Abstract # 33:

Scheduled for Thursday, June 21, 2007 02:00 PM-02:15 PM: Session 6 (North Main Hall F/G) Oral Presentation

Throwing in Chimpanzees (Pan troglodytes): A Behavioral Marker of Nonhuman Primate Differences in Social Cognition?

W. Hopkins1,2
1Yerkes Reg. Prim. Res. Ctr., Div. of Psychobiology, Emory Univ., Atlanta, GA 30322, USA, 2Department of Psychology, Agnes Scott College
     Throwing is a form of tool use and scientists, zoo personnel, and lay persons that encounter apes in captivity often remark on their habits of throwing materials, notably feces, at strangers or spectators. Interestingly, it is seldom noted that other nonhuman primates engage in throwing. Here we describe the results of a long-term study on the incidence of throwing in a sample of 247 captive chimpanzees. During a 13 year observation period, 90 chimpanzees were observed to throw on 6 or more occasions. Neither sex nor rearing history nor group size significantly influenced the prevalence of throwing. However, chimpanzees that reliably threw (66%) were significantly more likely to solve a novel problem-solving task, notably, opening a coconut, than non-throwers (48%) [c2(1)=3.77, p<0.05]. Throwers were also more likely to use novel attention-getting signals in a communication task (81%) compared to non-throwers (50%). It is argued here that throwing represents an “innovative” tool using behavior in chimpanzees and develops and is maintained because it allows the apes to manipulate the behaviors of others. The ability to manipulate others, and the consequences associated with this action, are socially reinforcing to the apes and may be lacking or less developed in other nonhuman primates. This potential species difference may be the foundation for advanced social cognition including perspective taking and theory of mind in nonhuman primates.