Who's more distrustful: smarts or dulls? I'm aware of two opposite images of smart people: 1) the toughminded cynic who is suspicious of others; and 2) the airhead who always seems naive about people (one incident of this was E.O. Wilson being thoroughly surprised at the violent reaction to his Sociobiology).
The General Social Survey asked 1,302 respondents if they think of themselves as a trusting person. Answers ranged from "very trusting" (=1) to "very distrustful" (=4). Here are the means by IQ level:
Mean distrust score by IQ level
High IQ (125) 1.82
Medium IQ (98) 1.50
Low IQ (71) 1.31
The first image is supported here: Intelligent folks are almost a standard deviation more suspicious of others than slow people. As Erving Goffman claimed, people present an image of themselves to others that is better than the reality. Our public images are dishonest, we're all liars about ourselves, and dumb folks buy it while smarter people see through it.