The National Longitudinal Study of Adolescent Health (Add Health), conducted by a team of researchers at the University of North Carolina – Chapel Hill, is one of the very few social science datasets that take biological and genetic influences on human behavior seriously. As a result, Add Health routinely measures both the intelligence and physical attractiveness of its respondents. In the Wave III of Add Health, conducted in 2000-2001, respondents take an IQ test called the Peabody Picture Vocabulary Test. And then their physical attractiveness is measured objectively by an interviewer, who is unaware of their IQ test scores, on a 5-point scale (1 = Very unattractive, 2 = Unattractive, 3 = About average, 4 = Attractive, and 5 = Very attractive). The following graph shows the association between Add Health respondents’ physical attractiveness and their intelligence. The data come from a large (n = 15,197) nationally representative sample of young Americans (mean age = 22). As you can see, there is a clear monotonic positive association between physical attractiveness and intelligence. The more physically attractive Add Health respondents are, the more intelligent they are. The mean IQ is 94.2 for those rated “very unattractive,” 94.9 for those rated “unattractive,” 97.1 for those rated “about average,” 100.3 for those rated “attractive,” and 100.7 for those rated “very attractive.” Due partly to the large sample size, the association is highly statistically significant.