Multimodal cues displayed by submissive rats promote prosocial choices by dominants

Animals often display prosocial behaviours, performing actions that benefit others. Although prosociality is essential for social bonding and cooperation, we still know very little about how animals integrate behavioural cues from those in need to make decisions that increase their wellbeing. To address this question, we used a two-choice task where rats can provide rewards to a conspecific in the absence of self-benefit, and interrogated which conditions promote prosociality by manipulating the social context of the interacting animals. While 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 towards 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 in social distance. Interestingly, these more coordinated interactions were driven by submissive animals that modulated their position and movement towards their dominants and increased 50kHz vocalisation rate when their partners were going to behave selfishly. This display of multimodal cues by submissive animals while signalling need promoted social saliency and a faster emergence of prosocial choices from dominant rats. Multivariate analysis highlighted non-canonical body language as the main information dominants use on a trial-by-trial basis to learn that their actions have effects on others. Our results provide a refined understanding of the behavioural dynamics that rats use for action-selection upon perception of socially relevant cues and navigate social decision-making.