van den Berg Ronald, Roerdink Jos B T M, Cornelissen Frans W
Department of Mathematics and Computing Science and School of Behavioral and Cognitive Neurosciences, University of Groningen, Groningen, The Netherlands.
J Vis. 2007 Jul 17;7(2):14.1-11. doi: 10.1167/7.2.14.
Perception of peripherally viewed shapes is impaired when surrounded by similar shapes. This phenomenon is commonly referred to as "crowding". Although studied extensively for perception of characters (mainly letters) and, to a lesser extent, for orientation, little is known about whether and how crowding affects perception of other features. Nevertheless, current crowding models suggest that the effect should be rather general and thus not restricted to letters and orientation. Here, we report on a series of experiments investigating crowding in the following elementary feature dimensions: size, hue, and saturation. Crowding effects in these dimensions were benchmarked against those in the orientation domain. Our primary finding is that all features studied show clear signs of crowding. First, identification thresholds increase with decreasing mask spacing. Second, for all tested features, critical spacing appears to be roughly half the viewing eccentricity and independent of stimulus size, a property previously proposed as the hallmark of crowding. Interestingly, although critical spacings are highly comparable, crowding magnitude differs across features: Size crowding is almost as strong as orientation crowding, whereas the effect is much weaker for saturation and hue. We suggest that future theories and models of crowding should be able to accommodate these differences in crowding effects.
当被相似形状包围时，对周边视觉形状的感知会受到损害。这种现象通常被称为“拥挤效应”。尽管对字符（主要是字母）的感知进行了广泛研究，对方向的研究相对较少，但对于拥挤效应是否以及如何影响其他特征的感知却知之甚少。然而，当前的拥挤模型表明，这种效应应该相当普遍，因此不限于字母和方向。在此，我们报告了一系列实验，研究了以下基本特征维度中的拥挤效应：大小、色调和饱和度。这些维度中的拥挤效应与方向领域中的拥挤效应进行了对比。我们的主要发现是，所研究的所有特征都显示出明显的拥挤迹象。首先，识别阈值随着掩蔽间距的减小而增加。其次，对于所有测试特征，临界间距似乎大约是视觉偏心度的一半，并且与刺激大小无关，这一特性先前被认为是拥挤效应的标志。有趣的是，尽管临界间距高度可比，但不同特征的拥挤程度有所不同：大小拥挤几乎与方向拥挤一样强烈，而饱和度和色调的效应则弱得多。我们建议，未来关于拥挤效应的理论和模型应该能够适应这些拥挤效应的差异。
