Uncertain deduction and conditional reasoning

Evans, J. St. B.T.; Thompson, V.A.; Over, D.E.

doi:10.3389/fpsyg.2015.00398

Uncertain deduction and conditional reasoning

Evans, J. St. B.T.; Thompson, V.A.; Over, D.E.

Authors

J. St. B.T. Evans

V.A. Thompson

Emeritus Professor David Over david.over@durham.ac.uk

Abstract

There has been a paradigm shift in the psychology of deductive reasoning. Many researchers no longer think it is appropriate to ask people to assume premises and decide what necessarily follows, with the results evaluated by binary extensional logic. Most every day and scientific inference is made from more or less confidently held beliefs and not assumptions, and the relevant normative standard is Bayesian probability theory. We argue that the study of “uncertain deduction” should directly ask people to assign probabilities to both premises and conclusions, and report an experiment using this method. We assess this reasoning by two Bayesian metrics: probabilistic validity and coherence according to probability theory. On both measures, participants perform above chance in conditional reasoning, but they do much better when statements are grouped as inferences, rather than evaluated in separate tasks.

Citation

Evans, J. S. B., Thompson, V., & Over, D. (2015). Uncertain deduction and conditional reasoning. Frontiers in Psychology, 6, Article 398. https://doi.org/10.3389/fpsyg.2015.00398

Journal Article Type	Article
Publication Date	Apr 1, 2015
Deposit Date	May 12, 2016
Publicly Available Date	May 24, 2016
Journal	Frontiers in Psychology
Print ISSN	1664-1078
Publisher	Frontiers Media
Peer Reviewed	Peer Reviewed
Volume	6
Article Number	398
DOI	https://doi.org/10.3389/fpsyg.2015.00398

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Copyright Statement
Copyright © 2015 Evans, Thompson and Over. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.