THE SIMON EFFECT OCCURS RELATIVE TO THE DIRECTION OF AN ATTENTION SHIFT

We investigated whether the Simon effect depends on the orienting of a ttention. In Experiment 1, participants were required to execute left- right discriminative responses to 2 patterns that were presented to th e left or right of fixation. The 2 patterns were similar, and the disc rimination was difficult. A letter at fixation signaled whether the cu rrent trial was a catch trial. The results showed a reversal of the Si mon effect. That is, spatially noncorresponding responses were faster than spatially corresponding responses. In Experiment 2, the discrimin ation of the relevant stimulus attribute was easy. In Experiment 3, th e discrimination of the relevant stimulus attribute was difficult, but the stimulus exposure time was long. In either experiment, the regula r Simon effect was reinstated. In Experiment 4, the letter that signal ed a catch trial appeared to the left or right of the imperative stimu lus. The Simon effect occurred relative to the position of the letter.