On the basis of belief in causal and diagnostic conditionals

Jonathan St B T Evans*, Simon J. Handley, Constantinos Hadjchristidis, Valerie Thompson, David E. Over, Stephanie Bennett

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

12 Citations (Scopus)


According to the suppositional theory of conditionals, people assess their belief in a conditional statement of the form "if p then q" by conducting a mental simulation on the supposition of p in which they assess their degree of belief in q. This leads to them to the judge the probability of a conditional statement to be equal to the conditional probability, P(q|p). Evidence for this conditional probability hypothesis has been adduced in earlier studies for abstract, causal, and counterfactual conditionals. For the realistic conditionals, it is natural to assume that people perform such mental simulations by building causal mental models from prior causes to later effects. However, in the present study we show that the conditional probability hypothesis extends to diagnostic conditionals, which relate effects to causes. This new finding presents a major challenge for theoretical accounts of the mental processing of conditional statements.

Original languageEnglish
Pages (from-to)635-643
Number of pages9
JournalQuarterly Journal of Experimental Psychology
Issue number5
Publication statusPublished - May 2007
Externally publishedYes

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