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Jorge Morales, Chaz Firestone; Does the world look flat? Sustained representation of perspectival shape. Journal of Vision 2019;19(10):15. doi: https://doi.org/10.1167/19.10.15.
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© ARVO (1962-2015); The Authors (2016-present)
Arguably the most foundational principle in perception research is that our visual experience of the world goes beyond the retinal image; we perceive the distal environment itself rather than the proximal stimulation it causes. Shape, in particular, may be the paradigm case of such “unconscious inference”: When a circular coin is rotated in depth, for example, we experience it as the circular object it truly is, rather than as the perspectival ellipse it projects on the retina. But what is the fate of such perspectival shapes? Once our visual system infers that an elliptical projection arose from a distally circular object, do our minds continue to represent the “ellipticality” of the rotated coin? If so, objectively circular objects should, when rotated, impair search for objectively elliptical objects. Here, four experiments demonstrate that this is so, suggesting that perspectival shape representations persist far longer than is traditionally assumed. Subjects saw a simple two-item search array containing cue-rich images of differently shaped 3D “coins”; their task on each trial was simply to locate a distally elliptical coin. Surprisingly, objectively circular coins slowed search for elliptical objects when the circular coins were rotated in depth, even when subjects clearly reported seeing them as circular. This pattern arose for images containing both static (Exp.1) and motion-based (Exp.2) depth cues, and it held not only for speeded judgments but also in a delayed-judgment condition in which subjects viewed the coins for a sustained period before responding (Exp.3). Finally, a completely different paradigm (Exp.4) showed that viewing a rotated circular object boosted subsequent identification of an elliptical line-drawing, suggesting that rotated objects also prime their perspectival shapes. We conclude that objects in the world have a surprisingly persistent dual character in the mind: Their objective shape “out there”, and their perspectival shape “from here”.
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