Holliday I E, Braddick O J
Kenneth Craik Laboratory, Department of Experimental Psychology, University of Cambridge, UK.
Perception. 1991;20(3):355-62. doi: 10.1068/p200355.
Does the visual system represent stereoscopic depth purely as a map of local disparities, or does it explicitly represent local relationships of disparity, such as disparity gradients? Experiments are reported in which visual search for a target containing the same disparity range as other elements in the display, but differing in the relationship of the disparities (stereo slant), was used to determine whether the target showed 'pop-out' like a unitary feature, or the serial search characteristic of feature conjunctions. Each stereo pair of elements was selected randomly from a range of outline parallelograms leaning to the right or to the left, so that the target could not be identified using any monocular shape cue. Response times for detection of the target (present on 50% of the trials) were independent of the number of elements in the display. This result was confirmed by varying element size and spacing, and by using oblique crosses rather than parallelograms as stimuli. It is concluded that stereoscopically defined slant, or disparity gradient, can be processed and compared in parallel across the display, and acts in this respect as an explicit unitary visual property. This contrasts with findings in analogous experiments on movement, which show that targets defined by divergence or deformation of optic flow can only be identified by serial search.
视觉系统是纯粹将立体深度表征为局部视差图，还是明确表征视差的局部关系，比如视差梯度？本文报告了一些实验，其中利用对与显示屏中其他元素具有相同视差范围，但视差关系（立体倾斜）不同的目标进行视觉搜索，来确定该目标是像单一特征那样呈现“弹出”效应，还是具有特征联结的系列搜索特征。每对立体元素均从一系列向右或向左倾斜的轮廓平行四边形范围内随机选取，这样就无法使用任何单眼形状线索来识别目标。检测目标（在50%的试验中呈现）的反应时间与显示屏中的元素数量无关。通过改变元素大小和间距，以及使用倾斜十字而非平行四边形作为刺激，这一结果得到了证实。研究得出结论，立体定义的倾斜或视差梯度能够在整个显示屏上并行处理和比较，并且在这方面作为一种明确的单一视觉属性起作用。这与关于运动的类似实验结果形成对比，后者表明由光流发散或变形定义的目标只能通过系列搜索来识别。
