Word- and arrow-based Simon effects emerge for eccentrically presented location words and arrows.

Two experiments examined whether the location-based Simon effect and word- or arrow-based Simon effects, and their interaction, emerge in the same task situations by presenting location words and (left and right, Experiment 1) or single-headed arrows (left and right pointing, Experiment 2) in the left-right visual field. These tasks include two attributes of task-irrelevant location information, physical location and either location word (Experiment 1) or arrow direction (Experiment 2), when they vary jointly for a single stimulus. Moreover, the location-based Simon effect in these tasks was compared to that obtained in a pure location-based Simon task. Results showed that (1) the location-, word- and arrow-based Simon effects occurred on both mean RT and delta plots; (2) the word- and arrow-based Simon effects interacted with the location-based Simon effect on mean RT; (3) the Simon effect in the pure location-based Simon task differed little from the location-based Simon effect in the two joint Simon tasks. These results indicate that different task-irrelevant spatial attributes can influence responses in the same task, and that one of them can influence the effect of the other on responses. This latter result offers evidence that the different attributes do not provide separate sources of activation.