What makes us attractive?

The secret of beauty and attractiveness has been a quest of humans for as long as we have been civilized. Many women (and some "metrosexual" men) spend up to one-third of their income on looking good. Why?

Besides being popular, beautiful people get special attention from teachers, the legal system and employers. Good-looking people tend to make more money than their plain-Jane counterparts, according to a study by the Federal Reserve Bank of St. Louis. Researchers found that beautiful people tend to earn 5 percent more an hour than their less comely colleagues. If that weren't enough, the Fed also discovered a "plainness penalty," punishing below-average-looks with earnings of 9 percent less an hour.

While we instinctively know what appeals to our own sense of beauty -- we know it when we see it -- defining what determines attractiveness is not always easy. In frustration, we often give up and claim that "beauty is in they eye of the beholder." But is beauty really a personal phenomenon?

Recent studies have shown that the secret of beauty may at last be understood. It seems that attractiveness may be hard wired in our brains.

Experiments designed to measure attractiveness usually involve showing a series of images of human faces and asking subjects to rate their visual appeal. Surprisingly, people from a variety of different ages, races and cultures agree on what is and isn't beautiful. Babies as young as 3 months can identify and prefer faces that most adults would deem beautiful. Europeans can pick out the same beautiful Japanese faces as Japanese subjects; Japanese can agree on which European faces another Europeans will view as beautiful. In fact, humans can even agree on the attractiveness of monkey faces, thus ruling out most unique racial, cultural and even species influences. So what's going on?

Facial recognition is a complex process. Only recently, with the need to spot criminals and terrorists, computer facial recognition programs have been developed to analyze the subtle variations of such things as the space between our eyes, the size of our noses and the proportions of our facial features. Scientists have discovered certain mathematical facial proportions that identify beautiful people. But is there more to beauty than the mere arrangement of eyes, noses and chins?

Our brains seem to do much more than simply recognize a beautiful face. Most people can assess emotions, personality traits and fertility -- as well as beauty -- almost instantaneously. In fact, the human brain has special part called the fusiform, located in the back of the head near the spine. It's the same neural pathway needed to recognize faces of family, friends and people we have met. When it's damaged, the patients cannot recognize anyone, even people they has just met. Also, in experiments, they cannot discriminate between photographs of plain and beautiful faces.

Studies show that when we recognize a face as "beautiful" we are actually making a judgement about the health and vitality of that individual. We interpret facial symmetry (the similarity of left and right halves of a face) and the smoothness of the skin to mean that a person has good genes and has been free from diseases. This is part of what we mean by "beautiful" but it is just the beginning.

Studies have shown that facial symmetry is one of the best observational indicators of good genes and healthy development and that these traits are what we mean when we say someone is attractive. Look at these examples below.