Alexander Todorov and Nikolaas Oosterhof, two Princeton psychology researchers, have developed a computer program that allows them to construct computer-generated faces that display the most trustworthy or dominant faces possible.

To conduct the study, the scientists showed unfamiliar faces to test subjects and asked them to describe traits they could gauge from the faces. The scientists boiled down the list of traits to about a dozen of the most commonly cited characteristics -- including aggressiveness, unkemptness and various emotional states. The researchers showed the faces to another group and asked them to rate each face for the degree to which it possessed one of the dozen listed traits.

The study, published in the Proceedings of the National Academy of Sciences, found a trustworthy face, at its most extreme, has a U-shaped mouth and eyes that form an almost surprised look.

An untrustworthy face, at its most extreme, is an angry one with the edges of the mouth curled down and eyebrows pointing down at the center. The least dominant face possible is one resembling a baby's with a larger distance between the eyes and the eyebrows than other faces.