Page:Popular Science Monthly Volume 31.djvu/172

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IT is generally considered that a cardinal differentia of the human race is its poor endowment in the way of instincts. Brutes need instincts, it is supposed, because they have no reason. But man, with his reason, can do without instincts. "Instinctive actions," says Professor Preyer, in his careful little work, "Die Seele des Kindes," "are in man few in number, and, apart from those connected with the sexual passion, difficult to recognize after early youth is past. So much the more attention," he adds, "should science pay to the instinctive actions of young children."

I believe this doctrine to be a great mistake. Instead of having fewer, man has more instincts than any other mammal. He has so many that they bar one another's path, and produce an indeterminateness of action in him, supposed to be incompatible with that automatic uniformity which, according to popular belief, characterizes all instinctive performances. Popular belief is here in error. The more carefully instincts have been studied of late years, and the more clearly their mechanism has been laid bare, the more evident has it become that their effects are liable to be modified by various conditions. Instincts are due, at bottom, to the organization in the nerve-centers of certain paths of discharge, or reflex-arcs, as they are technically called. The disturbance produced in the way of sound, light, or other sensible emanation, by some object in the environment, runs in at an animal's senses, and then out through his muscles. Each special sort of disturbance or stimulus affects a special set of muscles, and makes the animal act in a special way, he knows not why, except that it seems the only natural way to act at the moment. Witness the fear of a natural enemy, the love of the opposite sex, the pursuit of a natural prey. Some of these reflex-arcs are transient. Some of the environing objects stimulate more than one arc at once (as when the presence of a strange dog awakens timorous, pugnacious, and sociable movements, all at the same time, in another dog), and then small accidents determine the resultant path of discharge. Finally, habits are formed of reacting on one particular object of a kind, and inhibit the application of the instinct to other individuals (limitation of the sexual instinct to one mate, etc.). In an article published elsewhere,[1] I have tried to trace these complications and variations, and to show that the presence of too many instincts in a creature, some of them transient, some of them tending in opposite ways, some of them inhibited in their application by the habits earliest formed, must needs produce a

  1. "Scribner's Magazine," March, 1887.