Did I do that? Detecting a perturbation to visual feedback in a reaching task

Elon Gaffin-Cahn, Todd E. Hudson, Michael S. Landy

Research output: Contribution to journalArticlepeer-review


The motor system executes actions in a highly stereotyped manner despite the high number of degrees of freedom available. Studies of motor adaptation leverage this fact by disrupting, or perturbing, visual feedback to measure how the motor system compensates. To elicit detectable effects, perturbations are often large compared to trial-totrial reach endpoint variability. However, awareness of large perturbations can elicit qualitatively different compensation processes than unnoticeable ones can. The current experiment measures the perturbation detection threshold, and investigates how humans combine proprioception and vision to decide whether displayed reach endpoint errors are self-generated only, or are due to experimenter-imposed perturbation. We scaled or rotated the position of the visual feedback of center-out reaches to targets and asked subjects to indicate whether visual feedback was perturbed. Subjects detected perturbations when they were at least 1.5 times the standard deviation of trial-to-trial endpoint variability. In contrast to previous studies, subjects suboptimally combined vision and proprioception. Instead of using proprioceptive input, they responded based on the final (possibly perturbed) visual feedback. These results inform methodology in motor system experimentation, and more broadly highlight the ability to attribute errors to one's own motor output and combine visual and proprioceptive feedback to make decisions.

Original languageEnglish (US)
Article number5
Pages (from-to)1-18
Number of pages18
JournalJournal of vision
Issue number1
StatePublished - Jan 1 2019


  • Cue combination
  • Error detection
  • Feedback perturbation
  • Ideal observer
  • Sensorimotor

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems


Dive into the research topics of 'Did I do that? Detecting a perturbation to visual feedback in a reaching task'. Together they form a unique fingerprint.

Cite this