Diego JorratMarı́a Paz EspinosaMaría José Vázquez-De FranciscoPablo Brañas‐Garza2026-03-222026-03-22202510.1098/rspb.2025.1363https://doi.org/10.1098/rspb.2025.1363https://andeanlibrary.org/handle/123456789/53727Citaciones: 1Well-functioning human societies require the integration of vulnerable minorities, yet leading scientific theories conflict on how easily diverse groups cooperate. We experimentally investigate cooperation in 14 centres of a mentoring programme where participants have two possible natural identities-individuals raised under legal guardianship, suffering a negative stereotype (<i>G</i>; <i>n =</i> 112) and users without such a social stigma (<i>NG</i>; <i>n =</i> 82). Participants played a prisoners' dilemma game with an anonymous partner from the same centre (centre-ingroup) and from another centre (centre-outgroup). For individuals without a history within-centre interaction, we find centre-outgroup favouritism among <i>G</i> and centre-ingroup favouritism among <i>NG</i>. However, the longer <i>G</i> individuals have been in the centre the more centre-ingroup favouritism they display, while the opposite is true for <i>NG</i>. Regardless of within-centre history, both <i>G</i> and <i>NG</i> individuals cooperate less with the centre-ingroup (versus outgroup) as the probability that the centre-ingroup is <i>G</i> increases. Thus, we observe patterns of centre-outgroup and natural-outgroup favouritism among <i>G</i> which challenge theoretical frameworks exclusively focusing on ingroup favouritism. Our findings highlight the roles of system-justification and stereotypes in intergroup cooperation and have implications for the integration of vulnerable groups and the optimization of social policy programmes.enOutgroupIngroups and outgroupsSocial psychologyPsychologySocial identity theoryGroup conflictSocial groupDevelopmental psychologyarticle