Vection in Depth during Treadmill Walking

Abstract

Vection has typically been induced in stationary observers (ie conditions providing visual-only information about self-motion). Two recent studies have examined vection during active treadmill walking-one reported that treadmill walking in the same direction as the visually simulated self-motion impaired vection (Onimaru et al, 2010 Journal of Vision 10(7):860), the other reported that it enhanced vection (Seno et al, 2011 Perception 40 747-750; Seno et al, 2011 Attention, Perception, & Psychophysics 73 1467-1476. Our study expands on these earlier investigations of vection during observer active movement. In experiment 1 we presented radially expanding optic flow and compared the vection produced in stationary observers with that produced during walking forward on a treadmill at a 'matched' speed. Experiment 2 compared the vection induced by forward treadmill walking while viewing expanding or contracting optic flow with that induced by viewing playbacks of these same displays while stationary. In both experiments subjects' tracked head movements were either incorporated into the self-motion displays (as simulated viewpoint jitter) or simply ignored. We found that treadmill walking always reduced vection (compared with stationary viewing conditions) and that simulated viewpoint jitter always increased vection (compared with constant velocity displays). These findings suggest that while consistent visual-vestibular information about self-acceleration increases vection, biomechanical self-motion information reduces this experience (irrespective of whether it is consistent or not with the visual input). Our study expands on these earlier investigations of vection during observer active movement. In experiment 1 we presented radially expanding optic flow and compared the vection produced in stationary observers with that produced during walking forward on a treadmill at a 'matched' speed. Experiment 2 compared the vection induced by forward treadmill walking while viewing expanding or contracting optic flow with that induced by viewing playbacks of these same displays while stationary. In both experiments subjects' tracked head movements were either incorporated into the self-motion displays (as simulated viewpoint jitter) or simply ignored. We found that treadmill walking always reduced vection (compared with stationary viewing conditions) and that simulated viewpoint jitter always increased vection (compared with constant velocity displays). These findings suggest that while consistent visual-vestibular information about self-acceleration increases vection, biomechanical self-motion information reduces this experience (irrespective of whether it is consistent or not with the visual input).

The Role of Perceived Speed in Vection: Does Perceived Speed Modulate the Jitter and Oscillation Advantages?

“…Logically, it could be argued that if perceived speed was greater for oscillating than for jittering stimuli, but the vection advantages were the same, then the mechanism underlying both could still be the same but something other than perceived speed. However, previous research suggests a close relationship between perceived speed and vection strength; manipulations which increase perceived speed, such as adding stereoscopic cues [35], [36] and increasing display size [37] also increase vection, while manipulations which decrease perceived speed, such as treadmill walking [40], also decrease vection. To the authors' knowledge, there are no clear reports of displays with slower perceived speeds inducing greater vection.…”

Future challenges for vection research: definitions, functional significance, measures, and neural bases

“…Observers in such studies typically viewed computer-generated self-motion displays while their bodies were physically in motion. The physical motions that accompanied these optic flow displays have been passive (i.e., externally generated) whole-body motions (Wright et al, 2005), or active (i.e., self-generated) head motions while seated (Kim and Palmisano, 2008, 2010; Ash et al, 2011a,b; Ash and Palmisano, 2012), active breaststroke body movements while standing (Seno et al, 2013a), or active walking on the spot (Palmisano et al, 2014a) or even on a treadmill (Onimaru et al, 2010; Seno et al, 2011a; Ash et al, 2013; Palmisano et al, 2014a). Using the illusory definitions of ‘vection’ outlined above to describe self-motion perception in these situations appears problematic.…”

“…In principle, vection could be defined even more broadly as the conscious subjective experience of self-motion (as in Ash et al, 2013). Interestingly, the earliest definitions that we are able to find (Fischer and Wodak, 1924; Fischer, 1928; Fischer and Kornmüller, 1930) appear to use vection (or rather ‘vektionen’) in exactly this way.…”

Evidence against an ecological explanation of the jitter advantage for vection

“…On different trials, these self-motion displays were viewed either while standing still, walking in place, or walking forward on the motorized treadmill (ProForm PF 4.0). Participant head position and orientation were continuously recorded during both types of walking trial, via an ultrasonic Logitech 3-D head tracker (see Ash et al, 2013 for details). For safety reasons, participants wore a ceiling mounted B-Safe body harness throughout the entire experiment (during both walking and standing still blocks).…”