Trustworthy? Subjects' faces (left) were morphed with unfamiliar faces (right) to make the center faces used in the study. The female morph draws on shape and color information from both faces, whereas the male draws only shape information from the

In Me I Trust

People apparently really do like seeing themselves in others. A new study reveals that players bargaining for money in games are more likely to trust faces that remind them of their own. The researchers suggest that it's not narcissism at play, but nepotism--an unconscious yen that evolved to help bind together kinfolk.

Animal studies have revealed that many critters favor conspecifics that resemble them, a phenomenon called kin selection. "Since relatives share your DNA, it's another way of making sure your genes survive," explains evolutionary psychologist Lisa DeBruine of McMaster University in Hamilton, Ontario.

To see if humans have the same preference, DeBruine set up two-person games in which subjects, playing via computer, either divide a few dollars equally or trust the other player to divide a larger sum. In each bargaining round a subject interacted with one of 16 possible partners, whose faces were shown on the monitor. All of these faces were "morphs": Some combined the subject's own face with the face of a stranger, while others blended two totally unfamiliar faces together.

In a paper in the 7 July issue of the Proceedings of the Royal Society, DeBruine reports that the subjects trusted faces resembling their own more than two times out of three, whereas they trusted unfamiliar faces only half the time. DeBruine tried morphs resembling celebrities such as Ben Affleck and Sarah Michelle Gellar to see if mere familiarity led to increased trust, but it was only the self-resemblance that inspired confidence. Interviews with subjects afterward revealed that none had any suspicion that they weren't playing against real people or that the images were manipulated, although one subject noted that one of his partners strongly resembled his brother.

Social psychologist Gene Burnstein of the University of Michigan, Ann Arbor, calls the work "a very nice demonstration of an important psychological mechanism." Although previous experiments showed that humans deliberately and consciously judge kinship based on physical similarities, Burnstein says most psychologists would be skeptical that humans automatically and unconsciously act on these resemblances. "DeBruine's research is the first I know of that indicates such skepticism is unwarranted," he says.

Related sites
Kin selection
Face morphing