Memory

The Multi Store Model of Memory

Atkinson and Shiffrin's 1968 - multi store model of memory is an explanation of how memory processes work. It is illustarted in the following diagram:

Sensory memory ---- Short term memory ---- Long Term memory

1. The stores  The frst thing multi store model says is that memory is made up of three different stores. A key thing about the multi store model of memory is that it states that these three atores are completely separate from one another.

Sensory Memory -The sensory registers everything our senses take in, that is everything we can hear, see, smell, and touch. It is likely that we have a sensory memory for each sense but so far only the iconic store.

Short term memory - The main features of STM have already been discussed. To briefyly recap, the stm uses acoustic encoding, has a capcity of 5-9 and duration of around 18 seconds without rehearsal.

Long Term Memory - The main features of LTM have also already bgeen discussed. To recap, the LTM uses semantic encoding, has an unlimited capacity and an infinite duration.

2. Processes -In addition to describing the main memory stores the multi store model also specifies how the information travels from one store to another.

Attention = The multi store model states that for information to be passed from the sensory memeory to the short term memory it should be paid attention to. As the sensory memeory takes in absolutely everying in your environment it would be impossible to then attend to it all in the STM. For this reason only some material is attended to. This is done below a conscious level in that we are aware of this process. 

Rehearsal = Rehearsal falls into two types. Maintenance rehearsal is simply repeating information over and over. This acoustic method of rehearsal can keep information in the STM for longer than 18 seconds.  Elaborative rehearsal is when you add to the information in some way, e.g. by linking the material to your own experiences. This method of rehearsal is most effective at transferring information for STM to LTM although it should be rememebered that that maintance rehearsal is enough alone to get information into the LTM. The key point here is that the multi store model states that the only way to get information passed to LTM is through rehearsal 

Evaluation of the Multi Store Model 

A strength of the multi store model of memory is that the idea of the STM and the LTM being two separate stores is supported by research evidence. PET scans and fMRI scans have indicated that the prefrontal cortex is active when individuals are working on a task in STM - Beardsley, 1997. With regards to the LTM, there is speculation that the hippocampus plays a key role.

Another strength of the multi store model is that clinical studies of amnesics support the idea that the STM and LTM are completely separate stores. Amnesia refers to memory loss. People with amnesia tend to either lose their STM or their LTM but not both. As with the research above, this strongly suggests that the STM and LTM are located in separte stores well away from each other. For example, K.F. had an extremely poor STM only one or two digits following a motorbike accident, yet his LTM for events after the accident was normal. 

A limitation is that whilst on first glance the case of KF seems to support the assumption that the STM and LTM are completely diofferent stores, the case is not as straightforward as that. This is because K.F's deficit in STM was only for verbal information. His STM for visual material was normal. This suggests the existence of more than one type of STM, an idea which has not been incorporated into the multi store model. 

Evaluation of the Multi Store Model 

A finial Limitation is that the notion of 'rehersal' is too vague. Atkinson and Schiffrin 1968 merely stated that the more you rehearse something the more likley it is to be transferred into the LTM. This is not necessarily the case. Bekerian and Baddeley 1980 found that people didn't know of changes to BBC radio wavelength despite hearing the information on average, well over a thousnad times. This suggests that rehearsal is not the only factor that causes information to pass from STM to LTM.

The Working memory Model 

Baddeley and Hitch 1974; argued that the concept of STM should be replaced with that of working memory. Their working memeory system has three conponents;

• A modality free central executive resembeling attention.
• A phonological lopp holding information in phonological form.
• A visuo spatial sketchpad specified for spatial and/or visual encoding.

As with the multi store model of memory a key assumption is that whilst each component communicates with each other, they are completely separate stores:

                                                   Central Executive 

Phonological loop                                                                   visuo-spatial sketchpad

- Articulatory loop                                                                       - Inner Scribe 

- Phonological store                                                                    - Visual Cache 

The central Executive - is the key conponent of the working memory model. It is involved in highrt mental processes such a decision making. It allocates resources to the phonological loop or the visuo spatial sketchpad depending on the task at hand. It has limited capacity but is very felxible as it can process  information from any of these senses. 

The phonological Loop - deals with speech based information. There are two conponents:

• The articulatory loop - this is verbal rehearsal loop that holds words. The capcity of the loop is about 2 seconds. This is sometimes known as ' the inner voice'. We use the articulatory loop to process words thart are presented visually.
• The phonological store - this holds the words we hear and is sometimes known as 'the inner ear'. We use the phonological store for words that are presented in speech based information.

The Visuo-Spatial Sketchpad - deals with visual/spatial information. There are two components:

• The visual cache - this stores information aout visual form and colour.
• The inner scribe - this deals with spatial and movement information.

Evaluation of the Working Memory Model 

A strength of the working memory model is that research evidence has supported the idea that STM is made up of three separate stores. The way such research is carried out is to ask paricipants to do tasks either involving separate conponents e.g. visual and verbal task or taks involoving the same conponent e.g. two verbal tasks stimultaneously. If the working memory model were correct in saying that there were three separate conponents. We would expect tasks that involved the same component to be much more difficult than tasks involoving different conponents. This is because if you are doing two tasks involving the same component e.g. verbal tasks, the component will become overloaded and unable to function at its best. This was illustarted in a study bt Robbins et al 1966.

Evaluation of the Working Memory model 

Robbins et al 1996 

Considered the involvement of the three components of working memory in the selection of chess moves. The main task was to select continuation from various chess positions. This is a task that makes use of the central executive and the visuo-spatial sketchpad. Paricipants had to perform this task while either:

• Tapping repetitively (this was the control condition)
• Randomly generating numbers (this used the central executive)
• Pressing keys on a keypad in a clockwise fashion (this used the visuo- spatial sketchpad)
• Rapidly repeating the word 'see saw' (this used the phonological loop) 

The findings were that participants in the control condition performed best, that is they chosse the best moves. Participants in the fourth condition (repating see saw) performed second best. This is presumably because the phonological loop was not involved in the task chess. However, participants in both the second and third condictions performed poorly. This is presumably because the resources o the central executive and visuo-spatial sketchpad were overstretched. 

Another strength of the working memory model is that it nis very influential model. It moved away from the multi store model's view of STM being a unitary store. It recognised and showed that STM could actually be sub-divided into different stores and so was helpful in moving research forwards.

A limitation of the working memory model is that the central executive is too vague. This is an issue that Baddeley openly admitted to. Further research has suggested that the central executive is not a unitary store but much more complex. Elsinger and Damasio 1985 describe a case study of a man with brain damage resulting from the removal of a brain tumour.  His reasoning was good, his IQ was high and he coped well with interference during memeory tasks- all of which indicated that his cental executive was working well.However his decision making was very poor, for example, it took him hours to decide what to eat. If the central executive was a simple system, we would expect all or none of these abilities to be affected, therefore, this case suggests that it is not a single system.