Human Factors in VR

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Human Factors in VR
Electrical and Computer Engineering Dept.
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System architecture
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Human factors in VR
(Stanney et al., 1998)
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Human factors in VR
Will the user get sick in VR?
How should VR technology be improved to better
meet the users needs?
?
Which tasks are most suitable for users in
VR?
How much feedback from VR can the user process?
Which user characteristics will influence VR
performance?
Will the user perceive system limitations?
Will there be negative societal impact from
users misuse of the technology?
What kind of designs will enhance users
performance in VR?
(Stanney et al., 1998)
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• Human factors vocabulary
• HF study series of experiments in very
  rigorous conditions aimed at the user (can be
  controlled or case study)
• Experimental protocol establishes a structured
  sequence of experiments that all participants
  need to perform
• Trial a single instance of the experiment
• Session - a sequence of repeated trials
• Rest period time between sessions
• Experimental database files that store
  experimental data
• Institutional Review Board (IRB) watchdog
  office regulating HF experiments
• Principal Investigator (PI) person conducting
  the HF study. Needs to be certified by the IRB

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• H. F. vocabulary - continued
• Subject - a participant in a HF study (male or
  female, age, volunteer or paid, right handed or
  left handed, normal or disabled, etc)
• Experimental group subjects on which the
  experiments are done
• Control group a number of subjects used for
  comparison with the experimental group
• Controlled study a study that uses both an
  experimental and control group
• Case study (also called pilot study) smaller
  study with no control group.
• Consent form needs to be signed by all
  participants into the study
• Baseline test measurement of subjects
  abilities before trial

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Human factors in VR
Health and Safety
Societal Implications
(Stanney et al., 1998)
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Determine focus
Develop experim. protocol
The stages of human factors studies
Recruit subjects
Conduct study
Analyze data
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Determine focus
Develop experim. protocol
The stages of human factors studies
Recruit subjects
Conduct study
Analyze data
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• Human factors focus
• What is the problem? (ex. People get headaches)
• Determines the hypothesis (ex. Faster graphics
  is better)
• Establishes type of study (usability,
  sociological, etc.)
• Objective evaluation, subjective evaluation or
  both?

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Determine focus
Develop experim. protocol
The stages of human factors studies
Recruit subjects
Conduct study
Analyze data
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• Experimental protocol
• What tasks are done during one trial?
• How many trials are repeated per session?
• How many sessions per day, and how many days for
  the study?
• How many subjects in experimental and control
  group?
• What pre and post-trial measurements are done?
• What variables are stored in the database?
• What questions on the subjective evaluation form?

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Determine focus
Develop experim. protocol
The stages of human factors studies
Recruit subjects
Conduct study
Analyze data
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• Subject recruitment
• Sufficient number of subjects need to be
  enlisted in the study to have statistical
  significance
• Place advertisements, send targeted emails, web
  posting, go to support/focus groups, friends,
  etc.
• Subjects are screened for unsuitability to
  study
• Subjects sign consent form
• Subjects are assigned a code to protect
  identity
• Subjects sign release for use of data in
  research, etc.
• Subjects may get exposure to technology

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Determine focus
Develop experim. protocol
The stages of human factors studies
Recruit subjects
Conduct study
Analyze data
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Determine focus
Develop experim. protocol
The stages of human factors studies
Recruit subjects
Conduct study
Analyze data
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• Data Collection
• VR can sample much larger quantity of data and
  at higher temporal density than classical
  paper-and-pencil methods
• Measurements need to be sensitive (to distinguish
  between novice and expert users), reliable
  (repeatable and consistent) and valid (truthful)
• Latencies and sensor noise adversely affect
  these requirements.

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• Data Analysis
• Experiments store different variables, depending
  on the type of test
• task completion time time needed to finish the
  task (system time, sequence of actions, or
  stopwatch)
• task error rate number or percentage of errors
  done during a trial
• task learning a decrease in error rate, or
  completion time over a series of trials
• Analysis of Variation (ANOVA) statistical
  package used to analyze data and determine if
  statistical difference exists between trials or
  conditions.

