Do Visual Pathways for Action and Perception Respond Differently to the Ebbinghaus Illusion



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Evidence from anatomical investigations and neurological patients suggests that visual pathways projecting to the posterior parietal cortex and the inferotemporal cortex may independently process visual information for action and perception, respectively (Goodale and Milner, 1992). The processing abilities of these pathways has been investigated using the Müller-Lyer and Ebbinghaus illusions by testing for significant differences in illusion magnitude when the illusion is evaluated perceptually or through grasping. Results from various studies have been inconsistent. The current study compared four compositions of the Ebbinghaus illusion and evaluated the effects of changes in the presentation of the illusion on perceptual and grasping illusion measures. When collapsed across condition, the perceptual illusion (M= 2.0 mm) was significantly larger than the grasping illusion (M= 0.2 mm). These results support the Goodale and Milner interpretation of vision for action and vision for perception.