A confirmation bias is a type of cognitive bias in which people tend to seek out information that agrees with their previously held beliefs. They also lend more weight to informational input that supports their beliefs, while discarding contradictory information. This is one of the most common cognitive biases, and it can also be the most dangerous, because it can lead people into very poor decisions on the basis of questionable information. Learning to recognize this type of bias is very important, and individuals can use one or more of several techniques to avoid it, whether carrying out scientific research or buying produce.
There are a number of reasons why the confirmation bias is so strong. Like any cognitive bias, it is a shortcut in the brain to process information, but the shortcut has some shortcomings. It is probably related to a common human desire to be right, and to avoid embarrassment by recanting a previously held belief. This bias can also ensure that entrenched religious, ideological, and ethical beliefs are not challenged, making believers feel more confident.
There are some obvious dangers to only looking at certain information, of course. For example, in scientific research, scientists could skew the results of a study by only seeking out information that confirmed their hypothesis. In a study looking at the effects of the lunar cycle on human behavior, a scientist might believe that humans engage in more dangerous behavior around the new moon, and this hypothesis might be tested by tracking emergency room admissions. If the scientists only looked at admissions during this time period, it would not provide a complete picture that might not support the hypothesis.
A confirmation bias can also create a logic trap for people trying to engage in critical thinking. Many critical thinking classes encourage people to come up with views that are antithetical to their own opinions, to make people aware of the potential for bias in critical thinking. In fields that require strong critical thinking skills, it is very important for people to constantly challenge their beliefs, and people should also not be afraid of being wrong.
To avoid this bias, people should try to analyze their beliefs and ideas from a wider point of view. Those who are testing a personal hypothesis should gather as much information as possible before determining whether or not the hypothesis is true; for example, if someone believes that melons of a certain shape taste the best, he should collect a wide sample of melons of varying sizes and conduct a blind tasting test to confirm or refute this hypothesis. Individuals should also not be afraid to play the devil's advocate in a discussion or argument, thinking through the opposing point of view.