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Spatial Factors in the Integration of Speed InformationWe reported that, for a 21FC task with multiple Gabor patches in each interval, thresholds for speed discrimination decreased with the number of patches, while simply increasing the area of a single patch produced no such effect. This result could be explained by multiple patches reducing spatial uncertainty. However, the fact that thresholds decrease with number even when the patches are in fixed positions argues against this explanation. We therefore performed additional experiments to explore the lack of an area effect. Three observers did a 21FC speed discrimination task with 6 Gabor patches in each interval, and were asked to pick the interval in which the gratings moved faster. The 50% contrast patches were placed on a circle at 4 deg. eccentricity, either equally spaced and maximally separated (hexagonal array), or closely-spaced, in consecutive positions (string of pearls). For the string-of-pearls condition, the grating phases were either random, or consistent with a full-field grating viewed through multiple Gaussian windows. When grating phases were random, the thresholds for the hexagonal and string-of-pearls layouts were indistinguishable. For the string-of-pearls layout, thresholds in the consistent-phase condition were higher by 15 +/- 6% than in the random-phase condition. (Thresholds increased by 57 +/- 7% in going from 6 patches to a single patch of equivalent area.). For random-phase patches, the lower thresholds for 6 patches does not depend on a specific spacing or spatial layout. Multiple, closely-spaced, consistent-phase patches that can be interpreted as a single grating, result in thresholds closer to that produced by a single patch. Together, our results suggest that object segmentation may play a role in the integration of speed information.
Document ID
20020017454
Acquisition Source
Ames Research Center
Document Type
Conference Paper
Authors
Verghese, P.
(NASA Ames Research Center Moffett Field, CA United States)
Stone, L. S.
(NASA Ames Research Center Moffett Field, CA United States)
Hargens, Alan R.
Date Acquired
August 20, 2013
Publication Date
January 1, 1995
Subject Category
Behavioral Sciences
Meeting Information
Meeting: Association for Research in Vision and Ophthalmology Meeting
Location: Fort Lauderdale, FL
Country: United States
Start Date: May 14, 1995
End Date: May 19, 1995
Sponsors: Association for Research in Vision and Ophthalmology
Funding Number(s)
PROJECT: RTOP 199-18-12-07
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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