Discrimination is more closely associated with perceived similarity than with distance and color

Diverse factors affect perceived similarity and discrimination, with high perceived similarity associated with poor discrimination. To investigate this hypothesis, college students made speeded same-different discriminations between 2 achromatic colors when they were contiguous and separated, did the same with 2 chromatic colors, and rated similarity. Compared with chromatic color, the separation for achromatic color impaired the performance on different stimuli more than on same stimuli with response bias controlled, which implied an increase in the perceived similarity of the discriminated stimuli, hurt overall performance, and elevated rated similarity. Thus, discrimination was more closely associated with 2 measures of perceived similarity than with distance and color, in support of the hypothesis.