CognitivePsychology Lectures: By StephenR.Schmidt, MTSU

Theories of Forgetting

Last Modified 10/24/2000
  1. Introduction
  2. Decay Theory
  3. Consolidation Theory
  4. Interference Theory
  5. Retrieval Failure
  6. Repression
  7. Conclusions

I. Introduction

A. Focusing on Forgetting from LTS

Forgetting from SIS: decay, masking
Forgetting from STS: displacement
Forgetting from LTS?

B. Multiple Factors

II. Decay Theory

A. Definition: Spontaneous loss of information over time.

Classic Shape of the forgetting curve (Woodworth, 1938).
 

 
Woodworth & Schlosbeg (1961)


Is this evidence for logarithmic decay?

B. Jenkins & Dallenback (1924)

Two subjects studied non-sense syllables
They were tested either immediately, 1, 2, 4 or 8 hours later
During the retention interval they either were awake doing daily activities, or they slept.

If decay is the primacy source of forgetting, then the rates of forgetting should be similar in the awake and the sleep conditions.
 

Results


 

C. Studies of Very-Long-Term Memory

1) Bahrick et al. (1975)

Studied retention of names and faces of high school classmates.

2. Bahrick (1984)

Studied retention of Spanish Vocabulary


 
 

 Both studies showed stable memories lasting close to 50 years.
 

D.  Conclusions of Decay


1)  Shape of the forgetting curve is greatly influenced by the activities during the retention interval.

2)  The logarithmic function does not hold for autobiographical memories.

3)  Therefore, there is little evidence that decay is the primary cause of loss of information from long-term memory.

III. Consolidation Theory

A. Consolidation:

As a result of experience, certain neural activities responsible for permanent memories are set into motion. Disruption of these activities leads to poorly formed memories, and thus, forgetting.
 
 

B. Anecdotal evidence:  retrograde amnesia

C. Laboratory Evidence:

Passive avoidance training

apparatus:

Electro-Convulsive Shock

Chorover & Schiller (1965) Results:

D.  Consolidation and Sleep (Plihal & Born, 1997)

Participants learned one of two tasks
  paired associate lists
  mirror tracing
Learning occurred either:
  early (between 10:15 & 11 pm)
  late (after 3 hours of sleep)


Sleep conditions were then tested after 3 hours of sleep
Wake conditions were tested after 3 hours of viewing slides (either early or late)

Results:

Percent Improvement in Paired Asscociate Learning:


 

Percent Improvement in Mirror Tracing:

Conclusion:

Sleeping during a retention interval led to better memory than wakefulness:

 
  early sleep (non-REM) aids declarative memory
  late sleep (REM) aids procedural memory

E. Problems with consolidation theory

  1. Limited to special circumstances
    1. trauma - disrupts consolidation
    2. sleep - aids consolidation
  2. Does not explain the role of the “content” of the experiences during a retention interval.

IV. Interference Theory

A. Basic Assumptions

1. Forgetting is caused by interference between information being tested and other information that has been learned.

 2. Analysis of learning in terms of associations between stimulus and response terms.
 
 

S -> R

3. a) Interference occurs when the same stimulus is associated with more than one response.

 e.g.,

S -> R1

S -> R2

b) or, when similar stimuli (S and S') are associated with different responses.

 e.g.,

S' -> R1

S -> R2

4. Two mechanisms are responsible for interference:
 
 

B. Examples of interference in action:

phone numbers
tennis and racket ball
 
 

C. Experimental Designs for Studying Interference

Retroactive Interference:

Interference Group    Study A    Study B   Test A
Control Group         Study A       -      Test A

Proactive Interference:

Interference Group    Study A    Study B    Test B
Control Group            -       Study B    Test B

D. Illustrative Experiment:

Barnes & Underwood (1959)

1) Ss learned a list of paired-associates until perfect recall:

A-B (e.g., chair-dog)


 2) Ss then studied a second list with the first terms paired with new words:

A-C (e.g., chair-tree)


 They studied this second list 1, 5, 10, or 20 times

 3) Ss then tested on memory for both response terms:

A _____, _____ (e.g., chair _____, _____)

Results:

E. Problems with Interference Theory

    1. According to Interference Theory,  Proactive Interference (PI) is the result of response competition.  However, PI continues even when response competition is removed.

    2.  Interference theory did not satisfactorily explain retrieval failures.
 

V. Retrieval Failure Theory of Forgetting

A. Basic Assumption:

Forgetting is caused by the inability to access information that is represented in memory.

availability:  the information is represented in memory

accessibility:  the information that is available can be retrieved at a specific time/place.
 

