Cognitive Biases Index
A practical guide to how our minds understand the world around us. Each bias is grounded in peer-reviewed research with its original academic source.
Anchoring Effect
The tendency to rely too heavily on the first piece of information encountered when making decisions.
Tversky & Kahneman, 1974
Availability Heuristic
Estimating the likelihood of events based on how easily examples come to mind.
Tversky & Kahneman, 1973
Confirmation Bias
The tendency to search for, interpret, and recall information that confirms pre-existing beliefs.
Wason, 1960
Loss Aversion
Losses loom larger than equivalent gains — people are roughly twice as sensitive to losses as to gains.
Kahneman & Tversky, 1979
Status Quo Bias
Preference for the current state of affairs, with any change perceived as a loss.
Samuelson & Zeckhauser, 1988
Framing Effect
Drawing different conclusions from the same information depending on how it is presented.
Tversky & Kahneman, 1981
Dunning-Kruger Effect
People with limited knowledge overestimate their competence, while experts underestimate theirs.
Kruger & Dunning, 1999
Endowment Effect
People value things more highly simply because they own them.
Thaler, 1980
Sunk Cost Fallacy
Continuing a behaviour because of previously invested resources rather than future value.
Arkes & Blumer, 1985
Halo Effect
The tendency for a positive impression in one area to influence opinion in another area.
Thorndike, 1920
Bandwagon Effect
The tendency to adopt beliefs and behaviours because many other people do the same.
Leibenstein, 1950
Hindsight Bias
The inclination to see past events as having been predictable, also known as the "I-knew-it-all-along" effect.
Fischhoff, 1975
Default Effect
People tend to accept pre-set options rather than making an active choice to change them.
Johnson & Goldstein, 2003
Present Bias
The tendency to give stronger weight to payoffs that are closer to the present time.
O'Donoghue & Rabin, 1999
Mere Exposure Effect
People develop preferences for things simply because they are familiar with them.
Zajonc, 1968
Peak-End Rule
People judge experiences based on the most intense point and the ending, not the average.
Kahneman et al., 1993
Hyperbolic Discounting
The tendency to prefer smaller immediate rewards over larger later rewards, beyond what rational models predict.
Laibson, 1997
Social Proof
People copy the actions of others in an attempt to reflect correct behaviour in a given situation.
Cialdini, 1984
Authority Bias
The tendency to attribute greater accuracy to the opinion of an authority figure.
Milgram, 1963
Choice Overload
Having too many options can lead to decision paralysis, lower satisfaction, and no decision at all.
Iyengar & Lepper, 2000
Optimism Bias
The tendency to believe that we are less likely to experience negative events compared to others.
Weinstein, 1980
Reciprocity Bias
The social norm of responding to a positive action with another positive action.
Gouldner, 1960
Narrative Fallacy
The tendency to construct stories around facts, creating false causal links between events.
Taleb, 2007
Decoy Effect
Preferences change when a third, asymmetrically dominated option is introduced.
Huber, Payne & Puto, 1982