Do 9-month-old infants prefer prosocial others? Two conceptual replications and a meta-analysis of the Hamlin & Wynn box opening/closing paradigm

Two experiments were conducted in Norway and Indonesia between 2022 and 2023 to replicate Hamlin and Wynn's (2011) finding from a North American sample, in which 75% of 9-month-old infants preferred a prosocial (Helper) over an antisocial (Hinderer) puppet in the box opening/closing paradigm. In two independent samples of 9-month-olds, 58% of 24 Norwegian and 57% of 30 Javanese infants preferred the helper, which was not significantly different from chance. In a meta-analysis based on 15 experiments by seven labs, including ours, 58% (95% CI [56%; 64%]) of infants chose the Helper. The largest effects were observed in studies conducted in North America, nearly all originating from a single laboratory. Explanations for the observed heterogeneity in findings are discussed.