PSYCH 2220 Sensation and Perception I Lecture 6

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 DORSAL magnocellular layers of LGN parvocellular layers of LGN VENTRAL sustained cells

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

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

11. moving stationary High contrast Low Low spatial frequency High

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

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

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