Why is it necessary to have four separable components to working memory? Discuss the evidence that led to the inclusion the episodic buffer.
Working memory refers to the systems of the brain which work to store and manage information that is needed in the performance of seemingly complex mental tasks that may include reasoning, learning or overall understanding of the numerous information that one is bombarded with on a day to day basis. McLeod (2012) says that:
Working memory is involved in the selection, initiation, and termination of information- processing functions such as encoding, storing, and retrieving data (n.p).
This brain system (working memory) handles this information for comparatively short time spans and this would explain why in yester years the working memory was known as the Short-Term Memory (STM). This short term memory has enable psychologist to better understand human and animal remembrance and learning processes. A lot of capabilities that human beings have are hinged on their working memory. Problem solving abilities, ability to solve mathematical problems, reasoning and linguistic skills are highly dependent on this working memory. Questions abound on just how much information can be retained in the STM, the extent to which the working memory can be stretched as well as questions on just how the working memory works i.e. is it a separate system to the long-term memory.
Researchers have as well come up with tests that are designed to test individuals working memory capabilities. An example of such a test is the test on individual’s memory span which is basically the number of items that one can recall from a list for instance. For example, a researcher may read out a list of fruits in random order to an individual. The names of the fruits are to be read out at the speed on one fruit name per second. Once the entire list has been read out, it will be expected of the individual being tested to recall the fruit names in the order in which they were read out to him/ her. Typically, researchers have established that the average memory span for adult individuals is normally 7 items (Frederic et al, 2010). The working memory can as well be impaired and when it does become impaired, illnesses such as the Alzheimer’s disease are a common problem which often leads to dementia in such patients (Andrade, 2001).
Necessity for Four separate components
The working memory works such that all the information that is to be processes is not committed to a single section in the brain but rather, there exists several components that are designated for the different information types that are to be processed.
- The Central Executive
- The Phonological Loop and
- The Visuo-Spatial Sketchpad
- The Episodic Buffer
(Alloway & Alloway, 2014)
The figure above shows the working memory model with the various components labeled and with the lower tier making an attempt at showing the functions of the various components i.e. the different types of information that each component processes. As per the model, the phonological loop processes audio information i.e. that which is speech oriented such as the language individuals have used; the Visuo-spatial sketch pad is on the other hand responsible for processing overall visual information i.e. that which is seen by the eye; the episodic buffer as depicted in the diagram relays information from the working memory (STM) to the long term memory whereas the central executive, as depicted, works to control all the processes that the lower tier components perform, coordinating and monitoring the processes (Andrade, 2001).
Based on the foregoing it can be seen that the working memory heavily relies on all its four components to perform its functions (Alloway & Alloway, 2014). Each component is dedicated to a particular process, manipulating different kinds of information, that the other component would not be able to process. it means that if one component, say the phonological loop, was absent, then certain information would not be processed by the brain in this case, one would not be able to differentiate and understand languages or understand audio messages completely. Were the central executive to be absent from the working memory, coordination, monitoring and control of information would be in shambles in the brain. Based on the above model as well, it can be seen that the various components are dependent on each other, with the central executive depended on feedback from the various components it controls meaning that the capabilities of each component is therefore limited hence the need for all the components to be present so that they can work in a dependent manner to comprehensively perform brain memory functions (Andrade, 2001).
Empirical Evidence for the different Working Memory Components
A study carried out Baddeley and Hitch in 1976 sought to find out whether individuals can use the different components simultaneously (Baddeley, 2010). The method that was used involved the following:
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?). (Baddeley 2010, p. 137).
The results that were got were such that with increase in the digit numbers, the tasks that required reasoning from the participants took longer to be accomplished, though not very long (a difference of seconds). Also, the results noted were that there were no errors made by the participants in their verbal reasoning task even as the digit numbers increased in the other task. The study therefore concluded that several working memory components were at play in this experiment and as Baddeley (2010) notes, the central executive worked to control the task that was verbal reasoning whereas the phonological loop was used in the digit span task.
This experiment gave credence to the fact that various components exist in the working memory with each performing several tasks. These different components are further discussed.
The Central Executive
This happens to be the most important component. All of the slave systems depend on it for coordination and their monitoring as well as their overall operations. The central executive as well controls how the sketch pad and phonological loop communicate with the Long Term Memory. The central executive therefore is concerned with deciding what information is important enough to be attended to and as well decides on which component certain information is meant for.
