Abstract: Task switching refer to the process frequently from one task to another task, and the switching process is an important function of executive control, which control switching course between two tasks which compete for the same cognitive resources in working memory. In task switching, switch cost is the performance differences in task-switch and task-repetition trials. Based on the theories of the subtractive method reaction time, switch cost is the index of executive control. Recently, some researches have attempted to specify nature and origins of switch cost to uncover the mechanisms underlying task switching performance. Theoretically, there is disagreement as to whether switch cost actually represents the task-set reconfiguration or the task-set inertia. The aim of the present study was to investigate the effect of delay time and foreknowledge on task switching.
Explicit task-cueing paradigm was used in the present study. There were 29 participants (12 males and 17 females) volunteered to take part in the experiment. A 3 (delay time: 100ms, 600ms and 1000ms) × 3 (foreknowledge type: no foreknowledge, part foreknowledge and full foreknowledge) ×2 (task type: switch task and repetition task) within-subject design was conducted to examined the mechanisms of effects of foreknowledge on task switching under the conditions of difference delay time. The correct RT and switch cost were measured.
The results showed: (1) the main effect of delay time was significant, the switch cost with 100ms was larger than with 1000ms, however, no difference significantly among 600ms and 100ms or 1000ms. (2) The amount of switch cost depend on foreknowledge, switch cost was smaller with full foreknowledge than with part and no foreknowledge, but no difference significantly between the later two. (3) The interaction between delay time and foreknowledge did not appear.
The findings suggested that delay time and foreknowledge acted on task-set inertia and task-set reconfiguration severally, which were two differences cognitive processes underlying switch cost.

Key words: task switching, switch cost, executive control