Li Wang On, Khuu Sieu K, Hayes Anthony
Department of Psychology, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, China.
Vision Res. 2008 Jan;48(2):167-78. doi: 10.1016/j.visres.2007.10.019.
We investigated how different types of complex motion patterns interact in the perception of shape. We used global dot-motion stimuli which consisted of two superimposed groups of dots; one group of dots moved along an ellipsoidal trajectory (target pattern), while the other group of dots was divided into quadrants with dots in alternating sectors moving in radial expanding and radial contracting directions (background pattern). In the first experiment, observers judged whether the major axis of an ellipsoidal motion pattern oriented at 45 degrees or -45 degrees from vertical lay to the right or to the left of a central vertical line. Ellipsoids with different aspect ratios, which controlled both the tilt (left or right of vertical) and the extent of ellipsoidal curvature, were presented to observers using method of constant stimuli. The appearance of the ellipsoidal target pattern was distorted in the presence of background motion. The aspect ratio of the target at which observers perceived the figure to be circular was approximately 0.86 (an aspect ratio of 1.0 indicates a circle), with the pattern's major axis lying in the two sectors that contained contracting motion. This finding may constitute evidence that background motion distorts the perception of space, resulting in a distorted target pattern. However, the distortion effect is limited to conditions for which the speed of the target pattern and background pattern was slow and high contrast, and for when dots forming the target and background patterns were of the same luminance polarity.
我们研究了不同类型的复杂运动模式在形状感知中是如何相互作用的。我们使用了全局点运动刺激，它由两组叠加的点组成；一组点沿着椭圆形轨迹移动（目标模式），而另一组点被分成象限，交替扇区中的点沿径向扩张和径向收缩方向移动（背景模式）。在第一个实验中，观察者判断一个与垂直方向成45度或 -45度角的椭圆形运动模式的长轴是位于中心垂直线的右侧还是左侧。使用恒定刺激法向观察者呈现具有不同纵横比的椭圆体，这些纵横比既控制了倾斜度（垂直方向的左侧或右侧），也控制了椭圆体曲率的程度。在存在背景运动的情况下，椭圆形目标模式的外观会被扭曲。观察者将图形感知为圆形时目标的纵横比约为0.86（纵横比为1.0表示圆形），模式的长轴位于包含收缩运动的两个扇区中。这一发现可能构成证据，表明背景运动会扭曲空间感知，从而导致目标模式被扭曲。然而，这种扭曲效应仅限于目标模式和背景模式速度缓慢且对比度高的情况，以及构成目标和背景模式的点具有相同亮度极性的情况。