When it comes to performing multiple tasks, for instance, when one is for example cycling on a busy road and talking on the phone at the same time, chances are that in performing these multiple tasks one might wobble and get hit by a car. The central executive will decide on which task the individual should prioritize at the expense of another, in this case, cycling and not talking. This particular working memory component has as well been noted as less of a memory storage location unlike its slave systems but rather works to choose which information is to be attended to by the working memory and which to ignore altogether.
The Phonological Loop
The Phonological loop is concerned with spoken as well as written information. It can be further compounded into two parts i.e. the phonological store and the articulatory control process. The store branch of the phonological loop holds information that is spoken for some two seconds. Speech enters this store directly. The other part, the articulatory control process on the other hand works to change material that is read from written material into speech form before it enters into the phonological store. It acts as an inner voice with ‘speaks’ the words being read (Gathercole & Baddeley, 1993). This process will circulate information in a loop-like manner so that it can be remembered before it is converted into a speech form as demanded by this component and reaches the store.
The Visuo-Spatial Sketch Pad
This component of working memory works with visual and spatial information. Spatial information relates to our positions in relation to other objects in the environment (Dehn, 2013). The spatial component will enable us be aware of things in the environment so that we do not for example bump into tress as we walk. Visual things refer to how we things appear i.e. how we see things like tables, cups e.t.c.
This particular component also relates to the long term memory in that it will also retrieve information held in the long term memory so that we are able to recall how for example our classrooms and homes are arranged and where to find certain things in the house and class.
The Episodic Buffer
Baddeley (2000) came up with the Episodic Buffer zone to further explain results of studies that found a key component missing from the earlier memory models that had been developed. The episodic buffer is basically a kind of backup memory location that is able to relate with and relay information from the Long term memory to the working memory.
Evidence that led to inclusion of the Episodic Buffer
Some of the issues raised about the previous model of the working memory included that the phonological and Visuo-spatial sketchpad components alone could not explain certain cognitive capabilities of individuals such as the fact that semantics could contribute to recall of word sequences by individuals; the fact that patients, though with impaired STM’s still reported impressive sentence recall spans as well as the chunking phenomenon (Nobre et al, 2013). The episodic buffer was therefore included to cater for these shortcomings. Its ability to integrate information from the working memory as well as retrieve information from the long term memory seemed to address the said shortcomings of previous models that lacked it (Baddeley, 2000). The fact that individuals are able to store great volumes of information and the integration of different verbal and visual tasks i.e. perceptions, semantic and syntactic tasks at the same time gives credence to the presence of the episodic buffer. In particular the episodic buffer is quite important when it comes to memory of sentences and prose in individuals (Conway, 2007).
Evidence from studies has as well further established the episodic buffer. Of these studies, a common factor is the fact that words are used as the primary test material. “The Test of Memory and Learning – Paired recall (TOMAL), Recalling Sentences task from the Clinical Evaluation of Language Fundamentals, 4th edition (CELF-4), California Verbal Learning Test (CVLT), and Rey Auditory Verbal Learning Test (RAVLT) – immediate and delayed recall” (Nobre et al, 2013, p. 338)
The TOMAL test involves the tested individuals being introduced to paired words which significant portions (half) are semantically associated, to learn. The CELF-4 involves sentences being repeatedly read out to subjects who are expected to repeat what is read out. The CVLT presents two word lists to the subject i.e. list 1 and list 2. The first list is read out to the subject five times, who is expected to recall the words read out after each round. The second list, a ‘control’ list, is then read out and the subject is expected to freely recall all that is read. After the second list has been read, the participant is expected to try and recall the first list that was read (it is not re-read) and the subject is provided with categories (cues) to recall from or can recall freely. A delay of about half an hour is then given before the subject is again expected to recall words in list 1 using their memory as well cues being provided. Once this has been done, again, a quarter an hour delay is provided after which the subject is given choices from which he is expected to recall the list 1 words. (Nobre et al, 2013)
These experiments worked to test the EB component of the working memory to find out the extent to which individuals could recall words based on their semantic similarities and sentences based on their flow (prose).
The multistore model was limited in the number of components it held and the inclusion of the episodic buffer is crucial given the limitations of the other working memory components as discussed.
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