Coherent probability from incoherent judgment.

People often have knowledge about the chances of events but are unable to express their knowledge in the form of coherent probabilities. This study proposed to correct incoherent judgment via an optimization procedure that seeks the (coherent) probability distribution nearest to a judge's estimates of chance. This method was applied to the chances of simple and complex meteorological events, as estimated by college undergraduates. No judge responded coherently, but the optimization method found close (coherent) approximations to their estimates. Moreover, the approximations were reliably more accurate than the original estimates, as measured by the quadratic scoring rule. Methods for correcting incoherence facilitate the analysis of expected utility and allow human judgment to be more easily exploited in the construction of expert systems.

New Evidence for Distinct Right and Left Brain Systems for Deductive versus Probabilistic Reasoning.

Deductive and probabilistic reasoning are central to cognition but the functional neuroanatomy underlying them is poorly understood. The present study contrasted these two kinds of reasoning via positron emission tomography. Relying on changes in instruction and psychological 'set', deductive versus probabilistic reasoning was induced using identical stimuli. The stimuli were arguments in propositional calculus not readily solved via mental diagrams. Probabilistic reasoning activated mostly left brain areas whereas deductive activated mostly right. Deduction activated areas near right brain homologues of left language areas in middle temporal lobe, inferior frontal cortex and basal ganglia, as well as right amygdala, but not spatial-visual areas. Right hemisphere activations in the deduction task cannot be explained by spill-over from overtaxed, left language areas. Probabilistic reasoning was mostly associated with left hemispheric areas in inferior frontal, posterior cingulate, parahippocampal, medial temporal, and superior and medial prefrontal cortices. The foregoing regions are implicated in recalling and evaluating a range of world knowledge, operations required during probabilistic thought. The findings confirm that deduction and induction are distinct processes, consistent with psychological theories enforcing their partial separation. The results also suggest that, except for statement decoding, deduction is largely independent of language, and that some forms of logical thinking are non-diagrammatic.

Wisdom and aging: irrational preferences in college students but not older adults.

A decision-maker is "irregular" if she would choose B from [A, B, C] but not from [A, B] (for example, preferring vanilla ice cream in a choice between vanilla and chocolate, but chocolate in a choice among vanilla, chocolate and strawberry). Similarly to previous studies we observed irregular choices by college students faced with hypothetical discount cards for supermarkets. However, older adults showed no such tendency. The same pattern was observed in three separate studies. We interpret the results in terms of a choice strategy by older adults that protects them from excessive spending.

Distinct brain loci in deductive versus probabilistic reasoning.

Deductive versus probabilistic inferences are distinguished by normative theories, but it is unknown whether these two forms of reasoning engage similar cerebral loci. To clarify the matter, positron emission tomography was applied during deductive versus probabilistic reasoning tasks, using identical stimuli. Compared to a language comprehension task involving the same stimuli, both probabilistic and deductive reasoning increased regional cerebral blood flow (rCBF) bilaterally in the mesial frontal region and in the cerebellum. In the direct comparison, probabilistic reasoning increased rCBF in left dorsolateral frontal regions, whereas deductive reasoning enhanced rCBF in associative occipital and parietal regions, with a right hemispheric prevalence. The results suggest that reasoning about syllogisms engages distinct brain mechanisms, depending on the intention to evaluate them deductively versus probabilistically.

Extracting the coherent core of human probability judgement: a research program for cognitive psychology.

Human intuition is a rich and useful guide to uncertain events in the environment but suffers from probabilistic incoherence in the technical sense. Developing methods for extracting a coherent body of judgement that is maximally consistent with a person's intuition is a challenging task for cognitive psychology, and also relevant to the construction of artificial expert systems. The present article motivates this problem, and outlines one approach to it.

Ampliative inference: on choosing a probability distribution.

Ampliative inference is the choice of a probability distribution on the basis of incomplete information. We consider some psychological and normative questions that arise about this kind of reasoning. The discussion is largely tutorial although a substantive hypothesis is also advanced.

Similarity, plausibility, and judgments of probability.

Judging the strength of an argument may underlie many reasoning and decision-making tasks. In this article, we focus on "category-based" arguments, in which the premises and conclusion are of the form All members of C have property P, where C is a natural category. An example is "Dobermans have sesamoid bones. Therefore, German shepherds have sesamoid bones." The strength of such an argument is reflected in the judged probability that the conclusion is true given that the premises are true. The processes that mediate such probability judgments depend on whether the predicate is "blank"--an unfamiliar property that does not enter the reasoning process (e.g., "have sesamoid bones")--or "non-blank"--a relatively familiar property that is easier to reason from (e.g., "can bite through wire"). With blank predicates, probability judgments are based on similarity relations between the premise and conclusion categories. With non-blank predicates, probability judgements are based on both similarity relations and the plausibility of premises and conclusion.

Typicality and reasoning fallacies.

The work of Tversky and Kahneman on intuitive probability judgment leads to the following prediction: The judged probability that an instance belongs to a category is an increasing function of the typicality of the instance in the category. To test this prediction, subjects in Experiment 1 read a description of a person (e.g., "Linda is 31, bright, ... outspoken") followed by a category. Some subjects rated how typical the person was of the category, while others rated the probability that the person belonged to that category. For categories like bank teller and feminist bank teller: (1) subjects rated the person as more typical of the conjunctive category (a conjunction effect); (2) subjects rated it more probable that the person belonged to the conjunctive category (a conjunction fallacy); and (3) the magnitudes of the conjunction effect and fallacy were highly correlated. Experiment 2 documents an inclusion fallacy, wherein subjects judge, for example, "All bank tellers are conservative" to be more probable than "All feminist bank tellers are conservative." In Experiment 3, results parallel to those of Experiment 1 were obtained with respect to the inclusion fallacy.

Is autism associated with anomalous dominance?

Geschwind and Galaburda (1985, 1985b) have advanced a theory of the development of anomalous dominance and its biological associations. The present article reviews existing literature in an attempt to apply this theory to the study of autism.