Baddeley's model of working memory is a model of human
memory
Memory is the faculty of the mind by which data or information is encoded, stored, and retrieved when needed. It is the retention of information over time for the purpose of influencing future action. If past events could not be remembered, ...
proposed by
Alan Baddeley
Alan David Baddeley CBE FRS, is a British psychologist. He is known for his research on memory and for developing the three-component model of working memory. He is a professor of psychology at the University of York.
Biography
Baddeley was ...
and
Graham Hitch
Graham Hitch is Emeritus Professor of Psychology at the University of York, best known for his work with Alan Baddeley in developing a Working Memory Model.
Education
He gained a Bachelor of Arts degree in Physics from the University of Cambridg ...
in 1974, in an attempt to present a more accurate model of primary memory (often referred to as
short-term memory
Short-term memory (or "primary" or "active memory") is the capacity for holding a small amount of information in an active, readily available state for a short interval. For example, short-term memory holds a phone number that has just been recit ...
).
Working memory
Working memory is a cognitive system with a limited capacity that can hold information temporarily. It is important for reasoning and the guidance of decision-making and behavior. Working memory is often used synonymously with short-term memory, ...
splits primary memory into multiple components, rather than considering it to be a single, unified construct.
Baddeley & Hitch proposed their three-part working memory model as an alternative to the short-term store in
Atkinson & Shiffrin's 'multi-store' memory model (1968). This model is later expanded upon by Baddeley and other co-workers to add a fourth component, and has become the dominant view in the field of working memory. However, alternative models are developing, providing a different perspective on the working memory system.
The original model of Baddeley & Hitch was composed of three main components: the ''central
executive
Executive ( exe., exec., execu.) may refer to:
Role or title
* Executive, a senior management role in an organization
** Chief executive officer (CEO), one of the highest-ranking corporate officers (executives) or administrators
** Executive dir ...
'' which acts as a supervisory system and controls the flow of information from and to its ''slave systems'': the ''phonological loop'' and the ''visuo-spatial sketchpad''. The phonological loop stores verbal content, whereas the visuo-spatial sketchpad caters to visuo-spatial data. Both the slave systems only function as short-term storage centers.
Baddeley & Hitch's argument for the distinction of two domain-specific slave systems in the older model was derived from experimental findings with
dual-task paradigms A dual-task paradigm is a procedure in experimental neuropsychology that requires an individual to perform two tasks simultaneously, in order to compare performance with single-task conditions. When performance scores on one and/or both tasks are lo ...
. Performance of two simultaneous tasks requiring the use of two separate perceptual domains (i.e. a visual and a verbal task) is nearly as efficient as performance of the tasks individually. In contrast, when a person tries to carry out two tasks simultaneously that use the same perceptual domain, performance is less efficient than when performing the tasks individually.
A fourth component of Baddeley's model was added 25 years later to complement the central executive system. The third slave system was designated as ''episodic buffer''. It is considered a limited-capacity system that provides temporary storage of information by conjoining information from the subsidiary systems, and long-term memory, into a single episodic representation.
Components
Central executive
The central executive is a flexible system responsible for the control and regulation of cognitive processes. It directs focus and targets information, making working memory and long-term memory work together. It can be thought of as a supervisory system that controls cognitive processes, making sure the short-term store is actively working, and intervenes when they go astray and prevents distractions.
[Wongupparaj, Kumari, & Morris. (2015). The relation between a multicomponent
working memory and intelligence: The roles of central executive and short-term storage
functions. Intelligence, 53, 166-180.]
It has the following functions:
* updating and coding incoming information and replacing old information
* binding information from a number of sources into coherent episodes
* coordination of the slave systems
* shifting between tasks or retrieval strategies
* inhibition, suppressing dominant or automatic responses
*
selective attention
Attentional control, colloquially referred to as concentration, refers to an individual's capacity to choose what they pay attention to and what they ignore. It is also known as endogenous attention or executive attention. In lay terms, attenti ...
The central executive has two main systems: the visuo-spatial sketchpad, for visual information, and the phonological loop, for verbal information.
Using the dual-task paradigm, Baddeley and Erses have found, for instance, that patients with
Alzheimer's
Alzheimer's disease (AD) is a neurodegenerative disease that usually starts slowly and progressively worsens. It is the cause of 60–70% of cases of dementia. The most common early symptom is difficulty in remembering recent events. As t ...
dementia are impaired when performing multiple tasks simultaneously, even when the difficulty of the individual tasks is adapted to their abilities. Two tasks include a memory tasks and a tracking task. Individual actions are completed well, but as the Alzheimer's becomes more prominent in a patient, performing two or more actions becomes more and more difficult. This research has shown the deteriorating of the central executive in individuals with Alzheimer's.
