Sharing for the common good: Children's levels of social inclusion within the group and their sharing decisions in a public goods game.

Across two studies, this research explored the relationship between levels of social inclusion within a group and cooperative sharing decisions among children, using the public goods game (PGG). In Study 1 (10-12 years old, N = 165), participants' social inclusion was experimentally manipulated using a modified version of the Cyberball paradigm that varied the number of ball tosses, after which they were asked about their willingness to contribute resources to the common pool in the PGG. In Study 2 (10-11 years old, N = 249), social inclusion was measured in a naturalistic context by assessing children's interactions with peers in their class and their actual contributions in the PGG at two time points, 1 week apart. In both studies, children who experienced higher levels of social inclusion within the group were more willing to contribute to the group, even at a personal cost, compared with children experiencing lower levels of social inclusion. Together, these findings deepen our understanding of how social inclusion within the group shapes prosocial behaviour during middle childhood-a pivotal period in social development.