Sunshine on my shoulders makes me happy. . . especially if I'm less intelligent: how sunlight and intelligence affect happiness in modern society.

The savanna theory of happiness proposes that, due to evolutionary constraints on the human brain, situations and circumstances that would have increased our ancestors' happiness may still increase our happiness today, and those that would have decreased their happiness then may still decrease ours today. It further proposes that, because general intelligence evolved to solve evolutionarily novel problems, this tendency may be stronger among less intelligent individuals. Because humans are a diurnal species that cannot see in the dark, darkness always represented danger to our ancestors and may still decrease our happiness today. Consistent with this prediction, the analysis of the National Longitudinal Study of Adolescent to Adult Health (Add Health) data shows that exposure to sunlight was associated with happiness but the association was significantly weaker among more intelligent individuals.