Behavioral development of an infant chimpanzee (Ayumu) and his relationship with his mother (Ai) during Token Experiments

Claudia Sousa1), Sanae Okamoto2), and Tetsuro Matsuzawa1)
1) Kyoto University, Japan, 2) Nagoya University, Japan

Infants go through several changes during their behavioral developmental. And it is during this period they acquire a lot of new behaviors, some of them through social learning. The conditions offered by the Token Experiment performed by Ai are ideal to study those developmental changes in the behavior of her infant, Ayumu. The experiment consists of 2 parts: a matching phase and exchange phase. Based on the video-recordings of the above mentioned experiment, we analyzed the variables as: Time spent near Food Tray for the Coins; Time spent near Food Tray for Food; Attempts and successes in touching the touch-sensitive panel for the matching phase; Attempts and successes in touching the touch-sensitive panel for the exchange phase; Attempts and successes in getting coins; Attempts and successes in getting food rewards; Attempts and successes in inserting coins. With 9 months and 23 days (16th February 2001), Ayumu showed a sudden interest for the matching phase of the experiment. He touched the touch-sensitive panel successfully completing a trial and receiving 1 coin. After that day and till he was 15 months of age, he sporadically touched the touch-sensitive panel. At 11 months of age Ayumu started to spend more time near the Food Tray for Food. The majority of the time he was trying to get the food-rewards. With 15 months of age, he started to show again a bigger interest for the Matching-to-sample task, completing several trials and receiving sometimes some coins. The data suggests that Ayumu already understands the flow of a trial and the outcome of completing one trial, which is getting a coin. As he does not receive any food when he completes a trial with success, his spontaneous behavior must be moved by a strong motivation. The fact that he also tries to get access to the food rewards before his mother also shows that he understands from where the food comes.

Sousa, C. & Matsuzawa, T. (2001). The use of tokens as rewards and tools by chimpanzees (Pan troglodytes). Animal Cognition, 4: 213-221

 

SOUSA, Claudia
Primate Research Institute,
Kyoto University
Inuyama, Aichi, 484-8506, Japan
sousa@pri.kyoto-u.ac.jp