Stewart, N., & Matthews, W. J. (2009). Relative judgment and knowledge of the category structure. Psychonomic Bulletin & Review, 16, 594-599.

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.

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