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UNIT TWO – The Working Model of Memory
Learning objectives:
- Understand what is meant by the concept of working memory.
- Describe the working memory model and understand the functions and limitations of its components.
- Describe and evaluate the evidence on which the working memory model is based.
4.Understand the strengths and weaknesses of the model.
According to Baddeley and Hitch, working memory is a complex and flexible system (especially with regard to STM) comprised of three main components.
Central Executive
The central executive is considered the most important part of the working memory, because it controls attention and coordinates the actions of the other components. It can briefly store information, but has limited capacity. The central executive is modality free, which means that it can store information in any sense modality. It has responsibility for a range of important control processes, which include: (Be familiar with 2 or 3 of the following to use as examples when describing the Central Executive):
setting task goals,
monitoring and correcting errors,
starting the rehearsal process,
switching attention between tasks,
inhibiting irrelevant information,
retrieving information from long-term memory,
switching retrieval plans
co-ordinating the activity needed to carry out more than one processing task at a time.
This core component is supported by two ‘slave’ systems, which can be used as storage systems, thereby freeing up some of its own capacity to deal with more demanding information-processing tasks. The slave systems have separate responsibilities and work independently of one another.
The slave systems are temporary stores with limited capacity.
Slave system 1
The phonological loop - The phonological loop holds verbal information in a speech-based form. The phonological loop consists of two parts:
- -Phonological store (the inner ear) uses a sound based code to store information, but this decays after about 2 seconds unless it is rehearsed by the articulatory control system. The phonological store receives its input either directly from the ears of from LTM. If you imagine your favourite piece of music you are using your phonological store.
- -Articulatory control system (the inner voice) rehearses information verbally and has a time based capacity of about 2 seconds whereby words can be maintained by sub vocal repetition / rehearsal (much like acoustic encoding in the multi-store model).
Slave system 2
The visuo-spatial sketchpad holds visual and spatial information. Thisstores and manipulates visual information, input from the eyes or LTM.
The Episodic buffer is a fairly recent addition to the WMM (Baddeley 2000). Its purpose is to bind together all of the information from the other components of the working memory with information about time and order. This prepares memories for storage in episodic LTM.
RESEARCH EVIDENCE FOR THE WORKING MODEL OF MEMORY
The working memory model developed the short-term memory from being a single unitary store to being more than one component. The rationale for this was explained by Baddeley and Hitch who pointed out that KF who had a digit span of two could still transfer new information to his LTM. This suggested that there had been selective disruption to his STM because while his digit span was impaired, other aspects of STM must have continued to function.
To test the idea that there is more than one component in STM, Baddeley and Hitch devised the dual task method.
- The dual task method – supports the concept of the model – that STM is more than just a unitary store
ProcedureParticipants were asked to perform a sentence-checking task (See below) while simultaneously reciting aloud a list of six digits (482917).
Sentence-checking task
1B is followed by ABATRUE / FALSE
2A is followed by BABTRUE / FALSE
3A is not followed by BBATRUE / FALSE
4B follows AABTRUE / FALSE
5B does not follow ABATRUE / FALSE
6B is not followed by AABTRUE / FALSE
7A follows BABTRUE / FALSE
8B is not preceded by AABTRUE / FALSE
9A is not followed by BBATRUE / FALSE
10B does not precede AABTRUE / FALSE
FindingsThe speed of verifying the sentences was slightly slower when doing the two tasks together than when it was done on its own.
ConclusionsSTM must have more than one component and must be involved in processes other than simple storage, such as reasoning, understanding and learning.
STM must be a sort of workspace where a variety of operations can be carried out on both old and new memories. Two tasks can be carried out simultaneously in STM provided that they are being dealt with by different parts of the memory systems. LTM is a passive store that maintains previously learned material for use by the STM when needed.
The overall purpose of the following research studies is to show that a component of the working memory can only be used once. If two tasks which use the same component are carried out at the same time (for example, watching the TV while doing homework) they will interfere with each other. You do not need to know the details of all of this research so be selective. Choose one or two that you could write about confidently as supporting evidence for the working model of memory.
1Evidence for the phonological loop - Thomson and Buchanan (1975)
ProcedureParticipants were given visual presentations of word lists for a very brief time and then asked to write them down in serial order.
Condition 1-five words from a list of familiar, one-syllable English words such as harm, wit, twice
Condition 2 - five words from a list of polysyllabic words, e.g. organisation, university, association
FindingsAverage recall was better for the short words. This was called the ‘word length effect’.
ConclusionThe capacity of the loop is determined by the length of time it takes to say words rather than by the number of items. The time was estimated to be 1.5 seconds.
For discussionIt could be that longer words are just less familiar than shorter words and are, therefore, harder to recall.
- Evidence for the of the articulatory loop - Baddeleyet al. (1975)
ProcedureAs for the word length effect (above) but with articulatory suppression. (saying ‘la lalala la’)
FindingsThe word length effect disappeared (short words were recalled no better than long words).
