Forgetting

1
Forgetting

• Thomas G. Bowers, Ph.D.
• Penn State Harrisburg
• 2000

2
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?

3
Examples of Hypermnesia

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

4
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

5
Theoretical Accounts of Forgetting

• I. Decay theory
• With the passage of time, memories fade or erode

6
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

7
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

8
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

9
Decay Theory
Sleep
Syllables Recalled
Waking
Hours
10
Decay Theory

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

11
Decay Theory
Percent Recall
Number of intervening games
12
Decay Theory

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

13
Decay
Residual Benefit
14
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

15
Forgetting With Time Asleep
Sleep
Retent
Wake
Hours
16
II. Interference Notion

• Our exercises have demonstrated aspects of
  interference on short term memory
• Can occur in serial learning or paired associate
  tasks

17
Interference Notion

• Proactive interference
• Learning that has come before can impact
  negatively if similar
• Retroactive interference
• Learning that has come latter can impact
  negatively as well

18
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

19
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

20
Cueing Eliminates Interference
Cued Recall
Recall
Free Recall
Number of Lists
21
III. Alternatives to Interference Theory

• Network theories may explain results better
• Activation of nodes or associative links

22
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

23
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

24
Repression

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

25
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

26
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

27
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