Perception & Pattern Recognition II

1. Perception & Pattern Recognition II

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?

5. Perception is active, not passive. PERCEPTION 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.

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

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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. 2.12 (p. 32)

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. 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 V 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

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. 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 V 0 0 0 0

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. 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

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 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

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 O N N N O O O N N O N O N N N O O 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 • 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

44. Parallel vs. serial processes • Serial process • 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. 2 X T O 8

47. What numbers did you see?

48. What numbers did you see? • Now what were the letters? • What color were they?

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)