AUTHOR=Evans Jonathan St. B. T. , Thompson Valerie A. , Over David E. TITLE=Uncertain deduction and conditional reasoning JOURNAL=Frontiers in Psychology VOLUME=6 YEAR=2015 URL=https://www.frontiersin.org/journals/psychology/articles/10.3389/fpsyg.2015.00398 DOI=10.3389/fpsyg.2015.00398 ISSN=1664-1078 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.