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 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.[1]
[Footnote 1: Thorndike: Educational Psychology, briefer course, pp. 345-46.]
That is, so far as experiments upon objectively measurable traits have been conducted, the specific differences that individuals display have comparatively nothing to do with the fact that an individual happens to be a man or a woman. These experiments have been conducted with boys and girls as young as seven, and with men and women ranging up to the age of twenty-five.[2]
[Footnote 2: There seems, as might be expected to be, a slightly higher differentiation between the two sexes after adolescence than before.]
These experiments have been conducted to test sensory discrimination, precision of motor response and some of the simpler types of judgment, such as those involved in the solution of simple puzzles with blocks, matches, etc. The fact of the negligibility of sex difference with regard to certain minor measurable traits has been adequately demonstrated by a wide variety of experiments. The fact of sex equality or mental capacity has been less accurately but fairly universally noted by popular consensus of observation and opinion of the work of women in the various trades and professions. There are differences between men and women in physical strength and in consequent susceptibility to fatigue. These are important considerations in qualifying the amount of work a woman can do as compared with that of a man, and have justly resulted in the regulation of hours for women, as a special class. But there do not seem to be, on the average, significant original differences in mental capacity.[3]
[Footnote 3: On this subject there has been collected a large amount of accurate experimental data. See Goldmark: Fatigue and Efficiency, part II, pp. 1-22. These refer to physiological differences.]
There do exist, as a matter of practical fact, some of the special attributes commonly ascribed to the masculine and feminine mental life, but it is generally agreed by investigators that these are to be accounted for by the different environment and standards socially established for men and for women. There are radical and subtle differences in training to which boys and girls are subjected from early childhood. There are deeply fixed traditions as to the standards of action, feeling, and demeanor to which boys and girls are respectively trained and to which they are expected to conform. If a boy should not live up to this training and expectation, he may be marked out as "effeminate." If a girl does not conform, she is defined as a "hoyden" or a "tomboy."
These social distinctions, which are emphasized even in the behavior of young boys and young girls, grow more pronounced as individuals grow older. One need hardly call attention to actions regarded as perfectly legitimate for men which provoke disapproval if practiced by women. Rigid training in these different codes of behavior may cause acquired characteristics to seem inborn. But whether these general features commonly held to distinguish the mental life of man or woman are or are not intrinsic and original, they have been marked out by certain investigators as socially fundamental. Thus Heymans and Wiersma, two German investigators, set down as the differentia of feminine mental life (1) greater activity, (2) greater emotionality, (3) greater unselfishness of the female.[1]
[Footnote 1: See Thorndike's Educational Psychology (1910), p. 136.]
There are some general differences noted by both layman and psychologist, which, though not subject to quantitative determination, yet seem to differentiate somewhat definitely between feminine and masculine mental activity. These may be set down in general as occurring in the field of emotional susceptibility. Thorndike traces them back to the varying intensity of two human traits earlier discussed: the fighting instinct, relatively much stronger in the male, and the nursing or mothering instinct, much stronger in the female. With this fact are associated important differences in the conduct of men and women in social relations. The maternal instinct is held by some writers, for instance, to be in large measure the basis of altruism, and is closely associated with sensitivity to the needs and desires of others. Thorndike writes: