Voluntary Interaction and the Principle of Mutual Benefit
研究发现，在自愿互动（如市场交易）中，存在一种“互惠原则”规范，要求参与者遵守共同预期，这导致的行为模式与现有社会偏好理论不符，且外部激励能增强可信赖行为。
Most social preference theories are based on observations of nonvoluntary interactions. Nonselfish behavior 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 behavior within them. This norm induces patterns of behavior 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.