Case file
Conjunction Fallacy
- Filed under
- Need To Act Fast
The charge
We judge a detailed, specific scenario as more likely than a broader, simpler one that actually contains it.
How it operates
A vivid, coherent story feels representative, and that feeling can override formal probability rules.
Logged incidents
- Incident 01
A recruiter thinks a candidate is more likely to be a strong operator and beloved people manager than simply a strong operator.
- Incident 02
An investor judges 'AI company with rapid international expansion' as more likely than 'AI company.'
- Incident 03
A PM thinks 'launch succeeds and goes viral on LinkedIn' is more likely than 'launch succeeds.'
What to watch for
It often shows up when a richer story feels more probable than a plain category. Ask: 'Is the specific story actually a subset of the general one?'
Recommended action
Translate probabilities into frequencies and use nested-set framing.
Known associates
- Optimism BiasEasily confusedWe expect our future to go better than base rates justify, especially for risks, timelines, and outcomes…
- Overconfidence EffectEasily confusedPeople's confidence in their judgments often exceeds their actual accuracy, especially for predictions,…
- Ambiguity EffectWe avoid options when the odds, rules, or outcome distributions are unclear, even if the expected payoff may…
- Information BiasWe seek more information even when it is unlikely to improve the decision.
- Belief BiasWe judge an argument by whether we like its conclusion, not by whether its logic is sound.
- Rhyme-as-Reason EffectStatements that rhyme are judged as more truthful or wise than equivalent non-rhyming statements.
Source of record