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Multi Store Model of Memory - Atkinson
and Shiffrin, 1968
The multi store model (Atkinson and Shiffrin, 1968) is a classic model of memory. It is
sometimes called the modal model or the dual process model.
Atkinson and Shiffrin (1968) suggest that memory is made up of a series of stores (see
below)
The multi store model (Atkinson and Shiffrin 1968) describes memory in terms of
information flowing through a system.
Information is detected by the sense organs and enters the sensory memory.
If attended to this information enters the short term memory.
Information from the STM is transferred to the long-term memory only if that information is
rehearsed.
If rehearsal does not occur, then information is forgotten, lost from short term memory
through the processes of displacement or decay.
Sensory Memory
• Duration: ¼ to ½ second
• Capacity: all sensory experience (v. larger capacity)
• Encoding: sense specific (e.g. different stores for each sense)
Short Term Memory
• Duration: 0-18 seconds
• Capacity: 7 +/- 2 items
• Encoding: mainly auditory
Long Term Memory
• Duration: Unlimited
• Capacity: Unlimited
• Encoding: Mainly Semantic (but can be visual and auditory)
Critical Evaluation
Strengths
Many memory studies provide evidence to support the distinction between STM and LTM
(in terms of encoding, duration and capacity). The model can account for primacy & regency
effects.
The model is influential as it has generated a lot of research into memory.
The model is supported by studies of amnesiacs: For example the HM case study. HM is
still alive but has marked problems in long-term memory after brain surgery. He has
remembered little of personal (death of mother and father) or public events ( Watergate ,
Vietnam War) that have occurred over the last 45 years. However his short-term memory
remains intact.
Weaknesses
The model is oversimplified, in particular when it suggests that both short-term and longterm memory each operate in a single, uniform fashion. We now know is this not the case.
It has now become apparent that both short-term and long-term memory are more
complicated that previously thought. For example, the Working Model of Memory proposed
by Baddeley and Hitch (1974) showed that short term memory is more than just one simple
unitary store and comprises different components (e.g. central executive, visuo-spatial etc.).
In the case of long-term memory, it is unlikely that different kinds of knowledge, such as
remembering how to play a computer game, the rules of subtraction and remembering what
we did yesterday are all stored within a single, long-term memory store. Indeed different
types of long-term memory have been identified, namely episodic (memories of events),
procedural (knowledge of how to do things) and semantic (general knowledge).
The model suggests rehearsal helps to transfer information into LTM but this is not
essential. Why are we able to recall information which we did not rehearse (e.g. swimming)
yet unable to recall information which we have rehearsed (e.g. reading your notes while
revising). Therefore, the role of rehearsal as a means of transferring from STM to LTM is
much less important than Atkinson and Shiffrin (1968) claimed in their model.
However, the models main emphasis was on structure and tends to neglect the process
elements of memory (e.g. it only focuses on attention and rehearsal).
The multi store model has been criticized for being a passive/one way/linear model
Working Memory
Atkinson’s and Shiffrin’s (1968) multi-store model was extremely successful in terms of the
amount of research it generated.
However, as a result of this research, it became apparent that there were a number of
problems with their ideas concerning the characteristics of short-term memory.
Building on this research, Baddeley and Hitch (1974) developed an alternative model of
short-term memory which they called working memory (see fig 1).
Baddeley and Hitch (1974) argue that the picture of short-term memory (STM) provided by
the Multi-Store Model is far too simple. According to the Multi-Store Model, STM holds
limited amounts of information for short periods of time with relatively little processing. It is
a unitary system. This means it is a single system (or store) without any
subsystems. Working Memory is not a unitary store.
Fig 1. The Working Memory Model (Baddeley and Hitch, 1974)
Working memory is STM. Instead of all information going into one single store, there are
different systems for different types of information. Working memory consists of a central
executive which controls and coordinates the operation of two subsystems: the phonological
loop and the visuo-spatial sketch pad.
Central Executive: Drives the whole system (e.g. the boss of working memory) and
allocates data to the subsystems (VSS & PL). It also deals with cognitive tasks such as mental
arithmetic and problem solving.
Visuo-Spatial Sketchpad (inner eye): Stores and processes information in a visual or spatial
form. The VSS is used for navigation.
