We've been told our entire lives that men and women are just plain different. However, a new study is turning that assumption on its head. The study, published in this month's issue of the journal American Psychologist, was actually a meta-synthesis of 106 meta-analyses (sort of a meta-meta-analysis). All the included studies looked at possible gender differences in a bunch of cognitive variables (such as math skills) as well as social or personality variables (such as aggression and leadership). Overall, the researchers were able to include data from more than 12,000,000 participants. Their results found an almost 80% overlap on 75% of the tested dimensions, including risk-taking and occupational stress. The largest differences the researchers found between men and women generally supported existing stereotypes: Men tended to be more aggressive and place more importance on physical attributes when selecting partners; women were more into peer attachment and more interested in people rather than material things. The authors conclude that they found more evidence for gender similarities than differences. This goes against our society's persistent belief that there are major, innate differences between men and women, but it does support another large (but controversial) study from 2005. In the end, what this study reveals is that we're probably tricking ourselves into thinking gender stereotypes matter more than they actually do. They can, however, become self-fulfilling prophecies simply because we believe them; even if they're not "real," they can still have a real impact on our lives.