The effects of source trustworthiness and inference type on human belief revision
Ann G. Wolf, Susann Rieger, Markus Knauff · Thinking & Reasoning · 2012
We investigated whether people revise their beliefs as a function of inference type or source trustworthiness. By doing so we aimed to find out if belief revision is better explained by mental model theory (Johnson-Laird & Byrne, 2002 Johnson-Laird, P. N. and Byrne, R. M. J. 2002. Conditionals: A theory of meaning, pragmatics, and inference. Psychological Review, 109: 211–228. [Crossref], [PubMed], [Web of Science ®] , [Google Scholar]) or by a conditional probability view (Evans, Handley, & Over, 2003 Over, D. E. and Evans, J. St. B. T. 2003. The probability of conditionals: The psychological evidence. Mind & Language, 18: 340–358. [Crossref], [Web of Science ®] , [Google Scholar]; Oaksford & Chater, 2001 Oaksford, M. and Chater, N. 2001. The probabilistic approach to human reasoning. Trends in Cognitive Science, 5: 349–357. [Crossref], [PubMed], [Web of Science ®] , [Google Scholar]). We used modified modes ponens (MP) and modus tollens (MT) problems in which the first two premises were uttered by persons with varying degrees of trustworthiness. A third statement was presented as a fact and established inconsistency in the set of propositions. The participants' task was to indicate which of the first two premises they believed more after receiving the fact. We found that the belief in the conditional premise dropped significantly when this premise was stated by a low- rather than a high-trustworthy source. Moreover we found that the conditional premise was believed more in MT than in MP problems. Both findings are best explained by the conditional probability hypothesis (e.g., Evans et al., 2003 Evans, J. St. B. T., Handley, S. J. and Over, D. E. 2003. Conditionals and conditional probability. Journal of Experimental Psychology: Learning, Memory, and Cognition, 29, : 321–335. [Crossref] , [Google Scholar]).