Biomedical subjects

Robert M Nosofsky

Publications and source records attributed to Robert M Nosofsky.

10 recordsLinked to original sources

PubMed2005

Speeded classification in a probabilistic category structure: contrasting exemplar-retrieval, decision-boundary, and prototype models.

Speeded perceptual classification experiments were conducted to distinguish among the predictions of exemplar-retrieval, decision-boundary, and prototype models. The key manipulation was that across conditions, individual stimuli received either probabilistic or deterministic category feedback. Regardless of the probabilistic feedback, however, an ideal observer would always classify the stimuli by using an identical linear decision boundary. Subjects classified the probabilistic stimuli with lower accuracy and longer response times than they classified the deterministic stimuli. These results are in accord with the predictions of the exemplar model and challenge the predictions of the prototype and decision-boundary models.

Analysis of Variance↗

PubMed2004

False prototype enhancement effects in dot pattern categorization.

Results from the classic dot pattern distortion paradigm have sometimes yielded prototype enhancement effects that could not be accounted for by exemplar models of categorization. However, in these experiments the status of the prototype was confounded with certain stimulus-specific properties as well as with the frequency of presentation of the prototype during testing. In two mock-subliminal experiments, participants made categorization judgments to patterns that were generated as prototypes, low-level distortions, or high-level distortions. The participants rated the prototypes as being more likely to be members of a category, although no patterns were presented during training, and there was no objective category structure. In two other experiments, greater prototype enhancement effects were observed when the prototype and low-level distortions were presented with greater frequency during transfer. These results suggest that classic prototype enhancement effects may not be due to the abstraction of a prototype at time of original learning, but rather to other factors not formalized in extant models.

Humans↗

PubMed2003

Categorization and recognition performance of a memory-impaired group: evidence for single-system models.

Previous research has demonstrated dissociations between categorization and recognition performance in amnesic patients, supporting the idea that separate memory systems govern these tasks. However, previous research has also demonstrated that these dissociations are predicted by a single-system model that allows for reasonable parameter differences across groups. Generally, previous studies have employed categorization tasks that are less demanding than the recognition tasks. In this study, we distinguish between single-system and multiple-system accounts by testing memory-impaired individuals in a more demanding categorization task. These patients, just like previous amnesic participants, show a dissociation between categorization and recognition when tested in previously employed paradigms. However, they display a categorization deficit when tested in the more challenging categorization task. The results are interpreted as support for a single-system framework in which categorization and recognition depend on one representational system.

Aged↗

PubMed2003

Prototype and exemplar accounts of category learning and attentional allocation: a reassessment.

In a recent article. J. P. Minda and J. D. Smith (2002; see record 2002-00620-002) argued that an exemplar model provided worse quantitative fits than an alternative prototype model to individual subject data from the classic D. L. Medin and M. M. Schaffer (1978) 5/4 categorization paradigm. In addition, they argued that the exemplar model achieved its fits by making untenable assumptions regarding how observers distribute their attention. In this article, we demonstrate that when the models are equated in terms of their response-rule flexibility, the exemplar model provides a substantially better account of the categorization data than does a prototype or mixed model. In addition, we point to shortcomings in the attention-allocation analyses conducted by J. P. Minda and J. D. Smith (2002). When these shortcomings are corrected, we find no evidence that challenges the attention-allocation assumptions of the exemplar model.

Attention↗

PubMed2003

A hybrid-similarity exemplar model for predicting distinctiveness effects in perceptual old-new recognition.

In 2 sets of experiments, the authors investigated the basis for old-item distinctiveness effects in perceptual recognition, whereby distinctive old items are recognized with higher probability than are typical old items. In Experiment 1, distinctive old items were defined as those lying in isolated regions of a continuous-dimension similarity space. In this case, any beneficial effects of distinctiveness were absent or small, regardless of the structure of the test list used to assess recognition memory. In Experiment 2, distinctive items were defined as those objects containing certain discrete, individuating features. In this case, large old-item distinctive effects were observed, with the nature of the effects being modulated by the structure of the test lists. A hybrid-similarity exemplar model, combining elements of continuous-dimension distance and discrete-feature matching, was used to account for these distinctiveness effects in the recognition data.

