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Philipp Sterzer, Marie Lacroix, Katharina Schmack; Perception of ambiguous visual stimuli is flexibly modulated by associative learning. Journal of Vision 2011;11(11):750. doi: 10.1167/11.11.750.
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© ARVO (1962-2015); The Authors (2016-present)
Our perception of the world is strongly influenced by prior expectations. Accordingly, it has been shown repeatedly that experimental modification of expectations can change the appearance of visual stimuli. We asked whether perception of ambiguous visual stimuli is influenced by short-term changes in prior expectations. Thirty-four volunteers participated in a probabilistic reversal learning experiment where high or low tones were associated with leftward or rightward rotation of a subsequently presented rotating sphere stimulus. The stimulus was a random-dot kinematogram (RDK) where the direction of rotation was determined by disparity cues that yielded an unambiguous 3D appearance. The associaton of tones with rotation directions changed unpredictably every 16 to 32 trials in a probabilistic fashion. Randomly interspersed were RDK stimuli that lacked diparity cues and were thus ambiguous with respect to rotation direction, but indistinguishable in appearance from the unambiguous 3D stimuli. Participants were instructed to respond as fast and accurately as possible with a key press indicating the direction of rotation, and they also indicated their confidence about the reported percept after each trial. Reaction times in response to unambiguous stimuli that matched the predominant tone-rotation association in a given block were faster than responses to non-matching stimuli. Most importantly, ambiguous stimuli were more frequently perceived as rotating in the direction matching the currently predominant association. This effect was unlikely to be due to a generally lower confidence in the perception of ambiguous stimuli, as it also held when only trials rated at the highest confidence level were analysed. Across individuals, this perceptual effect of learned associations correlated with the effect on reaction times, indicating a link between the strength of associative learning and its effect on perception. These findings indicate that the perception of visual information is flexibly updated in accordance with even rapidly changing prior expectations.
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