1. Forgetting and Interference in Short-term memory Brown-Peterson Task Proactive Interference (PI) Release from PI Retrieval of info from STM Sternberg (1966) Task Stages Findings

2. Forgetting and Interference in Short-term memory Brown (1959) Peterson and Peterson (1959) both tested a decay theory of immediate memory considered possibility of proactive interference Task (Brown-Peterson task)

3. Brown-Peterson task get 3 letters to remember get a number (start counting backward by 3s) recall letters when given a cue

5. + + +

6. X S V

7. 3 6 1

8. *****

10. + + +

11. D L F

12. 2 9 2

13. *****

14. P(r) 1.0 0.0 Proportion of Items Recalled as a Function of (Filled) Retention Interval Retention Interval (s) 0 3 6 9 12 15 18

15. P(r) 1.0 0.0 Proportion of Items Recalled as a Function of (Filled) Retention Interval Retention Interval (s) 0 3 6 9 12 15 18

16. P(r) 1.0 0.0 Proportion of Items Recalled as a Function of (Filled) Retention Interval Retention Interval (s) 0 3 6 9 12 15 18 Decay or Proactive Interference?

17. Considered Proactive Interference Looked at performance for 4 blocks of trials If PI occurred, then performance should get worse across the 4 blocks of trials

18. Considered Proactive Interference Looked at performance for 4 blocks of trials If PI occurred, then performance should get worse across the 4 blocks of trials Mean % Accuracy by Block Block 1234 33414043

19. Considered Proactive Interference Looked at performance for 4 blocks of trials If PI occurred, then performance should get worse across the 4 blocks of trials Mean % Accuracy by Block Block 1234 33414043 No evidence of PI; so, seems like evidence for decay (also thought retroactive interference was eliminated)

20. Peterson and Peterson (1959) used 2 practice trials then looked at mean performance for blocks of 12 trials Keppel and Underwood (1968) Maybe PI builds up quickly examined performance over first few trials If PI occurs, then performance should get worse across trials (the more trials, the more PI)

21. P(r) 1.0 0.0 Proportion of Items Recalled by Trial Number And Recall Delay Trial Number 123456123456 3-s delay 18-s delay

22. Keppel and Underwood (1968) Maybe PI builds up quickly examined performance over first few trials If PI occurs, then performance should get worse across trials (the more trials, the more PI) Conclusion: PI occurs, builds up quickly

23. P(r) 1.0 0.0 Proportion of Items Recalled by Trial Number And Recall Delay Trial Number 123456123456 3-s delay 18-s delay

24. Keppel and Underwood (1968) Maybe PI builds up quickly examined performance over first few trials If PI occurs, then performance should get worse across trials (the more trials, the more PI) Conclusion: PI occurs, builds up quickly Also, little forgetting without PI (evidence against decay theory)

25. Keppel and Underwood (1968) Maybe PI builds up quickly examined performance over first few trials If PI occurs, then performance should get worse across trials (the more trials, the more PI) Conclusion: PI occurs, builds up quickly Also, little forgetting without PI (evidence against decay theory) Note: distractor task is producing retroactive interference, too

26. Wickens (1968) obtained quick build-up of PI with different category exemplars (e.g., examples of professions, fruits, etc.) Manipulation – category switch continued with same category (no switch) vs. changed to a new category (switch)

27. P(r) 1.0 0.0 Proportion of Items Recalled by Trial Number And Recall Delay Trial Number 123456123456 professions fruitsfruit (no switch) fruit (switch)

28. Wickens (1968) obtained quick build-up of PI with different category exemplars (e.g., examples of professions, fruits, etc.) Manipulation – category switch continued with same category (no switch) vs. changed to a new category (switch) Release from PI due to a shift in material Conclusion: Build-up of PI due to similar material (interference from similar material)

29. Forgetting and Interference in Short-term memory Brown-Peterson Task Proactive Interference (PI) Release from PI Retrieval of info from STM Sternberg (1966) Task Stages Findings

30. Retrieval of info from STM Sternberg’s (1966) task first, get a set of letters to remember (B K V J) called the memory set (the memory set size can vary)

31. Retrieval of info from STM Sternberg’s (1966) task first, get a set of letters to remember (B K V J) called the memory set (the memory set size can vary) then get a probe (a letter): encode the probe

32. Retrieval of info from STM Sternberg’s (1966) task first, get a set of letters to remember (B K V J) called the memory set (the memory set size can vary) then get a probe (a letter): encode the probe scan items in STM

33. Retrieval of info from STM Sternberg’s (1966) task first, get a set of letters to remember (B K V J) called the memory set (the memory set size can vary) then get a probe (a letter): encode the probe scan items in STM make decision: Is the probe a letter in the memory set ?

