Via Geek Feminism:
A new study, performed by Dr. Akira Miyake at UC-Boulder, shows the power of removing stereotype threat for women in physics. A simple 15-minute writing exercise completely closed the gap between women and men on a standard test of basic physics concepts.
Even though I majored in physics, and even though I'm now in a much more gender-balanced STEM field, and even though I have struggled with self-confidence and stereotypes, I'm still always stunned by just how strong stereotype threat can be. Studies like this -- and the others referenced in that article -- show that it's a huge effect.