The Human Instincts

What is an Instinct? Instinct is usually defined as the faculty of acting in such a way as to produce certain ends, without foresight of the ends, and without previous education in the performance. "Every instinct is an impulse. Whether we shall call such impulses as blushing, sneezing, coughing, smiling, or dodging, or keeping time to music, instincts or not, is a mere matter of terminology. The process is the same throughout.
In his delightfully fresh and interesting work, G. H. Schneider subdivides impulses into sensation-impulses, perception-impulses, and idea-impulses. To crouch from cold is a sensation-impulse; to turn and follow, if we see people running one way, is a perception-impulse; to cast about for cover, if it begins to blow and rain, is an imagination-impulse. A single complex instinctive action may involve successively the awakening of impulses of all three classes.
Thus a hungry lion starts to seek prey by the awakening in him of imagination coupled with desire; he begins to stalk it when, on eye, ear, or nostril, he gets an impression of its presence at a certain distance; he springs upon it, either when the booty takes alarm and flees, or when the distance is sufficiently reduced; he proceeds to tear and devour it the moment he gets a sensation of its contact with his claws and fangs.
Seeking, stalking, springing, and devouring are just so many different kinds of muscular contraction, and neither kind is called forth by the stimulus appropriate to the other..."