いかに‘一緒に遊ぶ’のか: ニホンザルの取っ組み合い遊びの始まり方と終わり方

Abstract

Achieving ‘doing something together’ requires more than mere physical proximity and bidirectional behavior; interactants must construct a situation where both parties are intersubjectively engaged in a shared interactional space to achieve ‘togetherness.’ This paper summarizes how immature Japanese macaques （Macaca fuscata） achieve （and sometimes fail to achieve） ‘playing together’ by reviewing our research on the opening and closing phases of play fighting. Our research indicates （1） that the face-to-face configuration during the opening of play contributes to the establishment of intersubjective engagement, （2） that facial signals during the opening phase honestly reflect an individual's motivation to play but are not used tactically to invite reluctant or infrequent partners, and （3） that the ways in which play breaks down into overt conflict are related to interindividual differences determined by dominance ranks and developmental stages. These findings provide important insights into the evolutionary basis of togetherness, a characteristic of human interaction. The paper also highlights several points not addressed in our previous research and discusses future research directions.