Transcript Models of Memory Lesson 1

PSYB2
Cognitive Psychology
Remembering and Forgetting
Models of Memory
3 Main Processes in Memory
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REGISTRATION
The process by which the sense organs
detect information and enter that
information in the memory system.
STORAGE
The process by which information is kept
in the memory.
RETRIEVAL
The process by which information in
memory is recovered
The Multi-Store Model
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Developed by Atkinson and Shiffrin
(1968, 1971)
This model is often called the Two
Process Model
This model highlights the importance
of two stores.
The Short-term Memory (STM) &
The Long Term Memory (LTM)
How does this model describe
memory?
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As information flowing through a
system
Info detected by sense organs and
passed into the SENSORY REGISTER
Info can be kept there if it is
rehearsed
If we attend to this information it is
transferred to the STM
What happens after attending to
the information?
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Information from the STM is passed
to the LTM if it is rehearsed.
If the rehearsal does not occur, then
the information is forgotten.
Rehearsal: Craik & Watkins
identified 2 types of rehearsal
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Maintenance
Rehearsal
A word repeated
out loud a number
of times.
This is enough to
keep info in the
STM
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Elaborative
Rehearsal
Info processed in
term of it’s
meaning.
This is needed to
transfer info from
STM to LTM.
Comparing SM, STM and LTM
Sensory
Register
Capacity
Duration
Encoding
Small
0.25-2
seconds
Modalityspecific
STM
LTM
7 + or - 2 Unlimited
Up to 30
seconds
Indefinite
period
Mainly
acoustic
Semantic
Visual
Acoustic
Sensory Register
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The SR is what happens after info has
reached the sense organs, and it travels to
the brain for interpretation.
This lingering of information in the
nervous system (very briefly) gives the
brain time to interpret it.
The SR is modality specific, which means
information is held in the same sense that
it is registered. (a taste is held as a taste)
Storage in the SR
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Iconic Storage
Associated with visual information
Echoic Storage
Associated with heard or auditory
information.
The processing in sensory memory is
largely unconscious and therefore
has to be deduced from experiments.
Evidence for Iconic Storage in the
SR.
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Sperling (1960) used a tachistoscope
to display words for a very short,
controlled time.
He then tested memory recall in the
SR.
The Experiment was as follows
G B T F
S R D W
E N Z X
Write down the letters you can
remember.
G
S
E
B
R
N
T
D
Z
F
W
X
Results
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The participants could recall on average
about 4.5 of the 12 items.
This provides evidence for the capacity of
the Sensory Register.
Sperling produced research to prove
participants were reading an after image,
by asking participants to recall specific
words after the image had faded.
Recall got worse the longer the delay
between seeing and recall.
S.T.M
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The capacity of the short-term
memory has been listed as 7 + or –
2 items.
This idea was put forward by Miller
who suggested that there were
between 5 and 9 slots in the STM.
However, Miller didn’t specify the
amount of information that can be
held in each slot.
Remember the following list of
letters.
MSEHGFSBPACNI
ERPUSIGSOESS
AYTGTUD
Now try to remember these letters
MA
 SCI
 ENG
 HIST
 GEOG
 FRE
 SPA
BUSSTUD
 PSY
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Chunking
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As can be seen from this experiment,
you can recall more letters in the
second condition than in the first.
In terms of Miller’s ideas the first 32
letters are more than the 5 to 9
items stored in the STM.
However chunking the letters in to
meaningful structures allows you to
remember all 32 letters
Proof of the Rehearsal Loop
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Peterson and Peterson (1959) used
something known as the BrownPeterson technique to investigate the
STM.
Try to remember the following
trigrams (groups of 3 consonants)
QWS HRV JLM
TRW FBC XZM
PSB MNT PVX TLR
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Now count aloud back from 176 to 0
Implications of this experiment
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The main aim was to prevent the
participants from rehearsing the
trigrams.
They found that information was
easily forgotten; they concluded that
without rehearsal, material in the
STM is forgotten within 6-12
seconds.
Fill in the gaps.
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A______ and S_______ M______
S______ M______ described
information as flowing through a
system composed of s______
r_____, ____ and _______.
