CONCEALING FACIAL EVIDENCE OF MOOD - PERSPECTIVE-TAKING IN A CAPTIVE GORILLA

A captive female lowland gorilla was observed repeatedly to hide or in hibit her playface by placing one or both hands over the face. When th is behaviour was seen play usually did not follow immediately even if other signals associated with play were simultaneously being made by t he gorilla. By contrast, a playface predicted that play would follow w ithin a few seconds; this difference was statistically reliable. Sever al levels of interpretation of the behaviour are possible: hiding the playface may have functioned as a form of deception, a meta-communicat ion, or merely an attempt to suppress the playface. However, by any of these interpretations, the behaviour implies that the gorilla is awar e of her spontaneous facial expressions and the consequences they enta il. Among the great apes, manual suppression of a facial expression ha s previously been reported once for chimpanzees but never for gorillas .