The influence of sensory modality on the reversal of the Simon effect in an accessory-signal Simon task

In a Simon task subjects react to the identity of a stimulus, while ignoring the location of the stimulus. Even though stimulus location is irrelevant, responses are faster and more accurate when stimulus and response location correspond. To understand the relationship between the time course of the activation of relevant and irrelevant codes, we use accessory signal (AS) Simon tasks, where the different types of information are presented separately. Response information is presented centrally at the start of the trial, followed by a go/no-go signal 600 ms later. An irrelevant peripheral AS appears before, after or simultaneously with the go/no-go signal (SOA). When a visual peripheral AS was used, a Simon effect occurred when the AS was presented 150ms before or simultaneously with the go/no-go signal. Surprisingly, the effect reversed when the AS followed the go/no-go signal with 150 ms. When an auditory AS was used, Simon effects were found with the SOA of -150ms and 0ms, and no reversal occurred. We assume that the reversal is caused by the inhibition of exogenous activation caused by the AS. These results indicate that inhibition of exogenous irrelevant information only influences the execution of corresponding responses if a visual AS is used.