Iris pigmentation and behavioral inhibition

Two independent investigations of the association between the temperamental dimensions of inhibition and lack of inhibition to the unfamiliar, on the one hand, and the degree of pigmentation of the iris, on the other, revealed a statistically significant relation in Caucasian children between behavioral inhibition to the unfamiliar and blue irises and uninhibited behavior and brown irises. Several biochemical interpretations of this association were discussed and it was suggested that these behavioral styles might be influenced by biological factors that are partially marked by eye color in Caucasian populations.