It makes perfect sense when you think about it. Lots of women feel a bit fuzzy-headed during the week leading up to their period. And this latest study, published in the journal Brain and Cognition, confirms it.
Oestrogen, say the researchers, is known to play a significant role in learning and memory. And now, after carrying out tests on animals, they claim high oestrogen levels are linked with an inability to concentrate. So if you're thinking of taking your driving test, for instance, choose the date carefully.
But when exactly are your oestrogen levels at their highest? When you ovulate your hormone levels start to rise rapidly - that's around day 15-17 after the start of your last period. Oestrogen continues to soar until it peaks during days 24-28. Unsurprisingly that's also when your PMS symptoms are at their worst.
So when's the best time for concentration? Around four or five days after your period finishes your hormone levels are relatively low - this is when most women feel at their best. Your energy levels are never better and your ability to concentrate is at its height. In other words, it's the perfect time to take a test, go for an interview or learn anything complicated.
Do you agree? What's the dumbest thing you've done in the week before your period?