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W K Estes

Publications and source records attributed to W K Estes.

8 recordsLinked to original sources
PubMed1989

Base-rate effects in category learning: a comparison of parallel network and memory storage-retrieval models.

Exemplar-memory and adaptive network models were compared in application to category learning data, with special attention to base rate effects on learning and transfer performance. Subjects classified symptom charts of hypothetical patients into disease categories, with informative feedback on learning trials and with the feedback either given or withheld on test trials that followed each fourth of the learning series. The network model proved notably accurate and uniformly superior to the exemplar model in accounting for the detailed course of learning; both the parallel, interactive aspect of the network model and its particular learning algorithm contribute to this superiority. During learning, subjects' performance reflected both category base rates and feature (symptom) probabilities in a nearly optimal manner, a result predicted by both models, though more accurately by the network model. However, under some test conditions, the data showed substantial base-rate neglect, in agreement with Gluck and Bower (1988b).

Adult↗
PubMed1987

Application of a cognitive-distance model to learning in a simulated travel task.

A cognitive-distance model for choice, obtained by specializing a general class of models for categorization, was tested in a situation simulating the task of controlling speed of a vehicle in tasks defined by different relations between speed and probability of delay. Subjects exhibited significant learning whenever delay schedules permitted greater-than-chance performance, but on the average they did not approach optimal performance in the sense of choosing speeds so as to maximize distance attained in allowed time. Evidence was obtained that subjects encoded information about probabilities of delay and distributions of distance attained at different speeds quite accurately in memory and that suboptimal performance was due primarily to imperfect discrimination among representations of choice alternatives on a cognitive scale of expected distance.

Adult↗
PubMed1986

Memory storage and retrieval processes in category learning.

The detailed course of learning is studied for categorization tasks defined by independent or contingent probability distributions over the features of category exemplars. College-age subjects viewed sequences of bar charts that simulated symptom patterns and responded to each chart with a recognition and a categorization judgment. Fuzzy, probabilistically defined categories were learned relatively rapidly when individual features were correlated with category assignment, more slowly when only patterns carried category information. Limits of performance were suboptimal, evidently because of capacity limitations on judgmental processes as well as limitations on memory. Categorization proved systematically related to feature and exemplar probabilities, under different circumstances, and to similarity among exemplars of categories. Unique retrieval cues for exemplar patterns facilitated recognition but entered into categorization only at retention intervals within the range of short-term memory. The findings are interpreted within the framework of a general array model that yields both exemplar-similarity and feature-frequency models as special cases and provides quantitative accounts of the course of learning in each of the categorization tasks studied.

Adult↗
PubMed1985

Levels of association theory.

Three levels of association theory are distinguished: (a) empirical laws relating operationally definable units; (b) theoretical concepts of association, supported by converging lines of evidence; and (c) theories assimilating concepts of association into more elaborate structures. These levels correspond roughly to stages in the evolution of association theory from the mid-19th century to the present. Ebbinghaus's major contribution as a theorist was to accomplish the transition from the first level to the second. The analysis of serial learning in terms of his conception of multiple types of associations may prove to have greater generality than has yet been realized. However, to account for many phenomena of practical and theoretical interest, this model requires augmentation by a control concept that provides a basis for organization beyond serial linkages of units.

Association↗