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