PSYB2PSYB2Cognitive PsychologyCognitive Psychology

Remembering and ForgettingRemembering and Forgetting

Models of MemoryModels of Memory

3 Main Processes in Memory3 Main Processes in Memory

REGISTRATIONREGISTRATION The process by which the sense organs The process by which the sense organs

detect information and enter that detect information and enter that information in the memory system.information in the memory system.

STORAGESTORAGE The process by which information is kept The process by which information is kept

in the memory.in the memory. RETRIEVALRETRIEVAL The process by which information in The process by which information in

memory is recoveredmemory is recovered

The Multi-Store ModelThe Multi-Store Model

Developed by Atkinson and Shiffrin Developed by Atkinson and Shiffrin (1968, 1971)(1968, 1971)

This model is often called the This model is often called the Two Two Process ModelProcess Model

This model highlights the importance This model highlights the importance of two stores.of two stores.

The Short-term Memory The Short-term Memory (STM)(STM) & The & The Long Term Memory Long Term Memory (LTM)(LTM)

How does this model describe How does this model describe memory?memory?

As information flowing through a As information flowing through a systemsystem

Info detected by sense organs and Info detected by sense organs and passed into the passed into the SENSORY REGISTERSENSORY REGISTER

Info can be kept there if it is Info can be kept there if it is rehearsedrehearsed

If we attend to this information it is If we attend to this information it is transferred to the transferred to the STMSTM

What happens after attending to What happens after attending to the information?the information?

Information from the Information from the STMSTM is passed is passed to the to the LTMLTM if it is rehearsed. if it is rehearsed.

If the rehearsal does not occur, then If the rehearsal does not occur, then the information is forgotten.the information is forgotten.

Rehearsal: Rehearsal: Craik & Watkins Craik & Watkins identified 2 types of rehearsalidentified 2 types of rehearsal

Maintenance Maintenance RehearsalRehearsal

A word repeated A word repeated out loud a number out loud a number of times.of times.

This is enough to This is enough to keep info in the keep info in the STMSTM

Elaborative Elaborative RehearsalRehearsal

Info processed in Info processed in term of it’s term of it’s meaning.meaning.

This is needed to This is needed to transfer info from transfer info from STMSTM to to LTMLTM..

Comparing SM, STM and LTMComparing SM, STM and LTM

Sensory Sensory RegisterRegister

STMSTM LTMLTM

CapacityCapacitySmallSmall 7 + or - 27 + or - 2 UnlimitedUnlimited

DurationDuration 0.25-2 0.25-2 secondsseconds

Up to 30 Up to 30 secondsseconds

Indefinite Indefinite periodperiod

EncodingEncoding Modality-Modality-specificspecific

Mainly Mainly acousticacoustic

SemanticSemantic

VisualVisual

AcousticAcoustic

Sensory RegisterSensory Register

The SR is what happens after info has The SR is what happens after info has reached the sense organs, and it travels to reached the sense organs, and it travels to the brain for interpretation.the brain for interpretation.

This lingering of information in the nervous This lingering of information in the nervous system (very briefly) gives the brain time system (very briefly) gives the brain time to interpret it.to interpret it.

The SR is modality specific, which means The SR is modality specific, which means information is held in the same sense that information is held in the same sense that it is registered. (a taste is held as a taste)it is registered. (a taste is held as a taste)

Storage in the SRStorage in the SR

Iconic StorageIconic Storage Associated with visual informationAssociated with visual information Echoic StorageEchoic Storage Associated with heard or auditory Associated with heard or auditory

information.information. The processing in sensory memory is The processing in sensory memory is

largely unconscious and therefore largely unconscious and therefore has to be deduced from experiments.has to be deduced from experiments.

Evidence for Iconic Storage in the Evidence for Iconic Storage in the SR.SR.

Sperling (1960) used a tachistoscope Sperling (1960) used a tachistoscope to display words for a very short, to display words for a very short, controlled time. controlled time.

He then tested memory recall in the He then tested memory recall in the SR.SR.

The Experiment was as followsThe Experiment was as follows

GG BB TT FFSS RR DD WWEE NN ZZ XX

Write down the letters you can Write down the letters you can remember.remember.

GG BB TT FF

SS RR DD WW

EE NN ZZ XX

ResultsResults

The participants could recall on average The participants could recall on average about 4.5 of the 12 items.about 4.5 of the 12 items.

This provides evidence for the capacity of This provides evidence for the capacity of the Sensory Register.the Sensory Register.

Sperling produced research to prove Sperling produced research to prove participants were reading an after image, participants were reading an after image, by asking participants to recall specific by asking participants to recall specific words after the image had faded.words after the image had faded.

Recall got worse the longer the delay Recall got worse the longer the delay between seeing and recall.between seeing and recall.

S.T.MS.T.M

The capacity of the short-term The capacity of the short-term memory has been listed as 7 + or – 2 memory has been listed as 7 + or – 2 items.items.

