There is more to beauty than meets the stranger’s eye, according to results from three studies examining the influence of non-physical traits on people’s perception of physical attractiveness. The results, which show that people perceive physical appeal differently when they look at those they know versus strangers, are published in the recently released March issue of Evolution and Human Behavior.

In many studies evaluating physical attractiveness, people are often shown an array of strangers’ photos, computer-generated images or line drawings and asked to identify which ones, based on differences in physical features, are most attractive. Results from these studies suggest that physically attractive traits include high degrees of bilateral facial symmetries, such as eyes that are identical in shape and size, and waist-to-hip ratios of 0.7 for women and 0.9 for men.