1. Perception

2. The means by which information acquired from the environment via the sense organs is transformed into experiences of objects, events, sounds, tastes, etc.

3. “Box” Distal Stimulus Proximal Stimulus Representation Response Distal Stimulus Proximal Stimulus Representation Response

4. Lack of Correspondence Perceptual experience does not correspond to the distal stimulus Perceptual experience does not correspond to the distal stimulus Perceptual illusions are examples of lack of correspondence Perceptual illusions are examples of lack of correspondence Proximal Stimulus Representation Distal Stimulus

5. Paradoxical correspondence When proximal stimulus does not correspond to distal stimulus But our perceptual experience does (paradoxically!) 3-D 2-D

6. Paradoxical Correspondence Perceptual constancies are an example of paradoxical correspondence Size constancy Color constancy Shape constancy

7. Perceptual constancy: Size “Sculls” Gustave Caillebotte Our perceptions of the sizes of objects are constant despite the fact that the size of objects on the retina vary greatly with distance

8. Perceptual Constancy: Size

9. Perceptual constancy: Color HOPPER, Edward Nighthawks1942 Oil on canvas 30 x 60 in. The Art Institute of Chicago Our perception of the color of an object remains constant under different conditions of illumination

10. HOPPER, Edward Morning Sun 1952 Oil on canvas 28 1/8 x 40 1/8 inches Columbus Museum of Art, Ohio Perceptual constancy: Color

11. HOPPER, Edward Rooms by the Sea 1951 Oil on canvas 29 x 40 inches Yale University Art Gallery Perceptual constancy: Color

12. Perceptual constancy: Shape Our perception of the shape of an object remains constant despite changes in the shape of its retinal projection (i.e., the proximal stimulus) caused by the movement of the object relative to the viewer.

13. Perceptual constancy: Shape

14. Historical Approaches Structuralism Gestalt Psychology

15. Structuralism Sensations are the elementary building blocks of perception. Perceptions are created by the addition of numerous individual sensations

16. George Seurat - Sunday Afternoon on the Isle of La Grande Jatte (1884- 1886)

17. Gestalt Psychology “ The whole is different from the sum of its parts ” Max Wertheimer (1880-1943) Several Laws of Perceptual Organization Structural analysis ignores the relationships between stimuli Prägnanz: law of simplicity (overall principle)

18. Law of Proximity Things that are close together are seen as part of a group.

19. Similarity Things that are similar seem part of the same group.

20. Law of Good Continuation Things are grouped together if they seem to be lying on the same contour.

21. Law of Closure Gaps in figures are filled in to form a closed figure

22. Law of Common Fate Things are grouped together if they are moving in the same direction

23. Figure-Ground Segregation Part of an image will be treated as the figure (foreground object) and part will be treated as the ground (background).

24. Which one if the figure and which is the ground? Symmetric items tend to be seen as a figure.

25. Modern Theoretical Approaches Direct Perception vs. Constructivist Theory

26. Direct Perception Environment provides all the necessary information for us to create an accurate perception. All the information you need is in the proximal stimulus. Stimulus information is unambiguous. Our brains are pre-wired to pick up this information. Movement helps us to pick up the information. James J. Gibson

27. Movement helps: “optic flow”

28. Light Display

29. Constructivism Perception uses data from the world and our prior knowledge and expectations. Sensory information is often ambiguous. Must rely on knowledge/expectations. “We don’t see things as they are, we see things as we are” Anaïs Nin

30. Gregory (1968)

34. Necker Cube

35. Fig. 3-23, p. 73

36. Bottom-up vs. top-down Bottom-up: information processing driven by stimulus data only. Direct perception: perception is purely bottom- up. Top-down: information processing driven by prior knowledge and expectations Constructivism: perception combines bottom- up and top-down processing to perceive the external world.

38. Cues for Depth Perception

39. Linear Perspective

40. Lines that are parallel in the 3-D world will appear to converge in the image.

41. Linear Perspective

44. Texture Gradient Objects of the same size form smaller images when they are further away.

45. Texture Gradient

46. CAILLEBOTTE, Gustave Paris: A Rainy Day 1877 Oil on canvas 83 1/2 x 108 3/4" (212.2 x 276.2 cm) The Art Institute of Chicago Texture Gradient

47. Aerial Perspective The atmosphere scatters light. More distant objects are fainter and less distinct.

48. Relative Size If two objects are the same size, the more distant one will appear smaller in the image.

49. Interposition An object that breaks another object’s contour is perceived as the closer one.

50. Shadow Shadows in a scene are assumed to be produced by light shining from above.

51. Shadow

55. Binocular Disparity Distance information from the difference in the images seen by the two eyes.

56. Binocular Disparity Stereoscope (19 th century) Viewmaster

57. Motion parallax Closer objects appear to move faster than more distant objects.

58. Motion parallax

59. Accommodation Distance information based on muscles that control the shape of the lens.

60. Convergence Distance information based on muscles that control the direction of the eyes.

61. Sources of Depth Information Accommodation Depth Information Extraretinal Convergence Binocular Visual Static Cues Non-Static Cues Monocular Retinal Disparity Relative Size Shadow Interposition Linear Perspective Aerial Perspective Texture Gradient Motion Parallax Static Cues (monocular) (binocular)