A motor signal and "visual" size perception

David Peter Matthew Carey, Kevin Allan

Research output: Contribution to journalArticlepeer-review

30 Citations (Scopus)


Recent models of the visual system in primates suggest that the mechanisms underlying visual perception and visuomotor control are implemented in separate functional streams in the cerebral cortex. However, a little-studied perceptual illusion demonstrates that a motor-related signal representing arm position can contribute to the visual perception of size. The illusion consists of an illusory size change in an afterimage of the hand when the hand is moved towards or away from the subject. The motor signal necessary for the illusion could be specified by feedforward and/or feedback sources (i.e. efference copy and/or proprioception/kinesthesis). We investigated the nature of this signal by measuring the illusion's magnitude when subjects moved their own arm (active condition, feedforward and feedback information available), and when arm movement was under the control of the experimenter (passive condition, feedback information available). Active and passive movements produced equivalent illusory size changes in the afterimages. However, the illusion was not obtained when an after-image of subject's hand was obtained prior to movement of the other hand from a very similar location in space. This evidence shows that proprioceptive/kinesthetic feedback was sufficient to drive the illusion and suggests that a specific three-dimensional registration of proprioceptive input and the initial afterimage is necessary for the illusion to occur.
Original languageEnglish
Pages (from-to)482-486
Number of pages5
JournalExperimental Brain Research
Issue number3
Publication statusPublished - 1 Aug 1996


  • Afterimage
  • Arm
  • Feedback
  • Female
  • Functional Laterality
  • Humans
  • Kinesthesis
  • Male
  • Optical Illusions
  • Proprioception
  • Psychomotor Performance
  • Reference Values
  • Size Perception
  • Visual Perception
  • Efference Copy
  • Two Visual Systems
  • Emmert's Law


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