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Shai Azoulai, Donald MacLeod; Hemispheric Differences in the Kinetic Depth Effect. Journal of Vision 2009;9(14):51. doi: 10.1167/9.14.51.
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© 2015 Association for Research in Vision and Ophthalmology.
Rotating 3D silhouettes are bistable images, similar to Necker Cubes; because they lack any depth cues from shading they will occasionally appear to have a sudden change in their direction of rotation. This is due to the brain's reinterpretation of the depth information and a subsequent mirror reversal of the silhouette (Left becomes Right and vice-versa).
We presented subjects with a series of rotating 3D silhouettes and other moving bistable images. The images appeared to the Left, Right, or center of a focus point. Subjects were instructed to keep their eyes on the focus point and indicate when a direction change occurred.
The data showed that subjects experienced more direction changes when the image was in their Right visual field and being processed by the Left Hemisphere.
We believe this result may be related to the fact that in static images the left hemisphere has a bias to the details and the right hemisphere has a bias for the big picture, as demonstrated in stroke victims using hierarchical letters.
Since right hemisphere has a bias towards global processing it is possible that the bistable image is more “sticky” in the right hemisphere and thus less likely to get reinterpreted by the brain and switch directions.
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