類人猿の心の理論：ゴーグルテスト

抄録

Do nonhuman animals also have a "theory-of-mind", the ability to attribute an unobservable mental state to oneself and another? After decades of research, it is still controversial whether theory-of-mind is uniquely human or shared with nonhuman animals. One of such controversies regards whether nonhuman animals understand others' false-belief, namely that others' behavior is driven by beliefs about reality, even when those beliefs are false. One of the major alternatives to the theory-of-mind account is so-called the "behavior-rule" account, which proposes that animals rely on behavioral cues to predict others' behaviors. This study challenged this alternative using a version of "goggles" test, which asks whether animals could use their own past experiences of visual access to understand an agent's visual perception, without a reliance on any behavioral cues available in the test. This study integrated this paradigm into an established anticipatory-looking false-belief test. Two groups of apes first experienced either opaque barrier or see-through barrier. Both barriers appeared identical in a far distance, but the latter barrier was translucent and could be seen-though in a close distance. Both groups of apes subsequently watched the same video sequence in which an object was displaced in front of an actor while the actor was hiding behind the same barrier. The results showed that apes with an experience of opaque barrier did, apes with an experience of see-through barrier did not, anticipated the actions of the actor who had a false belief, thus supporting the theory-of-mind account in these species.