Generalized trust refers to trust in other members of society. In large social surveys, it is assessed with the question, “Generally speaking, would you say that most people can be trusted or that you can’t be too careful in dealing with people?” Notwithstanding the question’s simplicity, generalized trust is correlated with a large number of important variables. At the macro-level, countries with higher generalized trust experience faster economic growth (Algan and Cahuc, 2010; Bjornskov, 2012) and have more efficient public institutions (Putnam, 1993; Tabellini, 2008). At the micro-level, individuals with higher generalized trust report better health (Giordano et al., 2012) and claim to be happier with their lives over all (Helliwell and Wang, 2011).
In a paper just published in PLoS ONE, Francesco Billari and I report a strong association between generalized trust and intelligence, based on data from a large, nationally representative sample of Americans. This finding replicates several previous studies (including one we were not aware of when we wrote our paper). Specifically, Sturgis et al. (2010) found an association between generalized trust and intelligence in the U.K., Hooghe et al. (2012) found one in the Netherlands, and Oskarsson et al. (2012) found one in Sweden.
Why is generalized trust associated with intelligence? There seem to be at least two related explanations (Yamagishi, 2001). First, if individuals with higher intelligence are better at identifying untrustworthy people, they should tend to have fewer relationships in which their trust is betrayed. And second, if individuals with higher intelligence are better at identifying situations where any person would be unlikely to reciprocate trust, they should tend to have their trust betrayed less often. We were unable to test these two hypotheses in our paper. However, Yamagishi et al. (1999) have provided some experimental evidence for them.
The finding that generalized trust is associated with intelligence raises the possibility that previous studies have over-estimated the effect of generalized trust on micro-level outcomes such as health and happiness. For example, individuals who trust others might only report better health and greater happiness because they tend to be more intelligent. However, we found no evidence for this. In particular, the effects of trust on self-rated health and happiness did not decrease after we controlled for intelligence. This suggests that trust really is a valuable social resource, and is not simply a proxy for intelligence.
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