PROCESSING OF AN IRRELEVANT LOCATION DIMENSION AS A FUNCTION OF THE RELEVANT STIMULUS DIMENSION

The effect of an irrelevant location dimension on choice reactions to the relevant stimulus dimension was examined. Experiment 1 used variat ions of the spatial Stroop task and the Simon task that differed in wh ether the relevant dimension (location name or color) was similar to t he irrelevant location dimension. Congruity of the stimulus dimensions and stimulus-response (S-R) mapping had additive effects in the Simon task but overadditive effects in the Stroop task. Experiments 2-4 sho wed that each pattern could be obtained for both tasks, suggesting tha t dimensional similarity is not crucial; overadditivity occurred only when stimulus identification was prolonged. The results can be interpr eted in terms of the relative timing of activation for the relevant an d irrelevant information, if it is assumed that the activation functio n for irrelevant location varies across different stimulus-response ma ppings.