Memory: Retention and Retrieval
Thomas G. Bowers, Ph.D.
2001
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 viewProvided electric stimulation directly to the
brain while an individual was conscious
What Is Memory?
PenfieldReports of relatively vivid, clear
experiencesDoubtful if this is truly memory, however
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
Retention Functions
Retention functions are highly predictable and orderly
Dates back to Ebbinghaus studies
Negatively accelerated curve
Retention Functions
Wickelgren (1975) described a d’ functionMeasure of memory strength
TbAd log)'log(
Retention Functions
Where T is time
Can be transformed to linear curve
TbAd log)'log(
Retention Functions
Where T is still time, and C is a constant
C=10a
bCTd '
Retention Functions
D’
Time
Most recall is represented by this type of curve, a negatively accelerated effect
Retention Functions
Logof D’
Log of Time
These curves represent a power function, and the pattern is described as the power law of forgetting
Retention Functions
Wickelgren (1975) and associates demonstrated this effect
Forgetting appears to be highly predictable and orderly
Why should this be so?
Retention Functions
Bahrick (1975) demonstrated a similar effect for long-term retentionAlso noted the impact of increased
exposureClaimed later higher levels of drop off was
related to physiological deterioration in old age
Does Forgetting Exist?
While it appears obvious that forgetting exists, it is not clear how forgetting occursWhat is the process of forgetting?
1. A decay of memory?2. A failure of retrieval?3. Problems in interference?
Examples of Hypermnesia
Short story - Borges (1964) “Funes the memorious”
Could not forget anything - memory like a garbage heap
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
Theoretical Accounts of Forgetting
I. Decay theoryWith the passage of time, memories fade
or erode
II. Inference theoryMemories fade due to competing effects
Decay Theory
Testing the decay theoryOf course, memory for remote events is
weak relative to recent eventsNot a unique effect of decay however
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
Decay Theory
Testing the decay theoryClassical 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
Decay Theory
SyllablesRecalled
Hours
Sleep
Waking
Decay Theory
Braddeley and Hitch (1977)Tested inference theory on rugby players
recall of meaningful material (i.e. team names)
Decay Theory
PercentRecall
Number of intervening games
Decay Theory
With the passage of time, memories fade or erodeCells may dieNetworks may evolve
Decay Process
Depends on a frequency effect
Testing the decay notionContrast with the notion of interferenceForgetting occurs because new learning
works against older learningActual passage of time is a poor predictor
of forgetting
Forgetting With Time Asleep
Hours
Sleep
Wake
%
Retent
II. Interference Notion
It is hypothesized that competing cognitive demands account for forgetting
Interference Evidence
Interference paradigmList learning inference
Learn A-BLearn A-DTest A-B
List learning controlLearn A-BLearn C-DTest A-B
Interference Evidence
Interference paradigmResults
Non-interference yields better learning
Interference Notion - Types
Proactive interferenceLearning that has come before can impact
negatively if similar
Retroactive interference Learning that has come latter can impact
negatively as well
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 effort2. Unlearning must also occur
Similar to extinction
Evidence Against Interference
It was thought that interference could explain most or all forgetting
However, some efforts questioned that ideaCued recall versus free recall
Cueing Eliminates Interference
%
Recall
Number of Lists
Cued Recall
FreeRecall
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
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
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
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
Repression
Parkin, Lewinsohn & Folkard (1982)
Immediate Delayed
Emotional 24.1 Emotional 21.1
Neutral 27.6 Neutral 18.3
Repression
Processed by defenses as 1. Displacement2. Sublimation3. Projection
From this view, it is thought memories can be recoveredHypermnesia can be demonstrated
experimentally
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
Hypnosis
No evidence that hypnosis can enhance memory, although there may be a state dependent effect, and relaxed recall may also be helpfulHowever, individuals are also more suggestible in this stateRate recall as more certain, but doubtful increase in accuracy
Repression
There is dispute and controversy about repression and recovered memories in therapy
Recovered memories remain controversial
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
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
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