Attentional set mixing: Effects on target selection and selective response activation

Performance is impaired under set mixing conditions that require frequent readjustments of attentional focus over an extended time period. We compared set repetitions within pure blocks (constant focus of attention) to physically identical repetitions within mixed blocks (changing focus of attention). The aim was to investigate how set mixing affects target selection, indexed by the N2pc component, and selective response activation, indexed by the lateralized readiness potential (LRP). We found that set mixing prolonged the evolution of the N2pc while leaving its onset unaffected. Impaired target selection indicated by the N2pc mixing effect also delayed the start of response planning indexed by an onset delay of the stimulus-locked LRP, explaining one part of the behavioral mixing cost. A larger part of mixing cost could be attributed to a prolonged response planning phase, indexed by an earlier onset of the response-locked LRP.