Contrast discrimination with and without spatial uncertainty.
The main purpose of these experiments was to examine in detail how successfully the uncertainty reduction explanation accounts for the effects of spatial cues in a temporal forced-choice contrast discrimination task in which any one of four well-separated Gabor patches is incremented. In preliminary experiments, it was shown that in the absence of uncorrelated contrast jitter, observers could use either of at least two different decision strategies, whereas in the presence of random contrast jitter, their response was based on the largest contrast value in the two intervals of a trial. Independent spatial cues were used in each interval to minimize the likelihood of eye movement artifacts. Cues either preceded each stimulus presentation by 100 ms, or were coincident with it. Precues were only slightly more effective than simultaneous cues, and either of them improved performance nearly as much as could be expected from the uncertainty reduction account of spatial attention.
Nachmias
Jacob
J
Department of Psychology, University of Pennsylvania, 3815 Walnut Street, Philadelphia, PA 19104-6228, USA. nachmias@psych.upenn.edu
D001288:Attention / Q000502:physiology*; D015350:Contrast Sensitivity / Q000502:physiology*; D003463:Cues; D004192:Discrimination, Psychological / Q000502:physiology*; D006801:Humans; D016011:Normal Distribution; D011601:Psychophysics; D017603:Signal Detection, Psychological