I don't buy this argument, but it's a nice read..
Experiments led by Piotr Winkielman, of the University of California, San Diego, and published in the current issue of Psychological Science, suggest that judgments of attractiveness depend on mental processing ease, or being "easy on the mind."
"What you like is a function of what your mind has been trained on," Winkielman said. "A stimulus becomes attractive if it falls into the average of what you've seen and is therefore simple for your brain to process. In our experiments, we show that we can make an arbitrary pattern likeable just by preparing the mind to recognize it quickly."
Direct Link to Papers in PDF format: http://psy.ucsd.edu/~pwinkiel/