Transcript Memory - Personal.psu.edu

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
view

Provided electric stimulation directly to the
brain while an individual was conscious
What Is Memory?
Penfield
Reports of relatively vivid, clear
experiences
 Doubtful 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 reacquiring 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’
function

Measure of memory strength
log( d ' )  A  b log T
Retention Functions
Where T is time
Can be transformed to linear curve
log( d ' )  A  b log T
Retention Functions
Where T is still time, and C is a constant
C=10a
d '  CT
b
Retention Functions
D’
Most recall is represented by this type
of curve, a negatively accelerated
effect
Time
Retention Functions
These curves represent a power
function, and the pattern is described
as the power law of forgetting
Log
of
D’
Log of Time
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 retention
Also noted the impact of increased
exposure
 Claimed 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
occurs

What 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 theory

With the passage of time, memories fade
or erode
II. Inference theory

Memories fade due to competing effects
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

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 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

Decay Theory
Sleep
Syllables
Recalled
Waking
Hours
Decay Theory
Braddeley and Hitch (1977)

Tested inference theory on rugby players
recall of meaningful material (i.e. team
names)
Decay Theory
Percent
Recall
Number of intervening games
Decay Theory
With the passage of time, memories
fade or erode
Cells may die
 Networks may evolve

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

Forgetting With Time
Asleep
Sleep
%
Retent
Wake
Hours
II. Interference Notion
It is hypothesized that competing
cognitive demands account for
forgetting
Interference Evidence
Interference paradigm

List learning inference
Learn A-B
 Learn A-D
 Test A-B


List learning control
Learn A-B
 Learn C-D
 Test A-B

Interference Evidence
Interference paradigm

Results

Non-interference yields better learning
Interference Notion Types
Proactive interference

Learning 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 effort


2. 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
idea

Cued recall versus free recall
Cueing Eliminates
Interference
Cued
Recall
%
Recall
Free
Recall
Number of Lists
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. Displacement
 2. Sublimation
 3. Projection

From this view, it is thought memories
can be recovered

Hypermnesia 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 helpful
However, individuals are also more
suggestible in this state
Rate 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