Experimental Brain Research

, Volume 149, Issue 4, pp 470–477 | Cite as

Grasp effects of the Ebbinghaus illusion: obstacle avoidance is not the explanation

  • V. H. FranzEmail author
  • H. H. Bülthoff
  • M. Fahle
Research Article


The perception-versus-action hypothesis states that visual information is processed in two different streams, one for visual awareness (or perception) and one for motor performance. Previous reports that the Ebbinghaus illusion deceives perception but not grasping seemed to indicate that this dichotomy between perception and action was fundamental enough to be reflected in the overt behavior of non-neurological, healthy humans. Contrary to this view we show that the Ebbinghaus illusion affects grasping to the same extent as perception. We also show that the grasp effects cannot be accounted for by non-perceptual obstacle avoidance mechanisms as has recently been suggested. Instead, even subtle variations of the Ebbinghaus illusion affect grasping in the same way as they affect perception. Our results suggest that the same signals are responsible for the perceptual effects and for the motor effects of the Ebbinghaus illusion. This casts doubt on one line of evidence, which used to strongly favor the perception-versus-action hypothesis.


Motor control Visual pathways Illusions Prehension Human 



We wish to thank Martin S. Banks, Ian M. Thornton, Fiona N. Newell, and Alexander Holub for helpful comments on earlier versions of this manuscript. This work was supported by the grant FA 119/15-3 from the Deutsche Forschungsgemeinschaft (DFG) and by the Max Planck Society.


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Copyright information

© Springer-Verlag 2003

Authors and Affiliations

  1. 1.Max Planck Institut für Biologische KybernetikTübingenGermany
  2. 2.Human-NeurobiologieUniversität BremenBremenGermany

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