Task preparation and task repetition: Two-component model of task switching

The switch cost (the disadvantage of performing a new task vs. a repeated t ask) has been attributed to lack of preparation for the switched task or pr iming of the repeated task. These sources were examined by manipulating for eknowledge of task transition (repeat or switch), response-to-stimulus inte rval (RSI), and practice level. Regardless of foreknowledge, the cost decre ased with RSI and practice. The reduction was greater with foreknowledge th an with no foreknowledge, and the amount of switch cost did not depend on f oreknowledge. These results suggest that the switch cost with foreknowledge may consist of both inadequate preparation and repetition benefit but the switch cost with no foreknowledge may reflect repetition benefit only. An A CT-R (adaptive control of thought-rational) model was proposed, accommodati ng both preparation and priming effect with 2 independent processes: confli ct resolution among productions and decay of chunk activation.