, Volume 184, Issue 1, pp 13–27 | Cite as

Is the conjunction fallacy tied to probabilistic confirmation?

  • Jonah N. SchupbachEmail author


Crupi et al. (2008) offer a confirmation-theoretic, Bayesian account of the conjunction fallacy—an error in reasoning that occurs when subjects judge that Pr(h 1 & h 2|e) > Pr(h 1|e). They introduce three formal conditions that are satisfied by classical conjunction fallacy cases, and they show that these same conditions imply that h 1 & h 2 is confirmed by e to a greater extent than is h 1 alone. Consequently, they suggest that people are tracking this confirmation relation when they commit conjunction fallacies. I offer three experiments testing the merits of Crupi et al.’s account specifically and confirmation-theoretic accounts of the conjunction fallacy more generally. The results of Experiment 1 show that, although Crupi et al.’s conditions do seem to be causally linked to the conjunction fallacy, they are not necessary for it; there exist cases that do not meet their three conditions in which subjects still tend to commit the fallacy. The results of Experiments 2 and 3 show that Crupi et al.’s conditions, and those offered by other confirmation-theoretic accounts of the fallacy, are not sufficient for the fallacy either; there exist cases that meet all three of CFT’s conditions in which subjects do not tend to commit the fallacy. Additionally, these latter experiments show that such confirmation-theoretic conditions are at best only weakly causally relevant to the presence of the conjunction fallacy. Given these findings, CFT’s account specifically, and any general confirmation-theoretic account more broadly, falls short of offering a satisfying explanation of the presence of the conjunction fallacy.


Conjunction fallacy Confirmation Bayesianism Probability Experimental philosophy 


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Carnap R. (1950) Logical foundations of probability. University of Chicago Press, ChicagoGoogle Scholar
  2. Christensen D. (1999) Measuring confirmation. Journal of Philosophy 96: 437–461CrossRefGoogle Scholar
  3. Crupi V., Fitelson B., Tentori K. (2008) Probability, confirmation, and the conjunction fallacy. Thinking and Reasoning 14: 182–199CrossRefGoogle Scholar
  4. Crupi V., Tentori K., Gonzalez M. (2007) On Bayesian measures of evidential support: theoretical and empirical issues. Philosophy of Science 74: 229–252CrossRefGoogle Scholar
  5. Eells E. (1982) Rational decision and causality. Cambridge University Press, Cambridge, UKGoogle Scholar
  6. Fitelson B. (2001) A Bayesian account of independent evidence with applications. Philosophy of Science 68: S123–S140CrossRefGoogle Scholar
  7. Good I. J. (1950) Probability and the weighing of evidence. Griffin, LondonGoogle Scholar
  8. Hertwig R., Chase V. M. (1998) Many reasons or just one. Thinking & Reasoning 4: 319–352CrossRefGoogle Scholar
  9. Joyce J. (1999) The foundations of causal decision theory. Cambridge University Press, Cambridge, UKCrossRefGoogle Scholar
  10. Keynes J. M. (1921) A treatise on probability. Macmillan, LondonGoogle Scholar
  11. Lagnado D. A., Shanks D. R. (2002) Probability judgment in hierarchical learning. Cognition 83: 81–112CrossRefGoogle Scholar
  12. Levi I. (2004) Jaako Hintikka. Synthese 140: 37–41CrossRefGoogle Scholar
  13. Milne P. (1996) Log[p(h|eb)/p(h|b)] is the one true measure of confirmation. Philosophy of Science 63: 21–26CrossRefGoogle Scholar
  14. Sides A., Osherson D., Bonini N., Viale R. (2002) On the reality of the conjunction fallacy. Memory & Cognition 30: 191–198CrossRefGoogle Scholar
  15. Tversky A., Kahneman D. (1983) Extensional versus intuitive reasoning: The conjunction fallacy in probability judgment. Psychological Review 90: 293–315CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media B.V. 2009

Authors and Affiliations

  1. 1.Department of History and Philosophy of ScienceUniversity of PittsburghPittsburghUSA

Personalised recommendations