The hormone estrogen could give women the edge in tasts such as safe driving, researchers say.

Tests show attention span and ability to learn rules are far better among women than men.

Bradford University scientists told a hormone conference in London how tasks requiring mental flexibility favoured women over men.

They said a woman's estrogen levels might prime the frontal lobe - the part of the brain involved in such skills.

They asked 43 men and women aged 18 to 35 to perform tests that assessed skills such as spatial recognition memory, rule learning, attention, planning and motor control.

The women were far better at being able to shift their attention from one stimulus to another, making it easier for them to perform everyday actions.

The researchers said this might explain why girls found it easier than boys to concentrate at school and why women were more careful drivers.