Smarter People are More Trusting

Interesting research.

Both vocabulary and question comprehension were positively correlated with generalized trust. Those with the highest vocab scores were 34 percent more likely to trust others than those with the lowest scores, and someone who had a good perceived understanding of the survey questions was 11 percent more likely to trust others than someone with a perceived poor understanding. The correlation stayed strong even when researchers controlled for socio-economic class.
This study, too, found a correlation between trust and self-reported health and happiness. The trusting were 6 percent more likely to say they were "very happy," and 7 percent more likely to report good or excellent health.

Full study results.