Differential use of vocal and gestural communication by chimpanzees (Pan troglodytes) in response to the attentional status of a human (Homo sapiens).

Abstract

This study examined the communicative behavior of 49 captive chimpanzees (Pan troglodytes), particularly their use of vocalizations, manual gestures, and other auditory-or tactile-based behaviors as a means of gaining an inattentive audience's attention.A human (Homo sapiens) experimenter held a banana while oriented either toward or away from the chimpanzee.The chimpanzees' behavior was recorded for 60 s.Chimpanzees emitted vocalizations faster and were more likely to produce vocalizations as their 1st communicative behavior when a human was oriented away from them.Chimpanzees used manual gestures more frequently and faster when the human was oriented toward them.These results replicate the findings of earlier studies on chimpanzee gestural communication and provide new information about the intentional and functional use of their vocalizations.An affective communication system enables a signaler to intentionally transfer a message to an audience (Smith, 1977).This message can be either affective in nature by providing information about the signaler's emotional state or symbolic by expressing a more complex, semantic idea (Gouzoules, Gouzoules, & Ashley, 1995;Marler, 1980;Seyfarth & Cheney, 1997).In either case, the audience must receive the message intact with an understanding that is close to the original intent of the signaler or the communication is not effective.Therefore, although some simple forms of affective communication may be produced without the intention of the signaler, in order for a communication system to be valuable to a species in terms of obtaining a goal, both the message and the means of communication must be intentional on the part of the signaler.Otherwise, the meaning of communicative repertoire depends more on the subjective interpretation of the audience than on the actual desired message of the signaler.Therefore, for behavior to be truly communicative, it is necessary for communicative actions, whether they are vocal or nonvocal, to be intentional and controlled by the signaler.Unfortunately, establishing whether or not a behavior is intentionally communicative is not a simple task.Developmental researchers typically use the following three criteria in making such a distinction: (a) the behavior changes in accordance with the attentional states of the audience; (b) the behavior is accompanied by gaze alternation between an observer and a distal