The contributions of proprioceptive pitch and roll to visual tilt-induced effects for active and passive observers.

1. The contributions of proprioceptive pitch and roll to visual tilt-induced effects for active and passive observers. Jennifer E. Corbett & James T. Enns The University of British Columbia 6/4/04

2. Vision and proprioception calibrate our sense of upright.

3. Vision and proprioception calibrate our sense of upright. • We rely on: • Visual orientation cues

4. Vision and proprioception calibrate our sense of upright. • We rely on: • Visual orientation cues

5. Vision and proprioception calibrate our sense of upright. • We rely on: • Visual orientation cues • & • Proprioception

6. Vision and proprioception calibrate our sense of upright. • We rely on: • Visual orientation cues • & • Proprioception

7. Vision and proprioception calibrate our sense of upright. • We rely on: • Visual orientation cues • & • Proprioception To determine our perceptions of upright.

8. A fun example: Mystery Spots

9. Mystery Spots Vision

10. Mystery Spots Vision + Proprioception

11. Mystery Spots Vision + Proprioception Upright

12. In the present study…

13. In the present study… How does rolling Roll

14. In the present study… How does rolling Roll

15. In the present study… How does rolling Roll

16. In the present study… How does rolling and pitching the observer Pitch

17. In the present study… How does rolling and pitching the observer Pitch

18. In the present study… How does rolling and pitching the observer Pitch

19. Pitch Roll In the present study… How does rolling and pitching the observer interact with visual orientation cues

20. In the present study… How does rolling and pitching the observer interact with visual orientation cues to produce observers’ perceptions of upright? Pitch Roll

21. Introduction

22. Introduction • (Asch & Witkin, 1948)

23. Introduction • (Asch & Witkin, 1948) True vertical

24. Introduction • (Asch & Witkin, 1948) Visual tilt True vertical

25. Introduction • (Asch & Witkin, 1948):Tilt-induced effects Perceived vertical Visual tilt True vertical

26. Introduction • (Witkin & Asch, 1948): Tilting observers increases • tilt-induced effects.

27. Introduction • (Witkin & Asch, 1948): Tilting observers increases • tilt-induced effects. Untilted observers

28. < Tilt-induced effects Introduction • (Witkin & Asch, 1948): Tilting observers increases • tilt-induced effects. Untilted observers Congruently tilted observers

29. < < Tilt-induced effects Tilt-induced effects Introduction • (Witkin & Asch, 1948): Tilting observers increases • tilt-induced effects. Untilted observers Congruently tilted observers Incongruently tilted observers

30. < < Tilt-induced effects Tilt-induced effects Introduction • (Witkin & Asch, 1948): Tilting observers increases • tilt-induced effects. Untilted observers Congruently tilted observers Incongruently tilted observers 0.8o

31. Introduction • (Witkin & Asch, 1948): Tilting observers increases tilt-induced effects. Q1. What really happens to tilt-induced effects when observers are tilted?

32. Introduction • (Nelson & Prinzmetal, 2003): In vision, pitch and roll • are additive.

33. Introduction • (Nelson & Prinzmetal, 2003): In vision, pitch and roll are additive. Q2. Do pitch and roll of the observer independently/ interactively influence visual-tilt induced effects?

34. Introduction Q3. Does it matter whether observers are actively maintaining an upright posture on a tilted surface or whether they are passively tilted?

35. Summary of research questions

36. Summary of research questions Q1. Are visual tilt-induced effects really greater for tilted observers? For incongruently tilted observers?

37. Summary of research questions Q1. Are visual tilt-induced effects really greater for tilted observers? For incongruently tilted observers? Q2. Do pitch and roll of the observer independently/interactively influence visual-tilt induced effects?

38. Summary of research questions Q1. Are visual tilt-induced effects really greater for tilted observers? For incongruently tilted observers? Q2. Do pitch and roll of the observer independently/interactively influence visual-tilt induced effects? Q3. Do observers actively maintaining an upright posture on a tilted surface experience the same degree of visual tilt-induced effects as passively- tilted observers?

39. Apparatus for visual tilt-induced effects

40. Apparatus for visual tilt-induced effects A Rod-Frame box

41. Apparatus for visual tilt-induced effects A Rod-Frame box rolled 20o along the roll axis

42. Apparatus for visual tilt-induced effects A Rod-Frame box rolled 20o along the roll axis produced standard visual-tilt induced effects.

43. Perceptual measure “Say when the rod is vertical with respect to gravity”

44. Perceptual measure Angle of illusion

45. Perceptual measure A 10o illusion in rod adjustment:

46. Perceptual measure A 10o illusion in rod adjustment:

47. Perceptual measure A 10o illusion in rod adjustment:

48. Active observers • Tilted platform

49. Active observers • Tilted platform + standing observer

50. Active observers • Tilted platform + standing observer • Platform rotates to pitch and roll observer.