Hou Fang, Lu Hongjing, Zhou Yifeng, Liu Zili
School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230027, PR China.
Vision Res. 2006 Jun;46(13):2061-8. doi: 10.1016/j.visres.2005.12.010. Epub 2006 Feb 10.
Visual stimulus configuration can influence elementary visual processes. We provide empirical evidence to demonstrate this effect in stereoscopic depth discrimination. Two vertically aligned bars were presented in stereo such that one of them was closer to the human observer. Observers discriminated which of the two was closest. In the first, "occluded" condition, a horizontal bar, positioned closest in depth to the observer, was added to the display such that the two vertical bars perceptually completed to form a whole by connecting together behind the horizontal bar. In the second, control condition, the horizontal bar was placed furthest away from the observer such that there was a visible gap between the two vertical bars, which could no longer complete perceptually. We measured observers' psychometric functions using the method of constant stimuli, and found that their discrimination sensitivity d' was smaller when the two vertical bars perceptually completed than when they did not. We used a simple model to illustrate that when the two vertical bars perceptually completed, they also tended to be perceived as coplanar in the fronto-parallel plane. This consequence of completion made it more difficult to discriminate any difference in depth between the two vertical bars.
视觉刺激配置会影响基本视觉过程。我们提供实证证据以证明这种效应在立体深度辨别中的存在。以立体方式呈现两根垂直对齐的条，使得其中一根离人类观察者更近。观察者辨别哪根条离自己最近。在第一种“遮挡”条件下，将一根在深度上离观察者最近的水平条添加到显示中，这样两根垂直条在水平条后面连接在一起时在感知上就会完成形成一个整体。在第二种对照条件下，水平条放置在离观察者最远的位置，使得两根垂直条之间有可见的间隙，它们在感知上不再能完成连接。我们使用恒定刺激法测量观察者的心理测量函数，发现当两根垂直条在感知上完成连接时，他们的辨别敏感度d' 比未完成连接时要小。我们使用一个简单模型来说明，当两根垂直条在感知上完成连接时，它们在额状平行平面上也倾向于被感知为共面。这种完成连接的结果使得辨别两根垂直条之间的深度差异变得更加困难。
