Data from: Reverse audience effects on helping in cooperatively breeding marmoset monkeys

Cooperatively breeding common marmosets show substantial variation in the amount of help they provide. Pay-to-stay and social prestige models of helping attribute this variation to audience effects, i.e. that individuals help more if group members can witness their interactions with immatures, whereas models of kin selection, group augmentation, or ones stressing the need to gain parenting experience do not predict any audience effects. We quantified the readiness of adult marmosets to share food in the presence or absence of other group members. Contrary to both predictions we found a reverse audience effect on food sharing behaviour: marmosets would systematically share more food with immatures when no audience was present. Thus, helping in common marmosets, at least in related family groups, does not support the pay-to-stay or the social prestige model, and helpers do not take advantage of the opportunity to engage in reputation management. Rather, the results appear to reflect a genuine concern for the immatures' wellbeing, which seems particularly strong when solely responsible for the immatures.合作繁育的普通狨猴（common marmosets）在帮助行为的投入程度上存在显著个体差异。关于帮助行为的“付费居留”（pay-to-stay）与社会声望模型将该差异归因于观众效应——即当群体成员可目睹个体与幼崽的互动时，个体将提供更多帮助；而亲缘选择、群体扩增模型，或是强调需积累育幼经验的理论模型，均未预测到此类观众效应的存在。我们量化了成年狨猴在有、无其他群体成员在场时的食物分享意愿。与两类模型的预测均相悖，我们发现食物分享行为呈现反向观众效应：当无观众在场时，狨猴会系统性地向幼崽分享更多食物。由此可见，普通狨猴的帮助行为（至少在亲缘家庭群体中）并不支持付费居留或社会声望模型，且帮助者并未借机开展声誉管理。与之相反，实验结果似乎反映出对幼崽福祉的真切关怀，而这种关怀在个体独自负责照料幼崽时尤为强烈。