A feminine-looking man's face is more likely than a rugged-looking type to capture the eye of a heterosexual New Zealand woman, new international research tends to suggest.
The global online study by Aberdeen University psychologist Lisa DeBruine, and her husband, Ben Jones, found that women's preferences for male faces vary according to the state of health care in the nation where they live.
A small number of New Zealand women were among the 4500 they tested in 30 countries.
Dr DeBruine said she started with the theory that the craggy physical characteristics associated with masculinity in a male face often indicated a strong immune system and a likelihood of his producing healthier offspring than his softer-featured men.
But the same sort of men were also more likely to be more promiscuous and more likely to leave a woman to raise their children alone.
Her study found that in environments where disease is rampant and the child-mortality rate is high, women prefer masculine men. In developed nations with better health care effeminate-looking men were more competitive.
As health care improved, more masculine men fell out of favour, Dr DeBruine said.
"Women from NZ, on average, preferred the more masculine face 38 percent of the time and the more feminine face 62 percent of the time."
Only 26 NZ women were included in the study, with an average age of 24 years, but Dr DeBruine said their choices supported the evidence that improvements in health care in healthy western countries mean women do not have to worry about so much about the quality of their offspring - and so are picking more feminine looking men than in earlier times.
Biological theories suggest that masculine traits in men signal their genetic health, she said. Women historically chose "manly" men because features such as a square jaw, low brow and thin lips were linked to superior genes which would produce stronger and healthier offspring.
But the theories also suggested that the more masculine the man, the less likely he was to help out nurturing his child.
Now Dr DeBruine's team at Aberdeen University has found that in Sweden, which had the best health care in her study, most women (68 percent) preferred feminine-looking men.
In contrast in Brazil, which had the worst health care, the majority of women (55 percent) preferred masculine men.
The 62 percent of New Zealand women who preferred feminine-looking male faces was more than in Australia, where that preference was held by 56 percent of women tested on images of 20 different male faces.
The study subjects were white, heterosexual women aged between 16 and 40.
Women were shown two images of the same face side by side, but one picture was very subtly altered so it had more masculine traits, such as a bigger jaw and heavier and lower brow line, and the other was oppositely altered so it had more feminine traits.
Dr DeBruine said the confirmation of a link between population health and masculinity was new, but it complemented her previous research showing that individual differences in the extent to which women are disgusted by cues of pathogens - such as someone with open sores - predicted their preferences for male facial masculinity.
"Women who were more easily disgusted, which indicates how concerned they are about health, also preferred masculinity more," she said.
This suggested differences in ideals of beauty across cultures might be due not to arbitrary cultural differences, but systematic responses to differences in the environment.
Next the researchers will look at other environmental differences, to see if levels of women's equality and control of resources also affect what type of male partner they preferred.
The findings were published in the journal Proceedings of the Royal Society B, covering biological sciences.