Attention↗

PubMed2002

Assessing clinically relevant perceptual organization with multidimensional scaling techniques.

Multidimensional scaling (MDS) techniques provide a promising measurement strategy for characterizing individual differences in cognitive processing, which many clinical theories associate with the development, maintenance, and treatment of psychopathology. The authors describe the use of deterministic and probabilistic MDS techniques for investigating numerous aspects of perceptual organization, such as dimensional attention, perceptual correlation, within-attribute organization, and perceptual variability. Additionally, they discuss how formal quantitative models can be used, in conjunction with MDS-derived representations of individual differences in perceptual organization, to test theories about the role of cognitive processing in clinically relevant phenomena. They include applied examples from their work in the areas of eating disorders and sexual coercion.

Coercion↗

PubMed2002

Comparisons between exemplar similarity and mixed prototype models using a linearly separable category structure.

Nosofsky and Zaki (2002) found that an exemplar similarity model provided better accounts of individual subject classification and generalization performance than did a mixed prototype model proposed by Smith and Minda (1998; Minda & Smith, 2001). However, these previous tests used a nonlinearly separable category structure. In the present work, the authors extend the previous findings by demonstrating a superiority for the exemplar generalization model over the mixed prototype model in a case involving a linearly separable structure. Because this structure has numerous features that Minda and Smith argued should be conducive to prototype-based processing, the results pose a significant challenge to the mixed prototype view.

Generalization, Psychological↗

PubMed2002

Single-system models and interference in category learning: commentary on Waldron and Ashby (2001).

In a recent article, Waldron and Ashby (2001) observed that performing a concurrent task caused greater interference in learning a simple one-dimensional categorization rule than in learning a complex three-dimensional one. They argued that this result was incompatible with all existing single-system models of category learning but was as predicted by the multiple-system COVIS model (Ashby, Alfonso-Reese, Turken, & Waldron, 1998). In contrast to Waldron and Ashby's argument, we demonstrate that the single-system ALCOVE model (Kruschke, 1992) naturally predicts the result by assuming that its selective-attention learning process is disrupted by the concurrent task.

Attention↗

PubMed2002

Exemplar and prototype models revisited: response strategies, selective attention, and stimulus generalization.

J. D. Smith and colleagues (J. P. Minda & J. D. Smith, 2001; J. D. Smith & J. P. Minda, 1998,2000; J. D. Smith, M. J. Murray, & J. P. Minda, 1997) presented evidence that they claimed challenged the predictions of exemplar models and that supported prototype models. In the authors' view, this evidence confounded the issue of the nature of the category representation with the type of response rule (probabilistic vs. deterministic) that was used. Also, their designs did not test whether the prototype models correctly predicted generalization performance. The present work demonstrates that an exemplar model that includes a response-scaling mechanism provides a natural account of all of Smith et al.'s experimental results. Furthermore, the exemplar model predicts classification performance better than the prototype models when novel transfer stimuli are included in the experimental designs.

Attention↗

PubMed2002

Modeling individual differences in perceptual and attentional processes related to bulimic symptoms.

Attentional and perceptual differences between women with high and low levels of bulimic symptoms were studied with techniques adapted from cognitive science. Stimuli were pictures of young women varying in body size and facial affect. A multidimensional scaling analysis showed that the high-symptom women were significantly more attentive to information about body size and significantly less attentive to information about affect. In prototype classification tasks, the high-symptom women used significantly more information about body size and significantly less information about affect. There were strong associations between individual differences in attention in the similarity task and decision making in the classification tasks. The study shows the potential utility of cognitive science methods for the study of cognitive factors in psychopathology.

Adult↗