Ovulation helps women pick out a good mate by enhancing her ability to identify gay men from straight, according to new research.

Harold Lee Miller/Corbis

vulation doesn't just facilitate pregnancy by releasing a ripe egg, says Bonnie Rochman at TIME. New research has concluded that it also helps a woman select a partner by enhancing her "gaydar." Here, a brief guide to the role ovulation plays in picking a partner:

How did the researchers figure this out?
Psychologists at the University of Toronto and Tufts University asked 40 women, all heterosexual Tufts undergraduates, to look at 80 pictures showing men's faces. The men were roughly equivalent in terms of attractiveness and expressions, but half were straight and half were gay. The closer the women were to peak ovulation, the better they were at telling whether a man was straight or gay just by looking at his face.

Do ovulating women have 'gaydar' about lesbians?
No. A group of straight women were shown pictures of 200 women, but the test subjects weren't particularly adept at telling straight women and lesbians apart, no matter how close they were to ovulation.

What else did this study conclude?
Curiously, that mood-setting fiction can further improve ovulating women's gaydar: The women who were shown images of men were even better at sorting straight and gay men after reading a sexy story. The researchers, whose work was published in the journal Psychological Science, say all of these observations point to the same conclusion: Women who are at their most fertile make many unconscious judgments that increase their chances of getting pregnant.

Is this the only way ovulation affects a woman's senses?
No. Previous studies showed that ovulating women can identify a man's face quicker than they can a woman's. Lesbians, however, can identify women quicker than men. And ovulating women are only half as likely to telephone their dads. Researchers explain that since incestuous relationships can produce offspring with birth defects, women unconsciously shun their fathers when they're at their most fertile. "Around ovulation, the mind is reallocating its resources in ways that are relevant evolutionarily," says Nicholas Rule, an assistant professor of psychology at the University of Toronto and the study's lead author, as quoted bt TIME. "It shows us that the link between body and mind is greater than we often think."

Sources: Globe and Mail, Telegraph, TIME