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Jonathan St B T Evans

Publications and source records attributed to Jonathan St B T Evans.

12 recordsLinked to original sources
PubMed2006

The probability of causal conditionals.

Conditionals in natural language are central to reasoning and decision making. A theoretical proposal called the Ramsey test implies the conditional probability hypothesis: that the subjective probability of a natural language conditional, P(if p then q), is the conditional subjective probability, P(q/p). We report three experiments on causal indicative conditionals and related counterfactuals that support this hypothesis. We measured the probabilities people assigned to truth table cases, P(pq), P(p notq), P( notpq) and P( notp notq). From these ratings, we computed three independent predictors, P(p), P(q/p) and P(q/ notp), that we then entered into a regression equation with judged P(if p then q) as the dependent variable. In line with the conditional probability hypothesis, P(q/p) was by far the strongest predictor in our experiments. This result is inconsistent with the claim that causal conditionals are the material conditionals of elementary logic. Instead, it supports the Ramsey test hypothesis, implying that common processes underlie the use of conditionals in reasoning and judgments of conditional probability in decision making.

Analysis of Variance↗
PubMed2006

The negated conditional: a litmus test for the suppositional conditional?

Under the suppositional account of conditionals, when people think about a conditional assertion, "if p then q," they engage in a mental simulation in which they imagine p holds and evaluate the probability that q holds under this supposition. One implication of this account is that belief in a conditional equates to conditional probability [P(q/p)]. In this paper, the authors examine a further implication of this analysis with respect to the wide-scope negation of conditional assertions, "it is not the case that if p then q." Under the suppositional account, nothing categorically follows from the negation of a conditional, other than a second conditional, "if p then not-q." In contrast, according to the mental model theory, a negated conditional is consistent only with the determinate state of affairs, p and not-q. In 4 experiments, the authors compare the contrasting predictions that arise from each of these accounts. The findings are consistent with the suppositional theory but are incongruent with the mental model theory of conditionals.

Adult↗
PubMed2006

The heuristic-analytic theory of reasoning: extension and evaluation.

An extensively revised heuristic-analytic theory of reasoning is presented incorporating three principles of hypothetical thinking. The theory assumes that reasoning and judgment are facilitated by the formation of epistemic mental models that are generated one at a time (singularity principle) by preconscious heuristic processes that contextualize problems in such a way as to maximize relevance to current goals (relevance principle). Analytic processes evaluate these models but tend to accept them unless there is good reason to reject them (satisficing principle). At a minimum, analytic processing of models is required so as to generate inferences or judgments relevant to the task instructions, but more active intervention may result in modification or replacement of default models generated by the heuristic system. Evidence for this theory is provided by a review of a wide range of literature on thinking and reasoning.

Decision Making↗
PubMed2005

Suppositions, extensionality, and conditionals: a critique of the mental model theory of Johnson-Laird And Byrne (2002).

P. N. Johnson-Laird and R. M. J. Byrne proposed an influential theory of conditionals in which mental models represent logical possibilities and inferences are drawn from the extensions of possibilities that are used to represent conditionals. In this article, the authors argue that the extensional semantics underlying this theory is equivalent to that of the material, truth-functional conditional, at least for what they term "basic" conditionals, concerning arbitrary problem content. On the basis of both logical argument and psychological evidence, the authors propose that this approach is fundamentally mistaken and that conditionals must be viewed within a suppositional theory based on what philosophical logicians call the Ramsey test. The Johnson-Laird and Byrne theory is critically examined with respect to its account of basic conditionals, nonbasic conditionals, and counterfactuals.

Cognition↗
PubMed2005

Prior belief and polarity in multicue learning.

We report two experiments in which participants are trained using a multicue probability learning (MCPL) task, which attempts to simulate the acquisition of expert judgement by experience in the real world. Participants were asked to predict performance in certain occupations given a profile of personality test results with trial-by-trial outcome feedback. Only some cues were relevant, and the polarity of the cues (positive or negative predictors) was unspecified. In addition, 25% of random noise was added to the feedback to simulate real world uncertainty. The main factor of interest was that the role of prior belief (determined in a separate study of stereotypes) interfered with the learning process. Experiment 1 failed to find any influence of prior belief in the cues that were irrelevant to the criterion being trained. However, in Experiment 2 people learned to use the relevant cues better when their effect conformed with rather than conflicted with prior belief Both experiments showed strong effects of cue polarity, with positive predictors much more easily learned. The results are discussed with reference to the cognitive processes involved in MCPL and closely related tasks.

