CGMB 434 Virtual Reality

CGMB 434Virtual Reality

Human Factor

UserUser(programmer,(programmer,trainee, etc.)trainee, etc.)

Introduction

Human Factors in VR

Human Human Performance Performance

Efficiency Efficiency

Health and Health and Safety Safety

SocietalSocietal Implications Implications

(Stanney et al., 1998)

Will the user get sick in VR?


Which tasks are most suitable for users in VR?

Which user characteristics will influence VR performance?

Will there be negative societal impact from user’s misuse of

the technology?

What kind of designs will enhance user’s performance

in VR?

How much feedback from VRcan the user process?

Will the user perceivesystem limitations?

How should VR technologybe improved to better meet

the user’s needs?

??

Human Factors in VR

Human Factor 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

Human Factor Vocabulary

• 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 subject’s abilities before trial

Human Factors in VR






Determine Determine focusfocus

Recruit Recruit subjectssubjects

Conduct Conduct studystudy

Develop experim. Develop experim. protocolprotocol

Analyze Analyze datadata

The Stages of Human Factors Studies







Human Factor 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?







Experiment Protocols

• 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?







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







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.







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

Human Factors in VR






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.

Direct Effects of VR Simulations on Users

• Affect mainly the user’s 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)

Direct Effects of VR Simulations on Users

• 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.

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

• 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)

Prior Prior ExperienceExperience

SimulationSimulationsicknesssickness

HumanHumanBodyBody

Neural Neural Conflict Conflict

VirtualVirtualEnvironmentEnvironment

AdaptationAdaptation

AftereffectsAftereffects

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:

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.

Influence of User’s 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

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

AfterEffects

• 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.).

Guidelines for Proper VR Usage

• Meant to minimize the onset and severity of cybersickness. They are largely qualitative

Guidelines for Proper VR Usage

Human Factors in VR






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.

Social Implications of VR

• 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.

CGMB 434 Virtual Reality

Documents

pilot study smaller

hf study male

vr performance

control groupcase study

trialhuman factors

users performance

vr technologybe

etcexperimental group