Animals often display prosocial behaviours, actions that benefit others, which are essential for social bonding and cooperation. Most studies on prosociality come from the Primate Order and have highlighted how features of the social context influence the expression of prosocial behavior, contributing to intraspecific and interspecific variation. However, less effort has been devoted to the detailed investigation of the behaviours of subjects, which is necessary to determine the proximate mechanisms through which the social context influences prosociality, across different species. To address this point, we tested pair of rats in a prosocial choice task and studied how social relationships, including sex, degree of familiarity and dominance status, modulate the emergence of prosocial choices. Here, a decision-maker rat can choose on each trial between providing food to itself only (selfish choice) or to itself and a partner rat, recipient of help (prosocial choice). While sex and familiarity did not affect prosociality, dominance status revealed to be a potent modulator. We found faster emergence and higher levels of prosocial choices in pair of rats where the decision-maker was dominant and the recipient submissive. To get insights into the proximate mechanisms driving this effect, we quantified multimodal interactions during decision-making. Dynamics of nose position, movement and head orientation revealed that the more prosocial pairs showed interactions indicative of increased social attention. These interactions were mainly driven by submissive recipients when dominant decision-makers were behaving selfishly. Moreover, call rate of submissive recipients was positively correlated with the emergence of prosocial choices. We propose that multimodal cues displayed by submissive recipients may enhance the social salience of signalling need, facilitating the emergence of prosocial choices by dominant rats. Our work demonstrates how the study of behavioural dynamics can generate novel insights into how rats navigate social decision-making, where dominance status is an important factor.