Farell Bart, Ng Cherlyn
Institute for Sensory Research, Syracuse University, Syracuse, NY, USA.
Vision Res. 2014 Dec;105:137-50. doi: 10.1016/j.visres.2014.10.012. Epub 2014 Oct 23.
The separation between the eyes shapes the distribution of binocular disparities and gives a special role to horizontal disparities. However, for one-dimensional stimuli, disparity direction, like motion direction, is linked to stimulus orientation. This makes the perceived depth of one-dimensional stimuli orientation dependent and generally non-veridical. It also allows perceived depth to violate transitivity. Three stimuli, A, B, and C, can be arranged such that A > B (stimulus A is seen as farther than stimulus B when they are presented together) and B > C, yet A ⩽ C. This study examines how the visual system handles the depth of A, B, and C when they are presented together, forming a pairwise inconsistent stereo display. Observers' depth judgments of displays containing a grating and two plaids resolved transitivity violations among the component stimulus pairs. However, these judgments were inconsistent with judgments of the same stimuli within depth-consistent displays containing no transitivity violations. To understand the contribution of individual disparity signals, observers were instructed in subsequent experiments to judge the depth of a subset of display stimuli. This attentional instruction was ineffective; relevant and irrelevant stimuli contributed equally to depth judgments. Thus, the perceived depth separating a pair of stimuli depended on the disparities of the other stimuli presented concurrently. This context dependence of stereo depth can be approximated by an obligatory pooling and comparison of the disparities of one- and two-dimensional stimuli along an axis defined locally by the stimuli.
两眼之间的间距塑造了双眼视差的分布，并赋予水平视差特殊作用。然而，对于一维刺激而言，视差方向与运动方向一样，与刺激方向相关联。这使得一维刺激的感知深度依赖于刺激方向，且通常并非如实反映。这还使得感知深度会违背传递性。可以将三个刺激A、B和C进行如下排列：A > B（当刺激A和刺激B同时呈现时，刺激A看起来比刺激B更远）且B > C，但A ≤ C。本研究考察了视觉系统在A、B和C同时呈现时如何处理它们的深度，从而形成一个成对不一致的立体显示。观察者对包含一个光栅和两个方格图案的显示的深度判断解决了组成刺激对之间的传递性违背问题。然而，这些判断与在不包含传递性违背的深度一致显示中对相同刺激的判断不一致。为了理解各个视差信号的作用，在后续实验中指导观察者判断显示刺激子集的深度。这种注意力指导是无效的；相关和不相关的刺激对深度判断的贡献相同。因此，一对刺激之间的感知深度取决于同时呈现的其他刺激的视差。立体深度的这种上下文依赖性可以通过沿着由刺激局部定义的轴对一维和二维刺激的视差进行强制性合并和比较来近似。