This idea was put forward by Miller This idea was put forward by Miller who suggested that there were who suggested that there were between 5 and 9 slots in the STM.between 5 and 9 slots in the STM.

However, Miller didn’t specify the However, Miller didn’t specify the amount of information that can be amount of information that can be held in each slot.held in each slot.

Remember the following list of Remember the following list of letters.letters.

M S E H G F S B P A C N I 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 E R P U S I G S O E S S A

Y T G T U DY T G T U D

Now try to remember these lettersNow try to remember these letters

MAMA SCISCI

ENGENG HISTHIST

GEOGGEOG FREFRE SPASPA

BUSSTUDBUSSTUD PSYPSY

ChunkingChunking

As can be seen from this experiment, As can be seen from this experiment, you can recall more letters in the you can recall more letters in the second condition than in the first.second condition than in the first.

In terms of Miller’s ideas the first 32 In terms of Miller’s ideas the first 32 letters are more than the 5 to 9 letters are more than the 5 to 9 items stored in the STM.items stored in the STM.

However chunking the letters in to However chunking the letters in to meaningful structures allows you to meaningful structures allows you to remember all 32 lettersremember all 32 letters

Proof of the Rehearsal LoopProof of the Rehearsal Loop

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

Try to remember the following Try to remember the following trigrams (groups of 3 consonants)trigrams (groups of 3 consonants)

QWS HRV JLM TRW QWS HRV JLM TRW FBC XZM PSB MNT FBC XZM PSB MNT

PVX TLRPVX TLR

Now count aloud back from 176 to 0 Now count aloud back from 176 to 0

Implications of this experimentImplications of this experiment

The main aim was to prevent the The main aim was to prevent the participants from rehearsing the participants from rehearsing the trigrams.trigrams.

They found that information was They found that information was easily forgotten; they concluded that easily forgotten; they concluded that without rehearsal, material in the without rehearsal, material in the STM is forgotten within 6-12 seconds.STM is forgotten within 6-12 seconds.

Fill in the gaps.Fill in the gaps.

A______ and S_______ M______ S______ A______ and S_______ M______ S______ M______ described information as M______ described information as flowing through a system composed flowing through a system composed of s______ r_____, ____ and _______.of s______ r_____, ____ and _______.

____ has a very limited capacity and ____ has a very limited capacity and is m_______ based. Info is held only is m_______ based. Info is held only briefly in the s______ o______ through briefly in the s______ o______ through which it is received.which it is received.

STM uses an a______ code and has a STM uses an a______ code and has a capacity of __ + or - __ items. It lasts capacity of __ + or - __ items. It lasts between __ and __ secs, but can be between __ and __ secs, but can be extended by r______.extended by r______.

LTM has u______ capacity and can LTM has u______ capacity and can potentially last indefinitely. It mainly potentially last indefinitely. It mainly uses s_______ code, but information uses s_______ code, but information can also be encoded v_____ and can also be encoded v_____ and a______.a______.

Evidence for the multi-store modelEvidence for the multi-store model

Primacy and Recency effectPrimacy and Recency effect As far back as 1885, Ebbinghaus As far back as 1885, Ebbinghaus

carried out similar experiments using carried out similar experiments using nonsense syllables, e.g. LIF and DAK, nonsense syllables, e.g. LIF and DAK, and found that, typically, words near and found that, typically, words near the beginning and end of the list the beginning and end of the list were better recalled than those in were better recalled than those in the middle.the middle.

The effect whereby the first words in the The effect whereby the first words in the list are well recalled is known as the list are well recalled is known as the Primacy EffectPrimacy Effect and the effect whereby and the effect whereby the last few words are recalled is known as the last few words are recalled is known as the the Recency Effect.Recency Effect.

Evidence that the recency effect is due to Evidence that the recency effect is due to retrieval from STM is given by Glanzer and retrieval from STM is given by Glanzer and Cunitz (1966) who found that recency Cunitz (1966) who found that recency effect occurs only if the last items on the effect occurs only if the last items on the list are recalled immediately; if recall is list are recalled immediately; if recall is delayed, the effect disappears.delayed, the effect disappears.

Murdock (1962)Murdock (1962)

There is evidence for the functional There is evidence for the functional separation of STM and LTM from a study separation of STM and LTM from a study carried out by Murdock.carried out by Murdock.

Words of varying length (10 to 40 per Words of varying length (10 to 40 per participant) were presented at 2 second participant) were presented at 2 second intervals. When participants were asked to intervals. When participants were asked to recall in any order, they found that they recall in any order, they found that they remembered more of the words at the remembered more of the words at the beginning and the end of the list than beginning and the end of the list than words in the middle.words in the middle.

Serial Position CurveSerial Position Curve

A graph to show A graph to show the serial position the serial position effect (the effect (the percentage recall percentage recall of each word of each word according to its according to its position on the list) position on the list) in a free recall in a free recall task.task.

Explanation of Murdock’s resultsExplanation of Murdock’s results

The words in the middle of the list The words in the middle of the list have been have been displaced displaced from STM and from STM and not yet not yet consolidatedconsolidated into LTM. into LTM.

