Over the past several years at the Yerkes Laboratories, the authors have engaged in the study of the effects of various kinds of early experience on the psychological, social, and physical development of the chimpanzee. During the course of the study, we have been particularly impressed by the stereotyped behaviors exhibited by chimpanzee infants. These behaviors are characterized by the frequent, almost mechanical, repetition of a posture or movement which varies only slightly in form from time to time, and which to the human observer serves no obvious function.
The purpose of the present paper is to describe these stereotypies, and to indicate the resemblance of chimpanzee stereotypies to some repetitive behaviors which are commonly observed in mentally defective,1 blind,1 and psychotic15 humans. Evidence will be presented to show that stereotypy is related to rearing variables, developmental status, the immediate stimulus situation, and to various forms of