hind the frame, turned the frame about and searched behind it, tried to carry it with her into the nest-room, and finally was unwilling to let me take it from the cage with me. I could not see that there had been any abatement of interest in the mirror-image and I was extremely reluctant to discontinue observation because it would seem worth while to find out how long this peculiar social behavior would continue. Possibly further study might convince one that it is due primarily to lonesomeness for members of her species, or instead to slowness of intelligent adaptation to a novel type of situation. Perhaps after all this apparently innocent and almost absurdly simple type of experiment exhibits something which is extremely important in gorilla psycho-biology. Often we have heard that gorillas die of lonesomeness or as a result of separation from those they are attached to. Do these observations make the statements more easily believable and do they give us some clue to the social psychology of the gorilla, or are we putting together things which are unrelated? Whatever may be the answer, I suspect that we have happened on a line of inquiry which if properly followed up will help us to an understanding of the gorilla mind. The highly self-dependent attitude of Congo and her aloofness from human beings, except as she feels dependent upon them for her material needs, suggest the term introvert. Are we perhaps dealing in this case with a type of organism which when separated from its kind and compelled to associate with man becomes extremely introverted? And is this condition so far due to the unusual circumstances of life in captivity and of relative isolation from its species that we gain a very misleading notion of the mental traits of the gorilla? Or are shut-in-ness, negativism toward man, and a seeming haughty aloofness characteristic of this king among apes? I have recourse to questions because statements would be even more liable to misconstruction. Congo's behavior has deeply stirred my curiosity, and I have many times asked as I observed her and as I have worked over my notes and manuscript: What are the social and 4 other biological advantages and disadvantages of extraversion and introversion, and why has the gorilla, even as compared with the chimpanzee and orang-utan, lost in the struggle for existence? It is this question which leads me to consider in the following paragraphs, modes of adaptation of behavior as they appear in what I wish to designate as fooling, aping, and imitating. Fooling, in the sense of working with objects in a seemingly purposeless but exploratory fashion, is characteristic of certain types of mammal, and especially of the primates; characteristic also of certain periods of development, as for example human infancy and the early stages of many of the infrahuman primates. Presumably the more readily and persistently an animal fools with the objects of its environment, the more rapidly it learns their qualities and comes to adjust itself profitably to them. From one point of view what I term fooling or monkeying is the initial or primitive form of research! In aping, as contrasted with fooling, the influence of social suggestion or copy becomes dominant and determining. The act or assemblage of acts may be no more purposeful, or indeed profitable, than those of fooling, but they at least tend to reproduce more or less precisely the reaction of another organism or some other type of object, and are direct and immediate responses to those external events. In us yawning, coughing, sneezing, smiling, frequently occur in response to similar acts of other organisms and are in the sense of this paragraph instances of aping. I have reserved the term imitating for acts the stimulus of which is supplied by the activity of another organism and the form of which is determined primarily by the objective obviously attained by the other organism. There are, to be sure, many usages of the term imitation, and it is undeniable that imitative tendency in organisms expresses itself in varied forms of activity and with varying degrees of consciousness of end and of means as leading to that end. I have burdened the reader with these somewhat labored defi nitions in preparation for the following statements concerning Congo's activities. In the above sense of the term, she fools. surprisingly little with the objects in her new world. I have almost no convincing evidence of her tendency to ape. It is difficult to believe that she would not ape others of her kind, but I can truthfully say that I never saw her ape me or any other person. True, this may be a case of contrariness or of complete suppression of an ordinarily natural mode of expression. When it comes to imitating with reference rather to purpose than the precise means, the facts are in no wise different, for Congo simply does not imitate persons with such frequency, freedom, and explicitness that one can feel sure of it. Again I hesitate to believe that she is utterly non-imitative. It seems far more probable that she is non-imitative of us while perhaps somewhat imitative of others of her kind. What bearing, we may nów ask, has Congo's apparent negativism and peculiarity of responsiveness, as compared with the other great apes, on her ability to adapt herself to such problems as I busied myself in presenting to her? Offhand it would seem that she is at a very considerable disadvantage in learning new things because of her lack of abundant and impulsive activity, tendency to test and try everything that comes within reach, and to do what other persons or other animals do, or at least to imitate their actions to the extent of attaining the ends or goals which she sees them attain. If Congo is relaively impulsive, destructive, curious, imitative, she has deceived or misled me amazingly. Her behavior has filled my mind with the impression that she is too much aloof from her environment, too little adventurous, or, in the scientific sense, inquiring, to readily and quickly discover solutions of novel problems and adapt herself to extraordinary environmental demands. If this be true, one can understand why the gorilla should be a disappearing race, and perhaps also why so little relatively is known about its mental traits, and so little sympathy exists between man and gorilla: Fooling and aping, as do the infrahuman primates and we in J our infancy, are conducive to serviceable adaptation through the popularized process of "trial and error." But it would appear that learning on the basis of insight, understanding, or appreciation of relationships between environmental ends and means, or among means themselves, is relatively at least independent of fooling and aping, while conversely largely dependent on that crude form of the spirit of inquiry which we commonly call curiosity and on the tendency to attend to situations as wholes, to survey them completely and in a seemingly appraising way, and then to try out thoroughly and with patient persistence one after another the methods which are made available by the combined native and acquired reactive capacities of the individual. Just because the chimpanzee is much fuller of curiosity and more imitative than the gorilla, it has I suspect outstripped its gigantic fellow-ape in the race for anthropoid supremacy. VII EVIDENCES OF INSIGHT Insight is used throughout this report to designate varieties of experience which in us are accompaniments of sudden, effective, individually wrought adaptations to more or less distinctly new and problematic situations. For us as students of animal behavior its indications are aspects of the adaptive behavior itself, and in our work the essential thing is to observe and accurately describe the facts, irrespective of any interest or bias we may have respecting methods of learning or types of experience in the organism under observation. During my study of Congo I acquired new light on at least one important aspect of the methodology of psycho-biology. It was in connection with photographic record versus direct observation. Heretofore I have assumed that the span and distribution of my attention are adequate to enable me to see what my reacting subject does, my memory adequate to hold the facts in mind long enough for abbreviated description, and my training in objectivity adequate to enable me later safely and accurately to transcribe and elaborate my outline notes. It was a considerable shock when from comparison of the results of direct observation with still and motion picture records I discovered that I was overlooking, or otherwise missing or confusing, some of the most important aspects or phases of Congo's behavior. When, for example, she was reaching for something with hand or foot, using a stick or other object as tool, or manipulating the multiple-choice mechanisms, I succeeded as a rule in getting certain important points in the response, perhaps for the actual course and result of the behavior, the essential points. But as often as not I was uncertain which hand or foot had been used, or if both were used, in what order; or realizing that I had actually observed a certain series of acts, I could not be perfectly certain of the exact order or temporal relations. The photographic records in numerous instances, and to a |