There is ample evidence that confirmation bias permeates throughout investors' decisions. For example, once an investor likes a stock, he is likely to seek out information that validates that stock. In a 2010 study, researchers showed that investors used message boards to seek out information that validated rather than challenged, stocks they owned (Park et al. 2010). If we own a stock, we tend to look for anything that validates our decision to buy it, and to reinforce why we should keep holding it.