The task switch cost (difference between performing a new task versus the same task) has been attributed to either lack of preparation for the switched task or priming of the repeated task. To examine the relative importance of these two processes, foreknowledge of task transition (repeat or switch) and RSI (response-to-stimulus interval) were manipulated in two experiments. Latency was faster with foreknowledge than with no-foreknowledge, and this benefit increased with RSI. Although the switch cost decreased with RSI regardless of foreknowledge, the cost was greater with foreknowledge than with no-foreknowledge. 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. Supporting this idea, the amount of practice, which may improve the efficiency of both preparation and repetition, had greater impact on the switch cost with foreknowledge than with no-foreknowledge. An ACT-R model is proposed, accommodating both preparation and priming effect with two independent processes: conflict resolution among productions and decay of chunk activation.
ACT-R model