How 2 and 4 year old children coordinate joint actions with peers

The interaction engine hypothesis postulates a uniquely human ability and motivation for social interaction. A crucial juncture in the ontogeny of the interaction engine could be around 2-4 years of age, but observational studies of children in natural contexts are lacking. Moreover, data on the ontogenetic development of joint action coordination can provide critical human data for comparative research investigating the phylogenetic roots of the interaction engine. In this study we report on focal observations on 31 children aged 2 and 4 years old in 4 preschools (approximately 20h per child). Interactions were videotaped, transcribed and coded for the presence and duration of joint actions, their type (e.g., play, conflict) and the partners involved, as well as the presence and duration of entry, exit and main body phases of those joint actions. Children interact with a wide range of partners, many infrequently, but with one or two close friends. 4 year olds engage in cooperative join...