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Perceptual learning of contrast discrimination in macaca mulatta

Lookup NU author(s): Dr Xing Chen, Mehdi Sanayei, Professor Alexander Thiele



Rhesus monkeys underwent training in a contrast discrimination task, in which grating stimuli were presented at parafoveal and peripheral visual field locations. Subjects had to compare a sample stimulus that had a fixed contrast of 30% to a test stimulus that varied in contrast from trial to trial. Extensive practice yielded improvements in contrast discrimination that were observed across the full range of test stimulus contrasts. These improvements occurred across multiple sessions, as well as across trials within individual sessions. The finer the contrast discriminations required, the longer it took for subjects to improve. Improvements in psychophysical performance resulted in the steepening of psychometric functions and/or shifts in the point of subjective equality towards the contrast of the sample stimulus. Enhancement in discrimination was especially pronounced around the contrast level of the sample stimulus, to which the subject was consistently exposed. The changes resulted in increased accuracy overall, lower discrimination thresholds, and faster response times. Partial transfer of learning, from vertically oriented training stimuli to horizontally oriented testing stimuli, was observed, while transfer to stimuli with different spatial frequencies was less pronounced. The results demonstrate the existence of perceptual learning in the contrast domain, whereby learning affects multiple performance-related psychophysical metrics.

Publication metadata

Author(s): Chen X, Sanayei M, Thiele A

Publication type: Article

Publication status: Published

Journal: Journal of Vision

Year: 2013

Volume: 13

Issue: 13

Print publication date: 20/11/2013

Date deposited: 27/11/2013

ISSN (electronic): 1534-7362

Publisher: Association for Research in Vision and Ophthalmology


DOI: 10.1167/13.13.22

PubMed id: 24259674


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Funder referenceFunder name
G0700976Medical Research Council, UK