The modal consists of four components the first is the Central Executive this is a free attention system that has overall control of all the other components in the modal. The Central Executive allocates attention and directs the operation of the slave systems. The slave systems are:
- The Articulatory Loop (inner voice), this can be regarded as a verbal rehearsal loop used when, for example we try to remember a telephone number for a few seconds by saying it to ourselves. It is also used to hold words we are preparing to speak aloud.
- The Visuo-Spatial Scratch Pad (inner eye), this deals with visual or spatial information for example when we drive along a familiar road we will visualize the road ahead. It represents in the form of its visual features such as size shape and colour.
- The Primary Acoustic Store (inner ear), this receives auditory input directly, but visual input can only enter it indirectly after it has been processed by the Articulatory Loop and converted into a phonological form. It uses and acoustic code representing information such as pitch and loudness.
A number of experimental studies exist that support the modal or its components. Baddeley and Lewis (1981) gave their participants sentences to read and asked them to say whether the sentences were meaningful. Some of the sentences were not meaningful because two words in a meaningful sentence had been switched round (e.g. "The tree flew up into the birds"). When the participants were prevented from using the articulatory loop by saying something meaningless repeatedly, their ability to decide whether sentences were meaningful was reduced because they could not re-examine the sentences repeatedly. This suggests there are two separate components involved in reading, the articulatory loop and the primary acoustic store. Den Heyer and Barret (1971) gave their participants a grid in which letters were placed in some cells. This was displayed for ten seconds. Then one group was given a verbal task (resisting a poem) and the other group a special task to complete. They were then asked to recall the original grid. Recall of the letters was more disrupted by the verbal task where as recall of the positions was disrupted by the special task. This is evidence that the letters are stored acoustically and the positions are stored visually.
The study can also explain the problems experienced by KF. Because KF’s short term forgetting of auditory letters and digits was much greater than his forgetting of visual stimuli, this suggests that his articulatory loop was damaged but because he could still remember visual stimuli it would mean that his Visuo-spatial scratch pad was not damaged. KF could also remember meaningful sounds (for example a cat meowing) but he could not remember verbal materials like words or letters. This shows that his primary acoustic store was not damaged either.
The WWM has many strengths. The central executive links memory with attention. It is an advanced way of looking at short-term memory provided by the multi store model. It is superior because it is concerned with both the active processing and the brief storage of information. Therefore it is relevant to activities such as mental arithmetic, verbal reasoning and comprehension. The WWM views verbal rehearsal as an optional process that occurs within the articulatory or phonological loop. This is more realistic than the importance of rehearsal in the multi store modal. The WWM accounts for many findings, which are hard to explain within the multi store model. Baddeley and Hitch (1974) observed one of these findings. They carried out research using a dual task technique. The assumption that lies behind this technique is that each of the processors has only a limited capacity to process information. If two tasks using the same processor are carried out at the same time then performance on one or both of these tasks will be impaired. Another one of these findings that support the model is Gathercole and Baddeley (1990) they found that children with reading problems had an impaired memory span and had difficulties saying whether words rhymed, perhaps suggesting that there is a phonological deficit.
However the modal is not without its criticisms, although these mainly relate to the need to do further research to broaden our knowledge of the component parts. The limitations of the model are: not a lot is known about the central executive. It has limited capacity, but this capacity has not been measured accurately. The central executive does not rely on any manner of receiving information such as sound or vision it is used in many different processing operations but no one knows the precise details of its functioning. It is over simplistic to have a single central executive. Also the Visuo-spatial store has not been explored in as much depth as other slave systems.
The aim of the current investigation is to replicate Den Heyer and Barratt, 1971, experiment and investigate whether there are separate stores for verbal/phonological information, and for visual-spatial information. It is suggested that if doing a visual task interferes with one's memory of visual-spatial information, but not phonological information, and vice versa, then this provides evidence for there being at least two separate STM stores.
Research Hypothesis: I would predict that doing a visual task while processing spatial information would interfere with the participant’s results. This is because the Visuo-spatial sketch pad is being used for two different activities therefore its attention is limited for two instead of just one.
Null Hypothesis: I will predict that if my research hypothesis is wrong then the participants’ results will not be affected when doing a visual task.
