Resolving visual-tactual incongruity depends on sensory reliability
Multiple Paper Presentation

Marc O. Ernst
Max Planck Institute for Biological Cybernetics

Johannes Burge
School of Optometry, Vision Science Program, UC Berkeley

Martin S. Banks
School of Optometry, Vision Science Program, UC Berkeley

     Abstract ID Number: 11

Abstract
The visuomotor system recalibrates when visual and motor maps are in conflict, bringing the maps back into correspondence. For recalibration to occur, a conflict has to be detected. Here we investigate the effect of signal reliability on the rate of recalibration.

In a first study we showed that the rate of recalibration in a one-dimensional visually guided pointing task depends on the uncertainty of the feedback: faster recalibration with less uncertainty. We further also examined two-dimensional recalibration and how the specific form of visual feedback affects it. Subjects pointed with an unseen hand to a brief visual target. Visual feedback was given indicating where the point landed. We introduced a constant incongruity between pointing (tactual) and feedback (visual) location and examined the changes in pointing as the subject recalibrated. With this task we asked whether differential vertical and horizontal uncertainty in the visual feedback affects recalibration rate differentially, or whether rate is determined by the total uncertainty. We also varied feedback uncertainty in two ways. (1) We blurred the visual feedback, thereby reducing its localizability; in this condition, uncertainty could be determined on-line from one feedback stimulus. (2) We introduced random trial-by-trial perturbations in the feedback; in this condition, uncertainty had to be learned over time. In both cases, the distributions determining the vertical and horizontal uncertainties were 2D Gaussians.

Recalibration profiles (changes over time in the point location relative to the visual feedback) changed only in response to changes in localizability. Recalibration was slowest in the direction of greatest uncertainty when uncertainty was due to blur, but rate was unaffected by trial-by-trial variation. This means that subjects do not estimate uncertainty over time in order to adjust reaching. Rather, they adjust trial by trial based mostly on feedback from the previous trial.

To be Presented at the Following Symposium:
Experiencing objects through vision and touch
Other papers in this Symposium:

• Geke Ludden
  Industrial Design, Delft University of Technology
  *Rick Schifferstein
  Industrial Design, Delft University of Technology
  *Paul Hekkert
  Industrial Design, Delft University of Technology
  Visual – tactual incongruities as sources of surprise
• Fiona Newell
  Department of Psychology, Trinity College Dublin
  *Achille Pasqualotto
  Department of Psychology, Trinity College Dublin
  *Ignace Vendrell
  Institute of Neuroscience, Trinity College Dublin
  Visual and tactile spatial information is updated with observer movement.
• Soledad Ballesteros
  CEEN Research Institute UNED
  José Manuel Reales
  CEEN (UNED)
  Montserrat González
  CEEN (UNED)
  Beatriz García
  CEEN (UNED)
  Priming between modalities in normal aging and dementia