Human adults engage in joint activities with others for various reasons, for example, for the mere motivational goal of enjoying acting together with a partner. Human children seem to engage in joint activities with others in different contexts rather early in their ontogeny (e.g., Warneken et al. 2006). However, so far little is known about what young children effectively understand about joint activities, that is, whether they merely coordinate their actions with their partner in order to achieve an individual goal, or whether they truly understand joint activities as following shared goals creating joint commitments (e.g., Bratman 1992b, in press, Gilbert 1989, 1990).
The present thesis reports a series of studies investigating this question. To this end, young children were engaged in games that they could play either alone, in parallel with another player, or jointly with another player. The author then assessed whether children adapted their behavior to the established play context. Results revealed that 1- to 4-year-old children are highly motivated to play jointly with an adult partner even when they could play the games alone. Already by the age of 2 years children seem to regard their partner as an intentional agent with whom they share goals and intentions. However, they also seem to regard another person as acting jointly as long as that person acts in parallel with them. Only the 3- and 4-year-old children adapted their behavior to another person depending on whether or not they had already previously formed a joint commitment to play together with that partner. Together the findings thus suggest that children develop a relatively sophisticated understanding of joint activity between 2 and 3 years of age.
Human adults engage in joint activities with others for various reasons, for example, for the mere motivational goal of enjoying acting together with a partner. Human children seem to engage in joint