1. PSYCH 2220 Sensation and Perception I Lecture 6

2. Keywords for lecture 5 Dorsal/ventral streams, action/perception streams. Grandmother cell hypothesis. Face cells, hand cells (in ventral stream), prosopagnosia. Distributed processing. transient cells sustained cells magnocellular layers of LGN parvocellular layers of LGN DORSAL VENTRAL

3. SPATIAL VISION

4. FOURIER’S THEOREM: “any complex curve can be mathematically described as the sum of a series of sine waves” Variation of luminance across a scene can therefore be described as a series of sinewaves of different SPATIAL FREQUENCIES.

5. Just low spatial frequencies….

6. … all spatial frequencies

7. High spatial frequencies here are NOT telling you about the face but about the annoying squares….

8. …when the squares are too small to be seen, then the remaining information (i.e., the face) can be seen clearly.

9. visible invisible Spatial Frequency Threshold contrast CONTRAST SENSITIVITY FUNCTION Contrast sensitivity low high low

10. Low spatial frequency High High contrast Low THE CONTRAST SENSITIVITY FUNCTION

11. Low spatial frequency High High contrast Low stationary moving

12. .. which revises… Big rfs  best for low sf  found in periphery Where cells prefer MOVEMENT (on way to dorsal stream good for action…)

13. DEPTH PERCEPTION

14. Artist’s cues Stereopsis Parallax Perspective Size Overlay Texture gradient Accommodation and convergence Cues to DEPTH

16. David Hockney

18. The Ame’s room as conflict between SIZE and PERSPECTIVE

22. Ame’s room movie

23. perspective vs size

25. The IMPOSSIBLE TRIANGLE as conflict between PERSPECTIVE and OVERLAY (or OCCLUSSION)

27. The playing card illusion as conflict between overlay and size

29. Perspective and overlay cues

35. overlay > perspective perspective > size overlay > size

36. Size constancy: a given object seems the same size as its retinal image size varies with distance from the viewer. Mechanisms of size constancy can be clarified by looking at when it breaks down… 1 – Emmert’s Law 2 – Moon Illusion

37. EMMERT’s LAW If retinal image stays the same then perceived size will depend on distance small thing close big thing far

38. EMMERT’s LAW If retinal image stays the same then perceived size will depend on distance

40. DEMO ONLY!! They have been MADE different sizes here!!)

41. CRITICAL POINT: the moon always has the same visual angle, but different perceived distance.

42. Scale demo (from Lord of the Rings)

43. Binocular disparities and stereopsis

45. (red over left eye)

48. The correspondence problem: How does the brain know which dots in the right eye go with which dots in the left eye?

49. Floating Square

50. RIGHT EYE LEFT EYE

51. (red over left eye)

52. Reversing the glasses opposes stereopsis and artist’s cues

55. Necker cube

56. Cube

57. Pyramid (lots of depth) (red over right eye)

58. Checkerboard

60. AUTOSTEREOGRAM

61. Ame’s Window Demonstration

62. overlay > perspective perspective > size overlay > size overlay > stereopsis stereopsis > perspective …but only at close distances

63. Pulfrich illusion

65. Parallax

67. parallax video

68. Accommodation and convergence

69. need someone who hasn’t got stereopsis parallax doesn’t know about artist’s cues: (perspective, overlay, texture gradients,size) who could this be???

70. Accommodation cues can be used to solve the visual cliff.

71. Neural basis of stereopsis

73. Ocular dominance bands

74. RIGHT EYE LEFT EYE FAR NEAR FAR CELL

75. RIGHT EYE LEFT EYE FAR NEAR NEAR CELL

76. NEAR FAR

78. … motion in depth leads us nicely into…. VISUAL MOTION

79. My mother by David Hockney

80. The scrabble game by David Hockney

81. Visual motion

82. Active motion of real image INFLOW OUTFLOWDATA Passive motion of real image Active motion of after image Attempt to move paralyzed eye Passive motion of after image No movement No movement PREDICTIONS No movement YES movement YES movement YES movement YES movement No movement EXPERIMENTS No movement YES movement

84. Active motion of real image INFLOW OUTFLOWDATA Passive motion of real image Active motion of after image Attempt to move paralyzed eye Passive motion of after image No movement No movement PREDICTIONS No movement YES movement YES movement YES movement YES movement No movement EXPERIMENTS No movement YES movement No movement YES movement YES movement No movement YES movement