Contrast and assimilation in categorization and exemplar production.
We studied contrast and assimilation in three tasks: an exemplar-production task, a categorization task, and a combined categorization-then-production task. On each trial of the first task, subjects produced a circle when prompted with a category label. In the second task, they classified lines that differed in length into one of four categories. On each trial of the combined task, they classified two lines and then produced a line when prompted by a category label. All three tasks converged on the same conclusion: subjects' representation of the categories (measured in pixels in the production tasks and by the direction of errors in classification) shifted systematically from trial to trial. When successive stimuli were from the same category, the representation of that category was pulled toward the exemplar from the previous trial. When successive stimuli were from different categories, the representations of the neighbouring categories were pushed from the category of the initial stimulus. We conclude that accounts of categorization and identification must accommodate both assimilation and contrast as a function of trial-to-trial shifts in representation.
Defence R&D Canada, P.O. Box 2000, 1133 Sheppard Ave West, Toronto, Ontario, M3M 3B9, Canada. Vladimir.Zotov@drdc-rddc.gc.ca
Vladimir
V
Zotov
Michael N
MN
Jones
D J K
DJ
Mewhort
D001244:Association; D003210:Concept Formation; D005246:Feedback; D006801:Humans; D007600:Judgment; D009903:Optical Illusions; D009949:Orientation; D010364:Pattern Recognition, Visual; D011340:Problem Solving; D011597:Psychomotor Performance; D011601:Psychophysics; D012660:Semantics; D012858:Size Perception