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Journal of Vision (2004) 4, 838-842 http://journalofvision.org/4/10/1/ 838 Second-order motion conveys depth-order information
 

Summary: Journal of Vision (2004) 4, 838-842 http://journalofvision.org/4/10/1/ 838
Second-order motion conveys depth-order information
Jay Hegdé The Salk Institute for Biological Studies, La Jolla, CA, USA
Thomas D. Albright The Salk Institute for Biological Studies, La Jolla, CA, USA
Gene R. Stoner The Salk Institute for Biological Studies, La Jolla, CA, USA
Psychophysical and neurophysiological studies have revealed that the visual system is sensitive to both "first-order"
motion, in which moving features are defined by luminance cues, and "second-order" motion, in which motion is defined
by nonluminance cues, such as contrast or flicker. Here we show psychophysically that common types of second-order
stimuli provide potent cues to depth order. Although motion defined exclusively by nonluminance cues may be relatively
rare in natural scenes, the depth-order cues offered by second-order stimuli arise ubiquitously as a result of occlusion of
one moving object by another. Our results thus shed new light on the ecological importance of second-order motion.
Furthermore, our results imply that visual cortical areas that have been shown to be responsive to second-order motion
may be extracting information not just about object motion as has been assumed, but also about the relative depth of
objects.
Keywords: depth, 3D surface and shape perception, motion-2D
Introduction
Imagine a window shade being drawn shut. As the
shade is drawn, it progressively occludes scene elements
outside the window. Conversely, when the shade is pulled
open, those same scene elements are progressively disoc-

  

Source: Albright, Tom - Vision Center Laboratory, Salk Institute for Biological Studies
Boynton, Geoffrey M. - Systems Neurobiology Laboratories, Salk Institute for Biological Studies

 

Collections: Biology and Medicine