The nature of switch cost: task set configuration or carry-over effect?

The primary goal of the present study was to differentiate variants of each class of hypothetical models of task switching. Two event-related potentials, the lateralized readiness potential (LRP)and P-300 were analyzed to infer the roles of advance reconfiguration and carry-over effect upon task switching. Participants performed two tasks in a random order, so that on each trial, they either repeated the task from the previous trial or switched to another task. Pre-cues that preceded each stimulus were either informative (task-cueing conditions), specifying which of the two tasks to perform, or uninformative (no task-cueing conditions). The results showed that the mean reaction time (RT) and the interval between stimulus onset and LRP onset were longer for switch than for repeat trials. This suggested that task switching affected processes before LRP onset (including stimulus identification and response selection). A further analysis Of P-300 confined task switching to the process after the stimulus identification stage. Task cueing, meanwhile, influenced both the latency and peak amplitude of P-300, suggesting that the cueing effect occurred prior to the response selection stage. The model of configuration-execution with moderate modifications is a candidate to explain the present results. (C) 2004 Elsevier B.V. All rights reserved.