____ has a very limited capacity and
is m_______ based. Info is held only
briefly in the s______ o______
through which it is received.
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STM uses an a______ code and has
a capacity of __ + or - __ items. It
lasts between __ and __ secs, but
can be extended by r______.
LTM has u______ capacity and can
potentially last indefinitely. It mainly
uses s_______ code, but information
can also be encoded v_____ and
a______.
Evidence for the multi-store model
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Primacy and Recency effect
As far back as 1885, Ebbinghaus
carried out similar experiments using
nonsense syllables, e.g. LIF and
DAK, and found that, typically, words
near the beginning and end of the
list were better recalled than those in
the middle.
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The effect whereby the first words in the
list are well recalled is known as the
Primacy Effect and the effect whereby
the last few words are recalled is known
as the Recency Effect.
Evidence that the recency effect is due to
retrieval from STM is given by Glanzer and
Cunitz (1966) who found that recency
effect occurs only if the last items on the
list are recalled immediately; if recall is
delayed, the effect disappears.
Murdock (1962)
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There is evidence for the functional
separation of STM and LTM from a study
carried out by Murdock.
Words of varying length (10 to 40 per
participant) were presented at 2 second
intervals. When participants were asked to
recall in any order, they found that they
remembered more of the words at the
beginning and the end of the list than
words in the middle.
Serial Position Curve
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A graph to show
the serial position
effect (the
percentage recall
of each word
according to its
position on the list)
in a free recall
task.
Explanation of Murdock’s results
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The words in the middle of the list
have been displaced from STM and
not yet consolidated into LTM.
The P+R effect is strong evidence of
the existence of 2 separate
functioning stores.
Clinical evidence for the MSM
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Milner (1996)
Scoville and Milner described the
now classic case study of HM, a man
who had drastic brain surgery to cure
his epilepsy.
One consequence of this procedure
was that he suffered from
anterograde amnesia.
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He could recall events that happened
before the operation, such as details
of friends he knew before the
surgery, but very little of what
occurred afterwards.
He re-read newspapers unaware that
he had just read them, and only
knew what time it was for about 15
seconds after he looked at the clock
All the people he met after the
surgery had to be re-met everytime
they visited him, as he couldn’t
remember who they were.
Why the case of HM supports the
MSM
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It supports the idea that the brain uses
different mechanisms for holding
information for a short time, and for
holding it relatively permanently.
HM could remember a lot before the
surgery, so presumably his existing LTM
was unaffected by the operation, but he
did not seem to be able to transfer new
information from his STM into his LTM.
Different types of coding
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One other piece of evidence for the
MSM is that different types of
encoding are used in the STM and
LTM.
The fact that short-term encoding is
so different from long-term encoding
supports the idea that there are 2
distinct stores.
Further Evidence
KORSAKOV SYNDROME
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Further clinical evidence comes from
patients who suffer from Korsakov
syndrome (usually caused by alcohol
poisoning).
Patients with this syndrome forget all
new material within seconds of
receiving it, although their LTM is
intact. They seem to have a specific
difficulty in transferring info from
STM to LTM
Evaluative Comments
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The MSM proposed that rehearsal was the
key for transferring info from STM to LTM.
Although rehearsal may be important in
some cases (memorising a phone
number), in everyday life we rarely
rehearse info and yet we seem to store a
lot of things.
We may for example remember something
from a lesson because it was funny or
interesting. This is better explained by the
Levels of Processing theory
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The MSM has been criticised for
being oversimplified with its view of
STM and LTM structures operating in
a single, uniform fashion.
We now know that this is not the
case. The working memory model is
a more active model of human
processing where STM is more than
one unitary store but comprises a
number of different stores.
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Case studies of patients with brain
damage suggest that the multi-store
model is over-simplified. For
example, a patient known as KF
suffered brain damage following a
motorcycle accident, and underwent
brain surgery. Some years later he
was found to have normal LTM
storage but an STM capacity of only
2 items. If STM was necessary for
the transfer of information to LTM,
then KF’s LTM should have been
affected
Methodological Evaluation
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Many of the studies supporting the
MSM use lab experiments, and can
therefore be criticised in terms of
ecological validity and demand
characteristics. Findings from such
experiments may tell us very little
about how memory works in real life.