抄録
A series of experiments on body imitation in chimpanzees revealed a significant difference in the degree to which humans and chimpanzees imitate whole-body actions. Unlike humans, chimpanzees tend to reproduce demonstrated actions by attending only to aspects (e.g., directionality) of a manipulated object, not details of the body movements of an individual manipulating the object (Myowa-Yamakoshi & Matsuzawa, 1999, 2000). Such results may reflect a basic disparity in visual-motor information processing between humans and chimpanzees.
Humans show a strong tendency to view others' actions not simply as physical movements referenced to objects, but as movements reflecting intention or other psychological characteristics. Using eye tracking technology, we compared perceptual characteristics of humans and chimpanzees who viewed actions of another individual; the aim was to discover unique aspects of human perception. We tested eye movements of 8- and 12-month-old infants, adults, and chimpanzees. We found that chimpanzees anticipate action goals in the same way as human adults. Humans and chimpanzees, however, perceive the goal-directed actions of others differently: humans, particularly infants, refer to actors' faces, whereas chimpanzees rarely do.
These findings demonstrate that the two species differentially perceive the same actions within a framework of social relationships; chimpanzees predict an action goal based mainly on object-related information, whereas humans perceive goal-directed actions by integrating object-related information with information about the individual manipulating an object. Remarkably, the latter tendency is observed in humans within the first year of life (Myowa-Yamakoshi, Scola, & Hirata, submitted). Differences in perceiving others' actions between humans and chimpanzees may be closely related to the differences in imitative abilities of the two species.
In the case of humans, as early as 12 month of age, infants do not perceive others' goal-directed actions strictly on the basis of goal attainment. Rather, they perceive actions depending on social contexts (using communicative cues such as eye contact and facial expressions of others) of action demonstration and their own action experience. We found that 12-month-old infants consider the visual status of others engaging in goal-directed actions. Infants viewed video clips of successful and failed goal-directed actions performed by a blindfolded adult, who cannot see the external object. Half the infants have previously experienced being blindfolded. The results showed that 12-month-old infants who were previously blindfolded preferred to look longer at the demonstrator's successful actions, whereas no such preference was observed in 8-month-old infants (Myowa-Yamakoshi et al., 2011).
Infant's own perceptual experience influences their reaction to the perceptual status of others. By the end of the first year of life, humans not only perceive others' goal-directed actions on the basis of the visible end-state of the goal object, but also they react to the actions in a way that indicates an internalization of their own perceptual experience.
【Note】The research reported here was supported by a grant from JSPS and MEXT (No: 19680013, 20220004, and 23300103).
