Acute stress reduces effortful prosocial behaviour

Acute stress can change our cognition and emotions, but what specific consequences this has for prosocial behaviour is unclear. Previous studies have mainly investigated prosociality with financial transfers in economic games and produced conflicting results. We examined how acute stress changes our willingness to exert effort for others, which is a core feature of many types of real-life prosocial behaviour. Participants – half of whom were put under acute stress – made decisions whether to exert physical effort to gain money for themselves or another person. With this design, we could independently assess the effects of acute stress on prosocial, compared to self-benefitting, effortful behaviour. Compared to controls, stressed participants chose to exert effort more often for self- than for other-benefitting rewards. This was particularly pronounced for more selfish participants. Neuroimaging combined with computational modelling revealed a putative neural mechanism underlying these effects: more stressed participants showed increased activation to subjective value in the dorsal anterior cingulate cortex (dACC) and anterior insula when they themselves could benefit from their exerted effort relative to when someone else could. Activation differences in the dACC mediated the effect of perceived stress on effortful prosocial behaviour. Using effort-based paradigms to better approximate real-life prosocial behaviour and incorporating trait differences in prosocial tendencies could be key to understanding how acute stress affects prosociality. Considering the importance of such behaviours for our individual relationships and social cohesion, this highlights the need to tackle the sources of stress and help people better cope with stress when it occurs.