Derek J. Koehler

Support theory: A nonextensional representation of subjective probability.

This article presents a new theory of subjective probability according to which different descriptions of the same event can give rise to different judgments. The experimental evidence confirms the major predictions of the theory. First, judged probability increases by unpacking the focal hypothesis and decreases by unpacking the alternative hypothesis. Second, judged probabilities are complementary in the binary case and subadditive in the general case, contrary to both classical and revisionist models of belief. Third, subadditivity is more pronounced for probability judgments than for frequency judgments and is enhanced by compatible evidence. The theory provides a unified treatment of a wide range of empirical findings. It is extended to ordinal judgments and to the assessment of upper and lower probabilities. Both laypeople and experts are often called upon to evaluate the probability of uncertain events such as the outcome of a trial, the result of a medical operation, the success of a business venture, or the winner of a football game. Such assessments play an important role in deciding, respectively, whether to go to court, undergo surgery, invest in the venture, or bet on the home team. Uncertainty is usually expressed in verbal terms (e.g., unlikely or probable), but numerical estimates are also common. Weather forecasters, for example, often report the probability of rain (Murphy, 1985), and economists are sometimes required to estimate the chances of recession (Zarnowitz, 1985). The theoretical and practical significance of subjective probability has inspired psychologists, philosophers, and statisticians to investigate this notion from both descriptive and prescriptive standpoints.

Blackwell handbook of judgment and decision making.

The Handbook * Contains contributions by experts from various disciplines that reflect current trends and controversies on judgment and decision making. * Provides a glimpse at the many approaches that have been taken in the study of judgment and decision making and portrays the major findings in the field. * Presents examinations of the broader roles of social, emotional, and cultural influences on decision making. * Explores applications of judgment and decision making research to important problems in a variety of professional contexts, including finance, accounting, medicine, public policy, and the law.

Explanation, imagination, and confidence in judgment.

This article concerns a class of experimental manipulations that require people to generate explanations or imagine scenarios. A review of studies using such manipulations indicates that people who explain or imagine a possibility then express greater confidence in the truth of that possibility. It is argued that this effect results from the approach people take in the explanation or imagination task: They temporarily assume that the hypothesis is true and assess how plausibly it can account for the relevant evidence. From this view, any task that requires that a hypothesis be treated as if it were true is sufficient to increase confidence in the truth of that hypothesis. Such tasks cause increased confidence in the hypothesis at the expense of viable alternatives because of changes in problem representation, evidence evaluation, and information search that take place when the hypothesis is temporarily treated as if it were true.

Analytic cognitive style predicts religious and paranormal belief.

An analytic cognitive style denotes a propensity to set aside highly salient intuitions when engaging in problem solving. We assess the hypothesis that an analytic cognitive style is associated with a history of questioning, altering, and rejecting (i.e., unbelieving) supernatural claims, both religious and paranormal. In two studies, we examined associations of God beliefs, religious engagement (attendance at religious services, praying, etc.), conventional religious beliefs (heaven, miracles, etc.) and paranormal beliefs (extrasensory perception, levitation, etc.) with performance measures of cognitive ability and analytic cognitive style. An analytic cognitive style negatively predicted both religious and paranormal beliefs when controlling for cognitive ability as well as religious engagement, sex, age, political ideology, and education. Participants more willing to engage in analytic reasoning were less likely to endorse supernatural beliefs. Further, an association between analytic cognitive style and religious engagement was mediated by religious beliefs, suggesting that an analytic cognitive style negatively affects religious engagement via lower acceptance of conventional religious beliefs. Results for types of God belief indicate that the association between an analytic cognitive style and God beliefs is more nuanced than mere acceptance and rejection, but also includes adopting less conventional God beliefs, such as Pantheism or Deism. Our data are consistent with the idea that two people who share the same cognitive ability, education, political ideology, sex, age and level of religious engagement can acquire very different sets of beliefs about the world if they differ in their propensity to think analytically.

