Astrid J.A. Lubeck, MSc 1 Jelte E. Bos, PhD 1,2 John F. Stins, PhD 1 1 Research Institute MOVE, Faculty of Human Movement Sciences, VU University Amsterdam, the Netherlands 2 TNO Perceptual and Cognitive Systems, Soesterberg, the Netherlands Moving and still images can induce comparable amounts of postural sway, but different levels of sickness 1

Introduction Studies about the effect of moving images General design experiments 1.Pre- and post measurement 2.Variables: Postural Sway Visually induced motion sickness (VIMS) 3.Exposure to moving images Result – Postural sway ↑, VIMS ↑ Are these results caused by motion? 2

Introduction Research question and hypothesis Research question – Is motion essential for causing an increase in postural sway and VIMS? Hypothesis – Motion does cause an increase in postural sway and VIMS. No changes in still images condition. Changes in moving images condition. 3

Method Subjects and design Subjects – 15 subjects – 6 males, 9 females – Mean (SD) age: 29.5 (5.9) years Design – Within subject design – Experimental condition: Moving images – Control condition: Still images – 2 measurements: Pre and post 4

Method Images 5

Method Measurements Postural sway – Force plate – Normal double stance Eyes closed – Duration: 60 seconds – Center of pressure (CoP) data Sway path length Visually induced motion sickness (VIMS) – Simulator sickness questionnaire (SSQ; Kennedy et al., 1993) – Only total score 6

Results Total simulator sickness scores 7

Results Sway path length 8

Discussion Postural sway – Increase in SPL after exposure to both moving and still images VIMS – Only an increase in VIMS after exposure to moving images No difference in postural sway after exposure – Puzzling? 9 Puzzling results?

Discussion 10 2 possible explanations

Wallpaper illusions – Can cause changes in postural sway (Kelly et al., 2005) – Can cause disorientation (Cohn & Lasley, 1990) Discussion Moved by still images

Discussion Moved by a first person shooter (FPS) game 12

Vection – Illusion of self-motion Do players experience vection or some other sensation? – Images may not contain adequate flow Sustained and unidirectional – Other possible mechanisms at work? Discussion Vection in FPS games?

Still images can cause an increase in postural sway but only moving images cause motion sickness. Conclusion Take home message

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