Facial Attractiveness: The Role of Iris Ratio

Negar SammaknejadDepartment of Cognitive Sciences, UC Irvine & Institute for Brain and Cognitive Science, Shahid Beheshti University
Darren PeshekDepartment of Cognitive Sciences, UC Irvine
Donald HoffmanDepartment of Cognitive Sciences, UC Irvine

Abstract

The ratio of iris width to eye width is roughly 0.6 during infancy, falls to about 0.42 in young adulthood and middle age, and then increases again after age 50. Thus the iris-to-eye ratio (IER) is a nonlinear, probabilistic signal of age. Has natural selection shaped our judgments of facial attractiveness to be sensitive to the IER? Here we present an experiment suggesting that, for male observers, the answer is yes. On each trial, observers viewed two adult faces that were identical except for IER, and indicated which face was more attractive. Male observers preferred the larger IER (which signals youth) in all faces, suggesting that males have indeed been shaped by natural selection to be sensitive to the IER in their judgments of facial attractiveness, and to prefer IERs indicative of youth. Females showed no preference for larger or smaller IERs, a result that invites further exploration.

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