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R Hastie

Publications and source records attributed to R Hastie.

15 recordsLinked to original sources
PubMed2001

Causal knowledge and categories: the effects of causal beliefs on categorization, induction, and similarity.

Despite the recent interest in the theoretical knowledge embedded in human representations of categories, little research has systematically manipulated the structure of such knowledge. Across four experiments this study assessed the effects of interattribute causal laws on a number of category-based judgments. The authors found that (a) any attribute occupying a central position in a network of causal relationships comes to dominate category membership, (b) combinations of attribute values are important to category membership to the extent they jointly confirm or violate the causal laws, and (c) the presence of causal knowledge affects the induction of new properties to the category. These effects were a result of the causal laws, rather than the empirical correlations produced by those laws. Implications for the doctrine of psychological essentialism, similarity-based models of categorization, and the representation of causal knowledge are discussed.

Adult↗
PubMed2001

Problems for judgment and decision making.

This review examines recent developments during the past 5 years in the field of judgment and decision making, written in the form of a list of 16 research problems. Many of the problems involve natural extensions of traditional, originally rational, theories of decision making. Others are derived from descriptive algebraic modeling approaches or from recent developments in cognitive psychology and cognitive neuroscience.

Affect↗
PubMed1990

Tracing the footsteps of Sherlock Holmes: cognitive representations of hypothesis testing.

A well-documented phenomenon in opinion-revision literature is subjects' failure to revise probability estimates for an exhaustive set of mutually exclusive hypotheses in a complementary manner. However, prior research has not addressed the question of whether such behavior simply represents a misunderstanding of mathematical rules, or whether it is a consequence of a cognitive representation of hypotheses that is at odds with the Bayesian notion of a set relationship. Two alternatives to the Bayesian representation, a belief system (Shafer, 1976) and a system of independent hypotheses, were proposed, and three experiments were conducted to examine cognitive representations of hypothesis sets in the testing of multiple competing hypotheses. Subjects were given brief murder mysteries to solve and allowed to request various types of information about the suspects; after having received each new piece of information, subjects rated each suspect's probability of being the murderer. Presence and timing of suspect eliminations were varied in the first two experiments; the final experiment involved the varying of percentages of clues that referred to more than one suspect (for example, all of the female suspects). The noncomplementarity of opinion revisions remained a strong phenomenon in all conditions. Information-search data refuted the idea that subjects represented hypotheses as a Bayesian set; further study of the independent hypotheses theory and Shaferian belief functions as descriptive models is encouraged.

Adult↗
PubMed1990

Ultrastructure of human basophil leukocytes studied after spray freezing and freeze-substitution.

Normal human blood cells were prepared for transmission electron microscopy by spray freezing, freeze-substitution and embedment in Araldite. Spray freezing was found to damage many cells. Nevertheless, the method developed preserved some leukocytes well and spray frozen, freeze-substituted human basophils showed interesting differences from conventionally prepared cells. Surface vesicles and tubulovesicular structures, extragranular myelin figures, and membranous projections on putative thin membrane-bounded granules were all absent. Preservation of the basophilic granules was clearly improved and their membranes were usually intact. The bulk content of these granules did not look particulate, but showed a very fine texture. Intragranular myelin figure material was well preserved and often enclosed striking lucent areas. Charcot-Leyden crystals were clearly seen in basophils from some donors, always in well preserved granules. A fourth type of material, not seen in conventionally prepared human basophils, was also often observed in the granules. Large lucent vacuoles could be regularly distinguished from basophilic granules. The granules with partly concave outlines, seen in conventionally prepared human basophils to be associated with ill-defined lucent areas and irregularity or projections of the membrane, were absent. In freeze-substituted cells, images suggesting fusion of basophilic granules with each other were seen quite frequently. It is concluded that, while the techniques needed to be improved, rapid freezing and freeze-substitution afford a better understanding of the ultrastructure of human basophil leukocytes.

Adult↗
PubMed1985

Another look at sex stereotypes and social judgments: an analysis of the social perceiver's use of subjective probabilities.

