It is nearly impossible to concurrently initiate and execute two motor actions with independent timing. For example, it is difficult to tap one rhythm with the right hand while tapping a different rhythm with the left hand, even after these rhythms have been practiced individually. However, if this task is restructured so that it is represented internally as one action done by two hands rather than as two actions, one with each hand, these same rhythms can be produced easily. These findings, which indicate that motor action is limited to a single time base, are in marked contrast with the fact that it is easy to mechanically generate two independent rhythms simply by using mechanisms that are not linked to each other. After an in-depth review of the extensive research on this topic we propose a new theoretical interpretation. This attributes the difficulty to a fundamental constraint that prevents initiation of any motor action until after completion of programming the internal code that controls timing. The timing code is volatile in the sense that it must be generated immediately prior to the action to be controlled and then it must be implemented without delay. This constraint, which has been studied as it applies to single motor actions, can be extended to concurrent motor actions where it can account for the difficulty in doing two differently timed actions at once. Additional phenomena which may be attributed to this constraint are described in a concluding section.

中文翻译：

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无法同时执行两个不同时间的操作：问题是什么？


以独立的时序同时启动和执行两个电机动作几乎是不可能的。例如，很难用右手敲击一种节奏，同时用左手敲击不同的节奏，即使这些节奏已经单独练习之后。然而，如果对这项任务进行重组，使其在内部表示为两只手完成的一个动作，而不是每只手一个动作的两个动作，则可以轻松产生这些相同的节奏。这些发现表明运动动作仅限于单一时基，这与仅通过使用彼此不相关的机制很容易机械地产生两个独立节律的事实形成鲜明对比。在深入回顾有关该主题的广泛研究后，我们提出了一种新的理论解释。这将困难归因于一个基本约束，该约束阻止任何运动动作的启动，直到完成控制时序的内部代码的编程之后。时序代码是易失性的，因为它必须在要控制的动作之前立即生成，然后必须立即执行。这个约束已经被研究，因为它适用于单个运动动作，可以扩展到并发运动动作，它可以解释同时执行两个不同时间动作的困难。结论部分描述了可能归因于此限制的其他现象。