"Math class is tough!" The Teen Talk Barbie doll uttered these words in 1992, and women's groups forced Mattel to rethink its little protégé's lack of numerical confidence. Who knew that it would take a real scientific study to prove that negative stereotypes affect women's mathematical abilities?

But of course, since the airhead-embracing Mattel executives got an education in the math gap, it's not like there weren't still pockets of ignorance out there. Earlier this year Harvard University President Lawrence Summers resigned after controversy stemming from his comments about women's and men's innate differences in mathematical and scientific aptitude.

Now, a did-it-really-take-a-study news wire from the New Scientist reports that a University of British Columbia, Canada, study found that women told that their mathematic abilities are socially determined do better than those who are told that their skills (or lack thereof) spring from their genes.

For any mother of a little girl, the idea is a no-brainer. Tell someone they are bad at something because of an invisible substance in their bloodstream and you're going to get different results than if you tell them they're struggling because their jerky male teacher never calls on them.

Psychologists have long known stereotypes have a peculiar power over our perception of reality. What's different about this study is that explaining a stereotype's spuriousness seems to have a demonstrable and immediate influence on the listener. In the study 220 women were given math tests after being told one of two explanations for women's mathematical underachievement. One group was told differences were genetic; the other, that the differences were caused by social factors like classroom experiences.

The results of the study surprised even this pathologically nurturing mom. Those fed the "genes" myth got only about half as many correct answers as those told the "experiential" story. What's the true cause? Does it matter? It's an interesting conundrum -- pedagogically the search for genetic differences between genders or between any groups for that matter may not be terribly useful. In any case, if you're feeling a little down on your maths, perhaps it's time for a pep visit to Agnes Scott College's Web site devoted to the biographies of women mathematicians. Maybe they had better teachers than the rest of us.