Recent research on executive functions suggests that the 'central' executive is not as central as conceived in the Baddeley & Hitch model. Rather, there seem to be separate executive functions that can vary largely independently between individuals and can be selectively impaired or spared by brain damage.
Phonological loop
![baddeley phonological loop](https://upload.wikimedia.org/wikipedia/commons/8/85/Baddeley_phonological_loop.jpg)
The phonological loop (or articulatory loop) as a whole deals with sound or phonological information. It consists of two parts: a short-term ''phonological store'' with
auditory memory traces that are subject to rapid decay and an ''articulatory rehearsal component'' (sometimes called the ''articulatory loop'') that can revive the memory traces.
Any auditory verbal information is assumed to enter automatically into the phonological store. Visually presented language can be transformed into phonological code by silent articulation and thereby be encoded into the phonological store. This transformation is facilitated by the articulatory control process. The phonological store acts as an "inner ear", remembering speech sounds in their temporal order, whilst the articulatory process acts as an "inner voice" and repeats the series of words (or other speech elements) on a loop to prevent them from decaying. The phonological loop may play a key role in the acquisition of vocabulary, particularly in the early childhood years. It may also be vital for learning a second language.
Five main findings provide evidence for the phonological loop:
# The effect of
phonological
Phonology is the branch of linguistics that studies how languages or dialects systematically organize their sounds or, for sign languages, their constituent parts of signs. The term can also refer specifically to the sound or sign system of a ...
similarity:
Lists of words that sound similar are more difficult to remember than words that sound different.
Semantic
Semantics (from grc, σημαντικός ''sēmantikós'', "significant") is the study of reference, meaning, or truth. The term can be used to refer to subfields of several distinct disciplines, including philosophy, linguistics and comput ...
similarity (similarity of meaning) has comparatively little effect, supporting the assumption that verbal information is coded largely phonologically in working memory.
# The effect of
articulatory suppression Articulatory suppression is the process of inhibiting memory performance by speaking while being presented with an item to remember. Most research demonstrates articulatory suppression by requiring an individual to repeatedly say an irrelevant speec ...
:
Memory for verbal material is impaired when people are asked to say something irrelevant aloud. This is assumed to block the articulatory rehearsal process, leading memory traces in the phonological loop to decay.
# Transfer of information between codes:
With visually presented items, adults usually name and sub-vocally rehearse them, so the information is transferred from a visual to an auditory encoding. Articulatory suppression prevents this transfer, and in that case the above-mentioned effect of phonological similarity is erased for visually presented items.
# Neuropsychological evidence:
A defective phonological store explains the behavior of patients with a specific deficit in phonological short-term memory.
Aphasic
Aphasia is an inability to comprehend or formulate language because of damage to specific brain regions. The major causes are stroke and head trauma; prevalence is hard to determine but aphasia due to stroke is estimated to be 0.1–0.4% in t ...
patients with
developmental verbal dyspraxia
Development of the human body is the process of growth to maturity. The process begins with fertilization, where an egg released from the ovary of a female is penetrated by a sperm cell from a male. The resulting zygote develops through mitos ...
are unable to set up the speech motor codes necessary for
articulation, caused by a deficiency of the articulatory rehearsal process.
# On the other hand, patients with
dysarthria
Dysarthria is a speech sound disorder resulting from neurological injury of the motor component of the motor–speech system and is characterized by poor articulation of phonemes. In other words, it is a condition in which problems effectively ...
, whose speech problems are secondary, show a normal capacity for rehearsal. This suggests that it is the subvocal rehearsing that is crucial.
Evidence in support of a phonological short-term store
An accumulation of literature across decades has lent strong support to the theory of phonological STS. In a 1971 study, Stephen Madigan demonstrated that a larger
recency effect
Serial-position effect is the tendency of a person to recall the first and last items in a series best, and the middle items worst. The term was coined by Hermann Ebbinghaus through studies he performed on himself, and refers to the finding that r ...
is seen during forward serial recall when people are presented a list auditorally as opposed to visually. (A smaller effect is seen in backwards serial recall.) In his study, auditory presentation led to greater recall of the most recently studied items. Catherine Penney expanded on this discovery to observe that
modality effect
The modality effect is a term used in experimental psychology, most often in the fields dealing with memory and learning, to refer to how learner performance depends on the presentation mode of studied items.
