Chapter 5: Perceiving Objects and Scenes

1. Chapter 5: Perceiving Objects and Scenes

2. Figure 5-3 p97

3. Why Is It So Difficult to Design a Perceiving Machine? • The stimulus on the receptors is ambiguous. • Inverse projection problem: An image on the retina can be caused by an infinite number of objects. • Objects can be hidden or blurred. • Occlusions are common in the environment.

4. Figure 5-6 p98

5. Figure 5-7 p98

6. http://www.darkroastedblend.com/2010/09/mind-bending-optical-illusions.htmlhttp://www.darkroastedblend.com/2010/09/mind-bending-optical-illusions.html • http://www.youtube.com/watch?v=trKn04N2c1g

7. Why Is It So Difficult to Design a Perceiving Machine? - continued • Objects can be hidden or blurred

8. Figure 5-8 p99

9. Figure 5-9 p99

10. Why Is It So Difficult to Design a Perceiving Machine? - continued • Objects look different from different viewpoints • Viewpoint invariance: the ability to recognize an object regardless of the viewpoint • This is a difficult task for computers to perform

11. Figure 5-10 p99

12. http://www.youtube.com/watch?v=-n0FwA9SLQw

13. Perceptual Organization • Approach established by Wundt (late 1800s) • States that perceptions are created by combining elements called sensations • Structuralism could not explain apparent movement • Stimulated the founding of Gestalt psychology in the 1920s by Wertheimer, Koffka, and Kohler • The whole differs from the sum of its parts. • Perception is not built up from sensations, but is a result of perceptual organization.

14. Figure 5-14 p101

15. Figure 5-11 p100

16. Figure 5-12 p100

17. Figure 5-13 p100

18. Figure 5-15 p101

19. Perceptual Organization - continued • Illusory contours- contours that appear real but have no physical edge

20. Figure 5-16 p102

21. Gestalt Organizing Principles • Principles of perceptual organization. • Good continuation - connected points resulting in straight or smooth curves belong together • Lines are seen as following the smoothest path • Pragnanz - every stimulus is seen as simply as possible • Similarity - similar things are grouped together

22. Figure 5-17 p102

23. Figure 5-18 p102

24. Figure 5-19 p103

25. Gestalt Organizing Principles - continued • Proximity - things that are near to each other are grouped together • Common fate - things moving in same direction are grouped together • Common region - elements in the same region tend to be grouped together • Uniform connectedness - connected region of visual properties are perceived as single unit

26. Figure 5-22 p103

27. Figure 5-23 p104

28. Figure 5-24 p104

29. Perceptual Segregation • Figure-ground segregation - determining what part of environment is the figure so that it “stands out” from the background • Properties of figure and ground • The figure is more “thinglike” and more memorable than ground. • The figure is seen in front of the ground. • The ground is more uniform and extends behind figure. • The contour separating figure from ground belongs to the figure (border ownership).

30. Figure 5-25 p105

31. Figure 5-26 p105

32. Perceptual Segregation - continued • Factors that determine which area is figure: • Elements located in the lower part of displays • Convex side of borders

33. Figure 5-27 p105

34. Figure 5-28 p106

35. Subjective Factors That Determine Which are is Figure • Gestalt psychologists believed that experience and meaning play a minor role in perceptual organization. • Gibson Experiment showed that figure-ground can affected by meaningfulness of a stimulus.

36. Figure 5-31 p107

37. Figure 5-32 p108

38. Perceiving Scenes and Objects in Scenes • A scene contains: • background elements. • objects organized in meaningful ways with each other and the background. • Difference between objects and scenes • A scene is acted within • An object is acted upon

39. Perceiving Scenes and Objects in Scenes - continued • Research on perceiving gists of scenes • Potter showed that people can do this when a picture is only presented for 1/4 second • Fei-Fei used masking to show that the overall gist is perceived first followed by details.

40. Figure 5-33 p109

41. Perceiving Scenes and Objects in Scenes - continued • Global image features of scenes • Degree of naturalness • Degree of openness • Degree of roughness • Degree of expansion • Color • Such features are holistic and perceived rapidly

42. Figure 5-35 p110

43. Regularities in the Environment: Information for Perceiving • Physical regularities - regularly occurring physical properties • Oblique effect - people perceive horizontals and vertical more easily than other orientations • Uniform connectedness - objects are defined by areas of the same color or texture

44. Regularities in the Environment: Information for Perceiving – continued • Physical regularities - regularly occurring physical properties • Homogenous colors and nearby objects have different colors • Light-from-above heuristic - light in natural environment comes from above us

45. Figure 5-36 p111

46. Figure 5-37 p111

47. Figure 5-38 p112

48. Regularities in the Environment: Information for Perceiving - continued • Palmer experiment • Observers saw a context scene flashed briefly, followed by a target picture. • Results showed that: • Targets congruent with the context were identified 80% of the time . • Targets that were incongruent were only identified 40% of the time.

49. Figure 5-39 p113

50. Figure 5-40 p113