We've all met know-it-alls—people who think they know more than they actually do. If they're talking about products, like wine or motorcycles, they might actually know as much as they think. But when it comes to health plans, social policy, or nutrition, they might not, according to a new study in the Journal of Consumer Research. Authors Jay P. Carlson (Union Graduate College of Union University), Leslie H. Vincent, David M. Hardesty (both University of Kentucky), and William O. Bearden (University of South Carolina) conducted a meta-analysis of 103 consumer knowledge research studies that took place between 1980 and 2007. "Overall, our results suggest that people are not overly knowledgeable regarding how knowledgeable they are. They can deceive themselves into believing they are more knowledgeable than they are," they explain.