Locus of interference on the Stroop test.

On the Stroop test subjects are presented with a random sequence of color names printed in random colors of ink. They are asked to go through the list twice, once reading the words aloud and once naming the ink colors. In this experiment 36 college students were also asked to go through the lists using their fingers to make push button responses. With verbal responses naming the ink colors took nearly twice as long as reading the words, thus replicating the usual Stroop test results. With either the left hand or the right there was no difference between the time required by the subjects to respond to the words and to the ink colors. The disappearance of the Stroop effect with finger responses suggests strongly that the interference normally shown on the Stroop test occurs primarily in the processing of the verbal response.