Professors Barnaby J. Dixson and Rob C. Brooks of the University of New South Wales showed heterosexual men and women photos of men -- some clean-shaven, some with light stubble and some with 10 days of beard growth.
"We quantified men's and women's judgments of attractiveness, health, masculinity and parenting abilities for photographs of men who were clean-shaven, lightly or heavily stubbled and fully bearded," the researchers wrote in the study. "We also tested the effect of the menstrual cycle and hormonal contraceptive use on women's ratings."
The study, published in the journal Evolution & Human Behavior, said women judged faces with heavy stubble as most attractive and heavy beards, light stubble and clean-shaven faces as similarly less attractive. However, men rated full beards and heavy stubble as most attractive, followed closely by clean-shaven and light stubble as least attractive, the study said.
Men and women rated full beards highest for parenting ability and healthiness. Masculinity ratings increased linearly as facial hair increased and this effect was more pronounced in women in the fertile phase of the menstrual cycle, although attractiveness ratings didn't differ according to fertility, the researchers said.
"Our findings confirmed beardedness affects judgments of male socio-sexual attributes and suggested an intermediate level of beardedness was most attractive while full-bearded men might be perceived as better fathers who could protect and invest in offspring."