Editor's Note: This story is part of an In-Depth Report on the science of beauty. Read more about the series here.

What makes beauty? A flawless complexion? Inner serenity? A free gift-with-purchase just in time for Mother's Day (nudge, nudge—Sunday, May 10)?

Philosophers, artists and everyday consumers have long pondered the question of what beauty, that amorphous it-factor, really is. Science has taken a stab at the question, too, and the range of answers might be surprising.

Physical appearance seems to be only part of the equation. Despite the billions of dollars forked over every year for cosmetics and beautification procedures, looks aren't the whole kit and kaboodle. In fact, according to a 2008 study in the journal Vision Research, even a computer can be taught to recognize who is hot or not. So what else can real live humans bring to the table?

Beyond looks, it may be something in the way she (or he) moves, according to a 2007 study published in Proceedings of the National Academy of Sciences. Psychologists examined people's preferences for computer figures based on body shape and movement. Those with gaits and shapes that epitomized their gender (i.e. a curvy, hip-swinging woman or broad-shouldered, straight-walking gents) were perceived to be more attractive than those with one or the other.

But if a Marilyn Monroe saunter (or silhouette) isn't your forte, science has suggested a quick fix. It might be time to toss aside the potentially lead-filled red lipstick in favor of something as simple as red… clothes? As ScientificAmerican.com reported last year, both men and women in red were found by the opposite sex to be more attractive than those wearing other colors.  A group of 2008 studies, published in the Journal of Personality and Social Psychology, found that men judged photos of women wearing red (as opposed to blue, green or gray) as more fetching. And in preliminary follow-up research, study author Andrew Elliot, a psychology professor at the University of Rochester, found that women also tended to be more drawn to men sporting red.

Many find beauty in laughter. According to a study by psychologist Eric Bressler of Westfield State College in Massachusetts and Signal Balshine, an associate professor of behavioral ecology and evolution at McMaster University in Ontario, both men and women were attracted to people with a sense of humor.

So, although science has come a long way in helping us smooth wrinkles and understand how to take better care of our outer selves, it's also revealed that the many elements of beauty are more than skin deep.

Image © iStockphoto/JJRD