title: Grasping the Müller-Lyer illusion: not a change in perceived length.
abstract: Peak grip aperture has often been used to quantify the influence of illusions on judgments of size for action. However, a larger peak grip aperture need not mean that the object looks larger. It could also mean that it was grasped more carefully. These two possibilities can be distinguished on the basis of the velocity of grip closure just before contact. We let people grasp a bar that was placed on the shaft of a Müller-Lyer figure. The Müller-Lyer figure influenced the peak grip aperture. It did not influence the velocity of grip closure in the way that one would expect if size were mis-perceived. Thus there is no reason to assume that the perceived size guides the way that we reach and grasp an object.
authors.affiliation: Department of Neuroscience, Erasmus MC, Rotterdam, The Netherlands.
authors.forename: Marianne
authors.initials: M
authors.lastname: Biegstraaten
authors.forename: Denise D J
authors.initials: DD
authors.lastname: de Grave
authors.forename: Eli
authors.initials: E
authors.lastname: Brenner
authors.forename: Jeroen B J
authors.initials: JB
authors.lastname: Smeets
mesh_terms: D000704:Analysis of Variance; D018737:Hand Strength / Q000502:physiology*; D006801:Humans; D008954:Models, Biological; D009903:Optical Illusions / Q000502:physiology*; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods; D011237:Predictive Value of Tests; D011597:Psychomotor Performance / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D012858:Size Perception / Q000502:physiology*