At an early stage, 3 different systems independently extract visual motion information from visual inputs. At later stages, these systems combine their outputs. Here, we consider a much studied (>650 publications) class of visual stimuli, plaids, which are combinations of 2 sine waves. Currently, there is no quantitative theory that can account for the perceived motion of plaids. We consider only perceived plaid direction, not speed, and obtain a large set of data exploring the various dimensions in which same-spatial-frequency plaids differ. We find that only 2 of the 3 motion systems are active in plaid processing, and that plaids with temporal frequencies 10 Hz or greater typically stimulate only the first-order motion system, which combines the plaid components by vector summation: Each plaid component is represented by a contrast-strength vector whose length is contrast-squared times a factor representing the relative effectiveness of that component's temporal frequency. The third-order system, which becomes primary at low temporal frequencies, also represents a plaid as 2 vectors that sum according to their contrast strength: a pure plaid in which both components have equal contrast and a residual sine wave. Second-order motion is irrelevant for these plaids. These principles enable a contrast-strength-vector summation theory for the responses of the first-order and third-order motion systems. With zero parameters estimated from the data, the theory captures the essence of the full range of the plaid data and supports the counterintuitive hypothesis that motion direction is processed independently of speed at early stages of visual processing. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

中文翻译：

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等空间频率格子刺激的感知运动方向理论。

在早期阶段，三个不同的系统从视觉输入中独立提取视觉运动信息。在以后的阶段，这些系统将其输出合并。在这里，我们考虑了一个经过大量研究（> 650种出版物）的视觉刺激类，格子，它们是2个正弦波的组合。当前，没有定量理论可以解释格子的感知运动。我们仅考虑感知的格子方向，而不考虑速度，并获得大量数据，探讨同空间频率格子不同的各个维度。我们发现3个运动系统中只有2个在格子处理中处于活动状态，并且时间频率为10 Hz或更高的格子通常仅刺激一阶运动系统，该系统通过矢量求和来组合格子成分：每个格子组件由一个对比度强度矢量表示，其长度是对比度平方乘以一个表示该组件时间频率相对有效性的因子。三阶系统在较低的时间频率处变为主要频率，它还表示一个由2个矢量组成的格子，这些矢量根据其对比度强度求和：一个纯格子，其中两个分量具有相同的对比度和一个正弦波。对于这些格子而言，二阶运动无关紧要。这些原理为一阶和三阶运动系统的响应启用了对比度强度矢量求和理论。根据数据估算的零参数，该理论抓住了全部格子数据的本质，并支持了反直观的假设，即在视觉处理的早期阶段，运动方向的处理与速度无关。（PsycInfo数据库记录（c）2020 APA，保留所有权利）。