Conversational interactions depend on partners making contingent responses. This experiment examined the responses of five chimpanzees, Washoe, Moja, Tatu, Dar and Loulis, to four conversational conditions. Following the chimpanzee’s request, a human interlocutor either: complied with the request, provided an unrequested item or activity, refused to comply or did not respond to the request. The chimpanzees’ responses were contingent on the conversational input of the interlocutor. When their requests were satisfied, the chimpanzees most often ceased signing. However, when their requests (...) were misunderstood, refused or not acknowledged, the chimpanzees repeated and revised. This pattern of responses is comparable to patterns of conversational responses in human children. Keywords: chimpanzees; American Sign Language; requests; pragmatics; conversation; gesture; communication; Pan troglodytes. (shrink)

We propose that the fine discrete movements of the tongue as used in speech are what account for the extreme lateralization in humans, and that handedness is a mere byproduct of tongue use. With regard to syntax, we support the Armstrong et al. (1995) proposition that syntax derives directly from gestural motor movements as opposed to facial expressions.