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Angela M.W. Lam, Alan L.F. Lee; Effects of local motion ambiguity on perceptual confidence. Journal of Vision 2019;19(10):285d. doi: https://doi.org/10.1167/19.10.285d.
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Perceptual confidence refers to an observer’s judgment about his/her own performance in a perceptual task. It has been found to correlate with task performance in general, and is believed to be independent of stimulus features. However, certain stimulus feature could induce a subjective sense of uncertainty, which could potentially influence confidence judgments beyond task performance. The present study aimed at assessing the effects of the ambiguity of local motion signals on perceptual confidence on a global-motion task. The stimulus was a multiple-aperture array consisting of 188 randomly-oriented elements. Each element was either a Gabor, which is ambiguous in signaling a global motion direction, or an orthogonal plaid, which consists of an unambiguous local motion signal. In each trial, participants discriminated the global motion direction on a Gabor pattern and a plaid pattern, one after another. Then, they performed a two-interval, forced-choice confidence task by choosing which of the two perceptual responses they were more confident in being correct. Perceptual task performance was controlled by varying coherence, defined as the proportion of elements signaling a coherent global motion (leftward or rightward). A range of differences in coherence between Gabors and plaids was tested to create differences in perceptual task performance between the two types of stimuli. This allowed us to measure bias in confidence choices by fitting a psychometric function for confidence choices across differences in performance between Gabors and plaids. We found that the point of subjective equality (PSE) for confidence choice tended to favor better perceptual performance for Gabors. In other words, observers chose plaids more often than Gabors when task performance was matched between the two patterns. This suggests that, at the same level of objective task performance, ambiguous local motion signals are perceived to be more uncertain than unambiguous ones.
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