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:

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
differences in the general activities of the two sexes has not.
The fighting instinct is in fact the cause of a