Abstract
The representational ability of chimpanzees was tested and compared with that of humans in terms of two aspects: short-term memory reproduction and mental rotation. In the test of short-term memory reproduction, a chimpanzee and adult humans were trained to reconstruct 84 three-element figures after various delay intervals up to 32sec. The chimpanzee maintained performances slightly better than humans under all delay conditions. However, different from humans, accuracy of reconstruction of meaningful figures which stood for food was not higher than that of meaningless ones. In the test of mental rotation, another chimpanzee and adult humans matched rotated figures from samples. Humans showed a monotonous increase in the reaction time of matching response as a function of the rotational angles up to 180 degree between sample and comparison stimuli, while the chimpanzee showed a peak of reaction time for rotational angles of around 90 degree. These results suggest that although recent sutdies of primate cognition has stressed the parallel of nonhuman primates and humans, some fundamental aspects of representational ability are different in these species. The chimpanzees seem to have the difficulty in spontaneously integrating the information given in different contexts which are related to each other.
