An illusion of sex change

…rest assured that the both faces are actually versions of the same androgynous face neither male, nor female. One face was created by increasing the contrast of the androgynous face, while the other face was created by decreasing the contrast. The face with more contrast is perceived as female, while the face with less contrast is perceived as male…

via The Illusion of Sex Change | Mighty Optical Illusions.

androgynous face optical illusion

I suspect this is what underlies the effectiveness of makeup: it increases contrast between facial features.