Abstract
Human is a social animal and unique to communicate with language. We want to understand the neurobiological basis of this feature in the light of comparative neuroethology. Social animals, like primates and birds, could communicate with conspecific mates by vocalization. We have established the developmental model of social communication with domestic chick which is a precocial bird and can grow itself without parent care. This allows us to investigate the development of peer relationship without considering the effect of parent-infant relationship. We reared chicks under grouped or individual condition, and compared socialization between two conditions. We measured the association and calling behavior as indicating socialization. The chicks reared as a group for 8-14 days after hatching showed socialization. In contrast, the chicks reared under socially deprived condition showed strong fear response in the novel environment and could not develop socialization. We, next, tested uni-modal social deprivation, that is, either visual or vocal cue was presented during individually rearing. Under these conditions, the fear response was suppressed when the behavior was tested on 8-14th day. Socialization, however, was different between the sensory social cues presented. Only vocally communicated chick could develop socialization. These results suggest that social interaction during infant is critical to develop peer relationship and mutual vocalization is important. Now, we are localizing the neuronal substrate for the development of peer relationship [J Physiol Sci. 2006;56 Suppl:S24]
