Remembering and Forgetting
Models of Memory







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





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?




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?


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



Maintenance
Rehearsal
A word repeated out loud a number of times.
This is enough to keep info in the
STM



Elaborative
Rehearsal
Info processed in term of it’s meaning.
This is needed to transfer info from
STM to LTM .

Sensory
Register
STM LTM
Capacity
Small 7 + or - 2 Unlimited
Duration
Encoding
0.25-2 seconds
Modalityspecific
Up to 30 seconds
Mainly acoustic
Indefinite period
Semantic
Visual
Acoustic




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)






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.

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 B T F
S R D W
E N Z X





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.




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.
M S E H G F S B P A C N I
E R P U S I G S O E S S
A Y T G T U D

Now try to remember these letters





MA
SCI
ENG
HIST


GEOG
FRE

SPA
BUSSTUD

PSY




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


Peterson and Peterson (1959) used something known as the Brown-
Peterson technique to investigate the
STM.

Try to remember the following trigrams (groups of 3 consonants)

Now count aloud back from 176 to 0



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.



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.


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


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.



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.



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.


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


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.




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.




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


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.



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


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




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



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.


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


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.