Foley John M
Department of Psychological and Brain Sciences, University of California, Santa Barbara, CA, USA.
J Vis. 2011 Aug 25;11(9):15. doi: 10.1167/11.9.15.
Graham and Wolfson have shown that, after adaptation to an array of Gabor patterns, observers discriminate poorly between spatially identical Gabor arrays in which the contrasts are symmetrically above and below the adapt contrast. Ten experiments are reported that show that the effect occurs in simple contrast discrimination tasks and examine its properties using a two-alternative spatial forced-choice paradigm. The experiments show that the effect is quite robust and manifests itself in several different experimental paradigms. It occurs with masks as short as 50 ms, but it disappears when an interval as short as 30 ms intervenes between the test patterns and the masks. It occurs at 4 and 8 c/deg. The decrease in discrimination for straddle contrasts is accompanied by an increase in discrimination for contrasts above the mask contrast. A model is presented that describes and predicts the results. The key idea of the model is that patterns which suddenly change contrast produce two responses in the visual system, a V-response that is a function of the absolute value of the difference between the test contrast and the mask contrast and an S-response that is an increasing function of contrast.
格雷厄姆和沃尔夫森已经表明，在适应一系列伽柏模式后，观察者对空间上相同但对比度在适应对比度上下对称分布的伽柏阵列的辨别能力很差。本文报告了十项实验，这些实验表明这种效应在简单的对比度辨别任务中会出现，并使用二选一空间强制选择范式研究了其特性。实验表明，这种效应相当稳健，并且在几种不同的实验范式中都有体现。它在短至50毫秒的掩蔽条件下会出现，但当测试图案和掩蔽之间间隔短至30毫秒时就会消失。它在4和8周/度的情况下也会出现。跨骑对比度辨别能力的下降伴随着高于掩蔽对比度的对比度辨别能力的增加。本文提出了一个描述和预测这些结果的模型。该模型的关键思想是，对比度突然变化的图案在视觉系统中会产生两种反应，一种是V反应，它是测试对比度与掩蔽对比度之差的绝对值的函数，另一种是S反应，它是对比度的递增函数。
