I am Professor of Social and Economic Psychology at the University of Zurich, where our research group is interested in a deceptively simple question: why do humans cooperate at all, given how easy it would be not to? Our work examines how groups sustain cooperation despite the temptation to free-ride, how social norms take hold and persist within communities, and how cooperation can spread even across group boundaries. At the same time, we also investigate the darker sides of cooperation: collaborative corruption, intergroup conflict, and group-based discrimination, as well as how inequality results from and influences human cooperation. Since these topics are studied across several disciplines, we combine methods and approaches from psychology, economics, and biology. For example, we run incentivized group experiments in our social interaction lab, coordinate large-scale cross-cultural surveys, fit choice models to empirical data, and run simulations based on evolutionary game theory. Our research has been published in interdisciplinary and disciplinary journals, including Science Advances, Nature Human Behaviour, Nature Communications, PNAS, Trends in Cognitive Sciences, Journal of Personality and Social Psychology, and Psychological Science. Before coming to Zurich in 2022, I was a postdoctoral fellow at the University of Amsterdam and then an Assistant Professor at Leiden University. I completed my PhD jointly in economics and cognitive neuroscience at Maastricht University, following undergraduate studies at Goethe University in Frankfurt.

Cooperation

Humans possess a remarkable capacity for large-scale cooperation. Within groups, we share knowledge, coordinate actions, and establish and maintain public goods from which everyone can benefit. However, cooperation is vulnerable to exploitation and poses a social dilemma. When others do not cooperate, the optimal response is often to withhold cooperation as well. Conversely, when others do cooperate, individuals may be tempted to enjoy the benefits without contributing themselves. Our research seeks to understand how groups can overcome this free-rider problem, reveal mechanisms that sustain cooperation, and explore how group cooperation shapes expectations and trust dynamics among individual members. Furthermore, we investigate how cooperation across group boundaries can emerge.

Social Norms

Intricately linked to cooperation are social norms, which broadly encompass the implicit expectations shared among individuals that guide appropriate behavior across various contexts. Cooperation norms are particularly interesting, as they often require individuals to restrain self-interest in order to achieve collective benefits. Despite their importance, our understanding of how social norms emerge within groups, persist over time, and influence behavior remains incomplete. Moreover, groups can sometimes develop “anti-social” norms that legitimize harmful or unethical behavior toward others. Gaining deeper insights into the formation and impact of social norms would allow us to better predict the conditions under which groups are likely to cooperate, compete, or even collapse.

Conflict

Cooperation entails investing personal resources, such as time, money, and energy, for the benefit of others. However, humans also frequently devote substantial resources to hurting, exploiting, or competing with others. In conflicts, resources are often wasted, serving only to assert dominance or outcompete others. A key research goal is therefore to identify the circumstances under which individuals are inclined to invest time and effort in harming others. Particularly in intergroup contexts, understanding the microlevel mechanisms that escalate or de-escalate conflict may help break cycles of persistent hostility and perpetuating conflict spirales between groups.

Vollberg & Gross (2026). Selfish and prosocial individuals both distort their actions’ impact, but selfish distortions can be more contagious. Nature Human Behaviour. 
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Gross, Graf & Rossetti (2025). The hidden costs of human cooperation. Trends in Cognitive Sciences. 
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Gross, Meder, De Dreu, Romano, Molenmaker & Hoenig (2023). The evolution of universal cooperation. Science Advances.
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Gross & Vostroknutov (2022). Why do people follow social norms? Current Opinion in Psychology.
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Gross et al. (2021). When helping is risky: The behavioral and neurobiological tradeoff of social and risk preferences. Psychological Science.
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Gross & Böhm (2020). Voluntary restrictions on self-reliance increase cooperation and mitigate wealth inequality. Proceedings of the National Academy of Sciences.
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Gross & De Dreu (2019). Individual solutions to shared problems create a modern tragedy of the commons. Science Advances.
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Gross & De Dreu (2019). The rise and fall of cooperation through reputation and group polarization. Nature Communications.
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Gross, Leib, Offerman, & Shalvi (2018). Ethical free riding: When honest people find dishonest partners. Psychological Science.
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