In situations requiring the execution of two tasks at around the same time, we need to decide which of the tasks should be executed first. Previous research has revealed several factors that affect the outcome of such response order control processes, including bottom-up factors (e.g., the temporal order of the stimuli associated with the two tasks) and top-down factors (e.g., instructions). In addition, it has been shown that tasks associated with certain response modalities are preferably executed first (e.g., temporal prioritisation of tasks involving oculomotor responses). In this study, we focused on a situation in which task order has to be unpredictably switched from trial to trial and asked whether task-order representations are coded separately or integrated with the component task sets (i.e., in a task-specific manner). Across three experiments, we combined two tasks known to differ in prioritisation, namely an oculomotor and a manual (or pedal) task. The results indicated robust task-order switch costs (i.e., longer RTs when task order was switched vs. repeated). Importantly, the data demonstrate that it is possible to show an asymmetry of task-order switch costs: While these costs were of similar size for both task orders in one particular experimental setting with specific spatial task characteristics, two experiments consistently indicated that it was easier for participants to switch to their prioritised task order (i.e., to execute the dominant oculomotor task first). This suggests that in a situation requiring frequent task-order switches (indicated by unpredictable changes in stimulus order), task order is represented in an integrated, task-specific manner, bound to characteristics (here, associated effector systems) of the component tasks.

在需要大约同时执行两个任务的情况下，我们需要决定应该先执行哪个任务。以前的研究揭示了影响这种响应顺序控制过程结果的几个因素，包括自下而上的因素（例如，与两个任务相关的刺激的时间顺序）和自上而下的因素（例如，指令）。此外，已经表明，与某些反应模式相关联的任务最好首先执行（例如，涉及动眼神经反应的任务的时间优先级排序）。在这项研究中，我们专注于任务顺序必须不可预测地从试验切换到试验的情况，并询问任务顺序表示是单独编码还是与组件任务集集成（即，以特定于任务的方式）。在三个实验中，我们结合了两个已知优先级不同的任务，即动眼神经和手动（或踏板）任务。结果表明强大的任务顺序切换成本（即，切换任务顺序与重复任务顺序时更长的 RT）。重要的是，数据表明有可能显示任务顺序转换成本的不对称性：虽然在具有特定空间任务特征的特定实验设置中，两个任务顺序的成本大小相似，但两项实验一致表明它更容易让参与者切换到他们的优先任务顺序（即首先执行主要的动眼神经任务）。这表明，在需要频繁切换任务顺序的情况下（由不可预测的刺激顺序变化表示），任务顺序以集成的形式表示，