A controversial scientist argues that a widely held perception that physically attractive people are more competent and intelligent is actually based on fact.

London School of Economics evolutionary psychologist Satoshi Kanazawa blogs on Psychology Today that a large number of experiments over the years have shown people tend to rate attractive others as more intelligent and competent than unattractive others.

However, Mr Kanazawa argues that the evidence suggests concerns for mate selection isn’t the reason people think that beautiful people are more intelligent.

This is because of two reasons: children at kindergarten share the perception that beautiful people are more intelligent (and they aren’t concerned with mate selection), while more importantly among adults, the common perception holds both within and between the sexes.

Since most people are heterosexual, these two pieces of evidence suggest that there is more going on than concerns of mate selection.

Many sociologists and social psychologists are convinced that “beauty is only skin-deep,” and dismiss this widespread perception as “bias,” stereotype,” or “halo effect,” implicitly assuming that the perception is not accurate with no factual basis.

Mr Kanazawa refers to the US National Longitudinal Study of Adolescent Health (Add Health) which routinely measures the intelligence and physical attractiveness of its respondents.

During the 2000-2001 survey respondents took an IQ test called the Peabody Picture Vocabulary Test, before their physical attractiveness was measured by an objective interviewer (unaware of their IQ test scores) on a five point scale where 1 = very unattractive, through to 5 = very attractive.

The respondents were a nationally representative sample of just over fifteen thousand Americans with a mean age of 22.

The graph above shows a clear relationship between physical attractiveness and intelligence. The mean IQ is 94.2 for those rated “very unattractive,” through to an IQ of 100.7 for those rated “very attractive.” Mr Kanazawa argues that partly because of the large sample size, the association is highly statistically significant.

The graphs show the general positive association holds for both sexes with “very attractive” women more intelligent than “very unattractive” women by about 6 IQ points on average. For “very attractive” men, they are more intelligent than “very unattractive” men by about 8 IQ points on average.

Professor Kanazawa argues that it appears that the “stereotype” of beautiful people being more intelligent appears to be true empirically, “just as virtually all “stereotypes” are”.

The answer to the question this finding throws up - why are beautiful people more intelligent? Will be answered in his next post, promises Mr Kanazawa.

Satoshi Kanazawa is the co-author (with the late Alan S. Miller) of Why Beautiful People Have More Daughters (Perigee, 2007).