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Journal of the Optical Society of America A

Journal of the Optical Society of America A


  • Vol. 18, Iss. 9 — Sep. 1, 2001
  • pp: 2267–2272

First-order and second-order signals combine to improve perceptual accuracy

Andrew T. Smith and Nicholas E. Scott-Samuel  »View Author Affiliations

JOSA A, Vol. 18, Issue 9, pp. 2267-2272 (2001)

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The question of whether first-order (luminance-defined) and second-order (contrast-defined) stimuli can be combined in order to improve perceptual accuracy was examined in the context of two suprathreshold discrimination experiments, one spatial and the other temporal. The stimuli were either gratings of one type of image alone or else the sum of two gratings of the same orientation, spatial frequency, temporal frequency, and phase, but of different types. For both spatial frequency discrimination (static gratings) and speed discrimination (1-c/deg drifting gratings), performance was markedly better for a combined grating stimulus than predicted on the basis of independent processing of the two types of stimulus. But this was true only for stimuli of low contrast. Facilitation of discrimination performance occurred only in the contrast range where discrimination performance is contrast dependent. At higher contrasts, where performance has reached an asymptote for each type of pattern alone, there was no facilitation. The results suggest that first- and second-order stimuli, although believed by most researchers to be detected separately, can subsequently be combined in order to improve perceptual accuracy in conditions of low visibility.

© 2001 Optical Society of America

OCIS Codes
(330.0330) Vision, color, and visual optics : Vision, color, and visual optics
(330.4150) Vision, color, and visual optics : Motion detection
(330.5510) Vision, color, and visual optics : Psychophysics
(330.6100) Vision, color, and visual optics : Spatial discrimination
(330.6790) Vision, color, and visual optics : Temporal discrimination

Original Manuscript: November 30, 2000
Revised Manuscript: April 16, 2001
Manuscript Accepted: April 16, 2001
Published: September 1, 2001

Andrew T. Smith and Nicholas E. Scott-Samuel, "First-order and second-order signals combine to improve perceptual accuracy," J. Opt. Soc. Am. A 18, 2267-2272 (2001)

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