Stimulus-response compatibility as a determinant of interference in a Stroop-like task

The contribution of stimulus-response compatibility (SRC) to interference effects was tested in a Stroop-like task. Few previous studies have examined maximal compatibility for both dimensions of a stimulus. In the present study, the words UP, DOWN, LEFT, and RIGHT were presented on a computer screen. The word appeared at fixation and immediately began to move either up or down or left or right. Subjects responded either manually (by moving a joystick) or verbally according to (1) the verbal denotation of the word or (2) the direction the word was moving. Stimuli were congruent (e.g., UP moving up) or incongruent (e.g., UP moving down) and were presented in four conditions that varied in the degree of SRC (e.g., voice response to the meaning of the word = high SRC; voice response to the direction the word was moving = low SRC). Response times were slower in conditions with low SRC. The typical congruency effect was more pronounced in conditions with low SRC than in conditions with high SRC, showing that at least some of the interference observed in Stroop-type studies can be explained in terms of SRC.