Component processes in voluntary task switching. 
The present study investigated the involvement of bottom-up and top-down control in task-switching situations in which tasks are selected on a voluntary basis.  We tested for indices of both types of control in the reduction in switch cost that is observed when more time is available before executing a task.  Participants had to indicate their task choice overtly prior to the actual task execution, and two time intervals were manipulated: the interval between the task-execution response of the previous trial and task-indication response of the current trial and the interval between task-indication response and task-execution response of a particular trial.  In Experiment 1, the length of these intervals was manipulated orthogonally, and indices for top-down and bottom-up control were observed.  Concerned with the validity of these results, Experiments 2-3 additionally discouraged participants from preparing the upcoming task before their task-indication response.  Indices for bottom-up control remained, but not for top-down control.  The characteristics of top-down and bottom-up control in voluntary task switching and task switching in general are discussed.