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Emma Gregory, Michael McCloskey; Perceiving and representing the orientation of objects: Evidence from a developmental deficit in visual orientation perception. Journal of Vision 2010;10(7):1003. doi: 10.1167/10.7.1003.
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© ARVO (1962-2015); The Authors (2016-present)
Perceiving and representing the orientations of objects is important for interacting with the world. For example, accurate orientation information allows us to interpret visual scenes, comprehend symbols and pick up objects. Despite its importance, little is known about how the visual system represents object orientation. One potential clue, however, comes from the tendency to confuse mirror images. In previous work we explored mirror image confusion in normal adults' memory for orientation. The present study probes perceptual representations of object orientation by investigating the mirror image confusions made by AH, a woman with a remarkable developmental deficit in perceiving the locations and orientations of objects. We describe a framework that conceives of orientation as a relationship between reference frames. The COR (coordinate-system orientation representation) framework assumes that object orientation representations map an object-centered reference frame onto a reference frame extrinsic to the object, which may in turn be related to additional extrinsic frames. Moreover, for each of these mappings, the representations are compositional, involving several parameters. According to COR, mirror image confusions result from failures in encoding, retaining or processing specific parameters. We present new data from AH in support of COR assumptions. AH's systematic pattern of mirror reflection errors in copying pictures of objects provides evidence for the compositionality of orientation representations, and the role of object-centered frames and mappings between extrinsic frames in representation of orientation. AH makes similar mirror reflection errors when reaching for objects, suggesting the hypothesized orientation representations also play a role in visually-guided action. Finally, the fact that AH's errors arise at a perceptual level, in contrast with errors made by adults in memory, supports the idea that orientation representations have similar structure at multiple levels of processing.
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