these facts are added the fact that the age and previous habits of the child also influence his response, the immense complexity of the problem of discovering just what the situations are to which there are original tendencies to respond and just how these tendencies show themselves is evident.  And yet this is what psychologists must finally do if the use by teachers of these tendencies is to be both economical and wise.  Just as an illustration of the possibilities of analysis, Thorndike in his “Original Nature of Man” lists eleven different situations which call out an instinctive expression of fear and thirty-one different responses which may occur in that expression.  Under fighting he says, “There seem, indeed, to be at 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 known.  Three of the most important reasons for this lack of knowledge are:  first, the fact that all inborn tendencies mature gradually and do not burst into being; second, we do not know how transitory they are; and, third, the fact of the great influence of environment in stimulating or repressing such capacities.