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Human factors in VR
Human Performance Efficiency
Societal Implications
(Stanney et al., 1998)
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Effects of VR Simulations on users
The effects VR simulations have on users can be
classified as direct and indirect
Definitions Direct effects involve energy
transfer at the tissue level and are potentially
hazardous Indirect effects are neurological,
psychological, sociological,or cybersickness and
affect the user at a higher functional level.
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Direct Effects of VR Simulations on Users

• Affect mainly the users visual system, but also
  the auditory, skin and musculoskeletal systems
• Effects on the visual system occur when the user
  is subjected to high-intensity lights directed at
  his eyes (like Lasers used in retinal displays
  (if they malfunction), or IR LEDs as part of eye
  tracking systems
• An absence state can be induced in a user
  subjected to pulsing lights at low frequency
  (1-10 Hz)
• Bright lights coupled with loud pulsing sounds
  can induce migraines (20 of women and 10 of men
  are prone to migraines.
• Direct effects on the auditory system are due to
  simulation noise that has too high a level (115
  dB after more than 15 minutes)
• Effects on the skin and muscles are due to
  haptic feedback at too high a level.

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Cyber sickness

• User safety concerns relate primarily to cyber
  sickness, but also to body harm when haptic
  feedback is provided
• Cyber sickness is a form of motion sickness
  present when users interact with virtual
  environments
• Cyber sickness has three forms
• Nausea and (in severe cases) vomiting
• Eye strain (Oculomotor disturbances)
• Disorientation, postural instability (ataxia)
  and vertigo.
• Flight simulators have an incidence of up to 60
  of users experiencing simulation sickness
  (military pilots elite group)
• Studies suggest regular VR users are affected
  more (up to 95)
• (Stanney and Hash, 1998)

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Cyber sickness Model

• Since many users are affected, it is important
  to study cyber sickness, in order to reduce its
  effects, and allow wide-spread use of VR
• Few studies exist. Based on these the following
  model was developed

Simulation sickness
Neural Conflict
Adaptation
Prior Experience
Human Body
Virtual Environment
Aftereffects
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System characteristics influencing cyber
sickness

• When VR technology has problems, it can induce
  simulation sickness. Example
• Tracker errors that induce a miss-match between
  user motion and avatar motion in VR
• System lag that produces large time delays
  between user motion and simulation (graphics)
  response. Lag is in turn influenced by tracking
  sampling speed, computer power, communication
  speed, and software optimization.
• HMD image resolution and field of view. Poor
  resolution and small FOV are not acceptable.
  Large FOVs can also be problematic.

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Influence of users characteristics on cyber
sickness

• The user characteristics can play an important
  role in cyber sickness
• Age that induce a miss-match between user motion
  and avatar motion in VR
• Health status. Sick users, including those that
  take medication or drugs are more prone to cyber
  sickness.
• Pregnancy. Female users who are pregnant are
  more prone to simulation sickness.
• Susceptibility to motion sickness. Some people
  are more prone to motion sickness than others.
  Pilots are screened for such.

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Aftereffects

• Induced through adaptation to neural conflicts.
• Occur after the simulation session ended and can
  last for hours or days
• While adaptation is good, aftereffects may be
  bad. Forms of aftereffects are
• Flashbacks
• Sensation of self motion
• Headache and head spinning
• Diminished (remapped) hand-eye coordination
• Vestibular disturbances
• These aftereffects lead Navy and Marines to
  institute grounding policies after simulator
  flights. Other bans may be necessary (example
  driving, biking, roof repair, operating
  machinery, etc.).

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Guidelines for Proper VR Usage
Meant to minimize the onset and severity of
cybersickness. They are largely qualitative
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Guidelines for Proper VR Usage
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Human factors in VR
Human Performance Efficiency
Health and Safety
Societal Implications
(Stanney et al., 1998)
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Social implications of VR

• Violence of VR games are a concern, as additive
  response could result. Violence may also induce
  desensitization to real-world violence. This may
  be another negative after-effect of VR.
• Another social impact may be increased
  individual isolation, through reduced societal
  direct interaction and involvement.
  Avatar-mediated interaction, while allowing
  sharing of virtual worlds may not be a substitute
  to direct human-human interaction.
• Synthetic and distance learning using VR may not
  adequately replace direct student-professor
  interaction. Reduction in education quality may
  result
• Reduction in health-care quality may also be
  present especially for mental health and
  at-home rehabilitation.