Acute stress has a profound effect on our cognition and emotions. However, how acute stress affects our behaviour towards others is not clear with some studies decreases in prosocial behaviour under stress and other studies showing increases or no effects at all. We adopted a novel approach to tackle this question by asking participants to exert physical effort to gain rewards for themselves or for another person. We found that participants under acute stress were less likely to exert effort for someone else’s benefit compared to their own benefit at a low level of effort. This was not the case in a non-stressed control group. We used neuroimaging and computational modelling to show that two brain regions - dorsal anterior cingulate cortex and anterior insula - responded differently under stress when deciding whether to exert effort for oneself compared to someone else. Our study also showed the importance of individual differences when examining the effect of acute stress on prosocial behaviour. Participants who were more selfish in a resource allocation game before being stressed became more selfish in the effort task when stressed. We argue that laboratory tasks involving effort could be a good way to measure stress effects on prosocial behaviour going forward and could help to resolve previous inconsistencies in the field.

Forbes, P. A. G., Aydogan, G., Braunstein, J., Todorova, B., Wagner, I. C., Lockwood, P. L., Apps, M. A. J., Ruff, C. C. & Lamm, C. (2024). Acute stress reduces effortful prosocial behaviour. eLife, 12. https://doi.org/10.7554/eLife.87271.3