the multi-store model

STM (short term memory)

limited capacity and duration store. if the info is put into a rehearsal loop it will stay in the STM.

duration – about 18-30 seconds unless info is rehearsed 

capacity – between 5-9 items  

coding – acoustic 

LTM (long term memory)

a permanent memory store. to recall info stored in LTM it has to be transferred back to STM by a process called retrieval.

Duration – potentially a lifetime 

Capacity – potentially unlimited  

Coding – semantic 

the sensory register (SR)

- a stimulus from the environment, e.g. the sound of a person walking, passes into the SR along with lots of other sights, sounds, etc. 
- this part of the memory is 5 stores, for each of the senses
- duration – very brief – less than half a second 
- capacity – very high – over a hundred million cells in one eye storing data
- coding – depends on the sense – auditory, visual, tactile, etc. 

transfer from SR to STM

little of what goes into SR passes further into the memory system - needs attention to be paid to it

maintenance

- occurs when an individual repeats material to themselves
- we can keep info in STM as long as we rehearse it

retrieval

the process of recalling materials stored in LTM by transferring them back to STM 

elaborative rehearsal

- the process of linking info to existing knowledge, or thinking about what it means
- this means that info can be transferred to LTM without prolonged rehearsal

transfer of info from STM → LTM

- maintenance rehearsal occurs when someone repeats material to themself
- info can be stored in STM as long as it is rehearsed
- prolonged rehearsal causes info to be transferred from STM to LTM
- If rehearsed elaboratively the info will enter the LTM
- If not retrieved, then there will be retrieval failure and the memory will leave

explanation of the MSM

- Atkinson and Shiffrin (1968)
- explains the active processing of memories, separate memory stores
- SR
- transfer from SR to STM
- STM
- transfer from STM to LTM
- LTM

Miller (1956) ‘The Magic Number Seven, Plus or Minus Two’

aim: to investigate the capacity of STM

method: literature review of published investigations into perception and STM, from the 1930s to 1950s

results: this existing research suggested that organising stimulus input into a series of chunks enabled STM to cope with about seven ‘chunks’, and this was why more than seven digits, words or even musical notes could be remembered successfully.

conclusion: organisation or encoding can extend the capacity of STM and enable more info to be stored there.

evaluating Miller (1956)

AO3 - strength: supporting evidence
Jacobs (1887) conducted an experiment using a digit span test, to examine the capacity of STM for numbers and letters. Jacobs used a sample of 443 female students (aged from 8-19) from the North London Collegiate School. pps had to repeat back a string of numbers or letters in the same order and the number of digits/letters was gradually increased, until the pps could no longer recall the sequence. Jacobs found that the students had an average span of 7.3 letters and 9.3 words, which supports Miller’s notion of 7+/-2

AO3 - limitation: other factors
Miller’s (1956) research didn’t take into account other factors that affect capacity. e.g. age could also affect STM and Jacobs’ (1887) research acknowledged that STM gradually improved with age.

AO3 - limitation: ‘chunk size’
Miller’s (1956) theory didn’t specify how large each ‘chunk’ of info could be and thus we’re unable to conclude the exact capacity of STM. consequently, further research is required to determine the size of info ‘chunks’ to understand the exact capacity of STM.

Peterson & Peterson (1959) Duration of STM

aim: To investigate how different short intervals containing an interference task affect the recall of items presented verbally, and to infer the duration of STM.

method: The pps were 24 male and female uni students. The verbal items tested for recall were 48 three-consonant nonsense syllables (such as JBW or PDX) spelled out letter by letter. These have since been named 'trigrams'. There were also cards containing three-digit numbers (such as 360 or 294). The researcher spelled the syllable out and then immediately said a three-digit number. The pp had to count down backwards in either 3s or 4s (as instructed) from that number. This was to prevent repetition of the trigram by the pp. At the end of a preset interval of between 3 and 18 secs a red light went on and the pp had to recall the trigram.

results: the longer the interval the less accurate the recall. At 3 secs, around 80% of the trigrams were correctly recalled, whereas at 18 secs only 10% were correctly recalled.

conclusion: STM has a limited duration of approximately 18 secs. also, if we are unable to rehearse info it will not be passed to LTM, providing further support for the MSM and the idea of discrete components.

