The Adaptive Effects of Virtual Interfaces: Vestibulo-Ocular Reflex and Simulator Sickness

1. The Adaptive Effects of Virtual Interfaces: Vestibulo-Ocular Reflex and Simulator Sickness Oral Presentation of Dissertation Research Mark H. Draper 20 Jan 1998

2. Presentation Outline • Preliminaries • Introduction • Hypotheses and Specific Objectives • Experiments • Synthesis and Recommendations

3. Presentation Outline • Preliminaries • Preface • Acknowledgements • “This WAS a Journey!” • Introduction • Hypotheses and Specific Objectives • Experiments • Synthesis and Recommendations

4. Preface • Target Audiences • Human Factors Engineers/Designers • Motion/Simulator Sickness Researchers • Oculomotor Physiologists

5. Dissertation Committee Dr Thomas Furness - Chairperson Dr Erik Viirre Dr Albert Fuchs Dr Zelda Zabinsky Dr Joan Sanders - GSR Dr. Valerie Gawron - Outside Reader Others Dr Don Parker Zsolt Lorant Paul Schwartz Bob Burstein Jerry Prothero Konrad Schroder Chris Airola Acknowledgements

6. “This Ph.D. was a Journey” • Seattle • “Never-Never Land” • Victoria, Canada • Santa Monica, CA • Philadelphia, PA • Dayton, OH • “Demo-land” • Rosedale, Canada • Marbella, Spain! • Albuquerque, NM • Dayton, OH • (the “Oh-No-Not-Again Land”) • Seattle.

7. Presentation Outline • Preliminaries • Introduction • Nature of Virtual Interfaces • The Problem • Main Research Question • General Approach • Background Information • Simulator Sickness • The VOR • General Approach (graphically) • Hypotheses and Specific Objectives • Experiments • Synthesis and Recommendations

8. Nature of Virtual Interfaces (VIs) • Head-coupled, computer-generated scene • Potential for immersion • Natural interaction • High-bandwidth communication

9. THE PROBLEM: SICKNESS • Current VIs imperfectly simulate the motion dynamics of the real world... • …which may adversely effect the user • Possible consequences: • Simulator Sickness (SS) • Undesired Physiological and/ or Perceptual Adaptations • Re-adaptation issues VIs are being applied before their effects are fully understood

10. Main Research Question(s) Do VIs adversely affect users? If so, what are the provocative factors? ‘adversely’ means ??

11. General Approach • Possible Outcomes Of VI Exposure: • Characterize effects of commonly occurring stimulus rearrangements • Develop design guidelines to place interfaces in Cell #4 • Focus: SS and the VOR

12. Simulator Sickness • Occurs during and after • Symptoms • Metrics: • Subjective: • Oral ratings • SSQ • Physiological • Several • Holy Grail • Theories • Sensory Rearrangement Theory • Subjective Vertical Theory • Postural Instability Theory

13. The VOR: Definition • A eye movement reflex • Stimulated by head movements • Moves the eyes opposite of the head • Helps keep the retinal image stabilized The VOR contributes to clear vision during head movements

14. The VOR: How Measured • In the dark • Rotations: active or passive • horizontal in these exps. • Measure head and eye positions • Mental alerting task • Metrics: • Gain: eye velocity/ head velocity • Phase: relative timing • V-VOR: same but in the light

15. The VOR: Adaptation VOR can adapt to changing visual-vestibular patterns Ito, 1972 (Simplified by Robinson, 1976) Why study? • Adaptation Stimulus: visual-vestibular rearrangements • Symptoms similar to SS (e.g., oscillopsia)

16. General Approach (graphically) VR Visual-Vestibular Rearrangement VOR Adaptation Simulator Sickness

17. Presentation Outline • Preliminaries • Introduction • Hypotheses and Specific Objectives • Hypothesis 1: VR-VOR Hypothesis • Image Scale • Time Delays • Hypothesis 2: Adaptability Hypothesis • The Five Objectives • Experiments • Synthesis and Recommendations

18. Adaptation Stimulus Head-Coupled Immersive Virtual Interface with: -time delays -scene scale changes NO: stable vision visual-vestibular oculomotor sensory rearrangements compensation Retinal slip detector: Image slip? short exposure period VOR modulation YES: image slip Active, naturalistic, unrestricted head movements values VOR gain and/or phase adaptation processes VR-VOR Hypothesis

19. In virtual space Scene Magnification: GFOV < DFOV GFOV DFOV GFOV Scene Minification: GFOV > DFOV In physical reality DFOV DFOV GFOV Image Scale: Function of GFOV

20. How Image Scale Effects VOR Image scale changes affect VOR gain Normal 2.0X 1.0X 0.5X

21. System Time Delays Time Delays may affect VOR phase

22. Adaptability Hypothesis

23. 5 Objectives • VR-VOR Hypothesis • VR-SS • Adaptability Hypothesis • Assess alternative VOR gain adaptation protocol • Develop preliminary design guidelines

24. Presentation Outline • Preliminaries • Introduction • Hypotheses and Specific Objectives • Experiments • Overview of Research • The Facility • Physical Layout • Equipment Configuration • Image Scale Experiment • Design (VIDEO) • Results • Summary • Time Delay Experiment • Longitudinal Experiment • Step Experiment • Synthesis and Recommendations

