Research is one of many studies looking at differences in sexual interest of women throughout the menstrual cycle. For example, a 2007 study in the journal "Hormones and Behavior" found that around the time of ovulation, when pregnancy is possible, women prefer men very macho, very masculine. An April 2011 study even suggested that women are most fertile phase of the month are more likely to find the paintings of Georgia O'Keeffe suggestive and erotic.

This new study shows an increase in sexual fantasies, which leads to greater arousal in women during fertile periods. Women also spoke of a greater proportion of men in their fantasies in fertile periods of the month.

Dawson and her colleagues focused on the fantasies because these sexual fantasies do not depend on having or not having a partner. That means that fantasies are more dependent on sexual interest than the actual sex life is a woman.

The researchers counted for this study, with 27 single heterosexual women, mostly college students, which wrote an online diary of his sexual fantasies for a month. None of the women used hormonal birth control.

For 10 days, each one carries out a fertility test urine for ovulation and fertility tests available at pharmacies. The tests were delivered in envelopes without labels and women did not know they were evidence of ovulation.

The women studied reported an average of 0.77 sexual fantasies a day, much higher values ​​than those of previous works, which had suggested that men fantasize about once a day and women once a week.

In the three days around ovulation, the fantasies became more frequent, averaging about 1.3 per day. addition to these fantasies were more exciting than those of infertile periods.

The researchers expected to find that women become more fertile, say, "male" in his fantasies during fertile periods, taking into account the increase of interest in sex. The sexual fantasies of men are more visual and explicit than the female, which tend to place more emphasis on emotion. But in fact, the fantasies of the participants were even more "feminine" during her fertile days.