Redundancy gain in the Simon Task: Does increasing relevant activation reduce the effect of irrelevant activation?

In the present study, we tested the idea that relevant and irrelevant location-based activations are combined when selecting a response in the Simon task. For this purpose, we manipulated the strength of the relevant activation by using single versus redundant relevant stimuli to indicate the correct response. Assuming that relevant and irrelevant activations are summed during the decision process, the Simon effect should be reduced in the presence of the stronger relevant activation produced by redundant stimuli. Contrary to this expectation, the results revealed that the Simon effect was larger overall with redundant stimuli than with single stimuli. Importantly, distributional analyses indicated that the Simon effect was not reduced for redundant stimuli even when controlling for the opportunity for irrelevant location activation to dissipate after stimulus onset. These results are thus inconsistent with accounts in which the summation of decision-level activations is the cause of the Simon effect. Instead, these results are consistent with the idea that redundancy and irrelevant location information influence activations at different levels. Considering the findings of previous studies, the most likely account is that redundancy affects decision-level activations whereas relevant and irrelevant activation are integrated at the motor level to produce the Simon effect (i.e., decision locus of redundancy gain and motor locus of Simon effect). (PsycINFO Database Record