Simulator Sickness

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Simulator Sickness

• Mark Little
• November 14, 2007
• Psyc 562

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The Papers Involved

• Measurement of postural stability before and
  after immersion in a virtual environment
• Susan Valerie Gray Cobb
• Motion sickness and proprioceptive aftereffects
  following virtual environement exposure
• Kay M. Stanney, Robert S. Kennedy, Julie M.
  Drexler, Deborah L. Harm
• The nauseogenicity of two methods of navigating
  within a virtual environment
• P.A. Howarth, M. Finch

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Measurement of postural stability before and
after immersion in a virtual environment

• Postural stability or Postural equilibrium
• The ability of an individual to maintain balance
  and postural control
• Two major reflexes
• The vestibular ocular reflex (VOR) stability of
  objects on the retina
• The vestibular-spinal reflex stability while
  the individual is in motion

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Theories

• Sensory Conflict Theory
• Conflicting information from the three sensory
  inputs (visual, somatosensory, vestibular)
• Primary cause of motion sickness and postural
  instability
• Ecological theory of motion sickness and postural
  instability
• Postural instability is necessary for motion
  sickness.
• Motion sickness occurs when the individual cannot
  gain control of posture.

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Postural instability and Simulator Sickness

• Both are found after immersion in VE
• What is not clear is -
• Does the immersion induce both postural
  instability and simulator sickness
• Or
• Does pre-immersion postural instability
  predispose the individual to simulator sickness

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Experiment

• Pre-Immersion static and dynamic posture tests
• 20 min. immersion into virtual environment using
  a head mounted display
• Post-immersion static and dynamic posture tests.

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Results

• Found no significant effect for the dynamic
  tests.
• There was a significant effect found for the
  static test (mild)
• Low reliability in the static tests though
• Longer immersions in more dynamic virtual
  environments may induce higher levels of postural
  instability and simulator sickness.

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Motion sickness and proprioceptive aftereffects
following virtual environment exposure

• Proprioception and Postural stability
• This is study is looking at proprioception
  involving the arm and hand specifically, but the
  idea is similar
• Motion Sickness or Cybersickness
• Nausea and vomiting
• Oculomotor disturbances(eyestrain)
• Disorientation, Ataxia (postural stability)

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Proprioception

• Reaching movements in VE can be uncertain and
  inaccurate
• Example in virtual environment
• 59 error in perceived dimension of forward
  distance
• 28 error in height distance
• 50 error for lateral distance
• 59 error for speed perception
• Back in the real world
• After calibrating one self to the VE, it can take
  some time to go back.
• It can take hours or even days to adjust
• 60-90d after 12d of rotation

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Experiment

• Pointing task pre and post
• Simulator Sickness Questionaire Pre, Post, 30
  min Post
• VE Moving colored balls and running around
  columns

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Results

• Nausea, Oculomotor disturbances, and
  disorientation were all significant pre vs. post
• No significant differences between post and
  30min. Post questions
• Females tended to be more vulnerable to sickness
  than males (plt.0001)
• Subjects pointed significantly higher after the
  immersion, and to the left, though not
  significantly at plt.05

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The nauseogenicity of two methods of navigating
within a virtual environment

• Head secured vs. Head free and tracked

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Experiment

• Sickness Rating
• Every minute
• 20 min w/ head restrained
• 20 min w/o head restrained

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Results

• Feelings of sickness were significantly different
  between the two situations.

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Results cont.

• Restraining the head seems to have an effect on
  feelings of sickness under these situations.
• 1. 120 degree head turn resulted in 360 degree
  rotation in the game
• 2. Update lags when the head turned it would
  take a little time for that turn to appear on the
  visual display
• 3. When the head would stop, the visual display
  would continue to show motion for a little bit
• None of these were present under the
• Hand-control condition

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Sensory conflict theory

• The differences in these two conditions should be
  expected according to the sensory conflict
  theory.
• The authors also point out that novices initially
  explore virtual environments with considerable
  head movement, like they would in real life, but
  after a period of time, they change their
  strategy and use the hand controller for movement
  instead.