Psychology, Department of


Date of this Version



Published in Bulletin of the Psychonomic Society Volume 7. Copyright © 1976 Psychonomic Society. Used by permission.


The speed of classification of six alternative ink colors into two categories of three colors each was measured in tasks for which the colors were displayed as either XXXX patterns or incongruent words (Stroop stimuli). Substantial interference from the words occurred when the classification required grouping nonadjacent hues (red, yellow, and blue vs. orange, green, and purple) regardless of whether subjects received exclusive practice with this classification. Interference also occurred when the classification required grouping adjacent hues (red, orange, and yellow vs. green, blue, and purple), but only if this classification was intermixed within blocks of trials with the nonadjacent classification; subjects who received exclusive practice with the adjacent classification sorted the Stroop stimuli as rapidly as the XXXX stimuli.