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Ryosuke Niimi, Kazuhiko Yokosawa; Recognizing orientation of depth-rotated familiar objects. Journal of Vision 2006;6(6):317. doi: 10.1167/6.6.317.
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© ARVO (1962-2015); The Authors (2016-present)
Familiar objects can be seen in various orientations depending on viewpoints. Visual recognition of object orientation seems important for numbers of cognitive tasks including object recognition. Visual representation of object is either viewpoint-invariant or viewpoint-dependent, yet object orientation will not be coded in viewpoint-invariant representations. Then we hypothesized that visual recognition of object orientation is influenced by viewpoints. Subjects detected differences of object orientation between simultaneously presented two pictures of identical familiar objects (Experiment 1). The performances were best at 0 and 180 degrees (i.e. the front and back views). 90 degrees (side view) yielded better performance than other oblique orientations, yet further analysis suggested it was due to local visual features such as orientation of linear object contours. Experiment 2, in which two pictures of different objects were presented, again produced best performances at 0 and 180 degrees, although the error rate increased overall. These results showed that recognition of object orientation is highly viewpoint-dependent. We assumed three determinants of the phenomenon: (a) Since front and back views are accidental, they provide highly viewpoint-specific representation and precise coding of object orientation. (b) Since the stimulus objects were bilaterally symmetric, the front and back views had symmetric contours and others had not. A presence-absence judgment of 2D symmetry could contribute to the high sensitivity in those views, although the subjects reported no introspection about symmetry. (c) Orientation of linear contours, especially in the side view.
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