Observing others give & take: A computational account of bystanders’ feelings and actions

Social interactions influence people’s feelings and behavior. Here, we propose that a person’s well-being is influenced not only by interactions they experience themselves, but also by those they observe. In particular, we test and quantify the influence of observed selfishness and observed inequality on a bystanders’ feelings and non-costly punishment decisions. We developed computational models that relate others’ (un)selfish acts to observers’ emotional reactions and punishment decisions. These characterize the rules by which others’ interactions are transformed into bystanders’ reactions, and successfully predict those reactions in out-of-sample participants. The models highlight the impact of two social values—‘selfishness aversion’ and ‘inequality aversion’. As for the latter we find that even small violations from perfect equality have a disproportionately large impact on feelings and punishment. In this age of internet and social media we constantly observe others’ online interactions, in addition to in-person interactions. Quantifying the consequences of such observations is important for predicting their impact on society.Author summary: Social interactions can have a significant emotional impact on individuals. For example, being the recipient of generosity will likely make us feel good, while being the recipient of selfish behavior will likely make us feel bad. Here we tested the hypothesis that individuals’ feelings will be impacted by observing others interact, and that individuals may even choose to punish people who made selfish or inequal splits of resources. We recorded observers’ explicit affective reactions and non-costly punishment choices in response to other people’s decisions to allocate resources to themselves and another individual. Using a mathematical equation, we found that participants felt most negatively towards selfish allocators and punished them the most, which is a possible indicator of both selfishness aversion and inequality aversion. Intriguingly, participants felt more negatively towards generous allocators that gave more than half their share, and punished them more often, than those who split equally. Such behavior is consistent with inequality aversion. In fact, we find that even small deviations from equal splits resulted in especially large increases in observers’ negative feelings and punishments. This suggests that ‘pure equal split’ holds special status in the eye of the observer.