Each frame of the video above is a different face with the features slightly tweaked. If you're like the U.K. university students who took part in a new study, the faces should strike you as increasingly dominant personalities, peaking in the middle of the video and then becoming meek again by the end. The statistical model that underlies those cartoon faces was derived from a study of 1000 photographs of Caucasian faces that the students looked at and scored for various traits. Although there is plenty of noise in these data, people tended to judge faces similarly. But what is it exactly about the faces that was being judged? To find out, researchers measured 393 image properties, from the size of the eyes and cheeks to the shape of the chin. By mapping these properties to people's judgments of the faces, the researchers found that first impressions are surprisingly predictable—58% of the variation in judgments could be explained just by the relative size and position of a few facial traits, the team reports online today in the Proceedings of the National Academy of Sciences. For example, people with mouths that have a natural smile shape are seen as far more approachable, while larger eyes are the strongest factor in attractiveness. To make the face-morphing videos, the researchers then did the reverse, generating cartoon faces from scratch based on their statistical model to elicit predictable snap judgments. Wondering about the possible applications? By slightly tweaking a photograph of someone's face—a politician, for example—it may be possible to custom-design first impressions.