The phonological loop is the part of working memory that deals with spoken and written
material. It can be used to remember a phone number. It consists of two parts
o Phonological Store (inner ear) – Linked to speech perception Holds information in speechbased form (i.e. spoken words) for 1-2 seconds.
o Articulatory control process (inner voice) – Linked to speech production. Used to
rehearse and store verbal information from the phonological store.
Fig 2. The Working Memory Model Components (Baddeley and Hitch, 1974)
The labels given to the components (see fig 2) of the working memory reflect their function
and the type of information they process and manipulate. The phonological loop is assumed
to be responsible for the manipulation of speech based information, whereas the visuospatial sketch pad is assumed to by responsible for manipulating visual images. The model
proposes that every component of working memory has a limited capacity, and also that the
components are relatively independent of each other.
The Central Executive
The central executive is the most important component of the model, although little is known
about how it functions. It is responsible for monitoring and coordinating the operation of the
slave systems (i.e. visuo-spatial sketch pad and phonological loop) and relates them to long
term memory (LTM). The central executive decides which information is attended to and
which parts of the working memory to send that information to be dealt with.
The central executive decides what working memory pays attention to. For example, two
activities sometimes come into conflict such as driving a car and talking. Rather than hitting a
cyclist who is wobbling all over the road, it is preferable to stop talking and concentrate on
driving. The central executive directs attention and gives priority to particular activities.
The central executive is the most versatile and important component of the working memory
system. However, despite its importance in the working-memory model, we know
considerably less about this component than the two subsystems it controls.
Baddeley suggests that the central executive acts more like a system which controls
attentional processes rather than as a memory store. This is unlike the phonological loop and
the visuo-spatial sketch pad, which are specialized storage systems. The central executive
enables the working memory system to selectively attend to some stimuli and ignore others.
Baddeley (1986) uses the metaphor of a company boss to describe the way in which the
central executive operates. The company boss makes decisions about which issues deserve
attention and which should be ignored. They also select strategies for dealing with problems,
but like any person in the company, the boss can only do a limited number of things at the
same time. The boss of a company will collect information from a number of different
sources.
If we continue applying this metaphor, then we can see the central executive in working
memory integrating (i.e. combining) information from two assistants (the phonological loop
and the visuo-spatial sketch pad) and also drawing on information held in a large database
(long-term memory).
The Phonological Loop
The phonological loop is the part of working memory that deals with spoken and written
material. It consists of two parts (see Figure 3).
The phonological store (linked to speech perception) acts as an inner ear and holds
information in speech-based form (i.e. spoken words) for 1-2 seconds. Spoken words
enter the store directly. Written words must first be converted into an articulatory
(spoken) code before they can enter the phonological store.
Fig 3. The phonological loop
The articulatory control process (linked to speech production) acts like an inner
voice rehearsing information from the phonological store. It circulates information
round and round like a tape loop. This is how we remember a telephone number we
have just heard. As long as we keep repeating it, we can retain the information in
working memory.
The articulatory control process also converts written material into an articulatory
code and transfers it to the phonological store.
The Visuo-Spatial Sketch pad
The visuo-spatial sketch pad (inner eye) deals with visual and spatial information. Visual
information refers to what things look like. It is likely that the visuo-spatial sketch pad plays
an important role in helping us keep track of where we are in relation to other objects as we
move through our environment (Baddeley, 1997).
As we move around, our position in relation to objects is constantly changing and it is
important that we can update this information. For example, being aware of where we are in
relation to desks, chairs and tables when we are walking around a classroom means that we
don't bump into things too often!
The sketch pad also displays and manipulates visual and spatial information held in long-term
memory. For example, the spatial layout of your house is held in LTM. Try answering this
question: How many windows are there in the front of your house? You probably find
yourself picturing the front of your house and counting the windows. An image has been
retrieved from LTM and pictured on the sketch pad.
Evidence suggests that working memory uses two different systems for dealing with visual
and verbal information. A visual processing task and a verbal processing task can be
performed at the same time. It is more difficult to perform two visual tasks at the same time
because they interfere with each other and performance is reduced. The same applies to
performing two verbal tasks at the same time. This supports the view that the phonological
loop and the sketch pad are separate systems within working memory.
Empirical Evidence for the Working Memory Model
What evidence is there that working memory exists, that it is made up of a number of parts,
that it performs a number of different tasks?
The working memory model makes the following two predictions:
1. If two tasks make use of the same component (of working memory), they cannot be
performed successfully together.
