Bias List

Belief Biases


Affect Heuristic

The way you feel filters the way you interpret the world.


Ambiguity Effect

The tendency to avoid options for which missing information makes the probability seem "unknown".


Anchoring Effect

The tendency to rely too heavily, or "anchor", on one trait or piece of information when making decisions (usually the first piece of information that we acquire on that subject).


Attentional Bias

The tendency of our perception to be affected by our recurring thoughts.


Availability Cascade

A self-reinforcing process in which a collective belief gains more and more plausibility through its increasing repetition in public discourse (or "repeat something long enough and it will become true").


Availability Heuristic

The tendency to overestimate the likelihood of events with greater "availability" in memory, which can be influenced by how recent the memories are or how unusual or emotionally charged they may be.


Backfire Effect

When people react to disconfirming evidence by strengthening their beliefs.


Belief Bias

An effect where someone's evaluation of the logical strength of an argument is biased by the believability of the conclusion.


Cheerleader Effect

The tendency for people to appear more attractive in a group than in isolation.


Clustering Illusion

The tendency to see patterns in random events. This involves overestimating the importance of small runs, streaks, or clusters in large samples of random data.


Conservatism Bias

The tendency to believe prior evidence more than new evidence or information that has emerged.


Dunning-Kruger Effect

The tendency for unskilled individuals to overestimate their ability and the tendency for experts to underestimate their ability.


Galatea Effect

The tendency for people to succeed — or underperform — because they think they should. The motivation of individuals is influenced by their self-expectations.


Hawthorne Effect

A type of reactivity in which individuals modify or improve an aspect of their behavior in response to their awareness of being observed.


Hindsight Bias

Sometimes called the "I-knew-it-all-along" effect, the tendency to see past events as being predictable at the time those events happened.


Hot-Hand Fallacy

The belief that a person who has experienced success with a random event has a greater chance of further success in additional attempts.


IKEA Effect

The tendency for people to place a disproportionately high value on objects that they partially assembled themselves, such as furniture from IKEA, regardless of the quality of the end result.


Illusion of External Agency

When people view self-generated preferences as instead being caused by insightful, effective and benevolent agents.


Illusion of Truth Effect

The tendency to believe information to be correct because we are exposed to it more times.


Illusory Correlation

Inaccurately perceiving a relationship between two unrelated events.


Naïve Realism

The belief that we see reality as it really is – objectively and without bias; that the facts are plain for all to see; that rational people will agree with us; and that those who don't are either uninformed, lazy, irrational, or biased.


Observer Expectancy Effect

When someone's expectations unconsciously influence how they perceive an outcome. Researchers looking for a certain result in an experiment, for example, may inadvertently manipulate or interpret the results to reveal their expectations.


Optimism Bias

The tendency to be over-optimistic, overestimating favorable and pleasing outcomes.


Ostrich Effect

The decision to ignore dangerous or negative information by "burying" one's head in the sand, like an ostrich.


Outcome Bias

The tendency to judge a decision by its eventual outcome instead of based on the quality of the decision at the time it was made.


Overconfidence Effect

Excessive confidence in one's own answers to questions.



A vague and random stimulus (often an image or sound) is perceived as significant.


Pessimism Bias

When people exaggerate the likelihood that negative things will happen to them.


Pro-Innovation Bias

The belief that an innovation should be adopted by whole society without the need of its alteration.The innovation's "champion" has such strong bias in favor of the innovation, that he/she may not see its limitations or weaknesses and continues to promote it nonetheless.


Pygmalion Effect

The phenomenon whereby higher expectations lead to an increase in performance.


Rhyme as Reason Effect

Rhyming statements are perceived as more truthful.


Selection Bias

A distortion of evidence or data that arises from the way that the data is collected.


Self-Enhancing Bias

The tendency to take full credit for your success without acknowledging any external factors



Expecting a member of a group to have certain characteristics without having actual information about that individual.


Subaddivity Effect

The tendency to judge probability of the whole to be less than the probabilities of the parts.


Subjective Validation

Perception that something is true if a subject's belief demands it to be true. Also assigns perceived connections between coincidences.


Telescoping Effect

The tendency to displace recent events backward in time and remote events forward in time, so that recent events appear more remote, and remote events, more recent.


Valence Effect

The valence effect of prediction is the tendency for people to simply overestimate the likelihood of good things happening rather than bad things.


Well-Traveled Road Effect

Underestimation of the duration taken to traverse oft-traveled routes and overestimation of the duration taken to traverse less familiar routes.


Worse Than Average Effect

A tendency to believe ourselves to be worse than others at tasks which are difficult.