The differences can be noticed from early childhood, [psychologist Michael] Gurian said, such as when an adult gives a child a doll.

"That doll becomes life-like to that girl, but you give it to a two-year-old boy and you are more likely, not all the time, but you are more likely than not to see that boy try to take the head off the doll," he said.

"He thinks spatial-mechanical. He’s using the doll as an object".

Many women also seem to lack the "changing a flat tire" gene.