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Larissa D'Abreu, Timothy Sweeny; Shape interactions require more than feedforward representation. Journal of Vision 2017;17(10):46. doi: 10.1167/17.10.46.
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© ARVO (1962-2015); The Authors (2016-present)
At any moment, some objects in the environment are seen clearly whereas others elude visual awareness. Objects that go unseen may be missed because they fail to engage reentrant processing from higher- to lower-levels of visual analysis. Nevertheless, several investigations suggest that these unseen objects are processed, at least to some extent, in a feedforward wave of representation, and that this processing can influence attention and even bias other perceptual judgments. Here, we attempted to understand the depth of feedforward representation at an intermediate level of visual analysis. Object-substitution masking (OSM) is thought to prevent feedback activity while preserving feedforward activity. Thus, we used OSM to evaluate whether the feedforward representation of an unseen shape's aspect ratio is potent enough to influence the appearance of another nearby shape that is clearly visible. Observers viewed two simultaneously presented ellipses on each trial for 17msec. An arrow appeared after the ellipses disappeared, cueing observers to rate the aspect ratio (e.g. how tall or flat, using a magnitude matching screen) of one ellipse from the pair. On some trials, the uncued ellipse was masked by four adjacent dots that lingered after its offset for 240 msec. On each trial, we measured subjective awareness by asking observers how many ellipses they saw clearly. As expected, the aspect ratio of the cued ellipse was biased toward that of the uncued ellipse on control trials with no masking—perceptual averaging. Crucially, this averaging effect did not occur when the uncued ellipse was successfully masked. Interestingly, when observers indicated that they saw both ellipses, we found a significant effect of perceptual averaging intermediate between the other conditions. These results suggest that feedforward representation of an unseen object is insufficient to influence the perception of a nearby object, at least at intermediate levels of visual analysis.
Meeting abstract presented at VSS 2017
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