Voluntary interaction and the principle of mutual benefit

Andrea Isoni, Robert Sugden, Jiwei Zheng

Research output: Contribution to journalArticlepeer-review


Most social preference theories are based on observations of non-voluntary interactions. Non-selfish behaviour may take fundamentally different forms in voluntary interactions, such as market transactions. We investigate the Principle of Mutual Benefit – an injunctive norm requiring individuals who enter interactions voluntarily to conform to common expectations about behaviour within them. This norm induces patterns of behaviour inconsistent with existing social preference theories, and allows extrinsic incentives to crowd in trustworthiness. We embed this norm in a model consistent with evidence about promise-keeping, gift exchange, and ‘avoiding the ask’. We present new experimental evidence that people adhere to it.
Original languageEnglish
JournalJournal of Political Economy
Early online date16 Nov 2022
Publication statusE-pub ahead of print - 16 Nov 2022


  • voluntary interaction
  • Principle of Mutual Benefit
  • social norm
  • crowding in
  • non-selfish behaviour

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