Welcome to the Frankfurt Laboratory for Experimental Economic Research (FLEX)

The Frankfurt Laboratory for Experimental Economic Research (FLEX) is a research center at the Faculty of Economics and Business Administration at Goethe University Frankfurt. It was founded in 2008 and is located on Campus Westend. FLEX also maintains a field office in Addis Ababa, Ethiopia. FLEX is financially supported by a starting grant from the Alfons und Gertrud Kassel-Stiftung.

FLEX takes up a long tradition in experimental economics at Goethe University starting with the pioneering work of Nobel laureate Reinhard Selten and Heinz Sauermann in the late 1950s. Further contributors who worked in Frankfurt include Reinhard Tietz and Werner Güth.

Researchers at FLEX study human behavior and decision making in social and economic contexts employing experimental methods. We conduct experiments in the laboratory, via the Internet, and in the field. The purpose of experiments is manifold and ranges from testing economic theories, to the elicitation of preferences as well as policy and impact evaluations. Current research conducted at FLEX covers different areas including behavioral economics, development economics, organizational and personnel economics, and finance.

New Papers

One, Two, Many – Insensitivity to Group Size in Games with Concentrated Benefits and Dispersed Costs

Heiner Schumacher, Iris Kesternich, Michael Kosfeld, Joachim Winter

Review of Economic Studies forthcoming


We experimentally analyze distributional preferences when a decider chooses the provision of a good that benefits herself or a receiver, and creates costs for a group of payers. The treatment variation is the number of payers. We observe that subjects provide the good even if there are many payers so that the costs of provision exceed the benefits by far. This result holds regardless of whether the provision increases the decider’s payoff or not. Intriguingly, it is not only selfish or maximin types who provide the good. Rather, we show that a substantial fraction of subjects are “insensitive to group size”: they reveal to care about the payoff of all parties, but attach the same weight to small and large groups so that they ignore large provision costs that are dispersed among many payers. Our results have important consequences for the approval of policies with concentrated benefits and large, dispersed cost, as well as the analysis of ethical behavior, medical decision making, and charity donations. 

The effects of financial and recognition incentives across work contexts: The role of meaning

Michael Kosfeld, Susanne Neckermann, Xiaolan Yang

Economic Inquiry forthcoming


We manipulate workers’ perceived meaning of a job in a field experiment and interact meaning of work with both financial and recognition incentives. Results show that workers exert more effort when meaning is high. Money has a positive effect on performance that is independent of meaning. In contrast, meaning and recognition interact negatively. Our results provide new insights into the stability of incentive effects across important work contexts. They also suggest that meaning and worker recognition may operate via the same motivational channel.

Social identity and social free-riding

Mark Bernard, Florian Hett, Mario Mechtel

European Economic Review forthcoming


We model individual identification choice as a strategic group formation problem. When choosing a social group to identify with, individuals appreciate high social status and a group stereotype to which they have a small social distance. A group׳s social status and stereotype are shaped by the (exogenous) individual attributes of its members and hence endogenous to individuals׳ choices. Unless disutility from social distance is strong enough, this creates a strategic tension as individuals with attributes that contribute little to group status would like to join high-status groups, thereby diluting the latters’ status and changing stereotypes. Such social free-riding motivates the use of soft exclusion technologies in high-status groups, which provides a unifying rationale for phenomena such as hazing rituals, charitable activities or status symbols that is not taste-based or follows a standard signaling mechanism.

How individual characteristics shape the structure of social networks

Yann Girard, Florian Hett, Daniel Schunk

Journal of Economic Behavior and Organization 115, 2015, 197-216


We study how students’ social networks emerge by documenting systematic patterns in the process of friendship formation of incoming students; these students all start out in a new environment and thus jointly create a new social network. As a specific novelty, we consider cooperativeness, time and risk preferences – elicited experimentally – together with factors like socioeconomic and personality characteristics. We find a number of robust predictors of link formation and of the position within the social network (local and global network centrality). In particular, cooperativeness has a complex association with link formation. We also find evidence for homophily along several dimensions. Finally, our results show that despite these systematic patterns, social network structures can be exogenously manipulated, as we find that random assignments of students to groups on the first two days of university impacts the students’ friendship formation process.

Leader Punishment and Cooperation in Groups: Experimental Field Evidence from Commons Management in Ethiopia

Michael Kosfeld, Devesh Rustagi

American Economic Review 105, 2015, 747-783


We conduct a social dilemma experiment in which real-world leaders can punish group members as a third party. Despite facing an identical environment, leaders are found to take remarkably different punishment approaches. The different leader types revealed experimentally explain the relative success of groups in managing their forest commons. Leaders who emphasize equality and efficiency see positive forest outcomes. Anti-social leaders, who punish indiscriminately, see relatively negative forest outcomes. Our results highlight the importance of leaders in collective action, and more generally the idiosyncratic but powerful roles that leaders may play, leading to substantial variation in group cooperation outcomes.