ConclusionA verbal rehearsal system is needed for the advantage of short words over long words to be seen. If the articulatory loop is being used with irrelevant material, then it seems likely that short and long words are being processed elsewhere, probably in the central executive.
- Evidence for the visuo-spatial sketchpad – Shepard and Feng (1972)
ProcedureParticipants were asked to imagine folding a flat shape to form a cube and to say whether two arrows would meet up or not.
FindingsThe time taken to make the decision was systematically related to the number of folds that would have been required if the participants had actually been doing the folding for real.
ConclusionVisual images work in very similar ways to real-life perception. People are likely to find it difficult to do two tasks simultaneously if they both require the services of the visuo-spatial sketchpad.
- Evidence for the visuo-spatial sketchpad – Baddeley, Grant, Wright and Thomson (1973)Procedures Participants were given:
-a simple tracking task (following a spot of light with a pointer as it moved round a circular path)
-while carrying out a simultaneous visual imagery task (imagine looking at an angular block capital such H. T. F. E)
Participants were asked to hold the image in their heads and then starting at the bottom left-hand corner, to respond to each angle as a ‘yes’ if it included the bottom or top line of the letter and as a ‘no’ if it did not.
FindingsParticipants found it very difficult to track the spot of light and accurately classify the corners.
ConclusionThe two tasks were competing for the same limited resources of the visuo-spatial sketchpad. This was supported by the fact that participants were able to do the tracking task at the same time as performing a verbal task.
- Evidence for the central executive – Baddeley (1999)
Research tends to focus on the different functions of the central executive.
This study investigated selective attention when switching retrieval plans.
Procedure
Participants were asked to generate random strings of digits by pressing numbered keys on a keyboard. This task was carried out on its own or simultaneously with one of the following:
- Reciting the alphabet
- Counting from 1
- Alternating between letters and numbers i.e. 1 A B 2 C 3 D 4
Findings
The generated digit string became considerably less random in Condition 3
Conclusion
The task was more difficult when participants were competing for the same central executive resources.
Evaluation of laboratory experiments
USE THESE POINTS IF YOU ARE ASKED TO EVALUATE THE RESEARCH. DO NOT USE THEM FOR EVALUATING THE MODEL.
Lab experiments are highly controlled which means that cause and effect can be established because the results are due to the manipulation of the independent variables
The level of control also makes it possible for studies to be replicated in order to check the reliability of the findings.
However, they often involve the use of artificial tasks which may not represent how memory works in everyday life, e.g. trying to recall trigrams is not something we usually have to do.
Participants may respond to demand characteristics/cues if they know they are taking part in an experiment. They may guess the aims of the study which might affect the way they behave. For example, they may be extra vigilant when watching a film of a car crash if they suspect they may have to answer questions on it afterwards.
Laboratory experiments take place in an artificial setting and may therefore lack ecological validity. Behaviour (recall for events) may be different in an experimental situation compared with a real-life situation. This can be seen in the differences in findings in studies on the effects of anxiety on recall which seems to be worse in lab experiments than in real life.
OTHER EVALUATIVE POINTS
Strengths and weaknesses of the working model of memory
Make sure you can write about two positive points (smiley faces) in detail with a third as back up.
It is a much more plausible model than the multi-store model because it explains STM in terms of both temporary storage and active processing. It also incorporates verbal rehearsal as just one optional process within the articulatory loop instead of being the sole means of transferring information.
It is possible to apply the model to previous research data, e.g. the acoustic confusion effect, digit span etc and reinterpret it within the framework of working memory. It can also account for findings that are difficult for multi-store models to explain, e.g. some of the selective memory deficits that have been found in brain-damaged patients such as KF.
The working model attempts to explain how the memory functions rather than how it simply ‘stores’ information. For example, evidence (Baddlelyet al. 1998) shows that the phonological loop plays a key role in the development of reading and that the phonological loop is not operative in some children with dyslexia. While it seems to be less crucial for fluent, adult readers, it still has an important role in helping to comprehend complex text. It also helps in the learning of new spoken vocabulary.
The model can account for individual differences in memory processing. Research has found differences in ‘working memory span’ which is observed as a difference in ability to carry out various cognitive tasks such as reading comprehension, reasoning, spatial navigation, spelling, note-taking, etc. Differences have also been found within the components of the working memory. For example, Shah and Mayake (1996) found that an individual can score high on spatial working memory and low on verbal working memory and vice versa.
Working models do not offer a complete understanding of how memory works. The exact role played by the central executive remains slightly unclear and it has been questioned whether it can be a single component or whether there are separate verbal and spatial working memory systems.
Berz (1995) has criticised the model for failing to account for musical memory because we are able to listen to instrumental music without impairing performance on other acoustic tasks.
IMPORTANT NOTE
IN SOME TEXTS YOU WILL READ THAT THE WORKING MODEL DOES NOT ACCOUNT FOR LTM, BUT THIS IS NOT ACCURATE AND WILL NOT BE CREDITED BY THE AWARDING BODY.