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Extensive research by Satoshi Kanazawa and colleagues at the London School of Economics and Political Science have uncovered significant differences in sleep-timing preferences among people, depending on their IQ scores. The research shows that people with higher IQs tend to be more active nocturnally, going to bed later, and are more apt to be night-owls. People with lower IQs tend to restrict their activities primarily to daytime and usually retire to bed sooner after nightfall.

According to Kanazawa, ancestral humans were typically diurnal, and that a shift towards more nocturnal activities is an "evolutionarily novel preference" of the type normally found in more intelligent individuals, demonstrating "a higher level of cognitive complexity" in the practitioners. However, a study by psychologist Marina Giampietro indicates evening-types tend to be less reliable, less emotionally stable, and more apt to suffer from depression, addictions, and eating disorders.

http://www.winnipegfreepress.com/opinion/westview/smart-people-sleep-late-82486792.html