Object and Head Orientation Effects on Symmetry Perception Defined by Shape from Shading
Object and Head Orientation Effects on Symmetry Perception Defined by Shape from Shading
复制标题
物体和头部方向对由阴影形状定义的对称感知的影响
作者：
P. Wenderoth;N. Hickey
灰色圆盘呈现垂直阴影渐变，如果上面较浅，通常会显示为凸面，如果较浅，则会显示为凹面。Howard等人(1990)研究了这一现象，他们改变了相对于重力的阴影轴和头部的方向。他们的结果表明，头部中心或背向中心坐标决定了深度效应，而不是重力轴。然而，他们的研究也注意到了几个可能存在的问题，其中最重要的是他们使用的任务中可能存在反应干扰，而不是感知因素。在这里，我们试图使用一种间接测量阴影对深度的感知：我们不是询问受试者圆盘看起来是凸的还是凹的，而是构建了阴影圆盘的集合，就阴影的深度而言，这些圆盘围绕水平轴对称或不对称。这些刺激显示被短暂地闪现，以阻止关于光源方向的有意识的假设的干扰。受试者从来没有被问及是否有圆盘看起来凹凸不平，只是询问这组圆盘是否深度对称。结果与Howard等人的结果基本一致，并支持遮荫深度在很大程度上是一种低水平的自动机制的结论。
A grey disc which exhibits a vertical gradient of shading usually appears convex if lighter above and concave if lighter below. This phenomenon was investigated by Howard et al (1990) who varied both the shading axis relative to gravity and the orientation of the head. Their results indicated that head-centric or retinocentric coordinates determined the depth effect rather than gravitational axes. However, several possible problems with their study were noted, not the least of which was the possible intrusion of response rather than perceptual factors in the task they used. Here, we attempted to use an indirect measure of the perception of depth from shading: rather than asking subjects whether discs looked convex or concave, we constructed ensembles of shaded discs which, in terms of depth from shading, were or were not bilaterally symmetrical about an horizontal axis. These stimulus displays were briefly flashed to prohibit the intrusion of conscious assumptions about direction of light sources. Subjects were never asked whether any discs looked concave or convex, merely whether the set of discs was or was not depth symmetrical. Results were generally consistent with those of Howard et al and supported the conclusion that depth from shading is largely a low-level and automatic mechanism.