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Conjunction Fallacy

Written by Vladimir_Nesov, PeerInfinity, et al. last updated 17th Nov 2009

The conjunction fallacy consists in assuming that specific conditions are more probable than more general ones.

For the reasons related to , a fleshed-out story that contains typical amount of detail sounds more plausible than a stripped-down description of a situation that only states a few facts. There is a tendency for people to take that plausibility at face value, and assign probability accordingly. This intuition is wrong, because the conjunction rule of probability theory states that, for any event X, its conjunction with additional details Y will be less probable.

The conjunction fallacy suggests that one should be to any claim, as even though each such detail may make the claim so much more convincing, it also inevitably subtracts from its validity.

Blog posts

  • Conjunction Fallacy
  • Conjunction Controversy (Or, How They Nail It Down)

See also

representativeness heuristic
Representativeness heuristic
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very careful in adding details
Burdensome details
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Posts tagged Conjunction Fallacy
264Burdensome Details
Eliezer Yudkowsky
18y
46
62Conjunction Controversy (Or, How They Nail It Down)
Eliezer Yudkowsky
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57About Less Wrong
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56Conjunction Fallacy
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29Which cognitive biases should we trust in?
Andy_McKenzie
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28Disjunctions, Antipredictions, Etc.
Eliezer Yudkowsky
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26Conjunction fallacy and probabilistic risk assessment.
Dmytry
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11[SEQ RERUN] Conjunction Fallacy
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8Can Social Dynamics Explain Conjunction Fallacy Experimental Results?
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5y
Q
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7[Link] Using the conjunction fallacy to reveal implicit associations
HonoreDB
14y
5
7The Law of Least Effort Contributes to the Conjunction Fallacy
curi
5y
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7Asch Conformity Could Explain the Conjunction Fallacy
curi
5y
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3ChatGPT challenges the case for human irrationality
Kevin Dorst
2y
10
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