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Perceptions of Depth Elicited by Occluded and Shearing Motions of Random Dots

Royden, Constance S. and Baker, James F. and Allman, John (1988) Perceptions of Depth Elicited by Occluded and Shearing Motions of Random Dots. Perception, 17 (3). pp. 289-296. ISSN 0301-0066. doi:10.1068/p170289.

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A computer-controlled display of random dots was used to study perceptions of depth. In this display, a field of stationary random dots surrounded a rectangular area in which random dots moved with uniform velocity in a single direction. The boundaries of this rectangle did not move. When dot motion was perpendicular to the longer boundary of the rectangle (occluded motion), the rectangle seemed to be behind the stationary background surround. Motion parallel to the longer boundary of the rectangle (shearing motion) made it appear in front of the surround. The relative lengths of the sides of the rectangle determined which effect predominated. Thus, for motion perpendicular to the long axis of the rectangle the occlusion predominated and naive subjects reported that the central area seemed farther away than the surround. For shearing motion parallel to the long axis, the subjects reported that the rectangle was closer than the surround and the strength of both effects also depended on the length-to-width ratio of the rectangle. If there was occluded motion along the long axis, as the length-to-width ratio increased so did the likelihood that subjects would report seeing the rectangle behind the surround. Conversely, with shearing motion along the long axis, increasing the length-to-width ratio increased the likelihood that the rectangle would appear unambiguously in front of the surround. Some subjects integrated the two cues with the resulting perception being a rotating cylinder. The occlusion effect was stronger than the shearing effect. In fact, this ‘far’ depth effect was so powerful that it tended to override conflicting depth cues such as height in the visual field or stereopsis. The ‘near’ depth effect produced by shearing motion was definite but these other depth cues could often override it.

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Additional Information:© 1988 Pion. Received 23 November 1986, in revised form 12 May 1988. This research was supported by National Institutes of Health Grants NS-00178, EY-03851, and GM-007737; National Science Foundation Grant BNS-77-15605; a National Science Foundation Postdoctoral Fellowship Award to J F Raker; and the Pew Memorial Trust. We thank John Power and Michael Walsh for designing and constructing the system for stimulus presentation, and Dave Sivertsen and Richard Mooney for assistance in collecting the data.
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NSF Postdoctoral FellowshipUNSPECIFIED
Pew Memorial TrustUNSPECIFIED
Issue or Number:3
Record Number:CaltechAUTHORS:20200708-152146739
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Official Citation:Royden, C. S., Baker, J. F., & Allman, J. (1988). Perceptions of Depth Elicited by Occluded and Shearing Motions of Random Dots. Perception, 17(3), 289–296.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:104290
Deposited By: George Porter
Deposited On:09 Jul 2020 14:23
Last Modified:16 Nov 2021 18:30

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