Processes of task-set reconfiguration: switching operations and implementation operations.

When participants are asked to shift between four dimensionally organized tasks which differ in the type of judgment (numerical vs. spatial) and/or the judgment-to-response mapping (compatible vs. incompatible), a characteristic profile of shift costs can be observed. It can be accounted for in terms of two different types of operations: generalizing switching operations on a dimensionally organized set of task representations and implementation operations [T. Kleinsorge, H. Heuer, Psycholog. Res. 62 (1999) 300]. In a first experiment we corroborated our previous findings by way of a new procedure that makes it possible to estimate shift costs unconfounded by a number of factors that are likely to affect estimates of shift costs based on more conventional procedures. In a second experiment we investigated the endogenous and exogenous nature of the postulated types of operations. The characteristic profile of shift costs disappeared when long precue intervals (PCIs) were used. Augmented by a formal analysis, this finding suggests that both switching and implementation operations are endogenously controlled. In addition, there remained some residual shift costs which were essentially insensitive to the nature of the task shift but depended on the difficulty of the new task. Most likely they reflect a process of consolidation of an already configured task set.