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Marina Zannoli, Pascal Mamassian; The effect of expectancies on stereoacuity. Journal of Vision 2012;12(9):217. doi: 10.1167/12.9.217.
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© ARVO (1962-2015); The Authors (2016-present)
Classical conditioning can be used to teach the visual system to use new cues to bias visual percepts (Haijiang et al., PNAS, 2006). In the present study we investigated whether expectancies on the depth of a visual object can influence sensitivity to perceive its fine structure. To test this possibility, we measured stereoacuity: participants were asked to judge the relative depth of two black lines presented 0.2 degrees apart on a grey background for 200 ms. A 400 ms pure tone was presented starting 200 ms before the presentation of the visual stimulus. Participants were told to ignore the auditory tone and focus on the visual task. An adaptive staircase procedure was used to measure the disparity threshold corresponding to 75 percent correct performance. Stereoacuity was measured in four interleaved experimental conditions. Test lines were presented either behind (at a mean disparity of -15 arcmin) or in front (+15 arcmin) of a frame. When in front, the lines were accompanied by a high pitch sound (660 Hz pure tone) in 75% of the trials (expected condition) and by a low pitch sound (440 Hz) in 25% of the trials (unexpected condition). When behind, these proportions were reversed. Among seven participants tested, five showed shorter response times in the expected condition, indicating an efficient association between pitch and mean disparity. For three of these successfully associated participants we observe a trend for a worse sensitivity for the unexpected condition compared to the expected condition. These results suggest that the stereoscopic system is able to learn cues to predict the position of objects in depth and to use this prediction to increase its sensitivity.
Meeting abstract presented at VSS 2012
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