Belief Bias
Updated 2026-07-31
INTRODUCTION
English translation pending.
CORE DEFINITION
A reasoning bias documented in the psychology of deduction and studied extensively by Jonathan Evans and colleagues from the 1980s. People accept invalid arguments whose conclusions they agree with and reject valid arguments whose conclusions they dislike. The bias appears in syllogistic reasoning tasks where the believability of a conclusion competes with its logical validity, and it operates by letting prior beliefs override structural evaluation. It is closely related to motivated reasoning and confirmation bias, and formal logic training reduces it without eliminating it.
SCAFFOLDING EFFECT
Reduce cognitive load
- Logic purification: Separate the structure of an argument from whether you like its conclusion. - Symbol swap: Replace content with letters to test the form independently of meaning. - Symmetric testing: Apply the same validity standard to arguments you happen to disagree with.
Anchor fast decisions
Evaluating an argument properly requires holding the content aside and checking whether the premises entail the conclusion, which is cognitively costly. Prior beliefs are cheap to retrieve and arrive first, so they act as a shortcut that substitutes agreement for validity. The result is asymmetric: palatable conclusions get a pass on structure, while unpalatable ones face extra scrutiny of their form regardless of whether the reasoning holds.
MINIMUM ACTION
In progress 0/1Practice this model in one real situation:
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Source support: Explicit
- en.wikipedia.orghttps://en.wikipedia.org/wiki/Belief_biasverified
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