Who can be in a group? 3- to 5-year-old children construe realistic social groups through mutual intentionality

Recent research suggests that young children's causal justification for minimal group membership can be induced via a cognitive framework of mutual intentionality. That is, an individual can become a group member when both the individual and group agree to membership. Here, we investigated if children ages 3–5 understand groups formed by mutual intentions and whether they apply mutual intentions to realistic groups with varying entitative and essentialized qualities. In two studies (N = 197), we asked 3-, 4-, and 5-year-old children if a novel character could join an existing group based on intentionality (mutual, individual-, group-only) and group type (task, friends, family). We find that 4- and 5-year-olds robustly relied on mutual intentions to constitute group membership and 3-year-olds also demonstrated emerging usage of this cognitive framework. Moreover, children employed mutual intentionality across different group types, suggesting a general framework for children's understanding of different social groups.