Morrone M C, Burr D C, Ross J
Scuola Normale Superiore, Pisa, Italy.
Vision Res. 1994 Jun;34(12):1567-74. doi: 10.1016/0042-6989(94)90113-9.
It is well known that a staircase luminance profile is not seen veridically, but appears as the scallopy-like Chevreul illusion. We have shown that adding thin lines (either light or dark) to the centre of each step creates an illusory brightness change at the point of the line. The regions between the added lines and the edges seem to be uniform, with a clear change in brightness at the point where the line was added. The conditions under which the illusion occurred were measured systematically, both by contrast matching and by annulment. One model that can readily account for the illusion is the local-energy model of feature detection (Morrone & Burr, 1988 Proceedings of the Royal Society of London B, 235, 221-245). Adding the bar to the step creates a peak in local energy at all scales. At the higher scales, the phase of the energy is near zero, the signal for a line; but at the lower scales the phase is near pi/2, the signal for an edge. We propose that the edge signal of the lower scales causes the brightness illusion and that this brightness difference is structured by the feature defined sharply by the higher scales (even though that feature is not an edge). As well as predicting the existence of the illusion, simulations with the energy model predicted quantitatively the apparent contrast of the illusion as a function of stimulus contrast, bar-position and high-pass filter frequency.
众所周知，楼梯的亮度分布并非如实可见，而是呈现出类似扇贝状的谢弗勒尔错觉。我们已经表明，在每个台阶的中心添加细线（亮线或暗线）会在细线处产生虚幻的亮度变化。添加的线与边缘之间的区域似乎是均匀的，在添加线的位置亮度有明显变化。通过对比匹配和消除法系统地测量了产生错觉的条件。一个能够轻松解释这种错觉的模型是特征检测的局部能量模型（莫罗内和伯尔，《伦敦皇家学会学报B》，1988年，第235卷，第221 - 245页）。在台阶上添加线条会在所有尺度上产生局部能量峰值。在较高尺度上，能量的相位接近零，这是线条的信号；但在较低尺度上，相位接近π/2，这是边缘的信号。我们提出，较低尺度的边缘信号导致了亮度错觉，并且这种亮度差异是由较高尺度清晰定义的特征构建的（尽管该特征不是边缘）。除了预测错觉的存在，用能量模型进行的模拟还定量预测了错觉的表观对比度作为刺激对比度、线条位置和高通滤波器频率的函数。
