Abstract # 148:

Scheduled for Friday, June 22, 2007 05:00 PM-07:00 PM: Session 14 (South Main Hall) Poster Presentation

Causal Understanding of Connectivity and Functionality in a Tool Task by Chimpanzees (Pan troglodytes)

A. E. Bania and S. T. Boysen
The Ohio State University, Department of Psychology, 1835 Neil Avenue, 209 Psychology Building, Columbus, OH 43210, USA
     Numerous studies of chimpanzee tool use have shown that they are particularly capable of using tools to solve a variety of problems. In this experiment, nine chimpanzees were required to retrieve a food item by pulling a rake-like tool. Our aim was to determine specifically what properties of the tool subjects were attending to in determining the tool’s functional quality. In the first task, subjects were asked to make a selection between a rake with an intact handle, and one with a broken handle. In the second task, subjects selected between a u-shaped rake in continuous contact with the surface, and an inverted u-shape that was not continuously in contact with the surface. Each subject (N=9) was administered six sessions of eight trials. Rake and food position was randomized and counterbalanced for each session. Overall the chimpanzees performed significantly above chance [Binomial Sign Test, p(61:72,0.50)<0.0001] on the broken rake task (Sessions 1-4). However, the chimps’ performance on the inverted rake task (Session 5) was near chance level (38/72, 53%). An additional session (Session 6) was added to allow the chimps 60 seconds after they made an incorrect choice to manipulate the inverted tool. Given this opportunity, overall group success increased to 92% [p(66:72,0.50)<0.0001]. Results suggest that it may be the overall functionality of a tool rather than the exact orientation subjects are attending to in making their selection.