Confirmation Bias
The tendency to search for, interpret, and recall information in ways that confirm what we already believe — and to discount evidence that contradicts those beliefs.
Confirmation bias is one of the most thoroughly documented patterns in cognitive psychology. Once we hold a hypothesis — even a casually formed one — we unconsciously give more weight to evidence that supports it, ask questions whose answers will confirm it, and remember the wins while glossing over the misses. Peter Wason's classic 2-4-6 task showed people would invent elaborate rules to fit a hidden pattern but rarely tested cases that could disprove their guess. The bias shows up everywhere: in scientists clinging to a favored theory, in juries weighing testimony, in social-media feeds that quietly thicken into echo chambers. Nickerson's 1998 review in Review of General Psychology catalogued dozens of forms it takes — biased search, biased interpretation, biased recall — and noted that simply being warned about the bias is rarely enough to neutralize it. The mitigation that does work: deliberately constructing the case against your own position before you act on it.
Frequently Asked Questions
What is a simple example of confirmation bias?
You believe a coworker is always late. You start noticing every time they arrive after you, and forget the days they got in early. Within a few weeks the belief feels confirmed — but you were only counting evidence that fit it. Tracking the data without filtering is the corrective.
How do you reduce confirmation bias in your own thinking?
The most effective technique researchers have found is the consider-the-opposite prompt: before locking in a judgment, write down what evidence would change your mind, and actively look for it. Pre-committing to a falsification test — the same logic scientists use — is harder to skip than a vague intention to "be objective".
Where was confirmation bias first systematically studied?
Peter Wason's 1960 rule-discovery experiments are the classical reference. Raymond Nickerson's 1998 review article in Review of General Psychology is the standard modern survey, cataloguing the bias across reasoning, memory, social judgment, and scientific practice.