The influence of auditory velocity cues on distance reproduction during simulated self motion

Anna Siever, Frank Bremmer
Poster
Time: 2009-06-29  11:00 AM – 12:30 PM
Last modified: 2009-06-04

Abstract


Successful locomotion through space requires precise estimation of the direction and distance travelled (“path integration�). Previous studies showed that human subjects can use velocity information arising from visual, vestibular and somatosensory signals to reproduce passive linear displacements. In the present study, we investigated whether also auditory velocity cues influence the perception of travelled distances. In a first set of experiments, subjects had to reproduce a previously seen sequence of linear motion across a ground plane. Both in the passive and active displacement they heard a pure sinusoidal tone with a pitch being proportional to the simulated speed (test trials). Passive displacements had different constant velocities and distances. In twenty percent of the trials subjects heard white noise which was not modulated by the movement (catch trials). In both cases, test and catch trials, participants reproduced distances very accurately, i.e. the absence or presence of reliable auditory information had no apparent effect on the subject’s performance. In a second set of experiments, the passive displacements had different velocity profiles (constant, sinusoidal, complex). In one fifth of the trials the relationship between optical velocity and tone frequency was differently scaled during the active displacements, i.e. the pitch of the tone was either 30% higher or 30% lower than in the passive displacement (re-scaling, catch trials). Again, in trials without re-scaling, subjects reproduced distances very accurately and tended to replicate the velocity profile of the passive condition. In the catch trials, however, subjects’ performance was disturbed by the non-matching auditory velocity cue: When the pitch was 30% lower subjects used higher speeds, resulting in a substantial overshoot of travelled distance, whereas a higher pitch resulted in an undershoot of travelled distance. Our results clearly show that not only visual, vestibular and somatosensory signals but also auditory signals are used for path integration.

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