Chapter 10: Perceiving Depth and Size

1. Chapter 10: Perceiving Depth and Size

2. Figure 10-1 p228

3. Cue Approach to Depth Perception This approach focuses on information in the retinal image that is correlated with depth in the scene. Occlusion We learn the connection between the cue and depth. The association becomes automatic through repeat exposure.

4. Oculomotor Cues Oculomotor cues are based on sensing the position of the eyes and muscle tension Convergence - inward movement of the eyes when we focus on nearby objects Accommodation - change in the shape of the lens when we focus on objects at different distances

5. Figure 10-2 p229

6. Monocular Cues Monocular cues come from one eye Pictorial cues - sources of depth information that come from 2-D images, such as pictures Occlusion - when one object partially covers another Relative height - objects below the horizon that are higher in the field of vision are more distant Objects above the horizon lower in the visual field are more distant

7. Monocular Cues - continued Relative size - when objects are equal size, the closer one will take up more of your visual field Perspective convergence - parallel lines appear to come together in the distance Familiar size - distance information based on our knowledge of object size

8. Figure 10-3 p229

9. Figure 10-4 p230

10. Figure 10-5 p230

11. Monocular Cues - continued Atmospheric perspective - distance objects are fuzzy and have a blue tint Texture gradient - equally spaced elements are more closely packed as distance increases Shadows - indicate where objects are located Enhance 3-D of objects

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15. Figure 10-9 p232

16. Motion-Produced Cues Motion parallax - close objects in direction of movement glide rapidly past but objects in the distance appear to move slowly Deletion and accretion - objects are covered or uncovered as we move relative to them Covering an object is deletion Uncovering an object is accretion

17. Figure 10-10 p233

18. Table 10-1 p233

19. Binocular Depth Information Stereoscopic depth perception Differences between 2D and 3D movies “Stereo Sue” Strabismus

20. Seeing Depth With Two Eyes Differences between 2D and 3D movies “Stereo Sue” Strabismus

21. Figure 10-12 p234

22. Figure 10-13 p235

23. Binocular Disparity Binocular disparity - difference in images from two eyes Difference can be described by examining corresponding points on the two retinas The horopter - imaginary sphere that passes through the point of focus Objects on the horopter fall on corresponding points on the two retinas

24. Binocular Disparity - continued Objects that do not fall on the horopter fall on noncorresponding points These points make disparate images. The angle between these points is the absolute disparity. The amount of disparity indicates how far an object is from the horopter. Relative disparity is the difference between the absolute disparity of two objects.

25. Figure 10-14 p236

26. Figure 10-15 p236

27. Figure 10-16 p237

28. Figure 10-17 p238

29. Disparity (Geometrical) Created Stereopsis (Perceptual) Stereopsis - depth information provided by binocular disparity Stereoscope uses two pictures from slightly different viewpoints. Random-dot stereogram has two identical patterns with one shifted in position.

30. Figure 10-18 p238

31. Figure 10-19 p239

32. Disparity (Geometrical) Created Stereopsis (Perceptual) - continued Three types of 3D TV Passive – polarized glasses Active – electronic shutter glasses Lenticular – mini lenses on screen, no glasses needed

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34. Figure 10-21 p240

35. The Correspondence Problem How does the visual system match images from the two eyes? Matches may be made by specific features of objects. This may not work for objects like random-dot stereograms. A satisfactory answer has not yet been proposed.

36. The Physiology of Binocular Depth Perception Neurons have been found that respond best to binocular disparity. These are called binocular depth cells or disparity selective cells. These cells respond best to a specific degree of absolute disparity between images on the right and left retinas. Disparity tuning curve

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38. Figure 10-23 p242

39. The Physiology of Binocular Depth Perception - continued Experiment by Blake and Hirsch Cats were reared by alternating vision between two eyes. Results showed that they: had few binocular neurons. were unable to use binocular disparity to perceive depth.

40. The Physiology of Binocular Depth Perception - continued Experiment by DeAngelis et al. Monkey trained to indicate depth from disparate images. Disparity-selective neurons were activated by this process. Experimenter used microstimulation to activate different disparity-selective neurons. Monkey shifted judgment to the artificially stimulated disparity.

41. Figure 10-24 p242

42. Perceiving Size Distance and size perception are interrelated Experiment by Holway and Boring Observer was at the intersection of two hallways. A luminous test circle was in the right hallway placed from 10 to 120 feet away. A luminous comparison circle was in the left hallway at 10 feet away.

43. Figure 10-25 p243

44. Perceiving Size - continued Experiment by Holway and Boring On each trial the observer was to adjust the diameter of the test circle to match the comparison. Test stimuli all had same visual angle (angle of object relative to the observer’s eye). Visual angle depends on both the size of the object and the distance from the observer.

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48. Figure 10-29 p245

49. Perceiving Size - continued Part 1 of the experiment provided observers with depth cues. Judgments of size were based on physical size. Part 2 of the experiment provided no depth information. Judgments of size were based on size of the retinal images.

50. Figure 10-30 p245