We investigated a naive infant chimpanzee's learning of a food processing technique and the effect of his observations of the skilled mother during the learning process. Five pieces of "petit-mints" (tiny sweets) were put into a transparent plastic tube. One end of the tube was tied with a wire, which could not be untied by any means, and the other end was closed with a plastic clip. The food inside the tube could be obtained by opening this clip. Fifty tubes with petit-mints were provided in an experimental room and a pair of a mother chimpanzee and her 1.7 year-old son was introduced in the room. The mother had already known how to open the clip, while the son did not have a technique to open the clip in the beginning. In the first session, the mother chimpanzee successfully opened all of the 50 tubes and obtained the food inside, whereas the infant could not open any of the tubes although he showed several types of manipulations targeted to the tubes and clips. We have repeated the experiment once a day for more than 20 sessions. The infant chimpanzee spontaneously observed his mother very closely in the beginning when he was unskillful to obtain the food. Gradually he became able to open the clip by himself in the same way as his mother did, and the number of observations of his mother decreased accordingly. The infant's spontaneous observation of his mother evidently affected the increase in his performance. A detailed analysis shows that the learning was presumably completed by both of social learning from his mother and individual learning after his own trial and error.

Hirata, S., & Morimura, N. 2000 Naive chimpanzees' (Pan troglodytes) observation of experienced conspecifics in a tool-using task. Journal of Comparative Psychology, 114(3), 291-296.

HIRATA, Satoshi
Primate Research Institute,
Kyoto University
Inuyama, Aichi, 484-8506, Japan
hirata@pri.kyoto-u.ac.jp