Satoshi Kanazawa of the London School of Economics and Political Science says a longitudinal study tracked 17,419 British babies all born during one week in 1958. The study subjects were interviewed in 1965, in 1969, in 1974, in 1981, in 1991, in 1999 to 2000 and in 2004 to 2005. Several intelligence tests are taken. At ages 7 and 11, the teacher of each study subject is asked to describe the child's physical appearance.
The National Longitudinal Study of Adolescent Health involves 20,745 U.S. students who were personally interviewed at home in 1994 to1995, 1996 and 2001 to 2002. They were also given intelligence tests. The interviewer rated the respondent's physical attractiveness on a five-point ordinal scale.
The British sample has one of the best measures of general intelligence in all survey data, but a comparatively weak measure of physical attractiveness. In contrast, the American sample has a stronger measure of physical attractiveness, but a comparatively weak measure of general intelligence, Kanazawa says.
The study published in the journal Intelligence finds both the British and American data show physical attractiveness is significantly positively associated with general intelligence -- attractive men scored an average of 13.6 points above average and pretty women scored 11.4 points above average.