote a fairly large proportion of their

energy to bearing and rearing children. (3) Both the training given to

girls and the general atmosphere in which they grow up are unfavorable

to the inculcation of the professional point of view, and as a result

women are not spurred on by deep-seated motives to constant and

strenuous intellectual endeavor as men are. (4) It is also possible that

the emotional traits of women are such as to favor the development of

the sentiments at the expense of innate intellectual endowment.