Beasts & Beauties

the OBVIOUS example

Men are barraged by images of unobtainable women in the media, making it difficult for them to desire the ordinarily beautiful.
A series of studies over the past two decades have shown that judgments of attractiveness (of ourselves and of others) depend on the situation in which we find ourselves. For example, a woman of average attractiveness seems a lot less attractive than she actually is if a viewer has first seen a highly attractive woman. If a man is talking to a beautiful female at a cocktail party and is then joined by a less attractive one, the second woman will seem relatively unattractive.
The contrast principle also works in reverse. A woman of average attractiveness will seem more attractive than she is if she enters a room of unattractive women. In other words, context counts.
more HERE
and HERE