Nitzany Eyal I, Victor Jonathan D
Department of Computational Biology and Statistics, Cornell University, Ithaca, NY, USA.
J Vis. 2014 Apr 14;14(4):10. doi: 10.1167/14.4.10.
Extraction of motion from visual input plays an important role in many visual tasks, such as separation of figure from ground and navigation through space. Several kinds of local motion signals have been distinguished based on mathematical and computational considerations (e.g., motion based on spatiotemporal correlation of luminance, and motion based on spatiotemporal correlation of flicker), but little is known about the prevalence of these different kinds of signals in the real world. To address this question, we first note that different kinds of local motion signals (e.g., Fourier, non-Fourier, and glider) are characterized by second- and higher-order correlations in slanted spatiotemporal regions. The prevalence of local motion signals in natural scenes can thus be estimated by measuring the extent to which each of these correlations are present in space-time patches and whether they are coherent across spatiotemporal scales. We apply this technique to several popular movies. The results show that all three kinds of local motion signals are present in natural movies. While the balance of the different kinds of motion signals varies from segment to segment during the course of each movie, the overall pattern of prevalence of the different kinds of motion and their subtypes, and the correlations between them, is strikingly similar across movies (but is absent from white noise movies). In sum, naturalistic movies contain a diversity of local motion signals that occur with a consistent prevalence and pattern of covariation, indicating a substantial regularity of their high-order spatiotemporal image statistics.
从视觉输入中提取运动信息在许多视觉任务中都起着重要作用，比如从背景中分离出物体以及在空间中导航。基于数学和计算方面的考虑，已经区分出了几种局部运动信号（例如，基于亮度时空相关性的运动，以及基于闪烁时空相关性的运动），但对于这些不同类型的信号在现实世界中的普遍程度却知之甚少。为了解决这个问题，我们首先注意到，不同类型的局部运动信号（例如，傅里叶型、非傅里叶型和滑翔机型）的特征在于倾斜时空区域中的二阶及更高阶相关性。因此，可以通过测量时空斑块中每种相关性的存在程度以及它们在时空尺度上是否连贯，来估计自然场景中局部运动信号的普遍程度。我们将这种技术应用于几部热门电影。结果表明，所有三种局部运动信号在自然电影中都存在。虽然在每部电影的过程中，不同类型运动信号的平衡在不同片段之间有所变化，但不同类型运动及其子类型的普遍程度的总体模式，以及它们之间的相关性,在不同电影中惊人地相似（但在白噪声电影中不存在）。总之，自然主义电影包含多种局部运动信号，这些信号以一致的普遍程度和协变模式出现，表明其高阶时空图像统计具有显著的规律性。