Evaluating Peterson & Peterson (1959)

AO3 - limitation: not generalisable
Peterson & Peterson used a sample of 24 psychology students, which is an issue for two reasons. Firstly, the psychology students may have encountered the MSM of memory previously and thus may have demonstrated demand characteristics by changing their behaviour to assist the experimenter. Secondly, the memory of psychology students may be different from that of other people, especially if they had previously studied strategies for memory improvement. As a result we are unable to generalise the results of this study to non-psychology students.

AO3 - limitation: low ecological validity
In this study pps were asked to recall three-letter trigrams, which is unlike anything people would want to memorise in their everyday lives. As a result we’re unable to apply these results to everyday examples of memory and are unable to conclude if the duration of STM may be longer for more important info, such as a vital phone number.

AO3 - strength: highly controlled
took place in a lab of Indiana University. As a result Peterson & Peterson had a high degree of control for EVs, which makes their procedure easy to replicate to test reliability.

Bahrick (1975) Duration of LTM

aim: To investigate the duration of LTM.

method: 392 American uni graduates were shown photographs from their high skl yearbook and for each photograph pps were given a group of names and asked to select the name that matched the photographs.

results: 90% of the pps were able to correctly match the names and faces 14 yrs after graduating and 60% of the ps were able to correctly match the names and faces 47 yrs after graduation.

conclusion: people could remember certain types of info, such as names and faces, for almost a lifetime. These results support the MSM and the idea that LTM has a lifetime duration (at least 47 yrs), and is semantically encoded.

Evaluating Bahrick (1975)

AO3 - limitation: lacks population validity
sample of 392 American university graduates. Psychologists are unable to generalise the results of Bahrick's research to other populations, e.g. students from the UK or Europe. As a result, we’re unable to conclude whether other populations would demonstrate the same ability to recall names and faces after 47 yrs.

AO3 - limitation: reason for worsening of LTM
Bahrick found that the accuracy of LTM was 90% after 14 yrs and 60% after 47 yrs. His research is unable to explain whether LTM becomes less accurate over time cuz of a limited duration, or whether LTM simply gets worse with age. This is important cuz psychologists are unable to determine whether our LTM has an unlimited duration (like the MSM suggests), which is affected by other factors such as getting old, or whether our LTM has a limited duration.

AO3 - strength: high ecological validity
the study used real-life memories. In this study pps recalled real-life info by matching pictures of classmates with their names. thus, these results reflect our memory for real-life events and can be applied to everyday human memory.

AO3 - strength of MSM: supporting evidence (Tulving)

- evidence from neuroimaging (brain mapping) studies that different types of memory are stored in different parts of the brain
- Tulving scanned pps’ brains using a PET scanner while they performed various memory tasks
episodic and semantic memories – left prefrontal cortex was involved in recalling semantic memories and the right prefrontal cortex was involved in recalling episodic memories.
procedural memory – activation is associated with the cerebellum.  
- this supports the theory of multiple memory stores

COUNTER:

- it shows LTM is not a single type of memory

AO3 - strength of MSM: real life applications

- e.g. psychologists can target certain kinds of memory in order to improve people’s lives
- researchers have found that episodic memories can be improved in older people with mild cognitive impairments. 
- this highlights the benefits of distinguishing between STM and LTM/different types of LTM – it allows specific treatments to be developed which can improve people’s memory and thus quality of life. 
- this is becoming increasingly important as age-related memory conditions such as Alzheimer’s disease are becoming more common as a result of the aging population. 

AO3 - strength of MSM: research support (Baddeley)

studies showing that STM and LTM are different. e.g. Baddeley (1966) found that we tend to mix up words that sound similar when we are using our STMs. But we mix up words that have similar meanings when we use our LTMs.

COUNTERPOINT: Despite such apparent support, in everyday life we form memories related to all sorts of useful things - people's faces, their names, facts, places, etc. But many of the studies that support the MSM used none of these materials. Instead, they used digits, letters (Jacobs), and sometimes words (Baddeley). They even used what are known as consonant syllables that have no meaning (Peterson and Peterson). This means that the MSM may not be a valid model of how memory works in our everyday lives where we have to remember much more meaningful information.

AO3 - limitation of MSM: more than one STM store

evidence of more than one STM store. Shallice and Warrington (1970) studied a client they referred to as KF who had a clinical memory disorder called amnesia. KF's STM for digits was very poor when they were read out loud to him. But his recall was much better when he read the digits to himself.

Further studies of KF (and others) showed that there could even be another short-term store for non-verbal sounds (e.g. noises). This evidence suggests that the MSM is wrong in claiming that there’s just one STM store processing different types of info (e.g. visual, auditory, etc.).