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Noga Pinchuk-Yacobi, Ron Dekel, Dov Sagi; Expectation and the tilt aftereffect. Journal of Vision 2015;15(12):39. doi: https://doi.org/10.1167/15.12.39.
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© ARVO (1962-2015); The Authors (2016-present)
Exposure to oriented stimuli leads to a bias in the perceived orientation of subsequently viewed stimuli (tilt aftereffect, TAE). This is traditionally attributed to sensory adaptation, and viewed as a stimulus-driven process, independent of stimulus predictability. Here, we tested whether the magnitude of the TAE is modulated by expectations, and specifically, whether TAE depends on the congruency of adapted and expected orientations. Observers were presented at fixation with successive pairs of oriented Gabor patches (s=0.6°, l=0.3°). Each Gabor was presented for 50ms with 600ms interval between pair members (pairs were separated by 1-1.5secs). Gabor pairs were arranged in blocks, forming two experimental conditions with orientation either expected or not expected. For all blocks, the orientation of the first Gabor in each pair was randomized (±20° relative to vertical). In the ‘expected’ condition, the orientation of the second Gabor correlated, either positively or negatively, in different sessions, with that of the first Gabor. In the ‘not-expected’ condition, the orientation of the second Gabor was independent of the first Gabor (randomized ±20°). Intermixed test trials (33%) were used to measure the shift in subjects’ perceived vertical, with the second pair member serving as a target, oriented around the vertical, permitting a measurement of the TAE produced by the presentation of the first Gabor member. Presentation of the oriented Gabors led to a tilt aftereffect, which was modulated by the expected orientation. The aftereffect was significantly higher (N=5; p< 0.01, pairwise t-test) in the positively correlated blocks (1.6°±0.2SE) than in the corresponding ‘not expected’ blocks (1.0°±0.3SE). In the negatively correlated blocks (N=2), the aftereffect was lower (0.6°±1.1SE) than in the corresponding ‘not expected’ blocks (1.0°±0.7SE). These findings indicate a role of expectation in generating the perceptual tilt aftereffect and are in line with predictive coding models of perception. Acknowledgement: BRF/ISF.
Meeting abstract presented at VSS 2015
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