Arbuthnott Katherine D, Woodward Todd S
Department of Psychology, University of Regina, Regina, Saskatchewan, S4S 0A2.
Can J Exp Psychol. 2002 Mar;56(1):18-29. doi: 10.1037/h0087382.
Task-switching performance is strongly influenced by whether the imperative stimulus uniquely specifies which task to perform: Switch cost is substantial with bivalent stimuli but is greatly reduced with univalent stimuli, suggesting that available contextual information influences processing in task-switching situations. The present study examined whether task-relevant information provided by task cues influences the magnitude of switch cost in a parallel manner. Cues presented 500 ms prior to a trivalent stimulus indicated which of three tasks to perform. These cues either had a preexisting association with the to-be-performed task (verbal cues), or a recently learned association with the task (spatial and shape cues). The results paralleled the effects of stimulus bivalence: substantial switch cost with recently learned cue-task associations and greatly reduced switch cost with preexisting cue-task associations. This suggests that both stimulus-based and cue-based information can activate the relevant task set, possibly providing external support to endogenous control processes. Alternating-switch cost, a greater cost for switching back to a recently abandoned task, was also observed with both preexisting and recently learned cue-task associations, but only when all tasks were presented in a consistent spatial location. When spatial location was used to cue the to-be-performed tasks, no alternating-switch cost was observed, suggesting that different processes may be involved when tasks are uniquely located in space. Specification of the nature of these processes may prove to be complex, as post-hoc inspection of the data suggested that for the spatial cue condition, the alternating-switch cost may oscillate between cost and benefit, depending on the relevant task.
对于二价刺激，切换成本很高，但对于单价刺激，切换成本会大大降低，这表明可用的上下文信息会影响任务切换情境中的处理过程。本研究考察了任务线索提供的与任务相关的信息是否以类似的方式影响切换成本的大小。在三价刺激之前500毫秒呈现的线索表明要执行三项任务中的哪一项。这些线索要么与要执行的任务有预先存在的关联（言语线索），要么与任务有最近学习到的关联（空间和形状线索）。结果与刺激二价性的影响相似：对于最近学习到的线索-任务关联，切换成本很高，而对于预先存在的线索-任务关联，切换成本大大降低。这表明基于刺激和基于线索的信息都可以激活相关的任务集，可能为内源性控制过程提供外部支持。在预先存在的和最近学习到的线索-任务关联中，也观察到了交替切换成本，即切换回最近放弃的任务时成本更高，但只有当所有任务都呈现在一致的空间位置时才会出现这种情况。当使用空间位置来提示要执行的任务时，没有观察到交替切换成本，这表明当任务在空间中唯一确定位置时，可能涉及不同的过程。这些过程的性质的具体说明可能会很复杂，因为对数据的事后检查表明，对于空间线索条件，交替切换成本可能会根据相关任务在成本和收益之间波动。
