Wolpert D M, Miall R C, Winter J L, Stein J F
University of Oxford, University Laboratory of Physiology, Oxford, UK.
J Mot Behav. 1992 Dec;24(4):299-308. doi: 10.1080/00222895.1992.9941626.
Humans and monkeys show intermittent arm movements while tracking moving targets. This intermittency has been explained by postulating either a psychological refractory period after each movement and/or an error deadzone, an area surrounding the target within which movements are not initiated. We present a technique to detect and quantify the size of this deadzone, using a compensatory tracking paradigm that distinguishes it from a psychological refractory period. An artificial deadzone of variable size was added around a visual target displayed on a computer screen. While the subject was within this area, he received visual feedback that showed him to be directly on target. The presence of this artificial deadzone could affect tracking performance only if it exceeded the size of his intrinsic deadzone. Therefore, the size of artificial deadzone at which performance began to be affected revealed the size of the intrinsic deadzone. Measured at the subjects' eye, the deadzone was found to vary between 0.06 and 0.38 degrees, depending on the tracking task and viewing conditions; on the screen, this range was 1.3 mm to 3.3 mm. It increased with increasing speed of the target, with increasing viewing distance, and when the amplitude of the movement required was reduced. However, the deadzone size was not significantly correlated with the subjects' level of performance. We conclude that an intrinsic deadzone exists during compensatory tracking, and we suggest that its size is set by a cognitive process not simply related to the difficulty of the tracking task.
人类和猴子在跟踪移动目标时会表现出间歇性的手臂运动。这种间歇性可以通过假设每次运动后存在心理不应期和/或误差死区（围绕目标的一个区域，在该区域内不会发起运动）来解释。我们提出了一种技术，使用一种补偿跟踪范式来检测和量化这个死区的大小，该范式将其与心理不应期区分开来。在计算机屏幕上显示的视觉目标周围添加了一个大小可变的人工死区。当受试者处于这个区域内时，他会收到视觉反馈，显示他正好在目标上。只有当这个人工死区超过他的固有死区大小时，其存在才会影响跟踪性能。因此，性能开始受到影响时的人工死区大小揭示了固有死区的大小。在受试者的眼睛处测量，发现死区在0.06度到0.38度之间变化，这取决于跟踪任务和观察条件；在屏幕上，这个范围是1.3毫米到3.3毫米。它随着目标速度的增加、观察距离的增加以及所需运动幅度的减小而增大。然而，死区大小与受试者的表现水平没有显著相关性。我们得出结论，在补偿跟踪过程中存在一个固有死区，并且我们认为其大小是由一个认知过程设定的，而不仅仅与跟踪任务的难度相关。
