confirmation bias
Summary
Confirmation bias is the tendency to seek, notice, interpret, and remember information in ways that support what one already believes, while discounting evidence that contradicts it. It is a cognitive bias in judgment, and it often helps beliefs persist even when evidence is mixed.
Detail
Meaning: Confirmation bias is the tendency to favor information that fits an existing belief. People search for supporting evidence, read ambiguous evidence as supportive, and remember confirming cases better than disconfirming ones, while scrutinizing or dismissing contradicting evidence. This helps maintain stereotypes and first impressions.
On the MCAT: Passages show someone who forms a belief and then treats evidence selectively, such as a teacher who expects a student to struggle and mainly notices mistakes. A classic lab case is Wason's 2-4-6 task, where participants test a hypothesized rule by proposing triples that fit it rather than ones that could disprove it. Expect questions that ask you to name the bias, link it to stereotypes, belief perseverance, or the self-fulfilling prophecy, or spot how an experimenter's expectations could skew data, which blinding reduces.
Common confusion: Students mix it up with the availability heuristic and belief perseverance. The availability heuristic judges likelihood by how easily examples come to mind, whatever one believes. Belief perseverance is keeping a belief after its supporting evidence is discredited. Confirmation bias is the biased search for and reading of evidence, and it is one mechanism that can produce belief perseverance.
Sources
- Psychology (Myers)
- Psychology (Schacter, Gilbert, Wegner)
- Social Psychology (Aronson, Wilson, Akert)
Written for the MCAT and checked before it was published. For study reference only. Spotted an error? Let us know.