Human cooperation is thought to have evolved because it benefits everyone involved. But we also know that cooperation doesn’t always make sense when subjected to a cost-benefit analysis. For example, people will often do favors for others when there is no expectation of a personal reward—or without even bothering to think about whether there might be a reward.

A recent study published in PNAS presents evidence that humans may engage in these types of uncalculating cooperative activities because it helps their reputation. By cooperating in the moment, people signal to others that they can be trusted to cooperate in the future.

The authors of the paper used a two-stage incentivized economic game to study this phenomenon. The first stage of the game asked participants to decide if they wanted to pay to benefit another player. Players could decide to help without looking at the cost, which was considered to be an uncalculating behavior, or they could check the cost before deciding to assist, which was interpreted as a calculating behavior. This calculating behavior was thought to be analogous to the type of cost-benefit analysis people often do before deciding to be cooperative.