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Tasfia Ahsan, Laurie M. Wilcox, Erez Freud; Perceived depth modulates the precision of visual processing. Journal of Vision 2020;20(11):1179. doi: https://doi.org/10.1167/jov.20.11.1179.
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Humans constantly use depth information to support perceptual decisions about object size and location, as well as planning and executing actions. Given the unique role of depth information in human vision, it has been proposed that perceived depth might influence visual processing. In particular, objects that are perceived as closer to the observer are processed by dedicated neural resources because they are more behaviorally relevant for both perception and action. Consistent with this proposal, there is evidence that shape discrimination is better for objects perceived as being closer to the observer. However, it is not clear from these studies if the reported processing advantage reflects changes in psychophysical sensitivity or bias. Here we evaluate whether visual resolution is modulated by perceived depth defined by 2D pictorial cues (perspective and size). In a series of experiments, we used the method of constant stimuli to measure discrimination thresholds for the length (Experiment 1) and orientation (Experiment 2) of pairs of lines. Just Noticeable Differences (JND) as well as Reaction Times (RT) were measured for pairs of stimuli positioned either on the ‘near’ or ‘far’ portion of the Ponzo Illusion, as well as a neutral version with no depth cues ‘flat’. In both experiments, despite the fact that all stimuli were physically at the same distance, we found enhanced discrimination for objects perceived as closer in depth. Importantly, the improvement associated with location in depth was observed for both the JND and RT measures. Taken together, our results provide novel evidence that the location of an object in depth, as defined by pictorial cues, modulates the precision of visual processing.
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