From: A new two-alternative forced choice method for the unbiased characterization of perceptual bias and discriminability
Journal of Vision. 2014;14(3):20. doi:10.1167/14.3.20
Figure Legend:
Measuring perceptual bias with the standard 2AFC method. (a) Example experiment: In order to measure how dot
coherence c may bias the perceived direction of motion θ of a random-dot stimulus, a subject is presented with a pair of
stimuli (test/reference) that differ in both stimulus parameters, i.e., direction θ and dot coherence c. The subject's task is
to judge the relative difference in motion direction θ (primary parameter) between the two stimuli by indicating which
stimulus' motion direction is e.g., “… more counterclockwise than the other.” Ideally, the subject's choice is exclusively
based on the perceived difference in motion directions Δθ between the stimuli. However, it cannot be ruled out that the
subject
may employ
an alternative, mixed
decision strategy
that also
takes
into
account the Copyright
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coherence Δ . (b) Ideally, perceptual bias is quantified as the shift of the psychometric function due to the difference in