Locksley, Borgida, Brekke, and Hepburn (1980) assert that subjects fall prey to the base-rate fallacy when they make stereotype-related trait judgments. They found that subjects ignored their stereotypes when trait judgments were made in the presence of trait-related behavioral information. The present article reexamines those findings with respect to two issues: (a) the use of a normative criterion in comparison with subjects' judgments and (b) the level of analysis (group vs. individual) of subjects' judgments. We conducted a replication of the Locksley et al. (1980) Study 2, and the results were examined with respect to these two issues. We found no support for the base-rate fallacy. When a Bayesian normative criterion was constructed for each subject based on the subject's own stereotype judgments and was compared with assertiveness judgments made in the presence of individuating information, there was no evidence that subjects ignored or underused their stereotypes as the base-rate fallacy predicts.

Assertiveness↗
PubMed1985

Individual differences in the use of simplification strategies in a complex decision-making task.

Decision time results were used to assess the strategies that 90 college undergraduates used in a complex decision-making task. Trend analyses revealed that the functions relating choice time to the number of choice alternatives in a set and the number of attributes comprising those alternatives contained linear (increasing) components. In addition, for a portion of the subjects, there was a quadratic effect of the number of attributes available to the decision maker on choice time, suggesting that these subjects adopted simplification strategies at high levels of task complexity. Reliable individual differences in these trend components were observed, consistent with individual differences in motivation and/or processing capacities. These individual differences were included in an information-processing model of decision behavior that captured the choice time data observed in this study. Subjects' ratings of apartments were used as a basis to assess the extent to which the use of simplification strategies resulted in preference reversals. Contrary to expectation, subjects whose choice times contained quadratic components demonstrated fewer preference reversals at high levels of information load.

Cognition↗
PubMed1983

Dissociation of the site of origin from the site of cryo-termination of ventricular tachycardia.

We performed conventional electrogram mapping and cryomapping in dogs with one-week-old experimentally-induced myocardial infarctions and programmed stimulation-induced sustained ventricular tachycardias to assess whether there is a correlation between the "site of origin" and site of cryo-termination of ventricular tachycardia (VT). Electrogram maps showed that 4 of 8 induced sustained VTs were due to macro- and 4 of 8 to microre-entry. Local cooling of the site of origin terminated 4 of 4 microre-entrant VTs, but only 1 of 4 macrore-entrant VTs. In the other 3 macrore-entrant VTs, the sites of cryo-termination were 2, 2.5, and 4 cm distant from the sites of origin. In contrast, cooling of the mid-to-late diastolic portions of the re-entry loops terminated all 8 VTs. These data demonstrate a dissociation of the site of origin from the site of cryo-termination of macrore-entrant VT.

Animals↗
PubMed1977

The antigen-induced degranulation of basophil leukocytes from atopic subjects studied by electron microscopy.

Suspensions of washed leukocytes were prepared from the blood of atopic subjects and incubated with diluent, ragweed antigen E or rye grass group I antigen. Histamine release into the suspending medium was measured and directly correlated with changes in the ultrastructure of basophil leukocytes from the same tubes. Incubation of leukocytes with either diluent or an antigen to which the donor was not hypersensitive caused no significant histamine release and the morphology of the basophils was unaltered. By contrast, incubation of leukocytes with an intigen to which the donor was hypersensitive caused substantial histamine release and characteristic morphologic changes in the basophils, many of which underwent exocytotic degranulation. Degranulated human basophils showed the following features: (1) an irregular surface, to which platelets and leukocytes were often adherent; (2) reduction in the number of basophilic granules; (3) residual granular material, both in exocytotic cavities and at the cell surface; (4) coated vesicles and cisternae of smooth endoplasmic reticulum, frequently related to the plasma membrane at sites of exocytosis; (5) thin membrane-bounded granules appeared unaltered; (6) no consistent change was observed in centrioles, microtubules, 90 A filaments, mitochondria, or multivesicular bodies, and degranulated basophils appeared ultrastructurally viable; (7) in reaction cell suspensions, nondegranulated basophils often showed a more active contour than control cells; both reacting but nondegranulated basophils and degranulated basophils sometimes showed localized filamentous webs at their periphery.

Antigens↗
PubMedDate not supplied

Reasoning in explanation-based decision making.

A general theory of explanation-based decision making is outlined and the multiple roles of inference processes in the theory are indicated. A typology of formal and informal inference forms, originally proposed by Collins (1978a, 1978b), is introduced as an appropriate framework to represent inferences that occur in the overarching explanation-based process. Results from the analysis of verbal reports of decision processes are presented to demonstrate the centrality and systematic character of reasoning in a representative legal decision-making task.

Criminal Law↗