Probability Judgment in Medicine Discounting Unspecified Possibilities

Research in cognitive psychology has indicated that alternative descriptions of the same event can give rise to different probability judgments. This observation has led to the de velopment of a descriptive account, called support theory, which assumes that the judged probability of an explicit description of an event (that lists specific possibilities) generally exceeds the judged probability of an implicit description of the same event (that does not mention specific possibilities). To investigate this assumption in medical judgment, the au thors presented physicians with brief clinical scenarios describing individual patients and elicited diagnostic and prognostic probability judgments. The results showed that the phy sicians tended to discount unspecified possibilities, as predicted by support theory. The authors suggest that an awareness of the discrepancy between intuitive judgments and the laws of chance may provide opportunities for improving medical decision making. Key words: probability judgment; support theory; unpacking principle; cognition. (Med Decis Making 1995;15:227-230)Research in cognitive psychology has indicated that alternative descriptions of the same event can give rise to different probability judgments. This observation has led to the development of a descriptive account, called support theory, which assumes that the judged probability of an explicit description of an event (that lists specific possibilities) generally exceeds the judged probability of an implicit description of the same event (that does not mention specific possibilities). To investigate this assumption in medical judgment, the authors presented physicians with brief clinical scenarios describing individual patients and elicited diagnostic and prognostic probability judgments. The results showed that the physicians tended to discount unspecified possibilities, as predicted by support theory. The authors suggest that an awareness of the discrepancy between intuitive judgments and the laws of chance may provide opportunities for improving medical decision making.

On the Evaluation of One-sided Evidence

We examine predictions and judgments of confidence based on one-sided evidence. Some subjects saw arguments for only one side of a legal dispute while other subjects (called ‘jurors’) saw arguments for both sides. Subjects predicted the number of jurors who favored the plaintiff in each case. Subjects who saw only one side made predictions that were biased in favor of that side. Furthermore, they were more confident but generally less accurate than subjects who saw both sides. The results indicate that people do not compensate sufficiently for missing information even when it is painfully obvious that the information available to them is incomplete. A simple manipulation that required subjects to evaluate the relative strength of the opponent’s side greatly reduced the tendency to underweigh missing evidence.

Cognitive style and religiosity: The role of conflict detection

Recent research has indicated a negative relation between the propensity for analytic reasoning and religious beliefs and practices. Here, we propose conflict detection as a mechanism underlying this relation, on the basis of the hypothesis that more-analytic people are less religious, in part, because they are more sensitive to conflicts between immaterial religious beliefs and beliefs about the material world. To examine cognitive conflict sensitivity, we presented problems containing stereotypes that conflicted with base-rate probabilities in a task with no religious content. In three studies, we found evidence that religiosity is negatively related to conflict detection during reasoning. Independent measures of analytic cognitive style also positively predicted conflict detection. The present findings provide evidence for a mechanism potentially contributing to the negative association between analytic thinking and religiosity, and more generally, they illustrate the insights to be gained from integrating individual-difference factors and contextual factors to investigate analytic reasoning.

Implicit Quantification of Personality Traits

The common usage of personality trait terms in the language includes an implicit quantification that is part of the accepted meaning of the term. This aspect of a traits meaning is here called its scope. Traits with high scope, such as honest, require a high relative frequency of behavioral manifestation before they are attributed. In contrast, low-scope traits such as dishonest can be attributed on the basis of very few behavioral instances. A number of hypotheses are considered concerning the scope of trait terms within a language and between languages. Speakers of a given language (English or Hebrew) exhibit agreement in their ratings of scope; English and Hebrew speakers also agree with each other on the scope of trait terms even when they disagree about the behavioral manifestations of those traits. These findings are interpreted in terms of an informational view of personality traits: The scope of a trait is set at a level that makes it communicatively useful.

Probability matching and strategy availability

Findings from two experiments indicate that probability matching in sequential choice arises from an asymmetry in strategy availability: The matching strategy comes readily to mind, whereas a superior alternative strategy, maximizing, does not. First, compared with the minority who spontaneously engage in maximizing, the majority of participants endorse maximizing as superior to matching in a direct comparison when both strategies are described. Second, when the maximizing strategy is brought to their attention, more participants subsequently engage in maximizing. Third, matchers are more likely than maximizers to base decisions in other tasks on their initial intuitions, suggesting that they are more inclined to use a choice strategy that comes to mind quickly. These results indicate that a substantial subset of probability matchers are victims of “underthinking” rather than “overthinking”: They fail to engage in sufficient deliberation to generate a superior alternative to the matching strategy that comes so readily to mind.

The enhancement effect in probability judgment

Research has shown that the judged probability of an event depends on the specificity with which the focal and alternative hypotheses are described. In particular, unpacking the components of the focal hypothesis generally increases the judged probability of the focal hypothesis, while unpacking the components of the alternative hypothesis decreases the judged probability of the focal hypothesis. As a consequence, the judged probability of the union of disjoint events is generally less than the sum of their judged probabilities. This article shows that the total judged probability of a set of mutually exclusive and exhaustive hypotheses increases with the degree to which the evidence is compatible with these hypotheses. This phenomenon, which we refer to as the enhancement eAect, is consistent with a descriptive account of subjective probability called support theory. #1997 John Wiley & Sons, Ltd.