Heuristics & Judgement Biases

Heuristics are mental “rules of thumb” that help us make quick decisions under uncertainty. While often useful, they can lead to wrong decisions when applied in the wrong context.

Affect Heuristic
It’s when an easy, emotional assessment (“affect”) replaces a more complex assessment (“target attribute”) that requires more thought, such as e.g. a calculation. This is…
Anchoring and Adjustment
This is a judgment bias where an initial value (the “anchor”) influences subsequent estimates or decisions. While we might adjust from the anchor, the adjustment is usually…
Attention Bias
Attention bias occurs when we focus on the most visually or emotionally prominent features of a decision, rather than the most critical ones. Because our cognitive resources…
Aversion to Ambiguity
This bias describes a preference for choices with known probabilities over those with unknown probabilities, regardless of the expected value of each.
Base Rate Neglect
It’s when we overweigh specific information we have at hand (“representativeness”) over prior probabilities in the broader population, when making judgements.
Causality and Attribution
When trying to explain the causes of events, we make errors resulting from the prominence of available information, stereotypes etc.
Confirmation Bias
This bias refers to registering or recalling information that supports one’s pre-existing views while ignoring contradictory evidence.
Conjunction Fallacy
The Conjunction fallacy occurs when one believes that the probability of the conjunction of two events (i.e. occurring together) is greater than that of one of its…
Excessive Optimism
This bias describes the tendency to believe that good outcomes of events outside our control are more likely than bad outcomes, despite what objective probabilities might…
Extrapolation Bias
Extrapolation bias is the tendency to believe that recent trends will continue into the future, without accounting for the reasons that might cause them to reverse, such as…
Familiarity
The familiarity bias is related to the fact that people tend to fear change and the unknown. Repeated exposure to a brand, option, or idea creates a sense of comfort and…
Fluency Heuristic
The fluency heuristic is a variation of the Recognition Heuristic: when both options are recognised, the one retrieved from memory more easily (faster, more vividly) is…
Gambler’s Fallacy
The gambler’s fallacy is the mistaken belief that, after a run of one outcome of events, there’s bound to be a “reversal” or “balancing out”, and therefore the opposite…
Hindsight Bias
Hindsight bias is when we believe that we predicted the outcome of an event, after it has occured, even when we didn’t. The reason this happens is that, after an event…
Hot Hand Fallacy
The hot hand fallacy is the belief that long streaks are bound to continue, failing to account for systematic reasons or the statistical independence of events. It’s similar…
Illusion of Control
Illusion of control refers to believing that random events are subject to our control (see also the concept of Magical Thinking in psychology).
Illusion of Validity
To think your judgement is valid, even when the evidence you have at hand is weak or unreliable.
Law of Small Numbers
It’s the mistake to believe that a small sample accurately resembles the parent population. In reality, small samples have a small confidence interval and will eventually…
Overconfidence
Overconfidence is our tendency to overestimate our own skills and it might occur when (a) estimating our own performance (overestimation), (b) our own performance relative…
Recognition Heuristic
This bias involves assigning a higher value to an object we recognize. The heuristic is considered rational when the recognition criterion has some validity.
Self-Attribution Bias
When one attributes successful outcomes to their personal abilities but unsuccessful ones to external factors or “sabotage”. This leads to overconfidence, as one might expect!
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