We investigated if tufted capuchin monkeys (Cebus apella) can recognize the causal connection between seeing and knowing. At the beginning of every trial, the experimenter placed a piece of food under one of three opaque containers behind a cardboard screen so that the subjects could not see which container hid the reward. Then the Knower or the Guesser appeared in front of the subjects in random order. The Knower looked under each of the containers, whereas the Guesser simply touched the top of each container. The Knower then pointed to the correct container while at the same time the Guesser pointed to one of the three randomly. The subjects were rewarded if they reached toward the container the Knower suggested. All the four subjects learned to follow significantly the pointing of the Knower (Kuroshima et al, 2001). We further investigated whether the subjects' behavior reflected true understanding of the causal connection between seeing and knowing in three experiments. In Experiment 1, we introduced 6 types of new containers. Each container was of different shape and color. Two of the four subjects gradually learned to reach toward the container the knower suggested. In Experiment 2, we diversified the Knower's looking behavior. In Experiment 3, we diversified the Guesser's behavior. One subject adapted to these novel behaviors of the Knower and the Guesser, successfully discriminating the two trainers. Thus this monkey clearly learned to use the inspecting action of the knower as a discriminative cue to recognize the baited container. This result suggests that capuchin monkeys can learn to recognize the relationship between seeing and knowing.

KUROSHIMA, Hika
Department of Psychology,
Graduate School of Letters, Kyoto University
Yoshida Honmachi, Sakyo-ku, Kyoto
606-8501, Japan
kuroshi@psy.bun.kyoto-u.ac.jp