A small-scale study suggests that women’s ability to tell whether men are gay improves during the most fertile phase of their menstrual cycle.

Researchers at the University of Toronto found that women who are ovulating are better at deciding which men are gay than women who are not.

Forty heterosexual female students were asked to look at 80 images of men’s faces: half were gay and all were of a similar expression and level of attractiveness.

According to Time, lead researcher Professor Nicholas Rule said: “The closer you get to peak ovulation, accuracy goes up, up, up, peaks at ovulation, then starts to go back down again. There is a linear effect.”

The participants were then asked to look at 100 pictures of female faces. Again, half were lesbians. However, no correlation was found between fertility and gaydar.

In a final experiment, half of the 40 women were asked to read an erotic story before looking at pictures of men’s faces. Those who had read the story – and were deemed to be in a ‘reproductive mood’ – were even more accurate at deciding which men were gay.

Researchers say that the three studies, taken together, suggest that ovulation has an effect on behaviour.

Professor Rule added: “”It’s not just that women are more attentive to non-verbal cues around ovulation. It’s really something specific about paying attention to men’s sexual orientation.

“Around ovulation, the mind is reallocating its resources in ways that are relevant evolutionarily. It shows us that the link between body and mind is greater than we often think.”