1. Perception & Pattern Recognition II
From last time: finish up illusions; and slide # 62 does NOT contain a typo after all.

2. Today’s agenda: Turn in CogLab Assignment #1
Today’s theme: Perception is active
More examples from Reed, Chapter 2
Finish up perceptual illusions
Next Tuesday: Face Recognition

3. What do you see?
From last time: finish up illusions; and slide # 62 does NOT contain a typo after all.

5. Perception is active, not passive.
Sensory input

6. Perception is active, not passive.
Knowledge, expectations
(Top-down processing)
PERCEPTION
(Bottom-up processing)
Sensory input

7. During perception, information is:
Omitted
Decomposed into features
Added
Categorized
Organized
Distorted

8. The Whole Report Procedure
An array of 12 letters is BRIEFLY flashed onto the screen.
After it’s removed, the observer tries to report what they saw.

9. +

10. T M F W
L R E P
A X C O

11. OK, write down what you saw.

12. +

13. L A P C
K R Z D
O S V Y

15. The Whole Report Procedure
An array of 12 letters is BRIEFLY flashed onto the screen.
After it’s removed, the observer tries to report what they saw.
People can typically report only 3-4 of the 12 letters.
Does this really mean that only 4 letters made it into perception?
Sperling invented the Partial Report Procedure, which answered this question.

16. The Partial Report Procedure (Sperling, 1960)
The subject fixates on a cross; then letters flash onto the screen just long enough to cause a visual afterimage.
High, medium, and low tones right after the letters are removed signal which row of letters to report.
(Fig. 2.11, p. 31) .

17. The information available in brief visual presentations (Sperling, 1960)
If the delay (after the
display disappears and
before the cueing tone)
is short, people can
report all or almost all
letters in the row they’re
cued to report!
What does this mean?
Reed Fig (p. 32)
NOTE: “letters available” on the Y axis is the number actually reported, multipled by 3 because there are 3 rows.
After the display is gone, people can continue to “read” letters off their visual icon if they get to focus attention on the cued row before the icon fades.

18. Evidence for sensory memory (Sperling, 1960)
After the display is removed, people can continue to “read” letters off their visual icon if (and only if) they’re able to focus attention on the cued row before the icon fades.
Sperling’s discovery led to the idea of an extremely short-lived visual icon (visual sensory store) with unbounded capacity.

19. Without attention, information in the visual icon (VSS) is rapidly lost.
(Reed, p. 3, Figure 1.1)

20. During perception, information is:
Omitted
Decomposed into features
Added
Categorized
Organized
Distorted

21. Feature integration theory
(Treisman & Gelade, 1980)
The popout phenomenon, discovered by Anne Treisman
This provides more evidence for low-level features, perceived automatically.

22. For the next slide, try to react as quickly as possible.
You’ll see a field of black 0’s.
Slap the desk IF (and only if) you see the letter V in the field of 0’s.

23. V

24. Straight lines pop out in a field of curved lines.
This task is pre-attentive (doesn’t demand attention).
Let’s try it again. Slap if you see a V.

25. V

26. Popout happens fast, regardless of the size of the display!
This means you’re searching it all at once - in parallel.
Let’s try it again. Slap if you see a V.

27.
ha HAH! Gotcha.

28. Straight lines pop out from curved lines, and vice versa.
What about angular orientation? In this next field of vertical lines, slap the desk if you see a slanted line.

29. | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
| | | | | | | | | | | | | | | | | | | | | / | | | | | | | | | | | | |

30. Now for color.
Slap if you see something red.

31. O N N N O O O N N O N O N N N O O N
O O O N O O O N N O N N N O O N O O
N O O N O O N O O N N O O O O N O N
O N O N O N O O O N O N O N N N O O
N O O N O O O N N O O N O N N O N N
N O N O O O N O N O N N N O O N O O

32. We know that color pops out, and so does curvature.
For the next slide, slap the desk if (and only if) you see a red O.

33. O O O N O O O N N O N N N O O N O O
N O O N O O N O O N N O O O O N O N
O N O N O N O O O N O N O N N N O O
O N N N O O O N N O N O N N N O O N
N O N O O O N O N O N N N O O N O O
N O O N O O O N N O O N O N N O N N

34. And again: Red O.

35. N N O
O N O

36. One last time:

37. O N N N O O O N N O N O N N N O O N
O O O N O O O N N O N N N O O N O O
N O O N O O N O O N N O O O O N O N
O N O N O N O O O N O N O N N N O O
N O O N O O O N N O O N O N N O N N
O N N N O O O N N O N O N N O N O N
N O N O O O N O N O N N N O O N O O

38. Conjunction search T X X T X T T T T T T T X X
Searching for a conjunction of features takes longer! You must search one at a time (serially) rather than in parallel (all at once).
For conjunction search, the display size (set size) matters, since you have to search every item for the particular combination of features. T X X T X T T T T T T T X X

39. Another demonstration of set size (find the white vertical bar)

40. 1 Distractor

41. 12 Distractors

42. 29 Distractors

43. Which of these represents parallel search, and which represents serial search?

44. Parallel vs. serial processes
Process each object, one at a time
The time it takes depends on # of objects
Parallel process:
Process multiple things at once or “in parallel”
The number of objects doesn’t matter -
it’s equally fast, whether there are
many or few objects.
Works for limited kinds of things
Sperling: We recognize letter in parallel but
report them serially.