The P+R effect is strong evidence of The P+R effect is strong evidence of the existence of 2 separate the existence of 2 separate functioning stores.functioning stores.

Clinical evidence for the MSMClinical evidence for the MSM

Milner (1996)Milner (1996) Scoville and Milner described the Scoville and Milner described the

now classic case study of HM, a man now classic case study of HM, a man who had drastic brain surgery to cure who had drastic brain surgery to cure his epilepsy.his epilepsy.

One consequence of this procedure One consequence of this procedure was that he suffered from was that he suffered from anterograde amnesia.anterograde amnesia.

He could recall events that happened He could recall events that happened before the operation, such as details before the operation, such as details of friends he knew before the of friends he knew before the surgery, but very little of what surgery, but very little of what occurred afterwards.occurred afterwards.

He re-read newspapers unaware that He re-read newspapers unaware that he had just read them, and only he had just read them, and only knew what time it was for about 15 knew what time it was for about 15 seconds after he looked at the clockseconds after he looked at the clock

All the people he met after the All the people he met after the surgery had to be re-met everytime surgery had to be re-met everytime they visited him, as he couldn’t they visited him, as he couldn’t remember who they were.remember who they were.

Why the case of HM supports the Why the case of HM supports the MSMMSM

It supports the idea that the brain uses It supports the idea that the brain uses different mechanisms for holding different mechanisms for holding information for a short time, and for information for a short time, and for holding it relatively permanently.holding it relatively permanently.

HM could remember a lot before the HM could remember a lot before the surgery, so presumably his existing LTM surgery, so presumably his existing LTM was unaffected by the operation, but he was unaffected by the operation, but he did not seem to be able to transfer new did not seem to be able to transfer new information from his STM into his LTM.information from his STM into his LTM.

Different types of codingDifferent types of coding

One other piece of evidence for the One other piece of evidence for the MSM is that different types of MSM is that different types of encoding are used in the STM and encoding are used in the STM and LTM.LTM.

The fact that short-term encoding is The fact that short-term encoding is so different from long-term encoding so different from long-term encoding supports the idea that there are 2 supports the idea that there are 2 distinct stores.distinct stores.

Further Evidence Further Evidence KORSAKOV SYNDROMEKORSAKOV SYNDROME

Further clinical evidence comes from Further clinical evidence comes from patients who suffer from Korsakov patients who suffer from Korsakov syndrome (usually caused by alcohol syndrome (usually caused by alcohol poisoning). poisoning).

Patients with this syndrome forget all Patients with this syndrome forget all new material within seconds of new material within seconds of receiving it, although their LTM is receiving it, although their LTM is intact. They seem to have a specific intact. They seem to have a specific difficulty in transferring info from difficulty in transferring info from STM to LTMSTM to LTM

Evaluative CommentsEvaluative Comments

The MSM proposed that rehearsal was the The MSM proposed that rehearsal was the key for transferring info from STM to LTM. key for transferring info from STM to LTM.

Although rehearsal may be important in Although rehearsal may be important in some cases (memorising a phone some cases (memorising a phone number), in everyday life we rarely number), in everyday life we rarely rehearse info and yet we seem to store a rehearse info and yet we seem to store a lot of things. lot of things.

We may for example remember something We may for example remember something from a lesson because it was funny or from a lesson because it was funny or interesting. This is better explained by the interesting. This is better explained by the Levels of Processing theoryLevels of Processing theory

The MSM has been criticised for The MSM has been criticised for being oversimplified with its view of being oversimplified with its view of STM and LTM structures operating in STM and LTM structures operating in a single, uniform fashion. a single, uniform fashion.

We now know that this is not the We now know that this is not the case. The working memory model is case. The working memory model is a more active model of human a more active model of human processing where STM is more than processing where STM is more than one unitary store but comprises a one unitary store but comprises a number of different stores.number of different stores.

Case studies of patients with brain Case studies of patients with brain damage suggest that the multi-store damage suggest that the multi-store model is over-simplified. For model is over-simplified. For example, a patient known as KF example, a patient known as KF suffered brain damage following a suffered brain damage following a motorcycle accident, and underwent motorcycle accident, and underwent brain surgery. Some years later he brain surgery. Some years later he was found to have normal LTM was found to have normal LTM storage but an STM capacity of only storage but an STM capacity of only 2 items. If STM was necessary for the 2 items. If STM was necessary for the transfer of information to LTM, then transfer of information to LTM, then KF’s LTM should have been affectedKF’s LTM should have been affected

Methodological EvaluationMethodological Evaluation

Many of the studies supporting the Many of the studies supporting the MSM use lab experiments, and can MSM use lab experiments, and can therefore be criticised in terms of therefore be criticised in terms of ecological validity and demand ecological validity and demand characteristics. Findings from such characteristics. Findings from such experiments may tell us very little experiments may tell us very little about how memory works in real life.about how memory works in real life.