In search of an elusive hard threshold: a test of observer’s ability to order sub-threshold stimuli
In search of an elusive hard threshold: a test of observer’s ability to order sub-threshold stimuli
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寻找难以捉摸的硬阈值：测试观察者排序亚阈值刺激的能力
DOI：
10.1016/j.visres.2003.09.015
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发表时间：
2004
期刊：
影响因子：
1.8
通讯作者：
E. Vityaev
中科院分区：
文献类型：
--
作者：
A. Logvinenko;W. Byth;E. Vityaev
对比度传感器函数（d′vs.正弦光栅的对比度）是从某个非零对比度值而不是从原点产生的。这意味着在光栅对比度轴上存在一个点（硬阈值），在该点以下，观察者无法区分包含光栅的演示文稿和包含均匀场的演示文稿。我们研究了订购亚阈值方波光栅的能力，并发现，相反，无论对比度有多低，观察者都能够做到这一点。同时，当阈值下的光栅具有相同的对比度时，观察者不能对它们进行排序。后者与信号检测理论不一致，该理论预测观察者的判断是基于相同的感官状态的有序集合，而不管刺激是否不同或相同。另一方面，这些数据可以与阈值的概念相协调，如果后者被认为是一个模糊的，而不是一个鲜明的对比度轴上的边缘。
The contrast transducer function (d′vs. contrast) for sine gratings was claimed to come up from some non-zero contrast value rather than from the origin. This implies that there is a point (a hard threshold) on the grating contrast axis below which observers could not distinguish between presentations containing gratings and those containing a homogeneous field. We studied the ability to order sub-threshold square wave gratings and found, to the contrary, that observers were able to do this no matter how low the contrasts. At the same time, the observers failed to order the sub-threshold gratings when they were of the same contrast. The latter is inconsistent with signal detection theory which predicts that an observer’s judgements are based on the same ordered set of sensory states irrespective of whether the stimuli differ or are the same. On the other hand, these data can be reconciled with the notion of a threshold if the latter is thought of as a fuzzy rather than a sharp margin on the contrast axis.