Centre for Vision Research, York University, 4700 Keele Street, Toronto, ON, M3J 1P3, Canada.
Exp Brain Res. 2010 Apr;202(1):65-77. doi: 10.1007/s00221-009-2112-y. Epub 2009 Dec 5.
The influence of a secondary task on speeded responses, and its effect on the outcome of more complex tasks has been studied in detail. However, the consequence of task interference on specific movement parameters other than speed and accuracy has been largely ignored. The current study examines how performing a secondary task impacts the drawing of an unseen shape. Without vision of the hand, 15 subjects traced a shape on a graphics tablet. The shape and cursor were projected onto a screen. The shape disappeared and the subject attempted to draw three consecutive identical shapes. In the visual single-task condition, hand positions were represented by a cursor, but the resultant drawings could not be seen; in another, there was no visual feedback. In four remaining conditions, the 15 subjects drew the previously seen shapes without visual feedback while performing a secondary task of reporting the orientation of an arrow which appeared on the screen either in random or periodic timing. Subjects indicated the direction of the arrow either verbally or manually. Shapes were analyzed for scale, error of the corner angles as compared with 90 degrees, and drift, compared to the reference shape and across conditions. In dual-task conditions, performance of the primary, shape-drawing task deteriorated with respect to location and orientation, but not with respect to the pattern and proportion aspects of the shape. Vision was important for controlling position of the drawing, and also for controlling the shape and proportion of the drawing suggesting separate mechanisms for the location of a drawing and its shape and proportion. Furthermore, we propose that internal representations are more important than proprioception in the shape aspect of drawing well-known figures.
人们已经详细研究了次要任务对快速反应的影响，以及其对更复杂任务结果的影响。然而，任务干扰对速度和准确性以外的特定运动参数的后果在很大程度上被忽视了。本研究考察了执行次要任务如何影响对看不见的形状的绘制。在没有手部视觉的情况下，15 名受试者在图形平板电脑上追踪一个形状。形状和光标被投影到屏幕上。当形状消失时，受试者试图绘制三个连续的相同形状。在视觉单任务条件下，手的位置由光标表示，但无法看到绘制的结果；在另一种情况下，没有视觉反馈。在其余的四个条件中，15 名受试者在没有视觉反馈的情况下绘制之前看到的形状，同时执行报告出现在屏幕上的箭头方向的次要任务，箭头的方向要么随机出现，要么定期出现。受试者口头或手动指示箭头的方向。分析了形状的比例、与 90 度相比的角的误差以及与参考形状相比的漂移，以及在不同条件下的漂移。在双重任务条件下，相对于位置和方向，主要的形状绘制任务的性能下降，但相对于形状和比例方面没有下降。视觉对于控制绘图的位置很重要，对于控制绘图的形状和比例也很重要，这表明绘图位置和形状和比例的控制机制是分开的。此外，我们提出在绘制熟悉的图形时，内部表示比本体感觉对于形状方面更为重要。
