Researchers found women were more likely to consider full-bearded men as more attractive for long-term relationships.
Investigators found that women are more likely to be attracted to stubbled men for short-term relationships, while full-bearded men are the preferred choice for long-term relationships.
Study co-author Barnaby Dixson, of the School of Psychology at The University of Queensland in Australia, and team publish their findings in the Journal of Evolutionary Biology.
What makes a man attractive to a woman is a question that has divided researchers for decades.
According to Dixson and colleagues, studies have shown that in the short term, men with more masculine facial features - such as a wider jawline and a more pronounced brow ridge - are considered more attractive.
In other studies, researchers have suggested that for long-term relationships, women prefer men with less masculine facial features, perceiving them to be more caring and considerate.
So where does facial hair fit in? While beards are generally considered a more masculine facial feature, results have been mixed as to how they influence women's mating preferences.
Some studies, for example, have suggested that men with facial hair are the preferred choice for long-term relationships over clean-shaven men, contradicting the view that women opt for more masculine men in the short term.
"Why such divergent effects occur between preferences for two sexually dimorphic traits remains unresolved," note the authors.
Judging the attractiveness of facial hair for relationships
For their study, Dixson and colleagues set out to further investigate how facial hair affects a man's attractiveness for short- and long-term relationships.
The researchers photographed 36 men at three stages of facial hair: clean shaven, light stubble (5 days of hair growth), heavy stubble (10 days of hair growth), and a full beard (at least 4 weeks of untrimmed hair growth).
Additionally, the photographs of 16 of these men with varying facial hair growth were manipulated to look either more masculine or feminine.
The researchers asked 8,520 women to view the normal and manipulated photographs and rate how attractive they thought each man was in general, as well as how attractive they were for short- and long-term relationships.
"The 'short-term attractiveness' condition asked participants to rate the men when imagining the type of person who would be attractive in a short-term relationship. This implies that the relationship may not last a long time," the authors explain.
"The 'long-term attractiveness' condition asked participants to imagine they were looking for the type of person who would be attractive in a long-term relationship. Examples of this type of relationship would include someone you may want to move in with, settle down and, at some point, wish to marry," they add.
Beards may 'mask' unattractive features of masculinity, femininity
In general, among men who were were clean shaven, masculine faces were considered least attractive, followed by feminine faces. Unmanipulated faces were rated as most attractive.
On assessing the effects of facial hair on women's judgment of attractiveness, the team found that men with light and heavy stubble were considered most attractive, compared with full-bearded and clean-shaven men.
When it came to relationships, however, the researchers found women rated full-bearded men as most attractive for long-term relationships, while light and heavy stubble were considered most attractive for short-term relationships.
According to the team, in manipulated photographs, heavy stubble and full beards reduced the effects of small changes in facial shape, and these may have influenced women's judgments of attractiveness by "masking" such changes.
"Thus, beards may mask the unattractive features of having overly feminine or masculine face shapes," say the authors.
Commenting on the overall indications of their study, the researchers say:
"Our findings suggest that beardedness may be attractive when judging long-term relationships as a signal of intrasexual formidability and the potential to provide direct benefits to females.
More generally, our results hint at a divergence of signalling function, which may result in a subtle trade-off in women's preferences, for two highly sexually dimorphic androgen-dependent facial traits."