It is true that women and men often use different parts of their brains when solving problems, but we generally come to the same answer in the end. But I am a woman, so perhaps my view on this is biased. Personally, I believe the explanation lays in issues other than intellectual differences.
Young men and women both form stereotypical images of scientists. To many people, unfortunately, an engineering or science degree means you sit in a lab all day, wearing thick geeky glasses. Some scientists fit this description, but most of them are just ordinary people who love to solve problems. My own stereotypical view was that of a nerdy scientist. But then I discovered science was my passion!
A FAMILY MATTER. Most teenagers care about their image, but women are more protective of their image than men (at least this is true in my high school). If a teenager's peers equate an interest in science and math with negative personality traits -- geekiness, nerdiness, aloofness -- then he or she, particularly she, will try to avoid those subjects. Because women tend to value social skills highly, it is possible that they form more negative stereotypes of science. Whether this is factual would need to be researched. I throw it out as a suggestion.
The most likely reason for there being fewer women in science is family. Only women take maternity leave. Since well-educated parents know how critical the first years of childhood are, one of them will stay home to take care of the child to ensure a fast start on education. Usually it's the mother who stays home, as she was away from work before and after the baby was born.
After about two years of raising the child, a mother can finally enter the workforce again. But science and technology change constantly. It's hard enough going back to work at a routine office job, but for a scientist who has not been involved in two years of the progress in her field, going back to work is even more difficult. I know women who have a successful science career and a family, but they have overcome many tribulations.
TOUGH TRIAL. I am a woman, a scientist, and I plan on becoming a mother with a flourishing occupation. If I am the one who is to stay home with the children for a few years, I will gladly do so. However, I am determined to keep up with my career, too. I think women who are discouraged from a job in the sciences should note that if they can raise a family and go to back work, they have conquered a trial that most men have not.
I hope that no one, man or woman, is discouraged from going into science. There is something I cannot emphasize enough: Believe me, not all of us are geeks! Hess was a finalist in the 2005 Intel Science Talent Search