Evidence against an ecological explanation of the jitter advantage for vection.

Stephen Palmisano,Deborah Apthorp,Robert S Allison,April Ash,Shinji Nakamura

doi:10.3389/fpsyg.2014.01297

Abstract

Visual-vestibular conflicts have been traditionally used to explain both perceptions of self-motion and experiences of motion sickness. However, sensory conflict theories have been challenged by findings that adding simulated viewpoint jitter to inducing displays enhances (rather than reduces or destroys) visual illusions of self-motion experienced by stationary observers. One possible explanation of this jitter advantage for vection is that jittering optic flows are more ecological than smooth displays. Despite the intuitive appeal of this idea, it has proven difficult to test. Here we compared subjective experiences generated by jittering and smooth radial flows when observers were exposed to either visual-only or multisensory self-motion stimulations. The display jitter (if present) was generated in real-time by updating the virtual computer-graphics camera position to match the observer’s tracked head motions when treadmill walking or walking in place, or was a playback of these head motions when standing still. As expected, the (more naturalistic) treadmill walking and the (less naturalistic) walking in place were found to generate very different physical head jitters. However, contrary to the ecological account of the phenomenon, playbacks of treadmill walking and walking in place display jitter both enhanced visually induced illusions of self-motion to a similar degree (compared to smooth displays).

Highlights

As we move through the world, we detect our self-motion using multiple senses, including vision, the vestibular system of the inner ear, proprioception, somatosensation, and audition (Gibson, 1966; Dichgans and Brandt, 1978; Howard, 1982; Benson, 1990)
Sensory conflict theories have been challenged by findings that adding simulated viewpoint jitter to inducing displays enhances visual illusions of self-motion experienced by stationary observers
HEAD MOVEMENT ANALYSIS In the introduction we hypothesized that head jitter amplitudes and frequencies would differ significantly in the “more ecological” treadmill walking and“less ecological”walking in place conditions

Summary

Introduction

As we move through the world, we detect our self-motion using multiple senses, including vision, the vestibular system of the inner ear, proprioception, somatosensation, and audition (Gibson, 1966; Dichgans and Brandt, 1978; Howard, 1982; Benson, 1990). While the visual system is able to detect both constant and accelerating self-motions (based on the optical flow presented to the moving observer), the inertial sensors comprising the vestibular end organs only respond to acceleration (Howard, 1982; Benson, 1990) Given this limitation of the vestibular system, it was long considered that: (a) visually simulated smooth/constant self-motions should induce the strongest vection – since such displays would be expected to produce minimal visual-vestibular conflict in stationary observers; and (b) visually simulated self-acceleration would impair, or possibly even destroy, vection – since the vestibular stimulation normally accompanying this simulated self-motion would be absent (Zacharias and Young, 1981). Despite the expected increases in sensory conflict, adding visually simulated viewpoint jitter to optic flow has been shown to significantly decrease vection onset latencies, lengthen vection durations and strengthen vection ratings (e.g., Palmisano et al, 2000; see Palmisano et al, 2011 for a review)

Results

Discussion

Conclusion