Multi-store Model of Memory (MSM) (AQA AS Psychology): Revision Note

Sensory register: coding, capacity & duration

• The multi-store model of memory (MSM) was proposed by Atkinson & Shiffrin (1968-1971)

• MSM describes a system for how memories are made and stored

  • There are three stores:

    • Sensory register

    • Short-term memory

    • Long-term memory

  • The stores are linked by processes that enable information to flow from each store

Sensory register

• The sensory register (SR) (also referred to as sensory memory) is where all sensory information from the environment passes into or is held

• There are five senses that our body detects

  • Eyes for sight

  • Ears for sounds

  • Nose for smell

  • Tongue for taste

  • Skin for touch/pressure

• There are several registers (stores) within the brain for each of the senses

Coding

• Coding is how the memory is stored, e.g., acoustic codes, visual codes or semantic codes

• Coding in the SR depends on the sense involved; it is therefore modality-specific, e.g.,

  • Iconic memory is the register/store coding for visual information

  • Echoic memory is the register/store coding for acoustic (sound) information

Coding in the SR depends on the sense involved

Capacity

• Capacity refers to how much data can be held in the memory store

• The SR has a very high capacity, e.g., the cells in the eye contain over 100 million cells, each storing visual data

Duration

• Duration is how long a memory is held within a store

• Most sensory information is only held within the SR for milliseconds

• This is because the brain receives millions of pieces of information from the SR every second

• The brain would find it impossible to retain or give attention to this amount of data, nor does it need to

Attention

• Attention is a key process connecting the SR to the short-term memory store (STM)

• If attention is paid to the information passing into the SR then it can be passed onto STM

Short-term memory: coding, capacity & duration

• Information that enters the short-term memory (STM) is used for present and immediate tasks, e.g., following directions or recalling someone's name immediately after learning it

Coding

• Information entering the STM is typically acoustic (Baddeley 1966)

Research

• Baddeley (1966) investigated STM and LTM coding by giving participants four lists of words:

  • Group 1 (acoustically similar): words that sounded alike (e.g. cat, can, cap)

  • Group 2 (acoustically dissimilar): words with different sounds (e.g. pit, few, cow)

  • Group 3 (semantically similar): words with similar meanings (e.g. great, large, big)

  • Group 4 (semantically dissimilar): words with different meanings (e.g. good, huge, hot)

• Participants recalled the words immediately (STM condition) and again after 20 minutes (LTM condition)

• In the STM condition, participants performed worst with acoustically similar words

  • This suggests STM codes information acoustically

• In the LTM condition, participants performed worst with semantically similar words

  • This suggests LTM codes information semantically

Capacity

• The capacity of short-term memory is limited; only a certain number of items can be held at any one time

Research

• Jacobs (1887) developed the digit span technique to measure STM capacity

  • The researcher reads out a sequence of digits or letters; the participant must recall them in the correct order

  • The sequence increases in length until the participant can no longer recall it correctly

  • Jacobs found the mean span was 9.3 items for digits and 7.3 items for letters

• Miller (1956) made observations of everyday life, noting that many things come in sevens

  • E.g. 7 notes on a musical scale, 7 days of the week, 7 deadly sins

  • This led him to propose that STM capacity is 7 (± 2) items — the 'magic number 7'

• Miller also introduced the concept of chunking, which involves grouping individual items into larger meaningful units to increase STM capacity

  • E.g. remembering a phone number as chunks (07700 | 900 | 123) rather than 11 separate digits

Duration

• STM has a limited duration, around 18 seconds unless information is rehearsed

  • This means that STM is a temporary memory store

Research

• Peterson & Peterson (1959) investigated STM duration using trigrams, which are meaningless three-consonant strings (e.g. CHJ, YCG)

  • Participants were given a trigram and immediately asked to count backwards in 3s from a three-digit number

  • Counting backwards prevented rehearsal of the trigram

  • Participants recalled the trigram after retention intervals of 3, 6, 9, 12, 15, or 18 seconds

• Recall dropped sharply over time:

  • After 3 seconds, around 80% of trigrams were recalled correctly

  • After 18 seconds, this fell to approximately 10%

• This suggests STM has a very short duration of around 18 seconds without rehearsal

Rehearsal

• For information to be passed from STM into long-term memory (LTM), it must be rehearsed

  • Maintenance rehearsal is a surface-level repetition of the information

    • e.g., repeating a phone number in your head

  • Elaborative rehearsal involves deeper processing

    • e.g., learning lines for a play

Long-term memory: coding, capacity & duration

• Long-term memory is a permanent memory store of past events or items, e.g.,

  • your first day at primary school

  • a birthday party or celebration

  • the name of your favourite teacher

• To recall information that has passed into LTM it must be accessed and transferred to STM; this is known as retrieval

Coding

• Information in LTM is coded semantically (based on meaning)

Capacity

• The capacity of LTM is potentially unlimited

Duration

• Duration is thought to be for the lifetime of each individual

• Items in LTM may be prone to forgetting

  • Some research suggests that the memory was never actually stored in LTM in the first place, i.e., it was displaced from STM

  • Some LTMs may be unavailable, i.e., resistant to retrieval

    • This means that some memories in LTM decay

  • Research using brain scanning techniques indicates that STM and LTM may be stored in different brain regions, which may explain their differing durations

Evaluation of multi-store model of memory in A Level Psychology

Strengths

• The MSM is supported by a range of controlled lab studies on coding, capacity, and duration, giving the theory strong scientific credibility

  • Controlled conditions allow extraneous variables to be minimised, meaning findings are more likely to reflect genuine differences between STM and LTM

  • The findings of multiple studies point to the same conclusion, strengthening support for the existence of separate STM and LTM stores

• The case study of HM who suffered from epilepsy and underwent brain surgery to correct this, removing his hippocampus

  • Following this surgery, HM could remember events and some information and details from before the surgery (LTM) but he could not form new memories (STM could not be transferred to LTM)

    • This adds weight to the argument that the brain uses separate regions or structures for STM and LTM

Limitations

• The MSM may be too simple

  • Research suggests that STM and LTM are made up of more than one store

  • The working memory model supports the above idea, as it includes five components of STM

• Much of the research into the MSM uses artificial tasks such as recalling a string of digits/letters

  • Baddeley (1966) used artificial stimuli instead of meaningful material

    • This suggests there is a limited application to real world memory use

    • The use of artificial tasks and applications means that the study lacks ecological validity