BBC News Online: Health

'It's that time of the month'

And the stereotype that women are unable to throw a ball properly is legendary - as is that age-old query from a man to a woman: "Is it your period?"

If it is, perhaps you should take over finding the map-reading.

Research has found that women's spatial abilities differ during their menstrual cycle and are at its best during periods.

Higher levels of the female hormone oestrogen were linked to lower scores.

But when levels of the male hormone testosterone were higher, the women did better.

Researchers at the Ruhr-Universtitat, Bochum, Germany, gave women three separate tests to do at different stages of their menstrual cycle, reports the journal Behavioural Neuroscience.

Spatial tests

Twelve women in their 20s and 30s did the tests.

Blood samples were collected at three-day intervals over six weeks to check the levels of certain hormones, including male and female ones.

There was only one test in which researchers saw a difference.

The women were asked to perform the mental rotation test, in which they were asked to recognise rotated versions of a figure.

All but one scored more highly during the menstrual phase of their cycles.

The authors of the study, led by Dr Markus Hausmann, wrote: "We conclude that spatial performance is sensitive to hormonal fluctuations over the menstrual cycle and that different aspects of spatial abilities are related to different hormones or hormone combinations."