Intrahemispherical activation, visuomotor transmission, and the Simon effect: Comment on Wascher et al. (2001).

On the basis of 3 experiments, E. Wascher, U. Schatz, T. Kuder, and R. Verleger (2001; see record 2001-06699-017) concluded, "The variety of tasks subsumed under the term Simon effect turned out to be heterogeneous" (p. 749). This comment critically evaluates the validity of their conclusion by considering their hypotheses, methodology, specific conclusions, and proposed broader implications. Although the Simon effect is a behavioral phenomenon, E. Wascher et al. relied heavily on physiology in hypothesis generation, methodology, and interpretation of results. Moreover, methodological differences from most previous studies, combined with limited statistical support, nonreplication of previously reported behavioral phenomena, inconsistencies in results across experiments, and evidence against a contribution of intrahemispherical activation by visuomotor pathways, strongly suggest that their conclusion should be viewed with caution.