Beauty is in the eye of the beholder. Although there are some objective indicators that both men and women value when assessing a potential mate, such as healthy skin and physical fitness, there is also a great deal of variation in how people rate attractiveness. The greatest variation in perceived attractiveness is, arguably, among women, and a new study may explain why.

According to researchers at New York University, women find men’s faces more attractive if they have facial features that evoke certain personality traits that they value. Not every heterosexual woman values the same personality traits, which leads to significant variance in mate selection.

For their study, the researchers recruited 131 heterosexual women who had to rate the attractiveness of male faces that had prior been modified to have more masculine or more feminine features. The participants also had to rate how well a male’s face reflected certain personality traits.

Each woman ranked desired personality traits in a potential partner from a list that contained 8 stereotypical feminine traits (i.e. warmth, trustworthiness, empathy) and 8 stereotypical masculine traits (dominance, aggression, competitiveness).

Perhaps surprisingly, the participants of this study overall valued feminine personality traits more than masculine personality traits. The exception is independence, a stereotypical masculine trait that was highly valued across the board, while the stereotypically feminine trait of submissiveness was the least desired in a potential male partner.

The study found that the participants’ preferences for certain personality traits in a man led to biases in the perceived attractiveness of male faces. For instance, women who value a warm personality were more likely to perceive male faces that reflect warmth as more attractive than women who did not value this personality trait. Those who valued confidence in a potential mate rated confident faces more attractive than women who did not found this trait important, and so forth, the authors reported in the  Journal of Experimental Psychology: Human Perception and Performance.

What’s intriguing about this study is that it basically involves physiognomy, a pseudoscience that gained steam in the 17th and 18th centuries, which claimed a person’s mental character can be ascertained from physical appearance.

Charles Darwin almost missed his chances at his historic voyage on the Beagle because the captain of the ship, a fervent physiognomist, didn’t like his nose. The captain made up his mind that no man with such a nose could have energy for such a dangerous journey across the world. Fortunately, the rest of his facial features compensated for his undesirable nose. “His brow saved him,” Darwin’s daughter Henrietta later recalled.

Italian criminologist Cesare Lombroso thought physiognomy could be used to detect criminality. Those who had certain facial features such as a sloping forehead or facial asymmetry were more likely to engage in criminal behavior, Lombroso claimed in the 19th century.

These ideas were thoroughly abandoned after WWII after scientists showed that physiognomy is junk science. Of course, that doesn’t stop people from making snap judgments about people’s character, often with nothing more to go for than a person’s physical appearance.

Despite the fact we’re constantly told not to judge a book by its cover, studies show that within a tenth of a second of seeing a stranger’s face we make judgements about their character, whether they’re trustworthy, aggressive, competent and now with this new study, worthy of being candidate for a potential partner.