Description
Modality can refer to a nu ...
s can also be found in the case of free recall tasks. In 1965, Dallett had discovered that this observed modality effect is greatly reduced by the addition of a "suffix" item to the presented list; this suffix is a distractor item that is not to be recalled. Robert Greene utilized this observation in 1987 to discover that this suffix effect has a larger impact on lists learned auditorally as opposed to visually. The culmination of all of these findings results in strong support of the theory that there is a short-term store that phonologically stores recently learned items. In addition, Bloom and Watkins found that the suffix effect is greatly diminished when the suffix is not interpreted as linguistic sound, which agrees with the phonological short term store theory as it would be largely unaffected by non-linguistic distractors.
Visuo-spatial working memory
Alan Baddeley
Alan David Baddeley CBE FRS, is a British psychologist. He is known for his research on memory and for developing the three-component model of working memory. He is a professor of psychology at the University of York.
Biography
Baddeley was ...
's theory of
working memory
Working memory is a cognitive system with a limited capacity that can hold information temporarily. It is important for reasoning and the guidance of decision-making and behavior. Working memory is often used synonymously with short-term memory, ...
has yet another aspect to which memory can be stored short term. The visuo-spatial sketchpad is the store that holds visual information for manipulation.
The visuo-spatial sketchpad is thought to be its own storage of working memory in that it does not interfere with the short term processes of the phonological loop. In research, it has been found that the visuo-spatial sketchpad can work simultaneously with the phonological loop to process both auditory and visual stimuli without either of the processes affecting the efficacy of the other.
Baddeley re-defined the theory of
short-term memory
Short-term memory (or "primary" or "active memory") is the capacity for holding a small amount of information in an active, readily available state for a short interval. For example, short-term memory holds a phone number that has just been recit ...
as a working memory to explain this phenomenon. In the original theory of short-term memory, it is understood that a person only has one store of immediate information processing which could only hold a total of 7 items plus or minus two items to be stored in a very short period of time, sometimes a matter of seconds. The digit-span test is a perfect example of a measurement for classically defined short-term memory. Essentially, if one is not able to encode the 7 plus or minus two items within a few minutes by finding an existing association for the information to be transferred into long-term memory, then the information is lost and never encoded.
However, visuo-spatial short-term memory can retain visual and/or spatial information over brief periods of time.
When this memory is in use, individuals are able to momentarily create and revisit a mental image that can be manipulated in complex or difficult tasks of spatial orientation. There are some who have disparities in the areas of the brain that allow for this to happen from different types of brain damage.
There can also be a misunderstanding here in the differences between transient memories such as the visual sensory memory. A transient memory is merely a fleeting type of sensory memory; therefore, as the visual sensory memory is a type of sensory memory, there is a store for the information, but the store lasts for only a second or so. A common effect of the visual sensory memory is that individuals may remember seeing things that weren't really there or not remembering particular things that were in their line of sight. The memory is only momentary, and if it isn't attended to within a matter of seconds, it is gone.
There are two different pathways in the brain that control different functions of what is known inclusively as the visuo-spatial sketchpad. The sketchpad consists of the spatial short-term memory and the object memory. The spatial short-term memory is how one is able to learn and thus remember "where" they are in comparative representation to other objects. The object memory of the visuo-spatial sketchpad is essential in learning and remembering "what" an object is.
The differences between these two differing visual abilities is due in large part because of different pathways of each of the abilities in the brain. The visual pathway in the brain that detects spatial representation of a person to and within their environment is the
dorsal stream
The two-streams hypothesis is a model of the neural processing of vision as well as hearing. The hypothesis, given its initial characterisation in a paper by David Milner and Melvyn A. Goodale in 1992, argues that humans possess two distinct visu ...
. The visual pathway that determines objects shapes, sizes, colors and other definitive characteristics is called the
ventral stream
The two-streams hypothesis is a model of the neural processing of vision as well as hearing. The hypothesis, given its initial characterisation in a paper by David Milner and Melvyn A. Goodale in 1992, argues that humans possess two distinct vis ...
.
Each of these two streams runs independent of one another so that the visual system may process one without the other (like in brain damage for instance) or both simultaneously. The two streams do not depend on one another, so if one is functioning manipulatively, the other can still send its information through.
Logie's elaboration of the visuospatial sketchpad
Logie has proposed that the visuo-spatial sketchpad can be further subdivided into two components:
# The visual cache, which stores information about form and color.
# The inner scribe, which deals with spatial and movement information. It also rehearses information in the visual cache and transfers information to the central executive.
