Have hipsters whisked the sex factor out of beards?

Hollywood hunks Ryan Gosling, Jared Leto and Bradley Cooper realise the allure of sexy facial hair. Photo / AP

Too sexy for your beard?

It depends on how many other bearded men are around you.

A team of University of New South Wales researchers led by Kiwi Dr Barnaby Dixson has looked at how and when men's facial hair is seen as a sexual trait.

The researchers photographed 36 men when clean shaven, with light stubble, heavy stubble beard, and then showed them to a survey sample of 1453 heterosexual and bisexual women and 213 heterosexual men.

They found that heavy stubble and full beards were seen as more attractive when there were fewer of them shown together - but the more men who wore them, the less they were viewed as attractive.

"When beards were rare, hirsute faces were more attractive than when beards were common ..." the authors said.

"Conversely, when clean-shaven faces were rare, clean-shaven faces and light stubble enjoyed their greatest attractiveness, and beards became less attractive."

The authors however said there was not an "inversion of preferences", such as clean-shaven faces becoming more attractive than beards when rare, with clean-shaven faces rating lowest in all tests.

"However, the mean attractiveness of a suite of faces is altered by the frequency of beards, suggesting negative frequency dependence could alter the cultural dynamics by which facial hair fashions vary."

Novelty effects - possibly spurred by imitation of "influential early adopters" - could affect the rise in frequency of new fashions, they said.

The study was published today in Biology Letters.

The beard has enjoyed a resurgence in popularity over recent years, with bearded celebrities including George Clooney, Hugh Jackman and Bradley Cooper raising the appeal.

As a Victoria University PhD student in 2009, Dr Dixson made headlines with a study that showed men noticed women's breasts first - and could zoom in on a woman's most attractive features within 200 milliseconds.