Toronto, June 23 (IANS) A woman can more accurately tell whether a guy is gay or straight by looking at his face during her most fertile period.

 
 "This suggests that fertility influences a heterosexual woman's attention to potential mates rather than merely increasing sensitivity to sexual orientation or nonverbal cues more generally," says Nicholas Rule, professor in psychology at the University of Toronto.
 
 "This effect is not apparent when a woman is judging another female's orientation," added Rule, who led the study, the journal Psychological Science reports.
 
 In the first of three experiments, 40 undergraduate women judged the sexual orientation of 80 men by looking at heir face's images. Forty of the photos were of self-identified gay males while the other 40 were of straight men, according to a Toronto statement.
 
 The researchers correlated the participants' accuracy in judging sexual orientation with the point at which the women were in their fertility cycle -- women who were nearer to peak ovulation were more accurate at judging each male's sexual orientation.
 
 The second experiment featured 34 women who viewed a similar series of female faces, 100 of whom were self-identified lesbians while another 100 were straight. The researchers found no relationship between fertility and accurate judgments of the women's sexual orientation.
 
 "Together, these findings suggest that women's accuracy may vary across the fertility cycle because men's sexual orientation is relevant to conception and thus of greater importance as women are nearer to ovulation."
 
 The researchers further tested this hypothesis with a third experiment in which female participants were primed with a mating goal in order to manipulate reproductive relevance.
 
 Half of the 40 participants were asked to read a story which described a romantic encounter while the other half did not, before performing the same tasks in the two previous studies.
 
 Rule and his colleagues found that the women primed with a mating goal were significantly more accurate in their judgments than the women who were not, implying that inducing romantic or mating-related thoughts improved accuracy in identifying men's sexual orientations.