Hsieh Shulan, Yu Yen-Ting
Department of Psychology, National Chung Cheng University, 160 San-Hsing, Ming-Hsiung, Chia-Yi 621, Taiwan, ROC.
Brain Res Cogn Brain Res. 2003 Jul;17(2):228-37. doi: 10.1016/s0926-6410(03)00110-1.
Behavioral studies have documented that task switching incurs a longer reaction time than task repetition, and that advance cueing information about the forthcoming task reduces mean reaction time. The present study used P300 peak latency and two lateralized readiness potential (LRP) intervals--stimulus-locked and response-locked--to infer the loci of task switch and task-cueing effects and how they may interact in the basic task processing chain. Participants performed two tasks in a random order, so that on each trial they either repeated the task from the previous trial or switched to another task. In one condition, each stimulus was preceded by a cue informing participants which of the two tasks to perform; and in the other condition, each stimulus was preceded by a non-informative cue. Results indicated that both mean reaction times and the stimulus-locked LRP intervals were longer for switch than repeated trials, whereas P300 peak latencies and response-locked LRP intervals were identical for both trials. Similarly, both reaction times and the stimulus-locked LRP intervals were longer for no task-cueing than for task-cueing conditions, and P300 peak latencies and the response-locked LRP intervals were identical for both conditions. Finally, task switch and task-cueing effects appeared to be approximately additive, indicating the two factors influence distinct stage processes. We suggest that task switching resulted in prolongation of the response selection process by carry-over priming effects from the previous task, whereas task-cueing shortened the duration of the earlier process before response selection on both switch and repeated trials.
行为学研究已证明，与任务重复相比，任务切换会导致更长的反应时间，且关于即将执行任务的提前提示信息会缩短平均反应时间。本研究使用P300峰值潜伏期和两个侧化准备电位（LRP）时间间隔——刺激锁定和反应锁定——来推断任务切换和任务提示效应的位点，以及它们在基本任务处理链中可能如何相互作用。参与者以随机顺序执行两项任务，因此在每次试验中，他们要么重复上一次试验的任务，要么切换到另一项任务。在一种条件下，每个刺激之前会有一个提示，告知参与者要执行两项任务中的哪一项；在另一种条件下，每个刺激之前会有一个无信息提示。结果表明，与重复试验相比，切换试验的平均反应时间和刺激锁定的LRP时间间隔都更长，而两次试验的P300峰值潜伏期和反应锁定的LRP时间间隔相同。同样，与有任务提示条件相比，无任务提示时的反应时间和刺激锁定的LRP时间间隔都更长，且两种条件下的P300峰值潜伏期和反应锁定的LRP时间间隔相同。最后，任务切换和任务提示效应似乎大致具有可加性，表明这两个因素影响不同的阶段过程。我们认为，任务切换通过前一个任务的延续性启动效应导致反应选择过程延长，而任务提示在切换和重复试验中都缩短了反应选择之前早期过程的持续时间。
