In his new book The Folly of Fools, Robert Trivers hypothesizes that smart people are more likely to tell lies. This surprised me since I usually assume that intelligent people tend to act more prosocially. According to Trivers, if you compare across species, deception increases with intelligence. Better deception and manipulation require more mental ability.
Add Health participants (teens and young adults) were given a vocabulary test and were asked how often they lie to their parents about their whereabouts. I looked at the correlation between the two questions: it is a tiny .07 (sample size = 6,168). For males, it is a bit stronger--.10--while it is .only .05 for females. So, there is a tendency for smarter youths to lie more frequently, but it is very weak.
Anecdotally, I can see that my smartest child is the most dishonest. His lies are pretty clever for a 4 year old. A few more years, and he'll probably outsmart his old man. I'd like to think that I can teach him to be more honest, but behavioral genetic research makes me less optimistic.
By they way, Trivers seems to think that bright people not only deceive more; they are also more likely to self-deceive, which is contrary to what most intelligent people think about themselves.