The Rotating Snakes illusion is a motion illusion based on repeating, asymmetric luminance patterns. Recently, we found certain gray-value conditions where a weak illusory motion occurs in the opposite direction. Of the four models for explaining the illusion, one also explains the unexpected perceived opposite direction.We here present a simple new model, without free parameters, based on an array of standard correlation-type motion detectors with a subsequent nonlinearity (e.g., saturation) before summing the detector outputs. The model predicts (a) the pattern-appearance motion illusion for steady fixation, (b) an illusion under the real-world situation of saccades across or near the pattern (pattern shift), (c) a relative maximum of illusory motion for the same gray values where it is found psychophysically, and (d) the opposite illusion for certain luminance values. We submit that the new model’s sparseness of assumptions justifies adding a fifth model to explain this illusion.

旋转蛇幻觉是基于重复的不对称亮度模式的运动幻觉。最近，我们发现某些灰度值条件，在相反的方向上发生了虚弱的幻觉运动。在解释错觉的四个模型中，一个也解释了意想不到的相反方向。我们在此提出一种简单的新模型，该模型没有自由参数，它基于一系列具有相关非线性（例如饱和度）的标准相关类型运动检测器在对检测器输出求和之前。该模型预测（a）用于稳定注视的模式外观运动错觉，（b）在现实世界中，扫视横越或靠近模式（模式移位）时的错觉，（c）假象运动的相对最大值。在心理上可以找到相同的灰度值，（d）对于某些亮度值的相反错觉。我们认为，新模型的假设稀疏性有理由添加第五个模型来解释这种错觉。