Braje W L, Legge G E, Kersten D
Department of Psychology, Plattsburgh State University, NY 12901, USA.
Perception. 2000;29(4):383-98. doi: 10.1068/p3051.
Shadows are frequently present when we recognize natural objects, but it is unclear whether they help or hinder recognition. Shadows could improve recognition by providing information about illumination and 3-D surface shape, or impair recognition by introducing spurious contours that are confused with object boundaries. In three experiments, we explored the effect of shadows on recognition of natural objects. The stimuli were digitized photographs of fruits and vegetables displayed with or without shadows. In experiment 1, we evaluated the effects of shadows, color, and image resolution on naming latency and accuracy. Performance was not affected by the presence of shadows, even for gray-scale, blurry images, where shadows are difficult to identify. In experiment 2, we explored recognition of two-tone images of the same objects. In these images, shadow edges are difficult to distinguish from object and surface edges because all edges are defined by a luminance boundary. Shadows impaired performance, but only in the early trials. In experiment 3, we examined whether shadows have a stronger impact when exposure time is limited, allowing little time for processing shadows; no effect of shadows was found. These studies show that recognition of natural objects is highly invariant to the complex luminance patterns caused by shadows.
当我们识别自然物体时，阴影常常出现，但尚不清楚它们是有助于还是阻碍识别。阴影可以通过提供有关光照和三维表面形状的信息来提高识别能力，或者通过引入与物体边界混淆的虚假轮廓来损害识别能力。在三个实验中，我们探究了阴影对自然物体识别的影响。刺激物是有阴影或无阴影展示的水果和蔬菜的数字化照片。在实验1中，我们评估了阴影、颜色和图像分辨率对命名潜伏期和准确性的影响。即使对于灰度模糊图像（在这类图像中阴影难以识别），阴影的存在也不会影响表现。在实验2中，我们探究了相同物体的双色调图像的识别情况。在这些图像中，阴影边缘很难与物体边缘和表面边缘区分开来，因为所有边缘都是由亮度边界定义的。阴影损害了表现，但仅在早期试验中如此。在实验3中，我们研究了在曝光时间有限、几乎没有时间处理阴影的情况下，阴影是否有更强的影响；未发现阴影有影响。这些研究表明，自然物体的识别对由阴影引起的复杂亮度模式具有高度不变性。
