Chapter 4 Perception

1. Chapter 4Perception

2. Basic Principles of PERCEPTION • Perception is the process that organizes those stimuli into meaningful objects and events and interprets them.

3. Sound Localization • Sound localization: the ability to locate objects in space solely on the basis of the sounds they make • Because the ears are only 6 inches apart, the time lag between the sound reaching both ears is very short. • Even such small time lags provide the auditory system with sufficient information to locate the sound.

4. Sound Localization

5. Pitch Perception: Place Theory • Place theory: contends that we hear different pitches because different sound waves trigger hair cells on different places of the cochlea’s basilar membrane.

6. Pitch Perception: Frequency Theory • Frequency theory: contends that pitch is determined by the frequency with which the basilar membrane vibrates.

7. Pitch Perception • Place theory best explains high-frequency sounds, while frequency theory best explains low-frequency sounds. Mid-frequency sounds are best explained by volley theory, a revision of frequency theory.

8. Visual Perception • Organization and interpretation of incoming visual information.

9. Pathways from the Eyes to the Visual Cortex (Left-Right Visual Fields)

10. Cell’s responses Stimulus Visual Information Processing • Feature Detectors • nerve cells in the brain that respond to specific features of the stimulus • shape • angle • movement

11. Young-Helmholz Trichromatic Theory of Color Vision • Any color can be created by combining three primary colors—red, green, and blue. • The retina has three types of color receptors that produce the primary color sensations of red, green, and blue.

12. Additive and Subtractive Color Mixing

13. Color Vision LO 3.3 How Eyes See and How Eyes See Color • Trichromatic theory: theory of color vision that proposes three types of cones: red, blue, and green • Afterimages: images that occur when a visual sensation persists for a brief time even after the original stimulus is removed

14. Color Vision LO 3.3 How Eyes See and How Eyes See Color • Opponent-process theory: theory of color vision that proposes four primary colors with cones arranged in pairs: red and green, blue and yellow • lateral geniculate nucleus (LGN) of thalamus

15. Opponent Process Flag

16. Opponent Process Flag • Explanation: Color AfterimageStare at the white dot in the center of this oddly colored flag for about 30 seconds. Now look at a white piece of paper or a white wall. Notice that the colors are now the normal, expected colors of the American flag. They are also the primary colors that are opposites of the colors in the picture and provide evidence for the opponent-process theory of color vision.

17. Color Blindness LO How Eyes See and How Eyes See Color • Monochrome colorblindness: a condition in which a person’s eyes either have no cones or have cones that are not working at all • Red-green colorblindness: either the red or the green cones are not working • protanopia: lack of functioning red cones • deuteranopia: lack of functioning green cones • tritanopia: lack of functioning blue cones

18. The Ishihara Color Test

19. The Ishihara Color Test • In the circle on the left, the number 8 is visible only to those with normal color vision. In the circle on the right, peoplewith normal vision will see the number 96, while those with red-green color blindness will see nothing but a circle of dots.

20. Perceptual Organization:Necker Cube • Gestalt • an organized whole • tendency to integrate pieces of information into meaningful wholes

21. Gestalt Principles LO 3.9 Gestalt Principles of Perception • Figure–Ground • the tendency to perceive objects, or figures, as existing on a background • Reversible Figures • visual illusions in which the figure and ground can be reversed

22. Perceptual Organization • Figure – Ground • Organization of the visual field into objects (figures) and surrounding background (ground)

23. Gestalt Principles LO 3.9 Gestalt Principles of Perception • Similarity • the tendency to perceive things that look similar to each other as being part of the same group • Proximity • the tendency to perceive objects that are close to each other as part of the same grouping

24. Gestalt Principles LO 3.9 Gestalt Principles of Perception • Closure • the tendency to complete figures that are incomplete • Continuity • the tendency to perceive things as simply as possible with a continuous pattern rather than with a complex, broken-up pattern

25. Gestalt Principles LO 3.9 Gestalt Principles of Perception • Contiguity • the tendency to perceive two things that happen close together in time as being related

26. Proximity Similarity Continuity Closure Connectedness

29. Depth Perception • Depth perception: the ability to perceive objects three-dimensionally • Binocular cues: depth cues that require information from both eyes • Monocular cues: depth cues that require information from only one eye

30. The Visual Cliff

31. Depth Perception – Binocular Cues • Binocular cues- depend on use of two eyes • retinal disparity • images from the two eyes differ • closer the object, the larger the disparity • convergence • neuromuscular cue • two eyes move inward for near objects

32. Monocular Cues LO 3.10 What Is Depth Perception? • Monocular cues (pictorial depth cues): cues for perceiving depth based on one eye only • linear perspective: the tendency for parallel lines to appear to converge on each other • relative size: perception that occurs when objects that a person expects to be of a certain size appear to be small and are, therefore, assumed to be much farther away

33. Monocular Cues LO 3.10 What Is Depth Perception? • Monocular Cues (cont’d) • interposition (overlap): the assumption that an object that appears to be blocking part of another object is in front of the second object and closer to the viewer

34. Linear Perspective

35. linear perspective.

36. Relative Size

37. Overlap or Interposition

38. Monocular Depth Cues

39. Monocular Depth Cues:Height in Visual Field

40. Monocular Cues LO 3.10 What Is Depth Perception? • Aerial perspective: the haziness that surrounds objects that are farther away from the viewer, causing the distance to be perceived as greater • Texture gradient: the tendency for textured surfaces to appear to become smaller and finer as distance from the viewer increases

41. Texture gradient causes the viewer to assume that as the texture of the pebbles gets finer, the pebbles are getting farther away Notice how the larger pebbles in the foreground seem to give way to smaller and smaller pebbles near the middle of the picture. .

42. Texture Gradient

43. In aerial or atmospheric perspective, the farther away something is the hazier it appears because of fine particles in the air between the viewer and the object. Notice that the road and farmhouse in the foreground are in sharp focus while the mountain ranges are hazy and indistinct.

45. Monocular Cues LO 3.10 What Is Depth Perception? • Motion parallax: the perception of motion of objects in which close objects appear to move more quickly than objects that are farther away • Accommodation: as a monocular clue, the brain’s use of information about the changing thickness of the lens of the eye in response to looking at objects that are close or far away

46. Perceptual Constancy • perceiving objects as unchanging despite changes in retinal image • color • shape • size

47. Shape Constancy

48. Size-Distance Relationship

49. Perceptual Illusions – Ames Room

50. Size-Distance Relationship