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Atkinson and Shiffrin's Multi-Store Model of Memory (1968)
A Diagram of Atkinson and Shiffrin's Model
The Multi-store Model of Memory Basics
Atkinson and Shiffrin (1968) were the first to suggest a multi-store model of memory which consisted of two different types of memory stores. These stores had functional separation and each had a particular role to play in what the layman would call his 'memory.'
1. The first store is the short-term memory store (STM)
2. The second is the long-term memory store (LTM)
The Sensory Register
- As well as the two stores, there was a proposed 'sensory register' which was basically the facility that held information briefly (half a second) in the sense organ (skin, nose, tongue, eyes or ears) that sensed the information in the first place e.g. an ear holds a sound before the information is passed on.
- Experiments by George Sperling (1960) gave evidence that the sensory register holds at least 9 items for around half a second at a time.
Peterson and Peterson (1959)
- Peterson and Peterson found that the duration of the average STM is 18 seconds.
- They did this by giving people simple trigrams (a mixture of 3 random letters e.g. ASL) and asked them to recall them at different time intervals after hearing them (0-18 seconds). Only 10% of participants could remember a trigram after waiting 18 seconds.
- It was also found that rehearsing the trigrams would increase this duration.
Short Term Memory (STM
- The information that is not lost from the sensory register is first passed onto the STM store.
- If the information is rehearsed enough then it will be transferred into long term memory.
- George Armitage Miller provided support for the idea that the STM can hold an average of 7 items at any given time (between 5 and 9 in fact) in his paper called 'The Magical Number 7.'
- Chunking is an effective method of taking in many more than 9 items at a time.
More on STM
- In 1966 Baddeley found that when remembering words the STM uses an acoustic code - making it difficult to remember many similar sounding words after learning them - but a semantic code is used for the LTM, making semantically similar words more difficult to remember after learning them and waiting 20 minutes than acoustically similar words.
- Further research has found that other codes such as visual are used in STM.
Long Term Memory (LTM)
- Information that is rehearsed enough in the STM is transferred to the LTM.
- This information can potentially be held for the rest of our lives.
- The capacity of the LTM seems to be boundless.
- The LTM is a good example of evolution: only knowledge that has been rehearsed enough to be likely to be true and useful is allowed into the LTM for use throughout our lives, boosting our chances of survival more than if we were to remember everything we ever perceived - and since our brain's capacity seems to allow this, it isn't a completely crazy hypothetical as it may at first seem.
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Evidence and Support for the Functional Separation of Memory
- Found that if we are given a list of words, we will remember the first and last words much more often than the words in the middle.
- The explanation of this is given by the 'primacy recency effect.'
- The words at the start have been given more time to be transferred to LTM (primacy) and the words at the end of the list are still in the STM (recency).
- The words in the middle have been moved from the STM but not yet fully encoded into LTM and so are not readily recallable.
- This primacy and recency is difficult to explain without using the idea of the STM and LTM.
- Study of people with amnesia (a severe memory problem caused by memory loss) also support the multi-store model of memory.
- In 1953 a man, 'HM,' developed anterograde amnesia (post-event amnesia) after having a surgery to appease his seizures. As a result, he could remember things that just happened well (STM) but would struggle with consolidating any of that information for later use (LTM).
Alcoholics and Korsikov Syndrome
- Caused most commonly by excessive alcohol consumption, Korsikov syndrome results in sufferers not being able to remember anything new past a few seconds of taking it in (STM). Quite tellingly, they could still remember things from before having Korsikov syndrome (LTM).
Although there is a lot of evidence for the idea that our memory is split into two (three counting the sensory register) faculties, Atkinson and Shiffrin do not answer several queries with their theory.
- Rehearsal Unnecessary
Although it is clear that perceiving something again and again helps remember that thing in the future, it isn't rare for us to see, hear, taste or touch something only once and remember it for the rest of our lives. Particularly in the cases of something being particularly interesting, funny or traumatic, it's quite obvious that there are other factors that decide whether or not particular snippets of information are transferred to LTM or not.
Once again, although there is a lot of evidence for the idea that we have both a STM and a LTM, there is no evidence to suggest that either of these things are singular faculties: the STM and LTM could be a collection of hundreds of stores that would be responsibility for the many different types of information we must deal with: sound, taste, semantics, rhythm, emotions etc.
The case study of an unfortunate man named KF, a man who had a motorcycle accident and so had to undergo brain surgery. He was found years later to have a fully functional LTM but a very impaired STM (a capacity of 2 items). How can the LTM still be fully functional if the faculty where it draws its information from, the STM, is so impaired?
Note: many of these criticisms are tackled by Craik and Lockhart's theories of memory.
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