Conditionals and Conditional Probability

Jonathan St B T Evans*, Simon J. Handley, David E. Over

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

262 Citations (Scopus)


The authors report 3 experiments in which participants were invited to judge the probability of statements of the form if p then q given frequency information about the cases pq, p¬q, ¬pq, and ¬p¬q (where ¬ = not). Three hypotheses were compared: (a) that people equate the probability with that of the material conditional, 1 - P(p¬q); (b) that people assign the conditional probability, P(q/p); and (c) that people assign the conjunctive probability P(pq). The experimental evidence allowed rejection of the 1st hypothesis but provided some support for the 2nd and 3rd hypotheses. Individual difference analyses showed that half of the participants used conditional probability and that most of the remaining participants used conjunctive probability as the basis of their judgments.

Original languageEnglish
Pages (from-to)321-335
Number of pages15
JournalJournal of Experimental Psychology: Learning, Memory, and Cognition
Issue number2
Publication statusPublished - Mar 2003
Externally publishedYes


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