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Linking hypotheses underlying Class A and Class B methods

Morgan, M. J., Melmoth, D. & Solomon, J. A. (2013). Linking hypotheses underlying Class A and Class B methods. Visual Neuroscience, 30(5-6), pp. 197-206. doi: 10.1017/S095252381300045X


Class A psychophysical observations are based on the linking hypothesis that perceptually distinguishable stimuli must correspond to different brain events. Class B observations are related to the appearance of stimuli not their discriminability. There is no clear linking hypothesis underlying Class B observations, but they are necessary for studying the effects of context on appearance, including a large class of phenomena known as “illusions.” Class B observations are necessarily measures of observer bias (Fechner’s “constant error”) as opposed to Class A measures of sensitivity (Fechner’s “variable error”). It is therefore important that Class B observations distinguish between response biases, decisional biases, and perceptual biases. This review argues that the commonly used method of single stimuli fails to do this, and that multiple-alternative forced choice (mAFC) methods can do a better job, particularly if combined with a roving pedestal.

Publication Type: Article
Publisher Keywords: Psychophysics; Linking hypotheses; 2AFC; Method of single stimuli
Subjects: R Medicine > RE Ophthalmology
Departments: School of Health & Psychological Sciences > Optometry & Visual Sciences
Text - Published Version
Available under License Creative Commons: Attribution 3.0.

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