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Memory: Retention and Retrieval

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  1. Memory: Retention and Retrieval Thomas G. Bowers, Ph.D. 2001

  2. What Is Memory? • Some claim it is the exact neurological trace, even though it may not be obtained on attempts at recall • Penfield (1959) has been cited for this view • Provided electric stimulation directly to the brain while an individual was conscious

  3. What Is Memory? • Penfield • Reports of relatively vivid, clear experiences • Doubtful if this is truly memory, however

  4. What Is Memory? • Nelson (1971) • While later material may be lost to recall, there appears to be a large gain in re-acquiring the information

  5. Retention Functions • Retention functions are highly predictable and orderly • Dates back to Ebbinghaus studies • Negatively accelerated curve

  6. Retention Functions • Wickelgren (1975) described a d’ function • Measure of memory strength

  7. Retention Functions • Where T is time • Can be transformed to linear curve

  8. Retention Functions • Where T is still time, and C is a constant • C=10a

  9. Retention Functions Most recall is represented by this type of curve, a negatively accelerated effect D’ Time

  10. Retention Functions These curves represent a power function, and the pattern is described as the power law of forgetting Logof D’ Log of Time

  11. Retention Functions • Wickelgren (1975) and associates demonstrated this effect • Forgetting appears to be highly predictable and orderly • Why should this be so?

  12. Retention Functions • Bahrick (1975) demonstrated a similar effect for long-term retention • Also noted the impact of increased exposure • Claimed later higher levels of drop off was related to physiological deterioration in old age

  13. Does Forgetting Exist? • While it appears obvious that forgetting exists, it is not clear how forgetting occurs • What is the process of forgetting? • 1. A decay of memory? • 2. A failure of retrieval? • 3. Problems in interference?

  14. Examples of Hypermnesia • Short story - Borges (1964) “Funes the memorious” • Could not forget anything - memory like a garbage heap

  15. Examples of Hypermnesia • Luria (1968) described the case of “S” • Remembered everything - but on tests of intelligence, did not do well, because he was often distracted by rich details of memory

  16. Theoretical Accounts of Forgetting • I. Decay theory • With the passage of time, memories fade or erode • II. Inference theory • Memories fade due to competing effects

  17. Decay Theory • Testing the decay theory • Of course, memory for remote events is weak relative to recent events • Not a unique effect of decay however

  18. Decay Theory • Testing the decay theory • It is also possible the reduction of remote memory is due to interference as well • In most studies (usually classical conditioning), the mere passive of time is a poor predictor of forgetting

  19. Decay Theory • Testing the decay theory • Classical study by Jenkins and Dallenbach (1924) • Compared retention intervals under sleep and waking conditions, with intervals of 1, 2, 4, 8 hours • Nonsense syllable learning

  20. Decay Theory Sleep Syllables Recalled Waking Hours

  21. Decay Theory • Braddeley and Hitch (1977) • Tested inference theory on rugby players recall of meaningful material (i.e. team names)

  22. Decay Theory Percent Recall Number of intervening games

  23. Decay Theory • With the passage of time, memories fade or erode • Cells may die • Networks may evolve

  24. Decay Process • Depends on a frequency effect • Testing the decay notion • Contrast with the notion of interference • Forgetting occurs because new learning works against older learning • Actual passage of time is a poor predictor of forgetting

  25. Forgetting With Time Asleep Sleep % Retent Wake Hours

  26. II. Interference Notion • It is hypothesized that competing cognitive demands account for forgetting

  27. Interference Evidence • Interference paradigm • List learning inference • Learn A-B • Learn A-D • Test A-B • List learning control • Learn A-B • Learn C-D • Test A-B

  28. Interference Evidence • Interference paradigm • Results • Non-interference yields better learning

  29. Interference Notion - Types • Proactive interference • Learning that has come before can impact negatively if similar • Retroactive interference • Learning that has come latter can impact negatively as well

  30. Why Does Interference Occur? • Mechanisms • 1. Response competition • It does not appear that only intrusion errors account for interference • May instead be an interference or error in effort • 2. Unlearning must also occur • Similar to extinction

  31. Evidence Against Interference • It was thought that interference could explain most or all forgetting • However, some efforts questioned that idea • Cued recall versus free recall

  32. Cueing Eliminates Interference Cued Recall % Recall Free Recall Number of Lists

  33. III. Alternatives to Interference Theory • Network theories may explain results better • Activation of nodes or associative links • There is evidence of elaboration and inferential reconstruction • Tends to demonstrate semantically significant material

  34. Repression • Freud’s theory claimed that the conscious mind was denied access, but that the memories were not erased • Forgetting is thought to be selective in the service of the psyche • “Slips”, or returns when dreaming, or fatigued

  35. Repression • There have been some experimental demonstration of repression phenomenon • Other explanations may be possible, however • Some individuals have demonstrated later (a few days) superior recall of material thought to be subject to repression

  36. Repression • Parkin, Lewinsohn & Folkard (1982) • Tested recall to neutral words (window, cow, tree) • Tested recall to emotional words (quarrel, angry, fear) • Superior memory on immediate recall for neutral words, but better delayed (7 days) recall of emotional words

  37. Repression • Parkin, Lewinsohn & Folkard (1982) Immediate Delayed Emotional 24.1 Emotional 21.1 Neutral 27.6 Neutral 18.3

  38. Repression • Processed by defenses as • 1. Displacement • 2. Sublimation • 3. Projection • From this view, it is thought memories can be recovered • Hypermnesia can be demonstrated experimentally

  39. Hypnosis • There is considerable research on hypnosis, mostly focused on therapeutic aspects • Described as a relaxed state of narrowed awareness, with increased suggestibility • Eg. Reading an interesting book

  40. Hypnosis • No evidence that hypnosis can enhance memory, although there may be a state dependent effect, and relaxed recall may also be helpful • However, individuals are also more suggestible in this state • Rate recall as more certain, but doubtful increase in accuracy

  41. Repression • There is dispute and controversy about repression and recovered memories in therapy • Recovered memories remain controversial

  42. Emotions and Memory • We may expect to not remember unpleasant emotional events, but in fact we tend to recall dramatic experiences well • Flashbulb effects - clarity about highly significant events • Even so, memory is far from perfect

  43. Emotions and Memory • It has been hypothesized that there is a narrowing of memory and attention during emotionally charged events • Called the Easterbrook (1959) phenomenon • For example, a witness to a crime may only recall the gun

  44. Emotion and Memory • Emotion appears to have multiple effects on memory • Emotional arousal may disorganize early memory and recall, although some elements may be very vivid • Later recall may be enhanced by emotional arousal