Imitation of Other Monkeys 219 Learning apart from Motor Impulses 222 General Mental Development of the Monkeys 236 LAWS AND HYPOTHESES OF BEHAVIOR 241 THE EVOLUTION OF THE HUMAN INTELLECT 282 ANIMAL INTELLIGENCE CHAPTER I THE STUDY OF CONSCIOUSNESS AND THE STUDY OF BEHAVIOR The statements about human nature made by psychologists are of two sorts,—statements about _consciousness_, about the inner life of thought and feeling, the ‘self as conscious,’ the ‘stream of thought’; and statements about _behavior_, about the life of man that is left unexplained by physics, chemistry, anatomy and physiology, and is roughly compassed for common sense by the terms ‘intellect’ and ‘character.’ Animal psychology shows the same double content. Some statements concern the conscious states of the animal, what he is to himself as an inner life; others concern his original and acquired ways of response, his behavior, what he is to an outside observer. Of the psychological terms in common use, some refer only to conscious states, and some refer to behavior regardless of the consciousness accompanying it; but the majority are ambiguous, referring to the man or animal in question, at times in his aspect of inner life, at times in his aspect of reacting organism, and at times as an undefined total nature. Thus ‘intensity,’ ‘duration’ and ‘quality’ of sensations, ‘transitive’ and ‘substantive’ states and ‘imagery’ almost inevitably refer to states of consciousness. ‘Imitation,’ ‘invention’ and ‘practice’ almost inevitably refer to behavior observed from the outside. ‘Perception,’ ‘attention,’ ‘memory,’ ‘abstraction,’ ‘reasoning’ and ‘will’ are samples of the many terms which illustrate both ways of studying human and animal minds. That an animal perceives an object, say, the sun, may mean either that his mental stream includes an awareness of that object distinguished from the rest of the visual field; or that he reacts to that object as a unit. ‘Attention’ may mean a clearness, focalness, of the mental state; or an exclusiveness and devotion of the total behavior. It may, that is, be illustrated by the sharpness of objects illumined by a shaft of light, or by the behavior of a cat toward the bird it stalks. ‘Memory’ may be consciousness of certain objects, events or facts; or may be the permanence of certain tendencies in either thought or action. ‘To recognize’ may be to feel a certain familiarity and surety of being able to progress to certain judgments about the thing recognized; or may be to respond to it in certain accustomed and appropriate ways. ‘Abstraction’ may refer to ideas of qualities apart from any consciousness of their concrete accompaniments, and to the power of having such ideas; or to