Does Preparation Generate the Cost of Task Switching? A Recipe for a Switch Cost After Cue-Only Trials

A switch cost can be observed in cued task-switching on trials that follow a cue-only trial, which presents a task cue indicating a task to be performed but does not present a target stimulus to be responded to. This finding has provided important implications as to the source of the performance cost that emerges when switching tasks. However, cue-only trials differ from completed trials (for which the target occurs and is responded to) in several task parameters, and there are a few untested assumptions about a task-switch cost after cue-only trials, which restricted the conditions under which cue-only trials have been used. The present study first examined whether a switch cost emerged after cue-only trials when cue-only trials were matched with completed trials in as many task parameters as possible, which did not yield an expected switch cost in response time. In the subsequent six experiments, we explored critical task parameters to obtain a switch cost after cue-only trials. The present results indicate that the use of a short preparation interval was an important factor and that the switch cost was more short-lived and dissipated more quickly after cue-only trials than after completed trials. These outcomes are consistent with the proposal that there are two sources of a task-switch cost, one that originates from processing a task cue and another that originates from performing a cued task. Early processes of task preparation (e.g., cue or task identification) may be sufficient to produce the switch cost after cue-only trials.