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D. Alfred Owens, Xiaoyu Zhang, Alexander Nalbandian, Johnny Lawrence; Two Modes of Motion Perception: A Double-dissociation of the effects of contrast and field of view on perception of object-motion and self-motion. Journal of Vision 2011;11(11):917. doi: 10.1167/11.11.917.
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Several studies have shown that reduced contrast causes an illusory reduction in the perceived speed (e.g., Thompson, 1982). However, a more recent investigation of driving behavior found no effect of reduced contrast on drivers' perception and control of their vehicle's speed (Owens, Wood, & Carberry, 2002, 2010). This empirical discrepancy raised the question of whether the illusory changes in perceived speed with reduced contrast are specific to object motion. To answer this question, we tested the effects of reduced contrast and limited field of view (FOV) on visual perception of (a) object-motion and (b) self-motion. In Experiment I, participants matched the apparent speed of two rotating textured disks. Like the “Thompson Effect,” reduced contrast produced a significant decrease in perceived speed of rotation. Perceived speed was not affected, however, when FOV was reduced to 5°. In Experiment II, posture and vection were recorded while participants viewed the interior of a large rotating drum, which created roll vection. Unlike the “Thompson Effect,” reduced contrast had no effect on perception of self-motion or posture. Vection decreased significantly, however, when FOV was reduced to 5°. These results represent a double dissociation of two modes of motion perception: Contrast affects perception of object-motion but not perception of self-motion; whereas, reduced FOV affects perception of self-motion but not perception of object-motion. Consistent with previous investigations of the effects of blur and reduced luminance on vection and vehicle control (Leibowitz et al., 1979; Owens et al., 1999, 2007, 2010), the present findings add evidence for two functionally distinct “modes of vision:” a focal mode that mediates object perception and an ambient mode that mediates perception of posture and self-motion.
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