Grasp Point Selection, Perceptual Judgment and Object Symmetry

SJ Lederman, Alan Wing

Research output: Contribution to journalArticle

53 Citations (Scopus)


Object symmetry is a visual attribute that may contribute to perceptual judgement and to action. We evaluated the effects of varying the physical symmetry of planar objects (presence versus absence) on both aspects. In Experiment 1, subjects estimated the magnitude of visually perceived symmetry of the objects. The results confirmed the influence of physical symmetry on perceived symmetry, and supported our binary categorisation of stimulus objects in terms of presence versus absence of physical symmetry. In Experiment 2, participants used a precision grip to grasp and stably lift the same planar objects varying in degree of symmetry. Choice of grasp points was unrestricted. Participants selected a grasp axis (between thumb and middle finger) that limited the perpendicular distance from CM (i.e., grasp-axis error) to just a few millimetres. Moreover, they took advantage of visual cues to object symmetry to better determine CM, thus reducing their grasp-axis error for symmetric (vs. asymmetric) objects by 31%. We interpret these findings in terms of user and object-geometry constraints on grasp-point selection.
Original languageEnglish
Pages (from-to)156-165
Number of pages10
JournalExperimental Brain Research
Publication statusPublished - 1 Sept 2003


  • grasp
  • visually-guided action
  • object symmetry
  • perceived object symmetry
  • grasp-axis orientation


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