A test of the brain's electrical activity shows that women commonly use both sides of their brain while men rely more on one. Scientists already know that the two sides of the brain control different functions-one controlling the sense of space, for example, the other controlling language. Some researchers believe that the different ways men and women use their brains evolved from ancient times, when cave men hunted and women cared for the children. Men had to have good aim. Women had to talk to the kids.