اثرات همسالان و ترجیحات اجتماعی در همکاری داوطلبانه: تجزیه و تحلیل نظری و تجربی

Social preferences and social influence effects (“peer effects”) are well documented, but little is known about how peers shape social preferences. Settings where social preferences matter are often situations where peer effects are likely too. In a gift-exchange experiment with independent payoffs between two agents we find causal evidence for peer effects. Efforts are positively correlated but with a kink: agents follow a low-performing but not a high-performing peer. This contradicts major theories of social preferences which predict that efforts are unrelated, or negatively related. Some theories allow for positively-related efforts but cannot explain most observations. Conformism, norm following and social esteem are candidate explanations.

Is pro-social voluntary cooperation subject to ‘peer effects’, that is, influenced by the behavior of comparison others (‘peers’)? Or is pro-sociality a preference that is largely immune to social influence? These questions are at the heart of this paper. Understanding how peer effects shape social preferences is important because people normally do not act in a social vacuum but are constantly exposed to peers. The purpose of this paper is to understand how social preferences and peer effects are linked both by providing novel experimental evidence and by clarifying what theories of social preferences have to say on peer effects. We speak of a peer effect if an agent is influenced in his or her actions by what a comparison agent does, even if there are no material spillovers between agents and hence no direct social preference links exist between peers (indirect links are possible, as our theoretical analysis will show). Our definition is narrower than frequent usage of the term in the literature. Sometimes ‘peer effects’ is used as an umbrella term to describe behaviors where an agent reacts to other agents’ actions; such a behavioral reaction might be motivated by social preferences. As an example, think of voluntary contributions to a public good, where people contribute more the more other group members contribute. Such ‘conditional cooperation’ can be due to peer effects, but also social preferences.

We are grateful for helpful comments by Benjamin Beranek, Friedrich Breyer, Stefan Bühler, Rachel Croson, Tore Ellingsen, Urs Fischbacher, Yukihiko Funaki, Martin Kolmar, Tatiana Kornienko, Michael Kosfeld, Bentley MacLeod, Daniele Nosenzo, Rupert Sausgruber, Martin Sefton, Karl Schlag, Rudi Stracke, Jean-Robert Tyran, and participants at various seminars, conferences and workshops. We acknowledge financial support from the Grundlagenforschungsfonds of the University of St.Gallen. Simon Gächter also acknowledges support under the European Research Council Advanced Investigator Grant ERC-AdG 295707 COOPERATION, the ESRC-funded research Network of Integrated Behavioural Science (NIBS, ES/K002201/1), and the hospitality of the Institute for Advanced Studies at Hebrew University in Jerusalem while working on this paper.