A COMPUTATIONAL MODEL OF THE SIMON EFFECT

Even though stimulus location is task irrelevant, reaction times are f aster when the location of the stimulus corresponds with the location of the response than when it does not. This phenomenon is called the S imon effect. Most accounts of the Simon effect are based on the assump tion that it arises from a conflict between the spatial code of the st imulus and that of the response. In this paper a computational model o f this hypothesis is presented. It provides a computationally explicit mechanism of the Simon effect. Consistent with human performance, the model provides reaction times that indicate both an advantage for the ipsilateral, corresponding response (i.e., facilitation) and a disadv antage of the contralateral, noncorresponding response (i.e., inhibiti on). In addition, the model accounts for the fact that the size for th e effect depends on task difficulty.