What is confirmation bias?

Confirmation bias refers to when testing is directed towards the proving of an already existing hypothesis, as opposed to researching information in a non-biased objective way that may result in evidence that conflicts with the already existing hypothesis. For example, if someone was to conduct research into the effects of caffiene and concentration they would solely focus on the short-term effects of caffiene and the surge of focus, rather than also considering the long-term introduction of fatigue as a result of caffiene consumption.