Biological differences

New evidence that biology plays a major role in human differences:

Map reading and parking may prove difficult for some women because they were exposed to too little testosterone in the womb, researchers suggest.

The study, in the journal Intelligence, fuels the age-old male myth that women are deficient in these skills.

Scientists from the University of Giessen, Germany, found a lack of the hormone affects spatial ability.

Low testosterone levels are also linked to shorter wedding ring fingers, they say.

The research looked at the spatial, numerical and verbal skills of 40 student volunteers.

Spatial skill is the ability to assess and orientate shapes and spaces. Map reading and parking are spatial skills which men often say women lack. Women tend to disagree.

The researchers also looked at the length of the students' wedding and index fingers.

In women, the two fingers are usually almost equal in length, as measured from the crease nearest the palm to the fingertip. In men, the ring finger tends to be much longer than the index.

For one of the spatial tests, volunteers had to tell which of five drawings could not be rotated so it looked like the other four.

The other test involved the ability to think in 3D by mentally "unfolding" a complex shape.

Overall, men achieved higher scores in the tests than women.

But women with the male pattern of finger length did better than those whose wedding finger was shorter.

They also scored better on the numerical tests.

And this is not the only research to show such differences:

Other studies looking at finger length ratio have suggested that, in men a long ring finger and symmetrical hands are an indication of fertility, and that women are more likely to be fertile if they have a longer index finger.

Another study controversially suggested that finger length ration could also be linked to sexual orientation, with lesbian women have a greater difference in length between their ring finger and index finger than straight women do.