Theories of Forgetting
Last Modified 10/24/2000
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,
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.
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
3) Therefore, there is little evidence that decay is the primary
cause of loss of information from long-term memory.
III. Consolidation Theory
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
Chorover & Schiller (1965) Results:
D. Consolidation and Sleep (Plihal & Born, 1997)
Participants learned one of two tasks
paired associate lists
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)
Percent Improvement in Paired Asscociate Learning:
Percent Improvement in Mirror Tracing:
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
Limited to special circumstances
trauma - disrupts consolidation
sleep - aids consolidation
Does not explain the role of the “content” of the experiences during a
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.
S -> R1
S -> R2
b) or, when similar stimuli (S and S') are associated with different responses.
S' -> R1
S -> R2
4. Two mechanisms are responsible for interference:
response competition: multiple responses are elicited by a stimulus
unlearning: new associations cause extinction of the previous responses
B. Examples of interference in action:
tennis and racket ball
C. Experimental Designs for Studying Interference
Interference Group Study A Study B Test A
Control Group Study A - Test A
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 _____, _____)
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
availability: the information is represented in memory
accessibility: the information that is available can be
retrieved at a specific time/place.
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
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
weak associates: e.g., train-black
b) memory test contained either:
strong cues: e.g. white
weak cues: e.g. train
Strong (white ?) Weak (train ?)
Study Strong 20.2 9.2
Cues Weak 13.9 15.7
E. Applications of Encoding Specificity
1) Context Effects on Memory
Godden & Baddeley (1975) wet/dry study
Study Dry 13.4 8.5
Environment Wet 8.4 11.5
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
Schab (1990) Chocolate Study
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
Eich et al (1975) marijuana study
Results (free recall)
No Drug Drug
Study No Drug 11.5 9.9
Drug 6.7 10.5
Very rich description of memory failures
May be circular:
How could this theory be proved wrong?
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
2) repressed memories can be recovered through therapy
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
b) upon recovery of the memory, it is detailed
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
"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
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:
decay: minimal role in LTS forgetting
consolidation: disruption occurs under special circumstances
interference theory: explains some forgetting, but the mechanisms need
retrieval failure: richest, most complete explanation, but may be circular.
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