25. Overview of Previous Research • Image Scale Experiment • Time Delay Experiment • Longitudinal Experiment • Step Experiment

26. The Facility: VR Effects Lab • Physical Layout • Equipment Configuration

27. Head Tracker bookshelf + HMD Rotating Chair The Subject Area Balance Platform blinds ISCAN PC The General Area CRT The Shed Table Servo controller function generator WARP PC Macintosh VR Effects Lab: Physical Layout

28. 360 degrees Address GFOV VR Effects Lab: Equipment Configuration

29. Image Scale Experiment Design • 9 subjects; 3 sessions (2 hr. each) • IV: Image Scale • 0.5X (MIN), 1.0X (NEU), 2.0X (MAG) • VIDEO • DVs: • VOR: average gain and phase estimates • Tested PRE, POST, and also 10 min POST • Tested at 0.2, 0.4, and 0.8 Hz • SS: oral reports during and SSQ • Stimuli: 30 min exposure to immersive VI • Tasking: visual search • Active, unrestricted head movements

30. Image Scale Experiment Results: V-VOR

31. Image Scale Experiment Results: VOR Adaptation VOR Gain Adaptation: a function of GFOV

32. Adaptation was across all test frequencies…. ….though head movements were nearly all at the lowest frequencies Image Scale Experiment Results: VOR Adaptation by FREQ

33. Image Scale Experiment Results: SS SS occurred when GFOV different then DFOV

34. Image Scale Experiment Summary • VOR Adaptation occurred (6 - 16%) • generalized across testing frequency • SS occurred • GFOV is a modulating factor • VOR adaptation • SS • VOR-SS correlation weak (0.30) • Slight VOR Phase Adaptation occurred (< 2 deg) • VOR gain re-adaptation: incomplete after 10 min

35. Time Delay Experiment Design • Objective: Determine effects of system time delays • 9 Subjects: 2 sessions (2 hr each) • IV: System Time Delay • 125 ms, 250 ms • variable phase demand • VIDEO • Otherwise the same as Image Scale Exp

36. Time Delay Experiment Results: V-VOR PHASE GAIN

37. Time Delay Experiment Results: V-VOR (position traces)

38. Time Delay Experiment Results: VOR phase Small but statistically significant increase in phase lag

39. Time Delay Experiment Results: VOR gain Unexpected VOR Gain Decrease

40. Time Delay Experiment Results: SS

41. Time Delay ExperimentResults: SS (with NEU condition added)

42. Time Delay ExperimentSummary • VOR gain and phase adaptation occurred • Gain: 8 - 10% reduction, Phase: 2 -3 deg increase in lag • Neither increased with increasing Time Delay • Gain reduction: unexpected • Due to increased saccades or VOR suppression?? • SS not effected by increasing Time Delay • Strengthened when NEU condition added • VOR gain adaptation: generalized across test freq. • VOR-SS relationship: weak • Gain re-adaptation: more fully complete

43. Longitudinal Experiment Design • Objective: general VOR adaptation time course • 2 Subjects: 1 session (1.5 hr) • IV: Time exposed • 0 (PRE), 10 min, 20 min, 30 min (POST), & after 20 min • DV: VOR gain estimates • Tested at 0.2, 0.4, 0.8 Hz • Stimulus: VI with MIN scale and 125 ms Delay • Otherwise the same as before except: • During re-adaptation: subject free to move around

44. Longitudinal Experiment Results (by Subject)

45. Longitudinal Experiment Results (by Frequency)

46. Longitudinal Experiment Summary • VOR gain decreased • Most of the reduction occurred in first 10 min • Testing frequency: no effect on adaptation level • Gain Re-adaptation: complete after 20 min

47. Step Experiment Design • Objective: Examine incremental VOR adaptation stimulus • 4 Subjects (all previously in Image Scale Exp) • IV: Stimulus exposure method • Single (2.0X MAG) • Step (1.0X - 2.0X; 5 increments) • DV: VOR gain estimates • IV confounded with Treatment Order • Previous results indicate no effect of order on VOR adaptation

48. Condition N Pre Post % Gain Pre Post Phase Gain Gain Change Phase Phase Difference (deg) (deg) (deg) 5 0.65 (0.10) 0.68 (0.10) 0.0 -1.6 -1.6 STEP +4.6 STEP (4 subjects) 4 0.67 (0.09) 0.71 (0.09) 0.1 -0.8 -0.9 +5.0 SINGLE (4 subjects) 4 0.62 (0.09) 0.67 (0.11) -1.2 0.0 1.2 +8.0 Step Experiment Results SINGLE (total from 9 0.61 (0.09) 0.65 (0.09) -0.6 -1.1 -0.5 +5.9 MAG condition)

49. Step Experiment Summary • Step approach caused a significant VOR gain increase • Dizzy patients with low VOR had VOR increase with step approach • Will this help patients to get better?

50. Presentation Outline • Preliminaries • Introduction • Hypotheses and Specific Objectives • Experiments • Synthesis and Recommendations • Summary of Findings • Preliminary Design Guidelines • VOR Reconsidered • Future Research Opportunities