Social environment-based opportunity costs dictate when people leave social interactions.

There is an ever-increasing understanding of the cognitive mechanisms underlying how we process others' behaviours during social interactions. However, little is known about how people decide when to leave an interaction. Are these decisions shaped by alternatives in the environment - the opportunity-costs of connecting to other people? Here, participants chose when to leave partners who treated them with varying degrees of fairness, and connect to others, in social environments with different opportunity-costs. Across four studies we find people leave partners more quickly when opportunity-costs are high, both the average fairness of people in the environment and the effort required to connect to another partner. People's leaving times were accounted for by a fairness-adapted evidence accumulation model, and modulated by depression and loneliness scores. These findings demonstrate the computational processes underlying decisions to leave, and highlight atypical social time allocations as a marker of poor mental health.

Anterior cingulate cortex: A brain system necessary for learning to reward others?

Helping a friend move house, donating to charity, volunteering assistance during a crisis. Humans and other species alike regularly undertake prosocial behaviors-actions that benefit others without necessarily helping ourselves. But how does the brain learn what acts are prosocial? Basile and colleagues show that removal of the anterior cingulate cortex (ACC) prevents monkeys from learning what actions are prosocial but does not stop them carrying out previously learned prosocial behaviors. This highlights that the ability to learn what actions are prosocial and choosing to perform helpful acts may be distinct cognitive processes, with only the former depending on ACC.