Adams Wendy J
School of Psychology, University of Southampton, Southampton, England.
J Vis. 2007 Aug 31;7(11):11.1-7. doi: 10.1167/7.11.11.
The "light-from-above" prior is invoked to simplify and expedite complex visual processing. This prior is observed in visual search and shape judgments with shaded stimuli, where perceived shape and ease of target identification are both affected by stimulus orientation. In addition, perceived surface reflectance varies with surface orientation in a manner consistent with assumed overhead lighting. Do the light-priors exhibited by these different tasks have the same underlying mechanism or even lighting direction? Some evidence has suggested that an "above-left" rather than "above" prior guides behavior in some tasks, but not others. In the current study, the "light-from-above" prior was measured using visual search, shape perception, and a novel reflectance-judgment task. There were substantial differences between observers. However, strong positive correlations were found between the light-priors measured using all three tasks. The data imply that a single mechanism is responsible for a light-from-above prior in "quick and dirty" visual search behavior, shape perception, and reflectance judgments. Furthermore, the data support the notion that perceived shape is the preattentive feature in visual search with shaded targets.
“自上而下的光线”先验被用来简化和加速复杂的视觉处理。这种先验在对有阴影刺激的视觉搜索和形状判断中可以观察到，在这些情况下，感知到的形状和目标识别的难易程度都会受到刺激方向的影响。此外，感知到的表面反射率会随着表面方向的变化而变化，其方式与假定的头顶照明一致。这些不同任务所表现出的光线先验是否具有相同的潜在机制甚至照明方向呢？一些证据表明，在某些任务中，引导行为的是“左上方”而非“上方”的先验，但在其他任务中并非如此。在当前的研究中，使用视觉搜索、形状感知和一项新颖的反射率判断任务来测量“自上而下的光线”先验。观察者之间存在显著差异。然而，在使用所有三项任务测量的光线先验之间发现了很强的正相关。数据表明，单一机制负责“快速粗略”的视觉搜索行为、形状感知和反射率判断中的自上而下的光线先验。此外，数据支持这样一种观点，即感知到的形状是有阴影目标的视觉搜索中的前注意特征。