Three main findings provide evidence for the distinction between visual and spatial parts of the visuospatial sketchpad:
# There is less interference between visual and spatial tasks than between two visual tasks or two spatial tasks.
# Brain damage can influence one of the components without influencing the other.
# Results from brain-imaging show that working memory tasks with visual objects activate mostly areas in the left hemisphere, whereas tasks with spatial information activate more areas in the right hemisphere.
Episodic buffer
In 2000 Baddeley added a fourth component to the model, the episodic buffer. This component is a limited capacity passive system,
dedicated to linking information across domains to form integrated units of visual, spatial, and verbal information with time sequencing (or episodic chronological ordering
), such as the memory of a story or a movie scene. The episodic buffer is also assumed to have links to long-term memory and semantic meaning.
"It acts as a buffer store, not only between the components of Working Memory, but also linking Working Memory to perception and Long-Term Memory".
Baddeley assumes that "retrieval from the buffer occurred through conscious awareness".
The episodic buffer allows individuals to use integrated units of information they already have to imagine new concepts. Since this is likely "an attention-demanding process...the buffer would depend heavily on the Central Executive".
The main motivation for introducing this component was the observation that some (in particular, highly intelligent) patients with
amnesia
Amnesia is a deficit in memory caused by brain damage or disease,Gazzaniga, M., Ivry, R., & Mangun, G. (2009) Cognitive Neuroscience: The biology of the mind. New York: W.W. Norton & Company. but it can also be caused temporarily by the use ...
, who presumably have no ability to encode new information in long-term memory, nevertheless have good short-term recall of stories, recalling much more information than could be held in the phonological loop. "The episodic buffer appears...capable of storing bound features and making them available to conscious awareness but not itself responsible for the process of binding".
It is assumed that "conscious access to the phonological loop or sketchpad may operate via the buffer".
This is based on the assumption that both the visuo-spatial sketchpad and phonological loop act as minor buffers, combining information within their sensory area. The episodic buffer may also interact with smell and taste.
Biology/neuroscience
There is much evidence for a brief memory buffer, as distinct from the long term store. The phonological loop seems to be connected to activation in the left hemisphere, more specifically the temporal lobe. The visuo-spatial sketchpad activates different areas depending on task difficulty; less intense tasks seem to activate in the occipital lobe, whereas more complex tasks appear in the parietal lobe. The central executive is still a mystery, although it would seem to be more or less located in the frontal lobes of the brain. The episodic buffer seems to be in both hemispheres (bilateral) with activations in both the frontal and temporal lobes, and even the left portion of the hippocampus. In terms of genetics, the gene
ROBO1
Roundabout homolog 1 is a protein that in humans is encoded by the ''ROBO1'' gene.
Function
Bilateral symmetric nervous systems have special midline structures that establish a partition between the two mirror image halves. Some axons project t ...
has been associated with phonological buffer integrity or length.
Validity of the model
The strength of Baddeley's model is its ability to integrate a large number of findings from work on short-term and working memory. Additionally, the mechanisms of the slave systems, especially the phonological loop, has inspired a wealth of research in experimental psychology, neuropsychology, and cognitive neuroscience.
However, criticisms have been raised, for instance of the phonological-loop component, because some details of the findings are not easily explained by the original Baddeley & Hitch model, including the controversy regarding
the 7±2 rule.
The episodic buffer is seen as a helpful addition to the model of working memory, but it has not been investigated extensively and its functions remain unclear.
See also
*
Echoic memory
Echoic memory is the sensory memory that registers specific to auditory information (sounds). Once an auditory stimulus is heard, it is stored in memory so that it can be processed and understood. Unlike most visual memory, where a person can choo ...
*
*
The Magical Number Seven, Plus or Minus Two
"The Magical Number Seven, Plus or Minus Two: Some Limits on Our Capacity for Processing Information" is one of the most highly cited papers in psychology. It was written by the cognitive psychologist George A. Miller of Harvard University's De ...
*
Working memory
Working memory is a cognitive system with a limited capacity that can hold information temporarily. It is important for reasoning and the guidance of decision-making and behavior. Working memory is often used synonymously with short-term memory, ...
References
Notes
Bibliography
*
*
* Baddeley, A.D. (2007). ''Working memory, thought and action.'' Oxford: Oxford University Press.
*
* Baddeley, A.D., & Hitch, G. (1974). ''Working memory.'' In G.H. Bower (Ed.), ''The psychology of learning and motivation: Advances in research and theory'' (Vol. 8, pp. 47–89). New York: Academic Press.
External links
Working memory model
{{Memory
Memory