ABSTRACT

Over the last decade or so, trends that were apparent in the psychology of

reasoning since the early 1990s have reached fruition, culminating in what some have described as a “new paradigm” (Baratgin, Over, & Politzer,

in press; Chater & Oaksford, 2009; Elqayam & Over, 2012; Evans, 2012;

Manktelow, Over, & Elqayam, 2011; Over, 2009). This new development

emphasises the role of probability and utility judgements in human reason-

ing, with the aim of integrating the psychology of reasoning with the study

of judgement and decision making. It can thus be seen as a response in the

psychology of reasoning to the immense impact that Bayesian theories have

had in cognitive science (Chater & Oaksford, 2008). It goes beyond the traditional “deduction paradigm” (Evans, 2002), which was based on binary dis-

tinctions-between truth/falsity, consistency/inconsistency, and validity/

invalidity-and focused primarily on drawing inferences from arbitrary

assumptions according to the rules of extensional textbook logic

(Johnson-Laird & Byrne, 1991). These binary distinctions can still be made

in the new paradigm but it advances beyond them, most notably by distin-

guishing between different degrees of subjective probability and utility. This change has profoundly transformed the field, creating new research

questions and leading to novel research practices. We have looked up the

keyword “probability” in the indices of popular textbook introductions to

the field. In a survey from the heyday of the traditional binary paradigm

(Evans, Newstead, & Byrne, 1993) the term does not even appear, and a

total of only three pages (1% of the book pages) were devoted to

“probabilistic inference”. A textbook first published at the time the new par-

adigm was gaining momentum (Manktelow, 1999) had a later chapter on probability, and the index counts 46 pages of references to probability

(18%). In the latest, 2012, edition of the same text (Manktelow, 2012), the

chapter on probability is the first in the book, and the number of pages

devoted to the topic has almost doubled (to 30%). The very semantic field

associated with reasoning is changing.