Effects of visual illusions on grasping

In 2 experiments, the Muller-Lyer illusion (F. C. Muller-Lyer, 1889; N = 16 ) and the parallel-lines illusion (W. Wundt, 1898; N = 26) clearly affected maximum preshape aperture in grasping (both ps < .001). The grasping effec ts were similar but not perfectly equal to the perceptual effects. Control experiments show that these differences can be attributed to problems in ma tching the perceptual task and the grasping task. A model is described stat ing the assumptions that are needed to compare the grasping effects and the perceptual effects of visual illusions. Further studies on the relationshi p between perception and grasping are reviewed. These studies provide no cl ear evidence for a dissociation between perception and grasping and therefo re do not support the action versus perception hypothesis (A. D. Milner & M . A. Goodale, 1995).