Confirmation bias is the act of only taking on board information that supports a pre-existing theory or belief. This is a cognitive bias that most people use to justify their ideals. Individuals that use confirmation bias only seek out favorable information.
Beliefs come from years of experience and also the information that is available. Confirmation bias often occurs naturally over time, as most people form a view first and then look to back it up with evidence rather than the other way round. With confirmation bias, not only is favorable information sought after, but any evidence to the contrary is dismissed out of hand as not being reliable.
Confirmation bias has the danger of leading to poor choices, as not all information is looked at objectively and equally. Experiments from the 1960s showed that people like to seek out information that reinforces existing beliefs. An example of confirmation bias occurs during an election campaign, when certain voters who may already support one candidate over another only consume positive media toward their candidate. The problem with this practice is that important information can be missed and so an objective analysis cannot be made of the situation. Being aware of confirmation bias can help to limit its influence on decision making.