Hannus Aave, van den Berg Ronald, Bekkering Harold, Roerdink Jos B T M, Cornelissen Frans W
University Medical Center Groningen, The Netherlands.
J Vis. 2006 Jul 28;6(4):523-40. doi: 10.1167/6.4.15.
While searching for objects, we combine information from multiple visual modalities. Classical theories of visual search assume that features are processed independently prior to an integration stage. Based on this, one would predict that features that are equally discriminable in single feature search should remain so in conjunction search. We test this hypothesis by examining whether search accuracy in feature search predicts accuracy in conjunction search. Subjects searched for objects combining color and orientation or size; eye movements were recorded. Prior to the main experiment, we matched feature discriminability, making sure that in feature search, 70% of saccades were likely to go to the correct target stimulus. In contrast to this symmetric single feature discrimination performance, the conjunction search task showed an asymmetry in feature discrimination performance: In conjunction search, a similar percentage of saccades went to the correct color as in feature search but much less often to correct orientation or size. Therefore, accuracy in feature search is a good predictor of accuracy in conjunction search for color but not for size and orientation. We propose two explanations for the presence of such asymmetries in conjunction search: the use of conjunctively tuned channels and differential crowding effects for different features.
在寻找物体时，我们会整合来自多种视觉模态的信息。经典的视觉搜索理论假定，特征在整合阶段之前是独立处理的。基于此，有人会预测，在单特征搜索中同样可辨别的特征在联合搜索中也应如此。我们通过检验特征搜索中的搜索准确性是否能预测联合搜索中的准确性来验证这一假设。受试者搜索结合了颜色与方向或大小的物体；同时记录眼动情况。在主要实验之前，我们匹配了特征可辨别性，确保在特征搜索中，70%的扫视很可能会指向正确的目标刺激。与这种对称的单特征辨别表现不同，联合搜索任务在特征辨别表现上呈现出不对称性：在联合搜索中，指向正确颜色的扫视百分比与特征搜索中的相似，但指向正确方向或大小的情况则少得多。因此，特征搜索的准确性是联合搜索中颜色准确性的良好预测指标，但对大小和方向则不然。我们针对联合搜索中这种不对称性的存在提出两种解释：使用联合调谐通道以及不同特征的差异拥挤效应。
