Braun J
California Institute of Technology, Division of Biology, Pasadena 91125.
J Neurosci. 1994 Feb;14(2):554-67. doi: 10.1523/JNEUROSCI.14-02-00554.1994.
In more than one respect, visual search for the most salient or the least salient item in a display are different kinds of visual tasks. The present work investigated whether this difference is primarily one of perceptual difficulty, or whether it is more fundamental and relates to visual attention. Display items of different salience were produced by varying either size, contrast, color saturation, or pattern. Perceptual masking was employed and, on average, mask onset was delayed longer in search for the least salient item than in search for the most salient item. As a result, the two types of visual search presented comparable perceptual difficulty, as judged by psychophysical measures of performance, effective stimulus contrast, and stability of decision criterion. To investigate the role of attention in the two types of search, observers attempted to carry out a letter discrimination and a search task concurrently. To discriminate the letters, observers had to direct visual attention at the center of the display and, thus, leave unattended the periphery, which contained target and distractors of the search task. In this situation, visual search for the least salient item was severely impaired while visual search for the most salient item was only moderately affected, demonstrating a fundamental difference with respect to visual attention. A qualitatively identical pattern of results was encountered by Schiller and Lee (1991), who used similar visual search tasks to assess the effect of a lesion in extrastriate area V4 of the macaque.
在不止一个方面，在一组显示项中寻找最显著或最不显著的项是不同类型的视觉任务。本研究调查了这种差异主要是感知难度的差异，还是更具根本性且与视觉注意力有关。通过改变大小、对比度、颜色饱和度或图案来生成不同显著程度的显示项。采用了感知掩蔽，平均而言，在寻找最不显著的项时掩蔽开始的延迟比寻找最显著的项时更长。结果，根据性能的心理物理学测量、有效刺激对比度和决策标准的稳定性判断，这两种类型的视觉搜索呈现出相当的感知难度。为了研究注意力在这两种搜索类型中的作用，观察者试图同时进行字母辨别和搜索任务。为了辨别字母，观察者必须将视觉注意力指向显示的中心，从而使包含搜索任务的目标和干扰项的周边区域处于未被注意状态。在这种情况下，对最不显著项的视觉搜索受到严重损害，而对最显著项的视觉搜索仅受到适度影响，这表明在视觉注意力方面存在根本差异。席勒和李（1991年）也遇到了定性相同的结果模式，他们使用类似的视觉搜索任务来评估猕猴纹外区V4损伤的影响。
