Watamaniuk S N
Smith-Kettlewell Eye Research Institute, San Francisco, CA 94115.
Perception. 1992;21(6):791-802. doi: 10.1068/p210791.
Despite the sluggish temporal response of the human visual system, moving objects appear clear and without blur, which suggests that visible persistence is reduced when objects move. It has been argued that spatiotemporal proximity alone can account for this modulation of visible persistence and that activation of a motion mechanism per se is not necessary. Experiments are reported which demonstrate that there is a motion-specific influence on visible persistence. Specifically, points moving in constant directions, or fixed trajectories, show less persistence than points moving with the same spatial and temporal displacements but taking random walks, randomly changing direction each frame. Subjects estimated the number of points present in the display for these two types of motion conditions. Under conditions chosen to produce 'good' apparent motion, ie small temporal and spatial increments, the apparent number of points for the fixed-trajectory condition was significantly lower than the apparent number in the random-walk condition. The traditional explanation of the suppression of persistence based on the spatiotemporal proximity of objects cannot account for these results. The enhanced suppression of persistence observed for a target moving in a consistent direction depends upon the activation of a directionally tuned motion mechanism extended over space and time.
尽管人类视觉系统的时间响应较为迟缓，但运动的物体看起来清晰且无模糊现象，这表明当物体运动时，可见持续性会降低。有人认为，仅时空接近性就能解释可见持续性的这种调节，而运动机制本身的激活并非必要条件。本文报告的实验表明，存在一种对可见持续性的运动特异性影响。具体而言，沿恒定方向或固定轨迹运动的点，其持续性低于具有相同空间和时间位移但进行随机游走（即每帧随机改变方向）的点。受试者估计了这两种运动条件下显示屏中出现的点数。在选择产生“良好”表观运动的条件下，即小的时间和空间增量，固定轨迹条件下的表观点数显著低于随机游走条件下的表观点数。基于物体时空接近性对持续性抑制的传统解释无法说明这些结果。观察到的沿一致方向运动的目标对持续性的增强抑制取决于在空间和时间上扩展的方向调谐运动机制的激活。
