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Joshua A. Solomon; Noise reveals visual mechanisms of detection and discrimination. Journal of Vision 2002;2(1):7. doi: 10.1167/2.1.7.
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© ARVO (1962-2015); The Authors (2016-present)
When performance is limited by stochastically defined masks, (psychophysical) reverse correlation has proven to be an especially efficient tool for estimating the templates used by detection and discrimination mechanisms. Here I describe a maximum-likelihood approach to quantifying the significance of differences between estimates of template. Four methodologically related experiments illustrate the versatility of reverse correlation. Experiment 1 shows significant differences between the templates used by different observers when detecting a bright Gaussian blob. The results of Experiment 2 are consistent with observers not using information about the phase of a parafoveal wavelet when detecting it. Experiments 3 and 4 reveal not only the templates used by detection mechanisms but also aspects of their response functions. Both results are consistent with a sensory threshold. Experiment 3 shows that 2-alternative forced-choice detection errors are caused when the target’s effective contrast is reduced, not when the mask looks more like the expected target+mask than the actual target+mask. Experiment 4 suggests that observers use optimally tuned detection templates for orientation discrimination.
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