Category effects in color memory

Abstract

Abstract Categorical color perception has previously been tested using a naming method, and the data from 27 subjects so examined in several experiments have been combined to yield a “categorical color difference index” (CCDI) that can be computed for any pair of colors in the OSA set of 424 samples. A new experiment is performed in which categorical color perception is encouraged without the explicit use of names by allowing 10 seconds to elapse between the presentation of two stimuli before they are judged same or different. All of the colors being compared are either identical or nearest neighbors in the orange region of the OSA space. Nearest neighbors, which are separated by 2 OSA units, clearly differ when presented simultaneously; with the delay, errors (“same” responses) sometimes occur. These errors decrease as CCDI increases, suggesting that categorization occurs when colors must be remembered. Response time, on the other hand, is independent of CCDI and therefore may reflect color differences based upon discrimination, rather than identification.