Competition in context: response selection within the supervisory attentional system model.

We examined the effects of context bias and target exposure duration on error rates (ERR) and response times (RTs) in letter choice task within context. Surface Electromyography (sEMG) was recorded in both hands during context presentation, as a measure of readiness to respond. The goal was to affect the outcome of the task by manipulating relative schemata activation levels prior to target onset, as per the Supervisory Attentional System model. At short exposures, context bias and sEMG activity affected ERR, whereas at longer durations, RTs were affected. Context bias mediated the effect of sEMG activity. Increasing activity in both hands led to higher ERR and RTs in incongruent context. Non-increasing activity in the non-responding lead to lack of relationship between sEMG activity and behavior, irrespective of context. sEMG activity in both hands was found to be interrelated and context-sensitive. These results conform to the predictions of the Supervisory Attentional Model.