Understanding of others' knowledge in chimpanzee

Satoshi Hirata

Kyoto University, Japan

Can the chimpanzee understand another chimpanzee's knowledge or ignorance? This has been an interesting question regarding cognitive evolution in animals, especially in the framework of "theory of mind" proposed by Premack and Woodruff (1978). I tested pairs of captive chimpanzees to examine whether chimpanzees were able to understand the knowledge possessed by other conspecifics. utilizing with various modifications Menzel's (1974) pioneering work. The testing procedure was as follows: 1) an experimenter hid a banana in the chimpanzees' outdoor compound; 2) a chimpanzee (the witness) could see where the banana was hidden from an indoor room; 3) another chimpanzee (the bystander) could not see the baited location but could see the witness observing the baiting process; 4) the witness and the bystander were released together into the outdoor compound. This procedure was repeated once a day along with the introduction of role reversal. In addition, another condition was conducted as a control condition in which neither could see the baited location. During the course of the experiment, the witness and the bystander developed tactics and counter-tactics to obtain the hidden banana. A detailed examination of the progress of such tactics suggested that the bystander understood the witness's knowledge of the location of the hidden banana.

Hirata, Satoshi

Section of Language and Intelligence, Primate Research Institute,

Kyoto University

Inuyama, Aichi 484-8506, Japan

hirata@pri.Kyoto-u.ac.jp