B. Demonstration:

C. Encoding Specificity Principle (Tulving)

Specific encoding operations determine the type of memory trace stored in memory. The type of memory trace determines what retrieval cues will be successful at gaining access to the memory trace.
 
 

Diagram of ESP:

D.  Generate Edit Theory:  An alternative explanation of retrieval processes:

  Generate:  retrieval cues used to generate associates

  Edit:  recognize items generated based on familiarity

E. Encoding Specificity vs. Generate Edit theories of retrieval.

encoding specificity: stresses study-test cue overlap

 generate edit: stresses strength of cue-item association
 
 

Thomson & Tulving (1970) experiment:

a) Subjects studied either:

strong associates: e.g., white-black
or
weak associates: e.g., train-black

b) memory test contained either:

strong cues: e.g. white
weak cues: e.g. train
 
 

c) results

Results 
                                       Test Cues
                            Strong (white ?)    Weak (train ?)
Study       Strong             20.2             9.2
            (white-black)
Cues        Weak               13.9            15.7
            (train-black)

E. Applications of Encoding Specificity

1) Context Effects on Memory

a) water

Godden & Baddeley (1975) wet/dry study
                             Test Environment
                             Dry         Wet
Study              Dry        13.4       8.5
            
Environment        Wet         8.4      11.5

b) music

Smith (1985) music and memory
                              Music at Test
                         Mozart        Jazz       Quiet
Music       Mozart       18.2         12.7        13.3
at          Jazz         11.2         20.8         8.5
Study       Quiet        16.3         15.3        11.7

c) smell

Schab (1990) Chocolate Study
                         Test Cues
                      Odor     No Odor
Study       Odor      .21       .17
            
Cues        No Odor   .13       .14
Herz (1997) Odor & Memory

Distinctiveness of the odor is important.

2) State Dependent Effects on Memory

drugs

Eich et al (1975) marijuana study

 Results (free recall)
 
  

                                  Test
                       No Drug           Drug
Study       No Drug     11.5              9.9
               Drug      6.7             10.5

F. Conclusions:

Very rich description of memory failures
May be circular:
How could this theory be proved wrong?

VI. Repression

A. Definitions: Freud's original formulation

1) conscious process of burying memories to protect the ego.

2) the emotions associated with the repressed memory may be recovered, or express themselves.
 

3) such expression is metaphorical.
    (example: fear of Santa Claus)

 

B. Common contemporary definition:

  1) conscious and unconscious process of forgetting traumatic experiences.

 2)  repressed memories can be recovered through therapy and/or hypnosis.

 3)  recovered memories are taken as literal and accurate memories of the actual experience.
 

C.  Problems with contemporary views of repression:

1)  They predict an unlikely combination of factors wherein:

    a) an event is so traumatic that it is poorly recalled or completely forgotten
                       and
    b) upon recovery of the memory, it is detailed and accurate

That is, memory goes from 0 to 100%!
 

2)  The unlikely combination predicted contradicts research concerning the impact of arousal on memory.

a) Research suggests that mild arousal leads to improved memory for an event (e.g., Christianson et al., 1991)

b)  When arousal leads to forgetting,  the memories are poorly integrated, lack details, and may be little more than a record of the emotional response to the trauma (e.g., Metcalfís, 1998, work on hot/cold cognition).

Conditions that lead to repression will lead to poor memory!

3)  Existence of repression accepted as a mater of faith, incapable of disproof.

 Example:
 "When someone asks you, "Where you sexually abused as a child?" there are only two answers: One of them is "yes," and one of them is "I don't know." You can't say "no."
- Rosanne Arnold, on "Oprah"
 

4)  Evidence for repression comes from questionable sources:


 a) from uncorroborated reports of recovered memories from extended psychotherapy

 b) from profoundly disturbed individuals who have difficulty distinguishing between reality and fantasy, and between the remembered and the imagined.
 

D. Repression and theories of forgetting (Loftus & Polage, 1998)

Three ways in which memory failures are “mistaken” as repression.

1)  Retrieval failures:  misunderstood experiences (e.g. child sexual abuse) are often poorly remembered.

2)  Distorted views of one’s own memory.

  Memory for a period of forgetting.
3)  False memories:
Suggestive recovery techniques lead one to create a false memory.  These “memories” may help one to understand their anxiety, and for this reason are found to be quite compelling.

VII. Conclusions on Forgetting

Four different explanations:


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