34. Retrieval of info from STM Sternberg’s (1966) task first, get a set of letters to remember (B K V J) called the memory set (the memory set size can vary) then get a probe (a letter): encode the probe scan items in STM make decision: Is the probe a letter in the memory set ? press button for yes (a positive response) or button for no (a negative response)

35. Retrieval of info from STM Sternberg’s (1966) task first, get a set of letters to remember (B K V J) called the memory set (the memory set size can vary) then get a probe (a letter): encode the probe scan items in STM make decision: Is the probe a letter in the memory set ? press button for yes (a positive response) or button for no (a negative response) Collect reaction time (RT) for response

36. B V

37. V

39. R C

40. T

42. B V M S

43. S

45. R C G W

46. T

47. Encode probe Scan: Compare probe to items in memory set Decision yes/no Execute motor response

49. Encode probe Scan: Compare probe to items in memory set Decision yes/no Execute motor response How do we scan items in STM?

50. Encode probe Scan: Compare probe to items in memory set Decision yes/no Execute motor response How do we scan items in STM? all at the same time (parallel search)? one at a time (serial search)?

51. RT (ms) Reaction Time as of Memory Set Size Memory Set Size 123456123456 0 400 500 600 700

52. RT (ms) Reaction Time as of Memory Set Size Memory Set Size 123456123456 0 400 500 600 700 Scan all items at once (parallel search)

53. RT (ms) Reaction Time as of Memory Set Size Memory Set Size 123456123456 0 400 500 600 700 Scan items one at a time (serial search)

54. RT (ms) Reaction Time as Function of Memory Set Size Memory Set Size 123456123456 0 400 500 600 700

55. RT (ms) Reaction Time as Function of Memory Set Size Memory Set Size 123456123456 0 400 500 600 700 Scan items one at a time (serial search)!

56. RT (ms) Reaction Time as Function of Memory Set Size Memory Set Size 123456123456 0 400 500 600 700 RT = mx + b

57. RT (ms) Reaction Time as Function of Memory Set Size Memory Set Size 123456123456 0 400 500 600 700 RT = mx + b m, slope of line x, # of items in mem set b, y-intercept

58. RT (ms) Reaction Time as Function of Memory Set Size Memory Set Size 123456123456 0 400 500 600 700 RT = mx + b m = 38 ms (slope) x, # of items in mem set b = 397 ms (y-intercept)

59. RT (ms) Reaction Time as Function of Memory Set Size Memory Set Size 123456123456 0 400 500 600 700 RT = 38x + 397 m = 38 ms (slope) x, # of items in mem set b = 397 ms (y-intercept)

60. Encode probe Scan: Compare probe to items in memory set Decision yes/no Execute motor response

61. Encode probe Scan: Compare probe to items in memory set Decision yes/no Execute motor response Slope 38 ms per item in set y-intercept

62. Serial search Question: Exhaustive or Self-terminating Search? Exhaustive: Scan all the items in the memory set (no matter what) Self-terminating: Stop scanning if a match is found

63. Serial search Question: Exhaustive or Self-terminating Search? Exhaustive: Scan all the items in the memory set (no matter what) Self-terminating: Stop scanning if a match is found “no” vs. “yes” responses “no” responses: must scan all items (to know probe is not in the set) “yes” responses: could scan all items OR stop scanning if match found

64. Serial search -- “no” vs. “yes” responses “no” responses: must scan all items (to know probe is not in the set) “yes” responses: could scan all items OR stop scanning if match found Reasoning If the scanning is exhaustive (regardless of whether the probe is present in the memory set) then the slopes of RT functions should be the same for “yes” and “no” responses. If the scanning is self-terminating, then the slope of the “yes” RT function should be half that of the “no” RT function. Why? On average, the probe will occur half- way through the serial scanning.

65. RT (ms) Reaction Time as Function of Memory Set Size Memory Set Size 123456123456 0 400 500 600 700 Exhaustive search prediction “No” “Yes”

66. RT (ms) Reaction Time as Function of Memory Set Size Memory Set Size 123456123456 0 400 500 600 700 Self-terminating search prediction “No” “Yes”

67. RT (ms) Reaction Time as Function of Memory Set Size Memory Set Size 123456123456 0 400 500 600 700 Actual finding “No” “Yes”

68. Serial search Question: Exhaustive or Self-terminating Search? Exhaustive: Scan all the items in the memory set (no matter what) Self-terminating: Stop scanning if a match is found

69. Serial search Question: Exhaustive or Self-terminating Search? Exhaustive: Scan all the items in the memory set (no matter what) Seems kind of weird. Why not stop if there is a match?

70. Serial search Question: Exhaustive or Self-terminating Search? Exhaustive: Scan all the items in the memory set (no matter what) Seems kind of weird. Why not stop if there is a match? Don’t confuse scanning stage with the decision stage. If scanning is fast but decision is slow, then it is more efficient to scan all items, then make a single decision compared to making a decision after scanning each item (i.e., making multiple decisions).

71. Forgetting and Interference in Short-term memory Brown-Peterson Task Proactive Interference (PI) Release from PI Retrieval of info from STM Sternberg (1966) Task Stages Findings