least six separable sets of connections in the so-called 'fighting
instinct,'" in each of which the situation and the response differ from
any other one.

Very few of the instincts are present at birth; most of them develop
later in the child's life. Pillsbury says, "One may recognize the
food-taking instincts, the vocal protests at discomfort, but relatively
few others." This delay in the appearance of instincts and capacities is
dependent upon the development of the nervous system. No one of them can
appear until the connections between nerve centers are ready, making the
path of discharge perfect. Just when these various nervous connections
mature, and therefore just when the respective tendencies should appear,
is largely unknown. In only a few of the most prominent and
comparatively simple responses is it even approximately known. Holding
the head up is accomplished about the fourth month, walking and talking
somewhere near the twelfth, but the more complex the tendency and the
more they involve intellectual factors, the greater is the uncertainty
as to the time of development. We are told that fear is most prominent
at about "three or four" years of age, spontaneous imitation "becomes
very prominent the latter part of the first year," the gang instinct is
characteristic of the preadolescent period, desire for adventure shows
itself in early adolescence, altruism "appears in the early teens," and
the sex instinct "after about a dozen years of life." The child of from
four to six is largely sensory, from seven to nine he is motor, from
then to twelve the retentive powers are prominent. In the adolescent
period he is capable of thinking logically and reasoning, while maturity
finds him a man of responsibilities and affairs. Although there is some
truth in the belief that certain tendencies are more prominent at
certain periods in the development of the child than at others, still it
must be borne in mind that just when these optimum periods occur is not