Abstract # 24:

Scheduled for Saturday, September 19, 2009 10:30 AM-10:40 AM: Session 3 (Del Mar Room) Oral Presentation


J. P. Taglialatela1,2 and W. D. Hopkins2,3
1Clayton State University, Department of Natural Sciences, Morrow, Georgia 30260, USA, 2Yerkes National Primate Research Center, 3Agnes Scott College

Over the past several years, a number of studies have demonstrated that the manual gestures produced by chimpanzees (Pan troglodytes) are not simply failed attempts to obtain out of reach items, but deliberate requests. These results have led some to conclude that human language (Homo sapien) evolved from a manual communication system that arose in a common human and chimpanzee ancestor. However, more recent data indicate that chimpanzees use sounds to capture the attention of a human, and alter the production of their vocal signals as a function of the communicative demands of a situation. Nonetheless, it remains widely held that chimpanzee vocal production is bound to the arousal state of the caller. To directly assess this claim, we analyzed the behavior of 25 chimpanzees upon discovering a food cache. Subjects were briefly separated from their social groups and confined to the indoor portion of their home enclosures. A human experimenter then placed a relatively large quantity of preferred food (e.g. a bunch of grapes) just outside the outdoor portion of the subject’s enclosure, and then immediately left the area. The subject was then permitted to access the outdoor section of their enclosure, where they would discover the cache of food. The number of vocalizations produced by each subject was quantified, as was the number of self-directed scratches (an indicator of arousal). Vocal behavior and scratching behavior were not significantly associated [Pearson’s r=0.135, p=0.52], indicating that chimpanzee vocal production is not completely bound to the arousal state of the caller.