Why she looks pretty and why she doesn't

Ever wondered why you do not find your twin or cousin's crush attractive? That's because the uniqueness of an individual's face preferences is predominantly based on experiences, not genes, according to a new study.

The study found that the impact of such unique personal experiences is so deep that even identical twins don't agree.

"Of course, some aspects of attractiveness are pretty universal and may even be coded into our genes. For example, people tend to prefer faces that are symmetric," researchers Laura Germine from Harvard University and Jeremy Wilmer of Wellesley College said.

"Beyond such limited shared preferences, however, people really do have different 'types'," they added.

It's not about the school you went to, how much money your parents made, or who lived next door.

That pretty face you see apparently has a lot more to do with those experiences that are truly unique to you - faces you have seen in the media, the unique social interactions you have every day of your life, perhaps even the face of your first boyfriend or girlfriend.

They said that an individual's aesthetic preferences for faces agree about 50 percent, and disagree about 50 percent with others.

The researchers tested the preferences of 547 pairs of identical twins and 214 pairs of same-sex, non-identical twins by having them rate the attractiveness of 200 faces.

Comparisons between identical and non-identical twins allowed the researchers to estimate the relative contribution of genes and environments to face preferences.

The study was published in the journal Current Biology.