An ERP Analysis of Recognition and Categorization Decisions in a Prototype-Distortion Task (original) (raw)
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Classification in well-defined and ill-defined categories: evidence for common processing strategies
Journal of experimental psychology. General, 1980
Early work in perceptual and conceptual categorization assumed that categories had criterial features and that category membership could be determined by logical rules for the combination of features. More recent theories have assumed that categories have an ill-defined structure and have prosposed probabilistic or global similarity models for the verification of category membership. In the experiments reported here, several models of categorization were compared, using one set of categories having criterial features and another set having an ill-defined structure. Schematic faces were used as exemplars in both cases. Because many models depend on distance in a multidimensional space for their predictions, in Experiment 1 a multidimensional scaling study was performed using the faces of both sets as stimuli, In Experiment 2, subjects learned the category membership of faces for the categories having criterial features. After learning, reaction times for category verification and typ...
ERP signs of categorical and supra-categorical processing of visual information
Background: The aim of the present study was to investigate to what extent shared and distinct brain mechanisms are possibly subserving the processing of visual supra-categorical and categorical knowledge as observed with event-related potentials of the brain. Access time to these knowledge types was also investigated. Picture pairs of animals, objects, and mixed types were presented. Participants were asked to decide whether each pair contained pictures belonging to the same category (either animals or man-made objects) or to different categories by pressing one of two buttons. Response accuracy and reaction times (RTs) were also recorded. Results: Both ERPs and RTs were grand-averaged separately for the same–different supra-categories and the animal–object categories. Behavioral performance was faster for more endomorphic pairs, i.e., animals vs. objects and same vs. different category pairs. For ERPs, a modulation of the earliest C1 and subsequent P1 responses to the same vs. different supra-category pairs, but not to the animal vs. object category pairs, was found. This finding supports the view that early afferent processing in the striate cortex can be boosted as a by-product of attention allocated to the processing of shapes and basic features that are mismatched, but not to their semantic quintessence, during same–different supra-categorical judgment. Most importantly, the fact that this processing accrual occurred independent of a traditional experimental condition requiring selective attention to a stimulus source out of the various sources addressed makes it conceivable that this processing accrual may arise from the attentional demand deriving from the alternate focusing of visual attention within and across stimulus categorical pairs' basic structural features. Additional posterior ERP reflections of the brain more prominently processing animal category and same-category pairs were observed at the N1 and N2 levels, respectively, as well as at a late positive complex level, overall most likely related to different stages of analysis of the greater endomorphy of these shape groups. Conversely, an enhanced fronto-central and fronto-lateral N2 as well as a centro-parietal N400 to man-made objects and different-category pairs were found, possibly indexing processing of these entities' lower endomorphy and isomorphy at the basic features and semantic levels, respectively. Conclusion: Overall, the present ERP results revealed shared and distinct mechanisms of access to supra-categorical and categorical knowledge in the same way in which shared and distinct neural representations underlie the processing of diverse semantic categories. Additionally, they outlined the serial nature of categorical and supra-categorical representations, indicating the sequential steps of access to these separate knowledge types.
Neuropsychologia, 2007
Valid cueing has been shown to accelerate target identification and improve decision accuracy, however the precise nature and extent to which biasing influences the successive stages of target processing remain unclear. The present event-related potential (ERP) study used a "hybrid" task that combined features of standard cued-attention and task-switching paradigms in order to explore the effects of expectation on both identification and categorization of centrally-presented stimuli. Subjects made semantic judgments (living/nonliving) on word targets ("bunny"), and perceptual judgments (right/left) on arrow targets ("≪≪<"). Target expectancy was manipulated using cues that were valid (60% of trials), invalid (10%), or neutral (30%). Invalidly-cued targets required taskset switching before categorization could commence, and resulted in RT costs relative to validly-or neutrally-cued targets. Additionally, benefits from valid-cueing were observed for word targets. Invalid cueing of both arrow and word targets modulated early posterior visual potentials (P1/N1) and elicited a subsequent anterior P3a (270 ms). The temporal relationship of these effects suggests that the P3a indexed domain-general task-set switching processes recruited in response to the detection of unexpected perceptual information. Subsequent to the P3a and immediately preceding the behavioral response, validly-cued targets elicited enhanced stimulus-specific waveforms (arrows: parietal positivity [P290], words: inferior temporal negativity [late ITN: 400-600 ms]). The degree of neural enhancement relative to the invalid and neutral conditions mirrored the magnitude of corresponding RT benefits, suggesting that these waveforms indexed categorization and/or decision processes. Together, these results suggest that valid cueing increases the neural efficiency of initial stimulus identification, facilitating transmission of information to subsequent categorization stages, where increased neural activity leads to behavioral benefits.
