On the Interaction of Prior Knowledge and Stimulus Structure in Category Learning

Contemporary theories of categorization propose that concepts are coherent in virtue of being embedded in a network of theories about the world. Those theories function to pick out some of the many possible features of a set of objects as most salient for purposes of classification, a process that is complex and still poorly understood (Murphy & Medin, 1985). Part of what makes this account incomplete is a lack of information as to (1) what makes a feature salient on a given occasion and (2) how feature salience interacts with category structure to determine the course of learning. We report on the results of three studies of category learning using complex schematic drawings to show that (1) the contrast set defined by one's initial encounters with category exemplars can be a source of individual differences in feature salience assignments; (2) such effects are short-lived in the face of clear evidence about actual feature diagnosticity; and (3) more robust prior hypotheses interact with category structure to either enhance learning or impede it. The enhancement occurs when the hypothesis emphasizes category-relevant features, even if the hypothesis is in fact incorrect. A hypothesis that assigns high salience to irrelevant features impedes learning. Learning does occur as feedback concerning category structure leads to enhanced salience for relevant features. Salience of irrelevant features remains high, however, suggesting that such learning as occurs involves augmentation and not total revision of the (incorrect) prior hypothesis.     

Prophetic visions in 1988: A critical reappraisal

This paper reviews the research into a specific aspect of neardeath experiences (NDEs): the prophetic vision (PV). PVs are subjectively compelling flashforwards of planetary-wide cataclysms and eventual regeneration that sometimes occur during or in the immediate aftermath of an NDE. Previous research has shown that the most frequently mentioned year for the culmination of the geophysical calamities foreseen in PVs was 1988. I argue that PVs should be understood as manifestations of a collective prophetic impulse that historically tends to arise during periods of cultural crisis. PVs are thus expressions of the felt need for cultural renewal and therefore should not be taken literally as prognostic of drastic physical changes on Earth.     

On the flexibility and the fallibility of associative memory

We report the results of four experiments in which we explored the flexibility and fallibility of associative recognition memory. In each experiment, pairs were studied one or more times, and the task was to discriminate intact from rearranged pairs. The critical findings are that the pattern of false alarm rates was dependent on the nature of the recognition procedure (e.g., ratings vs. yes-no) and the situation in which the task was performed. The specific pattern of findings suggest that subjects adopt different recognition strategies in order to achieve a desired level of performance in the most efficient manner possible by varying the degree to which they base their decisions on familiarity versus recollected information. Implications for theories of recognition memory are discussed.