V.V. Rostovtseva

PhD thesis: Understanding human cooperativeness (2026)

Cooperation is a cornerstone of human sociality, deeply embedded in our evolutionary history and essential to the functioning of societies. Many experiments have been conducted to understand why, when, and with whom people engage in cooperative relationships. However, most experiments focus on a single aspect of cooperation, such as the risk of exploitation, and are conducted under tightly controlled lab conditions. The experiments reported in this thesis aim to bring cooperation closer to real life, where it has many facets and people have various means of forming impressions of their interaction partners. In some of our experiments, the participants had to make decisions across a range of situations designed to illuminate different aspects of cooperation, such as generosity, trust, trustworthiness, fairness, division of labour, and willingness to take cooperative risks. Despite similar socio-economic background, the participants differed considerably in their choices. This variation was highly structured and consistent: individuals who were more “cooperative” in one respect (e.g., being more generous) also tended to be more “cooperative” in other respects (e.g., being more trustworthy). Providing the participants with information about the sex, cultural background, or appearance of their interaction partner significantly affected their cooperative decisions. The presentation of a short silent video of their partner already had a substantial effect, exemplifying how strongly human behaviour is shaped by the subtle signals we read from each other’s faces. The sensitivity to the partner’s appearance improved coordination, but, interestingly, it had no or a negative effect on other facets of cooperation.