Source: Max Pixel

Perhaps more than any other trait, beards are perceived as a sign of gruff manliness. They visibly differentiate men from females, mask emotions, provide warmth, and shield skin from the elements.

While most evolutionary theorists believe beards evolved as a display of dominance, masculinity, and , what signals do they send in the modern world? And, specifically, what social information does a beard convey?

This was the question a group of Australian researchers explored in a new paper appearing in this month's issue of Psychological Science. First, they asked 227 participants to look at a series of photographs of people's faces and rate, as quickly as they could, whether the face displayed or anger. The photographs were of four kinds of faces—clean-shaven men displaying happiness, clean-shaven men displaying anger, bearded men displaying happiness, and bearded men displaying anger. Importantly, to avoid any experimental , photos of the same men were used in all conditions. The researchers write, "The men were photographed with happy and angry expressions when clean-shaven and again with a full beard (at least eight weeks of untrimmed facial-hair growth). […] This eliminated the influence of possible systematic facial-structure or expression differences between men who choose to be bearded and those who choose to be clean-shaven."

Interestingly, they found that participants were quicker to classify the angry bearded photos than other types of photos, suggesting that beards enhance visual cues associated with anger recognition. They also found that participants were quicker to classify clean-shaven faces as happy.

The researchers conducted a follow-up study to rule out the possibility that a general negativity bias toward men with beards could explain the results of their first study. To test this, they replicated their study, except that they swapped out the angry faces for sad faces. Their idea was this: If the same pattern of results emerged for sad bearded faces as it did for angry bearded faces, it's likely that a general negativity bias toward beards was producing the results. However, if the finding was found to be specific to the anger-beard association, then their original hypothesis seems more likely: The effect is limited to anger.

Indeed, the results of the follow-up study showed the effect to be limited to anger. The researchers wrote, "Participants were slower to recognize sad expressions on bearded faces than on clean-shaven faces, which indicates that the recognition advantage for bearded faces observed in Experiment 1 does not generalize to all negative expressions."

A third experiment tested the possibility that there might be social benefits associated with beardedness. Again, employing a similar experimental design, the researchers asked 450 participants to rate the faces used in the first experiment (clean-shaven men displaying happiness, clean-shaven men displaying anger, bearded men displaying happiness, and bearded men displaying anger) on measures of aggressiveness, masculinity, and prosociality.

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Not surprisingly, bearded faces were rated higher on masculinity and aggressiveness. But here's where it gets interesting: The researchers also found that bearded faces were rated as more prosocial than clean-shaven faces. Specifically, bearded happy faces were rated as more prosocial than clean-shaven happy faces.

What does this all mean? It seems that there is a duality in beardedness. Beards can convey a commanding presence, especially when expressing anger or frustration. But this rough edge may be disarmed with a smile, resulting in a face judged to be even more helpful, accepting, and friendly than a shaved face. Something to think about next time you or your significant other picks up the razor.