45. Illusory conjunction at the preattentive stage
Next, I will briefly flash a string
of black numbers and colored letters.
Try to report the number
at the beginning AND
the number at the end of the string.

46. X T O

47. What numbers did you see?
Everyone gets this mostly right.

48. What numbers did you see? Now what were the letters?
What color were they?
Anyone see a red X? A blue O? Anything green?

49. Illusory Conjunction Effect
Illusory Conjunction (Treisman & Schmidt, 1986)
People report incorrect combinations of features about 30% of the time.
due to lack of time to focus attention.
They recognize T and blue, but these features are “floating” -
This effect is pre-attentive
Attention is needed to “glue” features together! (binding)

50. Without attention, information in the visual icon (VSS) is rapidly lost.
(Reed, p. 3, Figure 1.1)

51. During perception, information is:
Omitted
Decomposed into features
Added
Categorized
Organized
Distorted

52. Knowledge, expectations
Information is added
Knowledge, expectations
(Top-down processing)
PERCEPTION
(Bottom-up processing)
Sensory input

53. Information is added
The blind spot
Speech perception with noise

54. Information is added I knew that the *eel was on the orange axle
shoe table
The phonemic restoration effect
(Warren & Warren, 1970)
Context helps us perceive speech

55. Reading words with noise

56. Word Superiority Effect (Reicher, 1969)
When is a given letter recognized fastest: alone, in a word, or in a non-word?
K WORK ORWK

57. Word Superiority Effect (Reicher, 1969)
Brief display
Mask & choice
Respond:
D or K?
(Fig. 2.13, p. 35)

58. Word Superiority Effect (Reicher, 1969)
Brief display
Mask & choice
Respond:
D or K?
(Fig. 2.13, p. 35)

59. Word Superiority Effect (Reicher, 1969)
Brief display
Mask & choice
Respond:
D or K?
(Fig. 2.13, p. 35)

60. Word Superiority Effect (Reicher, 1969)
Respond:
D or K?
(Fig. 2.13, p. 35)

61. Word superiority effect: An interactive activation model
Word level
Letter level
Feature level
Input
See Reed, p in addition to activation, there’s also inhibition.

62. Neural network models PDP - parallel distributed processing
Nodes - processing units used to abstractly represent elements such as features, letters, and words
Links, or connections between nodees
Activation - excitation or inhibition that spreads from one node to another

63. During perception, information is:
Omitted
Decomposed into features
Added
Categorized
Organized
Distorted

64. Information is categorized
The input to perception is continuous, but the output is categorical.

65. Variations in handwriting (Chapanis,1965)
Despite variation,
letters and words
are still categorized.
The same squiggle
may be categorized
differently in different
contexts.
Reed, Fig (p. 18)

66. Speech perception is categorical
Can we tell very similar sounds apart?
It depends!
Example: Voicing: when vocal folds vibrate
Early VOT (voice onset time) Late VOT
/p/ /b/
/g/ /k/
Expt: Subjects hear /ga/ - /ka/ sounds, judge if each is “ga” or “ka”; voicing varies slightly.
Then % “ga” judgments is graphed for each VOT

67. Speech perception is categorical
If we perceived what was actually out there in the world, what would the graph look like?

68. Speech perception is categorical
Surprise! People perceive sounds that vary continuously as suddenly in a different category.
Note that the perceptual boundary falls between ms for VOT

69. Speech perception is categorical
Discriminating between sounds that differ by only 10 ms in their VOT: Performance peaks at the boundary.
(Note: Task
is to judge
2 sounds
as “same”
or “different”)
Another way to look at this, using a discriimination task

70. Categorical perception
Helps us categorize information quickly
Helps us ignore irrelevant information
For speech sounds, the same amount of difference - say, 20 ms - leads to very different results, depending on whether it falls within or between phonetic categories

71. During perception, information is:
Omitted
Decomposed into features
Added
Categorized
Organized
Distorted

72. Information is organized
(For example, Gestalt properties of perception - see last lecture.)

73. Information is distorted
We don’t see what’s out there in the real world - we see what our perceptual system biases us to see.

74. Perceptual illusions Muller-Lyer illusion Ponzo illusion Ames room
Moon illusion
Relative size illusion
Perceptual illusions result from the helpful biases of constancy, depth perception cues, and Gestalt principles!

75. Muller-Lyer Illusion

76. Ponzo Illusion

77. Ames Room

78. Ames Room

79. Moon Illusion

80. Relative height Higher objects on the ground are seen as farther away
Lower objects in the sky are seen as farther away

81. Relative size illusion

82. Conclusions about perception
Perception is not passive; percepts are actively constructed by the system.
Perception uses both bottom-up and top-down information.
During perception, information may be omitted, added, decomposed, categorized, organized, or distorted.
Be able to think of one example of each of these perceptual operations.
Be able to give several examples of top-down and bottom-up information.