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Why some size illusions affect grip aperture.

Jeroen B J Smeets1, Erik Kleijn2, Marlijn van der Meijden2

  • 1Department of Human Movement Sciences, Vrije Universiteit Amsterdam, van der Boechorststraat 9, 1081 BT, Amsterdam, The Netherlands. J.B.J.Smeets@vu.nl.

Experimental Brain Research
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PubMed
Summary
This summary is machine-generated.

This study investigated how perceived object size influences grasping. Researchers found that visual illusions affecting perceived size did not impact grasping actions, regardless of object size, suggesting grasping relies on perceived positions, not just size.

Keywords:
GraspingInconsistencyPrehensionVisual illusionWeber’s law

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Area of Science:

  • Cognitive Psychology
  • Neuroscience
  • Motor Control

Background:

  • The role of perceived object size in guiding grasping actions remains debated.
  • Previous research suggests grasping may prioritize precise positional information over size judgments.
  • The Ebbinghaus illusion, affecting perceived size, has yielded mixed results on grasping, particularly with small objects.

Purpose of the Study:

  • To test the hypothesis that size information is used for grasping small objects but not large ones.
  • To investigate the influence of visual illusions on grasping actions.
  • To clarify the role of perceived size versus perceived position in motor control.

Main Methods:

  • A modified diagonal illusion was employed to manipulate perceived size.
  • Participants' perceptual judgments and grasping actions were recorded.
  • The study examined effects across different object sizes.

Main Results:

  • A significant ~10% effect of the illusion on perceptual judgments was observed.
  • No significant effect of the illusion on grasping actions was found, irrespective of object size.
  • The precision hypothesis was rejected based on these findings.

Conclusions:

  • Grasping movements appear to be guided by perceived object positions rather than perceived size.
  • Discrepancies in previous findings may stem from illusions affecting both perceived size and position.
  • The Ebbinghaus illusion's impact on perceived positions, unlike other size illusions, is a key factor.