Enhanced spatial stimulus-response mapping near the hands: the Simon effect is modulated by hand-stimulus proximity.

Emerging evidence has revealed that visual processing of objects near the hands is altered. The present study shows that the visuomotor Simon effect when the hands are proximal to stimuli is greater than that observed when the hands are far from stimuli, thereby indicating stronger spatial stimulus-response mapping near the hands. The visuomotor Simon effect is robustly enhanced near the hands even when hand visibility and stimulus-response axis-similarity are controlled. However, the semantic Simon effect with location words is not modulated by hand-stimulus proximity. Thus, consistent with the dimensional overlap model and the known features of the bimodal visuotactile neurons, hand-stimulus proximity enhances spatial stimulus-response mapping but has no effect on semantic processing of location words.