1. INTRODUCTION TO PSYCHOLOGY
Chapter 5
Perception

2. At the end of this Chapter you should be able to:
Understand what Distance Perception is
Understand what Motion Perception is
Understand what Form Perception is
Learn about Attention
Learn about Visual Illusions

3. Visual Perception
The retinal image is only two-dimensional; height and width...
From the two-dimensional images that fall on our retinas we somehow are able to see three-dimensional objects.

5. Visual Perception
Seeing objects in three dimensions, or depth perception, allows us to estimate distances between those objects and us.

6. Visual Perception
Psychologists are particularly interested in the cues which enable people to perceive depth and distance. These cues may be monocular, effective when using one eye as well as two, or binocular, requiring the usage of both eyes.

7. Depth & Distance Perception
Depth Perception: Ability to see three-dimensional space and to accurately judge distances
Depth Cues: Features that supply information about distance and space.

8. Depth & Distance Cues Binocular cues
We compare the retinal image in one eye to the retinal image in the other; they differ: each eye is a slightly different distance from an object in the world

9. Depth & Distance Cues Monocular cues Interposition Linear perspective
Texture Gradients
Relative Size
Light and Shadow
Motion Parallax

10. Binocular disparity
The disparity between the views serves as a powerful cue for depth

11. Monocular Cues: Interposition
Interposition: When one object partly blocks your view of another, you perceive the partially blocked object as farther away

12. Monocular Cues: Interposition
Interposition: The fact that mailbox blocks the view is a powerful cue that the mailbox must be closer to the observer than the sport car is

13. Monocular Cues: Interposition
Madonna of the Magnificat by Sandro Botticelli.

14. Monocular Cues: Linear Perspective
Linear Perspective: Parallel lines that are known to be the same distance apart appear to grow closer together, or converge, as they recede into the distance

15. Monocular Cues: Linear Perspective

16. Monocular Cues: Texture Gradient
Texture Gradients: The texture of objects tend to become smoother as the object gets farther away, suggesting that more detailed textured objects are closer. 

17. Monocular Cues: Relative Size
•Relative size: Larger objects are perceived as being closer to the viewer, and smaller objects as being farther away

18. Monocular Cues: Relative Size

19. Monocular Cues: Light and Shadow
Monocular cues: light and shadow: (A) Eight circular objects. To most viewers, the one in the middle looks concave, indented, whereas other seven look as if they are bulging out. (B) The same figure rotated 180 degrees. Now, the middle object looks convex, while others seem concave. The reason is the location of the shadow. If the shadow is at the bottom, the object looks convex, if the shadow is at the top, the the object looks concave.

20. Monocular Cues: Light and Shadow

21. Monocular Cues: Motion Parallax
When you ride in a moving vehicle and look at the side window, the objects you see appear outside move in opposite direction
Objects seem to be moving in different speeds-the ones that are closer to you seem to move faster, whereas objects far behind seem to move slower

22. Monocular Cues: Motion Parallax

23. Perceptual Constancy
The tendency to perceive objects as maintaining stable properties (e.g., size, shape, brightness, and color) despite differences in distance, viewing angle, and lighting

24. Size Constancy
Size constancy refers to our ability to see objects as maintaining the same size even when our distance from them makes things appear larger or smaller. 

25. Shape constancy   
Shape Constancy: Perceiving objects as having a stable or unchanging shape regardless of changes in the retinal image resulting from differences in viewing angle

26. VIDEO of Julian Beever, an English artist, who paints sidewalks in an amazing 3-D way....

27. Motion Perception
Perception of an event -motion- rather than an object
Motion tells us what the object is doing.

28. Apparent motion
When intervals between images occur at correct timing (not too far apart in time) we perceive motion
This principle used to create ‘motion’ from stills

29. Apparent motion
In movies, when still pictures are put together, it produces the sensation of movement for the viewer (audience). Even though there is no ACTUAL movement.
We do not only detect motion but we also interpret it.

31. Apparent Movement

32. Apparent motion
Motion

33. What about the variability in objects that we see?
The same animal but the features look different. So how can we classify all of them as a giraffe?

34. What about the variability in objects that we see?
We recognize giraffes as being giraffes whether we see them from the side, or the front, or close up, or from far away.
Do we actually pay attention to every detail (feature)?
We only interpret crucial information. We don’t have time in the real-world to pay attention to every little detail. Otherwise we cannot survive!

35. Form Perception Detecting object features (parts)
The importance of organization
Perceptual parsing
Separating the figure from the ground

36. Organization’s role in perception
Features: some we ignore, some we attend to
How do we decide whether to ignore or attend?
We interpret some features as being part of the object, other features as irrelevant
How do we group together features that belong with each other?

37. A hidden figure

38. Missing features

40. Gestalt Psychology
The German word "Gestalt" roughly means to "whole" or "form"
“The whole is greater than the sum of its parts.” 
In order to interpret what we receive through our senses, we attempt to organize this information into certain groups. 
Sense of shape: derived from the whole, not the sum of its parts

41. Gestalt principles organization
Perceptual parsing:
Segregating the “scene” into its constituent objects
The first step to organizing
Gestalt principles of organization:
Issues of figure/ground
Similarity
Proximity
Good continuation
“subjective contours”

42. Perseptual Parsing

44. Grouping by similarity

45. Grouping by proximity

46. Good Continuation

47. Subjective contours

48. Gestalt psychology Important: Is the object figure or ground?
Our interpretation of figure / ground will influence how we perceive an object

49. Reversible figure-ground pattern

52. The classical approach to perception
Emphasis on the active, constructive role of the perceiver, who routinely:
Resolves ambiguous figures
Determines identity of objects based on contextual clues and previous knowledge
Determines identity of objects based on contextual clues

53. Ambiguous Necker Cube

54. Contextual clues (and previous knowledge)

55. Illusions: How could we make such mistakes?
Cues sometimes cause an over-estimate or under-estimate;
Slight over/under interpretations can cause us to misinterpret the information we receive
Usually:
perceptions are accurate
are based on relevant experience
reflect the world we live in

56. The Ponzo Illusion

62. Brightness Illusion

64. Perceptual selection: Attention
What starts the synchrony? One possible mechanisms: ATTENTION
Selective control of orientation
Selective looking
Difficult when target represents multiple, rather than a single, feature

65. VIDEO on Attention 1(when you do not expect to see any changes) VIDEO on Attention 2 (when you expect to see changes)

66. Some final thoughts: Seeing, knowing, and the perceiver’s active role
Perception is not knowledge
Knowledge and perception are mutually influenced, but are not the same thing: the perceiver and the knower are distinct in many instances

67. In this experiment, subjects were asked to keep the track of the ball players in white shirts. Intent on their task, the subjects were not paying any attention to the black shirted players, even though they are looking directly at them.
AND THEY ALSO FAILED TO SEE .....

68. VIDEO about the blind Turkish artist Eşref Armağan

69. Web Links for Optical Illusions
Mueller-Lyer Illusion
Brightness Illusion
Checker-Shadow Illusion

70. Attention Demos
The Stroop Effect

71. As fast as you can, read the names
of the colors

72. As fast as you can, (don’t read the word) but read the name of the color of the word.

73. As fast as you can, (don’t read the word) but read the name of the color of the word.

74. As fast as you can, (don’t read the word) but read the name of the color of the word.