Multimodal cues displayed by submissive rats promote prosocial choicesby dominants

Abstract

Prosocial behaviors, behaviors that benefit others, are an integral part of the life of humans and other animals, promoting social bonding and cooperation among individuals and groups. Field and laboratory research has shown evidence that, in several species, animals perform actions that improve the welfare of conspecifics and that factors of the social context, including sex, familiarity between the individuals, and their dominance relationship, lead to variation in the expression of prosociality. However, less effort has been devoted to investigating the behavioral correlates underlying such variation, which would improve our understanding of how animals integrate behavioral cues from those in need to make prosocial decisions. Here we used a two-choice task where rats can provide rewards to a conspecific in the absence of self-benefit and investigated which conditions promote prosociality by manipulating the social context of the interacting animals. Although sex or degree of familiarity did not affect prosocial choices in rats, social hierarchy revealed to be a potent modulator, with dominant decision-makers showing faster emergence and higher levels of prosocial choices toward their submissive cage mates. Leveraging quantitative analysis of multimodal social dynamics prior to choice, we identified that pairs with dominant decision-makers exhibited more proximal interactions. Interestingly, these closer interactions were driven by submissive animals, which were better at communicating their need for help, by modulating their position and movement towards their dominants and whose 50-kHz vocalization rate correlated with dominants prosociality. Moreover, Granger causality revealed stronger bidirectional influences in pairs with dominant focals and submissive recipients, indicating increased behavioral coordination. Finally, multivariate analysis highlighted body language as the main information dominants use on a trial-by-trial basis to guide prosocial choices. Our results provide a refined understanding of the behavioral dynamics that rats use for action-selection upon perception of socially relevant cues and navigate social decision-making.