Can you tell what kind of a person someone is just by looking at his or her face? Apparently you can. New findings by researchers in the U.K. have shown a strong correlation between simple facial shape ratios and certain personality traits like trustworthiness and aggression, reports MedicalXpress.

Previous research has already hinted that men with large or wide faces are, on average, more apt to be aggressive and untrustworthy, but researchers wanted to look further at facial ratios and what they say about personality. For this new effort, women were included in the study, and more detailed facial measurements were taken. Researchers also relied on self-reporting by study participants to assess personality traits, rather than attempting to make generalizations from particular behavioral observations.

The study, published in the journal Biology Letters, found that facial width-to-height ratio can be a strong predictor of self-reported dominance, aggression and untrustworthiness in both men and women. Those with larger or wider faces were, on average, more aggressive, had worse tempers and reported being more dominant than did those with less wide faces.

Study participants included 54 men and 49 women between the ages of 18 and 30. Each was asked to fill out a questionnaire regarding their personality temperaments, and each had their faces measured from cheek to cheek and from just above the upper lip to the top of their eyelids.

It's still unclear why facial ratios correlate so strongly with certain self-reported personality traits, but several theories have been offered. First, it's possible that there exists cultural biases against certain types of faces — a kind of face-ism — that influences how people end up seeing themselves. There may also be biological connections, however. Other studies have found links between testosterone levels and wider faces, for instance. Researchers have also proposed an evolutionary reason for the correlations: People with wider faces tend to have stronger cheekbones, which could make it easier for them to take a punch from someone they've angered. In other words, wider faces make it easier for people to afford being aggressive toward others. 

Of course, your facial ratio does not determine your temperament. Those with wider faces merely tended, as a group, to be more aggressive. So this research obviously is not a license to discriminate against individuals due to their facial shape. But the research might help to reveal biases that we all possess but didn't previously realize we had about people.

Have you subconsciously been using facial ratio to unfairly judge others? If anything, this research gives us all a reason to take a long, hard look in the mirror.

Related on MNN:

Bryan Nelson ( @@brynelson ) writes about everything from environmental problems here on Earth to big questions in space.

What does your facial shape say about your personality?
New research establishes a firm link between facial ratio and self-reported behavioral tendencies in both men and women.