We all know our menstrual cycle plays havoc with our hormones. And given how unpredictable it can make our mood and cravings at certain stages of the month, it's easy to buy into the idea that ovulation could effect and be effected by our social behaviour, too.
There's a popular theory that our cycles sync with the women we live with because of the pheromones we emit. Despite a lack of supporting studies, this is a pretty persistent rumour.
Simon Oxenham has sifted the pop science from genuine neuroscience in his column on New Scientist to debunk some popularly-held myths about our period once and for all, including the idea of syncing up.
Oxenham says it can actually be explained by simple maths.
'If we imagine two women with cycles of 28 days, the maximum amount of time they could be out of sync would be 14 days,' he says. 'On average, we would expect them to be only seven days apart, with a 50 per cent likelihood that they are even more closely aligned, just through chance alone. If we assume menstruation lasts five days, it’s hardly surprising that in a group of close friends, there will be some overlap.'
He also looked at theories which suggest that women are attracted to different types of sexual partners depending on the stage of their cycle. Some studies have it that we like hyper-masculine men with 'good' genes while we're fertile. But can it really be possible that we're that fickle? And that driven by the need to procreate?
And in short, the answer is: no. A review by the University of Southern California of 58 studies on ovulation and sexual attraction proved that yes, 'women do prefer men with dominant, masculine, healthy traits, and more symmetrical faces.' But it isn't linked to ovulation or desire for short-term relationships at a certain time of the month.
Oxenham concludes that while these theories are unreliable, they remain popular because periods have so much historical and cultural significance that we can't help but be fascinated by anything that might connect our cycle to our social behaviour.
In short: don't believe everything you read about your period.