Self-control emerges in a rich sociocultural context. Do group norms around self-control influence the degree to which children use it? We tested this possibility by assigning 3- to 5-year-old children to a group and manipulating their beliefs about in-group and out-group behavior on the classic marshmallow task. Across two experiments, children waited longer for two marshmallows when they believed that their in-group waited and their out-group did not, compared with children who believed that their in-group did not wait and their out-group did. Group behavior influenced children to wait more, not less, as indicated by comparisons with children in a control condition who were assigned to a group but received no information about either groups' delay behavior (Experiment 1). Children also subsequently valued delaying gratification more if their in-group waited and their out-group did not (Experiment 2). Childhood self-control behavior and related developmental outcomes may be shaped by group norms around self-control, which may be an optimal target for interventions.
Keywords: cognitive development; executive function; open data; open materials; preregistered; self-control; social influences.