A professor at the Department of Cognitive Sciences University of California did a study of sexual attraction/youth by altering the limbus in the eyes of pictures of test subjects. Those subjects with larger more defined limbuses were rated more attractive. Even though the test subjects rating pics could not define why they showed preferences to those with altered limbuses. Limbuses are the dark ring around outside of the cornea, and they get smaller with age.
Here is an example the afgan girl, original and then reversed limbuses:(90 % in infanct, 41% in adults).
