Classifying biases

This is some text I’ve just added to WikiPedia:

Biases can be distinguished on a number of dimensions. For example, there are biases specific to groups (such as the Risky shift) as well as biases at the individual level.

Some biases affect decision-making, where the desirability of options has to be considered (e.g. Sunk Cost fallacy). Others such as Illusory correlation affect judgement of how likely something is, or of whether one thing is the cause of another. A distinctive class of biases affect memory (Schacter (1999)), such as consistency bias (remembering one’s past attitudes and behaviour as more similar to one’s present attitudes).

Some biases reflect a subject’s motivation, for example the desire for a positive self-image leading to Egocentric bias (Hoorens (1993)) and the avoidance of unpleasant cognitive dissonance. Other biases are due to the particular way the brain perceives, forms memories and makes judgements. This distinction is sometimes described as “Hot cognition” versus “Cold Cognition”, as motivated cognition can involve a state of arousal.

Among the “cold” biases, some are due to ignoring relevant information (e.g. Neglect of probability), whereas some involve a decision or judgement being affected by irrelevant information (for example the Framing effect where the exact same problem receives different responses depending on how it is described) or giving excessive weight to an unimportant but salient feature of the problem (e.g. Anchoring).

The fact that some biases reflect motivation, and in particular the motivation to have positive attitudes to oneself (Hoorens (1993)) accounts for the fact that many biases are self-serving or self-directed (e.g. Illusion of asymmetric insight, Self-serving bias, Projection bias). There are also biases in how subjects evaluate in-groups or out-groups; evaluating in-groups as more diverse and “better” in many respects, even when those groups are arbitrarily-defined (Ingroup bias, Outgroup homogeneity bias).

Many social institutions rely on individuals to make rational judgments . A fair jury trial, for example, requires that the jury ignore irrelevant features of the case (such as the attractiveness of the defendant), weigh the relevant features appropriately, consider different possibilities open-mindedly and resist fallacies such as appeal to emotion. The various biases demonstrated in these psychological experiments suggest that people will fail to do all these things. However, they fail to do so in systematic, directional ways that are predictable.

  • Hoorens, V. (1993) “Self-enhancement and Superiority Biases in Social Comparison” in European Review of Social Psychology 4, W. Stroebe and Miles Hewstone (Ed.), Wiley
  • Kunda, Z. (1990) “The Case for Motivated Reasoning” Psychological Bulletin Vol. 108, No. 3, 480-498
  • Schacter, D. L. (1999) “The Seven Sins of Memory: Insights From Psychology and Cognitive Neuroscience” American Psychologist Vol. 54. No. 3, 182-203
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