Bimanual Grasping adheres to Weber’s Law

Constanze Hesse* (Corresponding Author), Roisin Elaine Harrison, Martin Giesel, Thomas Schenk

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Weber's law states that our ability to detect changes in stimulus attributes decreases linearly with their magnitude. This principle holds true for many attributes across sensory modalities but appears to be violated in grasping. One explanation for the failure to observe Weber's law in grasping is that its effect is masked by biomechanical constraints of the hand. We tested this hypothesis using a bimanual task that eliminates biomechanical constraints. Participants either grasped differently sized boxes that were comfortably within their arm span (action task) or estimated their width (perceptual task). Within each task, there were two conditions: One where the hands’ start positions remained fixed for all object sizes (meaning the distance between the initial and final hand-positions varied with object size), and one in which the hands’ start positions adapted with object size (such that the distance between the initial and final hand-position remained constant). We observed adherence to Weber's law in bimanual estimation and grasping across both conditions. Our results conflict with a previous study that reported the absence of Weber's law in bimanual grasping. We discuss potential explanations for these divergent findings and encourage further research on whether Weber's law persists when biomechanical constraints are reduced.
Original languageEnglish
Number of pages16
Journali-Perception
Volume16
Issue number6
Early online date25 Nov 2021
DOIs
Publication statusPublished - Nov 2021

Keywords

  • perception–action dissociation
  • psychophysics
  • two-visual streams

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