You can tell a lot about a person by their face—even their political affiliation, new research claims.

In a study published in the January 18 issue of PLoS One, subjects were able to accurately identify candidates from the 2004 and 2006 U.S. Senate elections as either Democrats or Republicans based on black-and-white photos of their faces. And subjects were even able to correctly identify college students as belonging to Democratic or Republican clubs based on their yearbook photos.

To investigate the basis of these judgments, subjects were asked to rate photos of faces on a seven-point scale assessing personality traits such as assertiveness, maturity, likeability and trustworthiness. Subjects consistently associated Democrats with warmth (likeable and trustworthy) and Republicans with power (dominant and mature). These findings were independent of the gender of the person in the photo.

The authors concluded that people possess "a general and imperfect" ability to infer political affiliation based on facial appearance, which is related to stereotypes about Democrat and Republican personalities. The ability to surmise other perceptually ambiguous traits, such as sexual orientation and religious group membership, has been reported in similar studies.

The consequences of this general and imperfect ability are worrisome, with career opportunities, court rulings and financial success potentially falling subject to prejudicial judgments, according to the authors.

But surely these judgments don’t interfere with election results, do they?

In a study published in Science in February 2009, subjects were able to predict from a pair of photos of faces alone which political figure would win an election. Even children could pick the winner when asked who they would prefer to be captain of their boat. And in a study published in the Proceedings of the National Academy of Sciences in November 2007, researchers linked competence perceived from a candidate’s face to his or her electoral success.

The latest study adds to the growing body of evidence suggesting that certain traits once thought to be indistinguishable based on looks alone are in fact written all over our faces.

Image courtesy of iStockPhoto/southsidecanuck