The Simon effect and handedness: evidence for a dominant-hand attentional bias in spatial coding.

In two experiments, the relation between handedness and the size of the Simon effect in each visual hemifield was investigated. Experiment 1 showed that the Simon effect was larger in the right visual hemifield in right-handers and in the left visual hemifield in left-handers, whereas ambidextrous individuals showed a symmetric Simon effect. In Experiment 2, participants performed the same Simon task as in Experiment 1, but with their hands crossed. The right- and left-handed groups showed a reversed pattern of results with respect to Experiment 1. We explained this phenomenon as a part of a more general account in which perception and action are embedded in a perception-for-action system. In this system, an attentional bias originating from the field of operation of the dominant hand would be at the basis of the relationship between the asymmetry of the Simon effect and handedness.