Stereotyped Behaviors of Chimpanzees: Relation to General Arousal and Alternative Activities

Abstract

Chimpanzees raised without their mothers develop abnormal stereotyped behaviors not found in mother-raised animals. Two studies tested the hypotheses that moment-to-moment fluctuations of stereotyped behaviors are related to the level of general arousal and to the extent to which alternative activities are performed. The first study showed that body rocking or swaying is positively related to white noise level and to food deprivation. In the second experiment, rocking and swaying decreased during habituation to a novel situation and returned to a high level following administration of amphetamine. Activities alternative to stereotyped movements were evoked in a third experiment and produced a decrement in rocking and swaying. In general, the evidence suggests a positive relationship between arousal and rocking and swaying; the relationship of arousal to other stereotyped acts was not as regular. No behavior in the repertoire of mother-raised animals was found to be homologous to Rock-Sway. The relationship between the various behavior categories studied was related to S's rearing history, momentary arousal level, and the extent to which the cues in the situation evoked the various behaviors.