A field guide to flawed thinking
Bias indexKnow the trick. Break the spell.
Search 142 cognitive biases, see how they appear in real life, and learn a practical defense before your next decision.
SEARCH THE INDEX
Try “money”, “memory”, “work”, or a bias name.
THE OPEN INDEX
142 of 142 entries
DOCUMENTED CASES
These cases connect bias research to actual decisions. When a bias label is our interpretation rather than the source wording, it is marked as a lens.
A flight crew continued descending after mistaking a snow-covered field for the runway. The NTSB explicitly identified confirmation bias in the decision to continue below the decision altitude.
Post Office branch operators were made to accept Horizon accounting figures they said were wrong. Later reviews found bugs, weak investigation, and a major evidence imbalance behind unsafe convictions.
The Rogers Commission found that the Challenger launch decision relied on incomplete and misleading information, while continuing engineer opposition was not carried to key decision-makers.
When firms automatically enrolled workers in 401(k) plans, participation rose above 85 percent. Many employees stayed at the preset contribution rate and fund.
The FTC documented designs that use baseless countdown timers, false limited-time messages, preselected options, and invented demand to rush or steer consumers.
The NTSB has linked steep cockpit authority gradients with weaker communication and more errors, citing Tenerife and later accidents as part of the evidence base.
A UK Department for Transport review examined how predictable judgment errors appear in project delivery and assurance, especially around cost, schedules, and continuing commitment.
UK forensic guidance warns that irrelevant case information and knowledge of another examiner's conclusion can influence subjective interpretation.
THE DEFENSE KIT
Bias is normal. Good decisions depend less on feeling unbiased and more on a process that still works when everyone in the room is susceptible.
Write the choice, success measure, deadline, and owner before discussing solutions.
Use outcomes from comparable past cases before building the inside story about this one.
Collect independent estimates before the group sees a leader, anchor, or majority view.
State what would disprove the favored view, then actively look for that evidence.
Choose exit criteria before time, money, identity, or momentum make stopping painful.
Judge a decision using what was knowable at the time, not the luck of the outcome.
SOURCES & SCOPE
Bias labels overlap, taxonomies disagree, and some effects are more contested than others. This catalog favors useful, recurring concepts and plain-language examples. It is not a clinical tool, and no list can be literally complete.
Representative examples are illustrative. Named cases use the linked source.
Nobel Prize. Overview of Kahneman and Tversky's work on judgment under uncertainty.
Wikipedia reference index. Broad working index with references to original studies. Definitions here were rewritten in plain language.
UK Forensic Science Regulator. Practical guidance on context, confirmation, expectation, and anchoring risks in forensic work.
UK Department for Transport. Review of optimism bias, planning fallacy, sunk costs, and groupthink in project delivery.
US National Transportation Safety Board. The probable cause explicitly identifies confirmation bias in the flight crew decision.
US National Transportation Safety Board. Documents a steep cockpit authority gradient and cites its role in aviation error.
NASA History. Findings on incomplete information, communication failures, and the flawed Challenger launch decision.
UK Criminal Cases Review Commission. Explains system errors, poor investigation, unequal access to evidence, and unsafe convictions.
National Bureau of Economic Research. Administrative data showing how automatic enrollment and preset rates shape retirement saving.
US Federal Trade Commission. Documents false urgency, misleading defaults, hidden information, and other manipulative designs.