Topic: Improvement of contrast sensitivity with practice is not compatible with a sensory threshold account
Speaker: Prof. Joshua Solomon
Professor of Visual Psychophysics
Centre for Applied Vision Research, City, University of London EC1V 0HB
Time: 13:00-14:30, June 19th, 2018
Location: #1113, Wangkezhen Building, Peking University
Host: Prof. Cong Yu
Abstract
In forced-choice detection, incorrect responses are routinely ascribed to internal noise, because experienced psychophysical observers do not act as if they have a sensory threshold, below which all perceived intensities would be identical. To determine whether inexperienced observers have sensory thresholds, we examined psychometric functions (percent correct versus log contrast) for detection and detection in full-screen, dynamic visual noise. Over five days, neither type of psychometric function changed shape, but both shifted leftwards, indicating increased sensitivity. These results are not consistent with a lowered sensory threshold, which would decrease psychometric slope. Our results can be understood within the context of Dosher and Lu’s “stochastic” perceptual template model, augmented to allow intrinsic uncertainty. Specifically, our results are consistent with a combination of reduced internal additive noise and improved filtering of external noise.
