Visuomotor 'immunity' to perceptual illusion: A mismatch of attentional demands cannot explain the perception-action dissociation

Michaela T Dewar, David P Carey

Research output: Contribution to journalArticlepeer-review


Recent findings of visuomotor immunity to perceptual illusions have been attributed to a perception-action division of labour within two anatomically segregated streams in the visual cortex. However, critics argue that such experimental findings are not valid and have suggested that the perception-action dissociations can be explained away by differential attentional/processing demands, rather than a functional dissociation in the neurologically intact brain: perceptual tasks require processing of the entire illusion display while visuomotor tasks only require processing the target that is acted upon. The present study examined whether grasping of the Müller-Lyer display would remain immune to the illusion when the task required the direction of attention or a related resource towards both Müller-Lyer shafts. Twelve participants were required to match and grasp two Müller-Lyer shafts bimanually (i.e. one with each hand). It was found that bimanual grasping was not significantly affected by the illusion, while there was a highly significant illusion effect on perceptual estimation by matching. Furthermore, it was established that this dissociation did not result from a differing baseline rate of change in manual estimation and grasping aperture to a change in physical object size. These findings provide further support for the postulated perception-action dissociation and fail to uphold the idea that grasping 'immunity' to the Müller-Lyer illusions merely represents an experimental artefact.
Original languageEnglish
Pages (from-to)1501-1518
Number of pages8
Issue number8
Publication statusPublished - 2006


  • adult
  • analysis of variance
  • attention
  • female
  • hand strength
  • humans
  • male
  • optical illusions
  • visual pattern recognition
  • photic stimulation
  • psychomotor performance
  • space perception

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