Total sleep deprivation increases the costs of shifting between simple cognitive tasks.

In two experiments we studied the effects of one night of total sleep deprivation on task-shift costs. In different conditions shifts were between types of judgment (extradimensional shifts) and between stimulus-response mappings (intradimensional shifts). In addition, with an alternating-runs procedure we used short and long response-to-stimulus intervals and also external precues to vary the opportunities for advance configuration of task sets. Under all conditions sleep deprivation increased shift costs derived from the 20% slowest reaction times, which were insensitive to the opportunities for advance configuration. Shift costs derived from the 20% fastest reaction times were increased only for extradimensional shifts. As indicated by congruency effects, the increase of shift costs after a night without sleep cannot be attributed to increased interference between competing task sets. The findings suggest that total sleep deprivation increases task-set instability and thus lapsing, in particular in conditions with long stimulus-to-response intervals and in shift trials. In addition total sleep deprivation seems to increase the duration of an exogenously controlled process involved in extradimensional shifts.