On a common circle: Natural scenes and Gestalt rules

To understand how the human visual system analyzes images, it is essential to know the structure of the visual environment. In particular, natural ima ges display consistent statistical properties that distinguish them from ra ndom luminance distributions. We have studied the geometric regularities of oriented elements (edges or line segments) present in an ensemble of visua l scenes, asking how much information the presence of a segment in a partic ular location of the visual scene carries about the presence of a second se gment at different relative positions and orientations. We observed strong long-range correlations in the distribution of oriented segments that exten d over the whole visual field. We further show that a very simple geometric rule, cocircularity, predicts the arrangement of segments in natural scene s, and that different geometrical arrangements show relevant differences in their scaling properties. Our results show similarities to geometric featu res of previous physiological and psychophysical studies. We discuss the im plications of these findings for theories of early vision.