Achievement↗
PubMed2004

Belief bias and figural bias in syllogistic reasoning.

Belief bias is the tendency to be influenced by the believability of the conclusion when attempting to solve a syllogistic reasoning problem. Figural bias is the tendency to be influenced by the order in which the information is presented in the premises when attempting to solve a syllogistic reasoning problem. When studied simultaneously they enable an investigation of whether participants' reasoning on the syllogistic reasoning task is guided by the conclusion (backward reasoning) or the premises (forward reasoning). Experiments 1 and 2 found evidence of belief bias but not figural bias on the syllogistic evaluation task paradigm. Experiments 3 and 4 found evidence of figural bias but not belief bias on the syllogistic production task paradigm. The findings highlight that different task characteristics influence performance dependent upon the nature of task presentation. These findings are discussed in the context of current theories of belief bias in syllogistic reasoning.

Cognition↗
PubMed2003

In two minds: dual-process accounts of reasoning.

Researchers in thinking and reasoning have proposed recently that there are two distinct cognitive systems underlying reasoning. System 1 is old in evolutionary terms and shared with other animals: it comprises a set of autonomous subsystems that include both innate input modules and domain-specific knowledge acquired by a domain-general learning mechanism. System 2 is evolutionarily recent and distinctively human: it permits abstract reasoning and hypothetical thinking, but is constrained by working memory capacity and correlated with measures of general intelligence. These theories essentially posit two minds in one brain with a range of experimental psychological evidence showing that the two systems compete for control of our inferences and actions.

Journal Article↗
PubMed2003

Explicit and implicit processes in multicue judgment.

In two experiments, a multicue probability learning task was used to train participants in relating judgments to a criterion, on the basis of several cues that could or could not be relevant. The outcome feedback had 25% added noise to simulate real-world experience-based learning. Judgmental strategies acquired were measured by individual multiple linear regression analyses of a test phase (with no feedback) and were compared with self-ratings of cue relevance. In a third experiment, participants were instructed explicitly on cue relevance, with no training phase. The pattern of results suggested that both implicit and explicit cognitive processes influenced judgments and that they may have been sensitive to different task manipulations in the learning phase. On more complex tasks, despite weak explicit learning, explicit processes continued to influence judgments, producing a decrement in performance. These findings explain why studies of expert judgment often show only moderate levels of self-insight, since people have only partial access to the processes determining their judgments.

Cognition↗
PubMed2002

Logic and human reasoning: an assessment of the deduction paradigm.

The study of deductive reasoning has been a major paradigm in psychology for approximately the past 40 years. Research has shown that people make many logical errors on such tasks and are strongly influenced by problem content and context. It is argued that this paradigm was developed in a context of logicist thinking that is now outmoded. Few reasoning researchers still believe that logic is an appropriate normative system for most human reasoning, let alone a model for describing the process of human reasoning, and many use the paradigm principally to study pragmatic and probabilistic processes. It is suggested that the methods used for studying reasoning be reviewed, especially the instructional context, which necessarily defines pragmatic influences as biases.

Cognition↗
PubMed2002

Implicit and explicit processes in a hypothesis testing task.

We present the results of two experiments investigating the factors that determine responding on the pseudo-diagnosticity task. In Expt 1 we manipulated people's beliefs about the degree to which an initial piece of evidence supported a focal hypothesis and found decreased pseudo-diagnostic (PD) responding when the evidence offered low support for the focal hypothesis. In Expt 2 we manipulated the instructions given to participants. We found that instructions to select evidence to help decide between the focal and the complementary hypotheses produced fewer PD responses than both instructions to decide whether the focal hypothesis was the case and instructions to decide whether its complement was the case. The results are interpreted within the framework of recent dual process theories of reasoning.

Adolescent↗
PubMed2002

Background beliefs in Bayesian inference.

We report five experiments in which the role of background beliefs in social judgments of posterior probability was investigated. From a Bayesian perspective, people should combine prior probabilities (or base rates) and diagnostic evidence with equal weighting, although previous research shows that base rates are often underweighted. These experiments were designed so that either piece of information was supplied either by personal beliefs or by presented statistics, and regression analyses were performed on individual participants to assess the relative influence of information. We found that both prior probabilities and diagnostic information significantly influenced judgments, whether supplied by beliefs or by statistical information, but that belief-based information tended to dominate the judgments made.

Bayes Theorem↗