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Contrast and assimilation in categorization and exemplar production
Vladimir Zotov1, Michael N Jones, D J K Mewhort
1Defence R&D Canada, P.O. Box 2000, 1133 Sheppard Ave West, Toronto, Ontario, M3M 3B9, Canada. Vladimir.Zotov@drdc-rddc.gc.ca
Attention, Perception & Psychophysics
|January 26, 2011
Summary
This study reveals that category representations dynamically shift with each trial. Category perception is influenced by both assimilation (attraction to recent exemplars) and contrast (repulsion from differing categories).
Area of Science:
- Cognitive Psychology
- Perception Science
Background:
- Categorization and identification are fundamental cognitive processes.
- Understanding how category representations are updated is crucial for explaining perception.
Purpose of the Study:
- To investigate trial-to-trial shifts in category representations.
- To examine the roles of assimilation and contrast in these shifts.
Main Methods:
- Three tasks were employed: exemplar-production, categorization, and a combined task.
- Category representations were measured via stimulus production (pixels) and classification errors.
- Systematic shifts in category representations were observed across trials.
Main Results:
- Category representations were attracted towards previous exemplars within the same category (assimilation).
- Category representations were repelled from neighboring categories when stimuli differed (contrast).
- These assimilation and contrast effects were consistently observed across all three tasks.
Conclusions:
- Cognitive models of categorization and identification must account for dynamic, trial-dependent shifts in representation.
- Both assimilation and contrast are key mechanisms influencing category perception based on sequential stimulus exposure.
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