2. If two tasks make use of different components, it should be possible to perform them as
well as together as separately.
Key Study: Baddeley and Hitch (1976)
Aim: To investigate if participants can use different parts of working memory at the same
time.
Method: Conducted an experiment in which participants were asked to perform two tasks at
the same time (dual task technique) - a digit span task which required them to repeat a list of
numbers, and a verbal reasoning task which required them to answer true or false to various
questions (e.g. B is followed by A?).
Results: As the number of digits increased in the digit span tasks, participants took longer to
answer the reasoning questions, but not much longer - only fractions of a second. And, they
didn't make any more errors in the verbal reasoning tasks as the number of digits increased.
Conclusion: The verbal reasoning task made use of the central executive and the digit span
task made use of the phonological loop.
Update on the Working Memory Model - The Episodic
Buffer
The original model was updated by Baddeley (2000) after the model failed to explain the
results of various experiments. An additional component was added called the episodic
buffer. The episodic buffer acts as a 'backup' store which communicates with both long term
memory and the components of working memory.
Fig 3.Updated Model to include the Episodic Buffer
Evaluation of Working Memory
Strengths
Researchers today generally agree that short-term memory is made up of a number of
components or subsystems. The working memory model has replaced the idea of a unitary
(one part) STM as suggested by the multistore model.
The working memory model explains a lot more than the multistore model. It makes sense of
a range of tasks - verbal reasoning, comprehension, reading, problem solving and visual and
spatial processing. And the model is supported by considerable experimental evidence.
The working memory applies to real life tasks:
- reading (phonological loop)
- problem solving (central executive)
- navigation (visual and spatial processing)
The KF Case Study supports the Working Memory Model. KF suffered brain damage from a
motorcycle accident that damaged his short-term memory. KF's impairment was mainly for
verbal information - his memory for visual information was largely unaffected. This shows
that there are separate STM components for visual information (VSS) and verbal information
(phonological loop).
Working memory is supported by dual task studies (Baddeley and Hitch, 1976).
The working memory model does not over emphasize the importance of rehearsal for
STM retention, in contrast to the multi-store model.
Weaknesses
Lieberman criticizes the working memory model as the visuo-spatial sketch pad (VSS)
implies that all spatial information was first visual (they are linked). However, Lieberman
points out that blind people have excellent spatial awareness although they have never had
any visual information. Lieberman argues that the VSS should be separated into two different
components: one for visual information and one for spatial.
There is little direct evidence for how the central executive works and what it does. The
capacity of the central executive has never been measured.
Working memory only involves STM so it is not a comprehensive model of memory (as it
does not include SM or LTM).
The working memory model does not explain changes in processing ability that occur as the
result of practice or time.
Levels of Processing
The levels of processing model of memory (Craik and Lockhart, 1972) was put forward
partly as a result of the criticism leveled at the multi-store model.
Instead of concentrating on the stores/structures involved (i.e. short term memory & long
term memory), this theory concentrates on the processes involved in memory.
Unlike the multi-store model it is a non-structured approach. The basic idea is that memory is
really just what happens as a result of processing information.
Psychologists Craik and Lockhart propose that memory is just a by-product of the depth of
processing of information and there is no clear distinction between short term memory and
long term memory.
Craik defined depth as "the meaningfulness extracted from the stimulus rather than in terms
of the number of analyses performed upon it.” (1973, p. 48)
We can process information in 3 ways:
Shallow Processing
- This takes two forms
1. Structural processing (appearance) which is when we encode only the physical qualities
of something. E.g. the typeface of a word or how the letters look.
2. Phonemic processing – which is when we encode its sound.
Shallow processing only involves maintenance rehearsal (repetition to help us hold
something in the STM) and leads to fairly short-term retention of information. This is the
only type of rehearsal to take place within the multi-store model.
Deep Processing
- This involves
3. Semantic processing, which happens when we encode the meaning of a word and relate it
to similar words with similar meaning.
Deep processing involves elaboration rehearsal which involves a more meaningful analysis
(e.g. images, thinking, associations etc.) of information and leads to better recall. For
example, giving words a meaning or linking them with previous knowledge.
Summary
Levels of processing: The idea that the way information is encoded affects how well it is
remembered. The deeper the level of processing, the easier the information is to recall.
Key Study: Craik and Tulving (1975)
Aim
To investigate how deep and shallow processing affects memory recall.
