Kim Nam-Gyoon
1 Department of Psychology, Keimyung University, South Korea.
Percept Mot Skills. 2015 Jun;120(3):906-27. doi: 10.2466/24.PMS.120v16x0. Epub 2015 May 18.
As an object approaches an observer, the visual angle subtended by any two texture elements on the object surface expands, as does the solid angle corresponding to the object's contour. The inverse of the relative rate of each of these types of expansion specifies the time-to-contact (TTC) between the object and the observer. The former is referred to as local tau1 (LT1), and the latter as local tau2 (LT2). For LT1 and LT2 to be available, the shape of the object must remain constant during its approach. The present study examined human observers' perceptual capacity to estimate TTC of an approaching object under severely perturbed or impoverished optic flow. In Experiment 1, non-spherical, textureless objects approached the observer while rotating about either one or two axes. In Experiment 2, textured objects were depicted by random dots that varied in density. When the object rotated, the surface dots were displaced or even disappeared. These manipulations severely compromised the optical patterns specifying LT1 and LT2. However, human observers were able to estimate TTC, although less reliably, under these severely compromised conditions.
当一个物体靠近观察者时，物体表面任意两个纹理元素所张的视角会扩大，物体轮廓对应的立体角也会扩大。这两种类型的扩展的相对速率的倒数指定了物体与观察者之间的接触时间（TTC）。前者被称为局部tau1（LT1），后者被称为局部tau2（LT2）。为了能够得到LT1和LT2，物体在靠近过程中其形状必须保持不变。本研究考察了人类观察者在严重扰动或匮乏的视觉流条件下估计接近物体的TTC的感知能力。在实验1中，非球形、无纹理的物体在绕一个或两个轴旋转的同时靠近观察者。在实验2中，有纹理的物体由密度变化的随机点描绘。当物体旋转时，表面的点会发生位移甚至消失。这些操作严重破坏了指定LT1和LT2的光学模式。然而，在这些严重受损的条件下，人类观察者仍能够估计TTC，尽管可靠性较低。
