No study to date has examined the cognitive effects of bariatric surgery. To do so, the proposed study will prospectively assess cognitive performance in 125 bariatric surgery patients enrolled in the LABS project and 125 matched controls. Bariatric surgery patients will complete a computerized cognitive test battery at four time points: pre-operatively, 12 weeks post-operatively, 12 months post-operatively, and 24 months post-operatively. Matched control participants will complete the test battery at similar intervals. Demographic, medical, and psychosocial information will be collected to elucidate possible mechanisms of change. We hypothesize that the substantial weight loss following bariatric surgery will be associated with improved cognitive performance.