Memory: Retention and Retrieval

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Memory Retention and Retrieval

• Thomas G. Bowers, Ph.D.
• 2001

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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

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What Is Memory?

• Penfield
• Reports of relatively vivid, clear experiences
• Doubtful if this is truly memory, however

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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

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Retention Functions

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

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Retention Functions

• Wickelgren (1975) described a d function
• Measure of memory strength

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Retention Functions

• Where T is time
• Can be transformed to linear curve

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Retention Functions

• Where T is still time, and C is a constant
• C10a

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Retention Functions
Most recall is represented by this type of curve,
a negatively accelerated effect
D
Time
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Retention Functions
These curves represent a power function, and the
pattern is described as the power law of
forgetting
Logof D
Log of Time
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Retention Functions

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

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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

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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?

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Examples of Hypermnesia

• Short story - Borges (1964) Funes the memorious
• Could not forget anything - memory like a garbage
  heap

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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

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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

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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

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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

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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

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Decay Theory
Sleep
Syllables Recalled
Waking
Hours
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Decay Theory

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

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Decay Theory
Percent Recall
Number of intervening games
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Decay Theory

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

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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

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Forgetting With Time Asleep
Sleep
Retent
Wake
Hours
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II. Interference Notion

• It is hypothesized that competing cognitive
  demands account for forgetting

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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

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Interference Evidence

• Interference paradigm
• Results
• Non-interference yields better learning

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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

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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

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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

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Cueing Eliminates Interference
Cued Recall
Recall
Free Recall
Number of Lists
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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

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Repression

• Freuds 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

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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

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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

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Repression

• Parkin, Lewinsohn Folkard (1982)

Immediate Delayed Emotional 24.1 Emotional
21.1 Neutral 27.6 Neutral 18.3
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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

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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

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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

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Repression

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

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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

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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

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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