Why women’s sexual fantasies get kinkier towards the middle of the month

It must be the most common excuse for male infidelity: “men have evolved to pursue as many women as possible. It’s not my fault. It’s my genes.” Yes, what torture: to be a man, cursed by natural selection to think about sex every half a second. But very few of us – men at least – would expect women to be plagued by incessant sexual fantasies too. Well, we’d be right. Some of the time. Although research has shown that men report more diverse and frequent sexual fantasies than women, the pattern of women’s fantasies might be more changeable.

Samantha Dawson of the University of Lethbridge in Canada had thirty women complete a diary, recording their sexual fantasies for 30 days, over an entire menstrual cycle. The researchers found that when women were most fertile, around the time of ovulation, they experienced more frequent sexual fantasies. Admittedly, that only meant an increase from 0.6 fantasies per day at low fertility to 0.9 per day at ovulation. Still, fantasies at ovulation were rated as significantly more arousing than low fertility fantasies, when they were presumably somewhat more pedestrian. This was born out by an analysis of the gender of participants in the fantasies. Women fantasised more about multiple male partners when they were most fertile, whereas at other times of the month almost all fantasies featured a single man.

So, why should women’s fantasies vary according to their cycle? Well, as I’ve discussed before, the menstrual cycle is associated with a whole suite of changes in women’s sexuality, with preferences for masculine faces and the scent of symmetrical men peaking at ovulation, along with the tendency to wear more revealing clothes. It seems that when women are most likely to conceive, they become more interested in behaviours that are likely to lead to pregnancy, and specifically in pairing up with attractive men. More persistent fantasies could be the trigger that promotes these behaviours. If women think more about men when they ovulate, perhaps that will motivate their real world sexual activity.

As if often the case, men operate a far simpler strategy. Think about sex all the time, every day, and hope that it’ll translate into reality as often as possible. You can call that perverted if you like. In the light of Dawson’s research, a fairer word might be “prepared”.

And if that doesn’t sound convincing, you’ll have to excuse me. It’s not my fault. It’s my genes.


Dawson, S. J., Suschinsky, K. D., & Lalumière, M. L. (2012). Sexual fantasies and viewing times across the menstrual cycle: a diary study.Archives of Sexual Behavior, 41(1), 173–183. Read summary

The content of this post first appeared in the April 2012 episode of The Psychology of Attractiveness Podcast.

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