PHILADELPHIA -- We might not be able to resist a pretty face after all, according to a report from the University of Pennsylvania.   Experiments in which subjects were given a fraction of a second to judge "attractiveness" offered further evidence that our preference for beauty might be hard-wired.   People who participated in the studies were also more likely to associate pretty faces with positive traits.

"We're able to judge attractiveness with surprising speed and on the basis of very little information," said Ingrid Olson, a professor in Penn's Department of Psychology and researcher at Penn's Center for Cognitive Neurosciece.  "It seems that pretty faces 'prime' our minds to make us more likely to associate the pretty face with a positive emotion."

Olson, along with co-author Christy Marshuetz, of Yale University recently published their findings in the journal Emotion, a publication of the American Psychological Association.  The researchers set out to study cognitive processes behind a very real phenomenon: physically attractive people have advantages that unattractive people do not.

"Research has demonstrated time and again that there are tremendous social and economic benefits to being attractive," Olson said.  "Attractive people are paid more, are judged more intelligent and will receive more attention in most facets of life.

"This favoritism, while poorly understood, seems to be innate and cross-cultural.  Studies suggest that even infants prefer pretty faces," Olson said.

In their report, the researchers describe three experiments to investigate the preference for attractiveness.

The first study tested the idea that beauty can be assessed rapidly by asking study participants to rate faces pictures of non-famous males and females taken from three different high school yearbooks and the Internet shown for .013 seconds on a computer screen.  

Although participants reported that they could not see the faces and that they were guessing on each trial, they were able to accurately rate the attractiveness of those faces.

"There are no definite rules to what kind of face can be called beautiful, but we chose faces of either extreme very ugly or very pretty," Olson said. "Seen rapidly, viewers were able to make what amounted to an unconscious, albeit accurate, assessment of physical beauty."

In their second and third experiments, the researchers explored the notion of "priming" whether or not seeing a pretty face makes a viewer more likely to associate that face with positive attributes.  The second experiment involved rapidly showing a face on the screen, followed shortly thereafter by a word in white text on a black screen.  Participants were instructed to ignore the face and were timed on how quickly they could classify the word as either good or bad.  Almost uniformly, response times to good words, such as "laughter" or "happiness," were faster after viewing an attractive face.

"In a way, pretty faces are rewarding; they make us more likely to think good thoughts," said Olson.  "There are some underlying processes going on in the brain that prejudice us to respond to attractive people better even if we are not aware of it."

They repeated the priming test in a third experiment, this time using images of houses, to see whether the beauty bias is a general phenomenon or one that is limited to socially important stimuli such as faces.  Unlike faces, response times to good words were not faster after having viewed an attractive house.

"Faces hold a special power for us, perhaps more so than art or objects," Olson said.  "The beauty bias has a real influence upon us, something we should be mindful of when dealing with others."