Method
Participants were presented with a series of 60 words about which they had to answer one of
three questions. Some questions required the participants to process the word in a deep way
(e.g. semantic) and others in a shallow way (e.g. structural and phonemic). For example:
Structural / visual processing: ‘Is the word in capital letters or small letters?
Phonemic / auditory processing: ‘Does the word rhyme with . . .?’
Semantic processing: ‘Does the word go in this sentence . . . . ?
Participants were then given a long list of 180 words into which the original words had been
mixed. They were asked to pick out the original words.
Results
Participants recalled more words that were semantically processed compared to phonemically
and visually processed words.
Conclusion
Semantically processed words involve elaboration rehearsal and deep processing which
results in more accurate recall. Phonemic and visually processed words involve shallow
processing and less accurate recall.
Real Life Applications
This explanation of memory is useful in everyday life because it highlights the way in which
elaboration, which requires deeper processing of information, can aid memory. Three
examples of this are.
• Reworking – putting information in your own words or talking about it with someone else.
• Method of loci – when trying to remember a list of items, linking each with a familiar place
or route.
• Imagery – by creating an image of something you want to remember, you elaborate on it
and encode it visually (i.e. a mind map).
The above examples could all be used to revise psychology using semantic processing (e.g.
explaining memory models to your mum, using mind maps etc.) and should result in deeper
processing through using elaboration rehearsal. Consequently more information will be
remembered (and recalled) and better exam results should be achieved.
Critical Evaluation
Strengths
The theory is an improvement on Atkinson & Shiffrin’s account of transfer from STM to
LTM.
The levels of processing model changed the direction of memory research. It showed that
encoding was not a simple, straightforward process. This widened the focus from seeing
long-term memory as a simple storage unit to seeing it as a complex processing system.
Craik and Lockhart's ideas led to hundreds of experiments, most of which confirmed the
superiority of 'deep' semantic processing for remembering information. It explains why we
remember some things much better and for much longer than others. This explanation of
memory is useful in everyday life because it highlights the way in which elaboration, which
requires deeper processing of information, can aid memory.
Weaknesses
Despite these strengths, there are a number of criticisms of the levels of processing theory:
• It does not explain how the deeper processing results in better memories.
• Deeper processing takes more effort than shallow processing and it could be this, rather
than the depth of processing that makes it more likely people will remember something.
• The concept of depth is vague and cannot be observed. Therefore, it cannot be objectively
measured.
Eysenck (1990) claims that the levels of processing theory describes rather than explains.
Craik and Lockhart (1972) argued that deep processing leads to better long-term memory
than shallow processing. However, they failed to provide a detailed account of why deep
processing is so effective.
However, recent studies have clarified this point - it appears that deeper coding produces
better retention because it is more elaborate. Elaborative encoding enriches the memory
representation of an item by activating many aspects of its meaning and linking it into the
pre-existing network of semantic associations.
Later research indicated that processing is more complex and varied than the levels of
processing theory suggests. In other words, there is more to processing than depth and
elaboration.
For example, research by Bransford et al. (1979) indicated that a sentence such as, 'A
mosquito is like a doctor because both draw blood' is more likely to be recalled than the more
elaborated sentence, 'A mosquito is like a racoon because they both have head, legs and jaws'.
It appears that it is the distinctiveness of the first sentence which makes it easier to remember
- it's unusual to compare a doctor to a mosquito. As a result, the sentence stands out and is
more easily recalled.
Another problem is that participants typically spend a longer time processing the deeper or
more difficult tasks. So, it could be that the results are partly due to more time being spent on
the material. The type of processing, the amount of effort & the length of time spent on
processing tend to be confounded. Deeper processing goes with more effort and more time,
so it is difficult to know which factor influences the results.
The ideas of 'depth' and 'elaboration' are vague and ill defined (Eysenck, 1978). As a result,
they are difficult to measure. Indeed, there is no independent way of measuring the depth of
processing. This can lead to a circular argument - it is predicted that deeply processed
information will be remembered better, but the measure of depth of processing is how well
the information is remembered.
The levels of processing theory focuses on the processes involved in memory, and thus
ignores the structures. There is evidence to support the idea of memory structures such as
STM and LTM as the Multi-Store Model proposed (e.g. H.M., serial position effect etc.).
Therefore, memory is more complex than described by the LOP theory.