How robust are the deviations in haptic parallelity?

Astrid M L Kappers*, Albert Postma, Roderik F. Viergever

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review


Several studies have shown that physically parallel bars do not feel parallel and vice versa. The most plausible cause of this deviation is the biasing influence of an egocentric reference frame. The aim of the present study was to assess the strength of this egocentric contribution. The deviations from veridicality were measured in six experiments where subjects were presented with either haptic or visual information about parallelity or their deviations. It was found that even direct error feedback (either haptically or visually) did not even nearly result in veridical performance. The improvements found were attributed to a shift in focus towards a more allocentric reference frame, possibly reflecting the same mechanisms as found in delay and noninformative vision studies. We conclude that the illusionary percept of haptic parallelity is rather robust and is indeed caused by a strong reliance on an egocentric reference frame.

Original languageEnglish
Pages (from-to)15-24
Number of pages10
JournalActa Psychologica
Issue number1
Publication statusPublished - May 2008


  • Allocentric
  • Egocentric
  • Feedback
  • Frame of reference
  • Haptic spatial perception
  • Parallel
  • Training


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