The Illusion of Sex

The Illusion of Sex, by Harvard psychologist Richard Russell, won Third Prize at the 2009 Best Visual Illusion of the Year Contest. The two side-by-side faces are perceived as male (right) and female (left). However, both of them are versions of the same androgynous face. The two images are exactly identical, except that the contrast between the eyes and mouth and the rest of the face is higher for the face on the left than for the face on the right. This illusion shows that contrast is an important cue for determining the sex of a face, with low-contrast faces appearing male and high-contrast faces appearing female. And it may also explain why females in many cultures darken their eyes and mouths with make-up. A made-up face looks more feminine than a fresh face.
@'Scientific American'