Trust has long been recognized as one of the most important ingredients of social and economic life. People’s expectation of others’ trustworthiness is the precursor of these people’s trust in others. The answer to how people form trustworthiness expectations is therefore key to answering why they (do not) trust others in particular situations. Theoretically, people’s trustworthiness can be inferred from any behavioral or contextual signs the occurrence of which is (1) correlated with these people’s trustworthiness and (2) regarded as indicative of trustworthiness by observers. Experimental research shows that generosity could be such a sign because it is correlated with trustworthiness and used to infer trustworthiness in social exchange with trust at stake. However, little is known about the prevalence and magnitude of the correlation between generosity and trustworthiness across different study designs and locations.

We conduct a meta-analysis based on experimentaldata from 25 studies in which generosity and trustworthiness were measured within subject. In these studies, generosity was measured by means of donations to charity, dictator game giving and first-mover transfers in ultimatum games; trustworthiness was measured by means of second-mover decisions in (binary) trust games, sequential prisoner’s dilemmas and second-mover transfers in investment games. We test the hypothesis that strategic generosity is a weaker sign of trustworthiness than natural generosity by comparing correlations between generosity and trustworthiness produced in two types of situations: (1) strategic situations, in which subjects know that their generosity could affect their interaction partners’ decisions and in turn affect their payoffs and (2) “natural” situations, in which subjects’ generosity cannot have such an effect by design or in which subjects are informed only later that it could.

Overall, generosity and trustworthiness are moderately correlated (r = 0.37). The correlation coefficients range from 0.03 to 0.69. In line with our hypothesis, we find that the correlation between strategic generosity and trustworthiness is smaller than the correlation between natural generosity and trustworthiness. These results substantiate that generosity can serve as a sign of trustworthiness and even more when generosity is exhibited naturally, i.e. without potential future rewards for generous acts. Our exploratory analysis reveals moreover that neither the proportion of female subjects, the use of strategy method to measure trustworthiness, nor game endowments have an effect on the correlation between generosity and trustworthiness. Our findings suggest that providing people with more opportunities to engage in and observe acts of generosity may promote trust in theirneighborhoods and society at large.