Switching between tasks of unequal familiarity: The role of stimulus-attribute and response-set selection

It has been reported that it is harder to switch to a strong, well-practiced task from a weaker, less-practiced task than vice versa. Three experiments replicated this surprising asymmetry and inves-tigated how it is affected by a reduction in interference between tasks. Experiment 1 progressively delayed the onset of the stimulus attribute associated with the stronger task. Experiments 2 and 3 separated the response sets of the tasks. Both manipulations reduced, without eliminating, interference of the stronger with the weaker task but reversed the asymmetry of switch costs, resulting in a larger cost of switching to the weaker task. The results are interpreted in terms of a model of the interactions between control input, task strength, and task priming. The central question addressed by task switching research is how a task set, an effective organization of the cognitive system, is imposed to ensure that the appropriate task is performed. In a typical task switching experiment, the participant is presented with a series of similar stimuli, some or all of which permit a response in two or more tasks, and is required to switch quickly and frequently between the tasks. Performance is usually slower and less accurate on switch trials, on which the task is changed from the previous trial, than on nonswitch trials, on which the task is repeated from the previous trial. The performance difference be-tween switch and nonswitch trials may reflect additional cognitive load on switch trials (i.e., a task switching cost) and/or facilitated performance when the task is repeated (i.e., a task repetition benefit) but is typically referred to as the switch cost. The switch cost has been used to probe the mechanisms of cognitive control that permit the observed flexibility of responding. Two principal sources of the switch cost have been proposed. Many theorists have attributed switch costs to the time taken by control processes to establish a changed task set, with task recon-figuration viewed as an extra processing stage (or stages) inserted prior to completion of task-specific processing (e.g., De Jong