Journal of Experimental Psychology: Learning, Memory, and Cognition, 2012
This special section brings together behavioral, computational, mathematical, and neuroimaging approaches to understand the processes underlying category learning. Over the past decade, there has been growing convergence in research on categorization, with computational-mathematical models influencing the interpretation of brain imaging and neuropsychological data, and with cognitive neuroscience findings influencing the development and refinement of models. Classic debates between single-system and multiple-memory-system theories have become more nuanced and focused. Multiple brain areas and cognitive processes contribute to categorization, but theories differ markedly in whether and when those neurocognitive components are recruited for different aspects of categorization. The articles in this special section approach this issue from several diverse angles.
Attention and learning processes in the identification and categorization of integral stimuli
The relationship between subjects' identification and categorization learning of integral-dimension stimuli was studied within the framework of an exemplar-based generalization model. The model was used to predict subjects' learning in six different categorization conditions on the basis of data obtained in a single identification learning condition. A crucial assumption in the model is that because of selective attention to component dimensions, similarity relations may change in systematic ways across different experimental contexts. The theoretical analysis provided evidence that, at least under unspeeded conditions, selective attention may play a critical role in determining the identification-categorization relationship for integral stimuli. Evidence was also provided that similarity among exemplars decreased as a function of identification learning. Various alternative classification models, including prototype, multiple-prototype, average distance, and "value-on-dimensions" models, were unable to account for the results.
Relative judgment and knowledge of the category structure
Psychonomic Bulletin & Review, 2009
For evenly spaced stimuli, a purely relative judgment account of unidimensional categorization performance is trivial-all that is required is knowledge of the size of stimulus difference corresponding to the width of a category. For unevenly spaced stimuli, long-term knowledge of the category structure is required. We argue that such knowledge does not necessitate a direct, absolute mapping between (representations of) stimulus magnitudes and category labels. We show that Stewart, Brown, and Chater's (2005) relative judgment model can account for data from absolute identification experiments with uneven stimulus spacing.
Attention and learning processes in the identification and categorization of integral stimuli
Journal of Experimental Psychology: Learning, Memory, and Cognition, 1987
The relationship between subjects' identification and categorization learning of integral-dimension stimuli was studied within the framework of an exemplar-based generalization model. The model was used to predict subjects' learning in six different categorization conditions on the basis of data obtained in a single identification learning condition. A crucial assumption in the model is that because of selective attention to component dimensions, similarity relations may change in systematic ways across different experimental contexts. The theoretical analysis provided evidence that, at least under unspeeded conditions, selective attention may play a critical role in determining the identification-categorization relationship for integral stimuli. Evidence was also provided that similarity among exemplars decreased as a function of identification learning. Various alternative classification models, including prototype, multiple-prototype, average distance, and "value-on-dimensions" models, were unable to account for the results. This article seeks to characterize performance relations between the two fundamental classification paradigms of identification and categorization. Whereas in an identification paradigm people identify stimuli as unique items (a one-to-one stimulus-response mapping), in a categorization paradigm people classify items into groups (a many-to-one stimulus-response mapping). The present study of the identification-categorization relationship is motivated by the recent "exemplar view" of categorization proposed by investigators such as Brooks (1978), Hintzman and Ludlam (1980), and Medin and Schaffer (1978). According to the exemplar view, people represent categories by storing individual category exemplars in memory. Classification decisions are based on the similarity of stimuli to the stored exemplars. This view contrasts with some other approaches that assume that people form category "summary" representations such as a prototype or a rule. A suggestion that follows from the exemplar view is that there may be highly regular and systematic relations between identification and categorization performance. Presumably, when subjects learn to identify stimuli, a unique representation of each stimulus is stored in memory. Furthermore, the extent to which individual stimuli are confused during identification is This article is b~tsed on portions of a PhD dissertation submitted to Harvard University and on subsequent work conducted at Indiana University.