The Multi-Store Model of Memory (MSM)

This section explores the multi-store model of memory. The Multi-Store Model of Memory (MSM), proposed by Atkinson and Shiffrin (1968), is a structural model that describes memory as consisting of three distinct stores: the Sensory Register, Short-Term Memory (STM), and Long-Term Memory (LTM). Each of these stores has unique characteristics in terms of coding, capacity, and duration. The model suggests that information passes through each store in a linear sequence, with the potential for information to be lost at each stage if it is not attended to or rehearsed.

Sensory Register (SR)

The Sensory Register is the first store of memory in the MSM. It holds sensory information received from the environment through the senses (e.g., sight, sound, touch) for a very brief period. This stage allows sensory input to be briefly registered and then processed further if attended to.

Features of the Sensory Register

Coding: The coding in the sensory register is modality-specific, meaning it matches the form of the original sensory input. For instance, visual information is stored in the iconic store, while auditory information is stored in the echoic store.

Iconic Memory: Visual information.

Echoic Memory: Auditory information.

Haptic Memory: Tactile information.

Capacity: The capacity of the sensory register is very large. It can hold a substantial amount of sensory information from the environment, but most of it is not attended to and therefore quickly decays.

Duration: The duration of the sensory register is extremely brief, lasting approximately 0.5 seconds for iconic memory and 2–4 seconds for echoic memory. Information decays rapidly if it is not transferred to short-term memory through attention.

Key Study on Sensory Register

Sperling (1960) conducted a study on the capacity and duration of the iconic store in the sensory register. Participants could recall only a small number of items from a grid of letters flashed briefly on a screen, suggesting the duration is very short, even though the capacity is high.

Short-Term Memory (STM)

Short-Term Memory (STM) is the second store in the MSM, where information is processed and held temporarily. It is limited in both capacity and duration, which means that without rehearsal, information in STM will be lost.

Features of Short-Term Memory

Coding: In STM, information is primarily coded acoustically (based on sound). Research suggests that we often recall words or letters in terms of how they sound rather than their meaning or appearance.

Conrad (1964) found that participants made more mistakes recalling letters that sounded similar (e.g., ‘B’ and ‘V’) than those that looked similar, supporting acoustic coding in STM.

Capacity: The capacity of STM is limited to about 7 ± 2 items (often cited as "7 plus or minus 2"), as proposed by Miller (1956). However, capacity can be increased through a process known as chunking, where information is grouped into larger, meaningful units.

Duration: STM has a short duration of around 18–30 seconds without rehearsal. Peterson and Peterson (1959) found that participants could only remember trigrams (three-letter combinations) for about 18 seconds when rehearsal was prevented, suggesting information is lost quickly unless maintained by rehearsal.

Maintenance Rehearsal

For information to move from STM to LTM, it requires maintenance rehearsal. Rehearsal keeps information active in STM and increases the likelihood of transfer to LTM for more permanent storage.

Long-Term Memory (LTM)

Long-Term Memory (LTM) is the third and final store in the MSM. It is the store for information that has been rehearsed and consolidated in STM, allowing it to be stored more permanently. LTM can hold vast amounts of information for long periods.

Features of Long-Term Memory

Coding: In LTM, information is primarily coded semantically (by meaning), although other forms of coding, such as visual and acoustic, can also occur. Semantic coding means that information is stored based on its meaning rather than its sound or appearance.

Baddeley (1966) showed that participants had more difficulty recalling semantically similar words than acoustically similar ones in LTM tasks, supporting the idea of semantic coding.

Capacity: The capacity of LTM is believed to be unlimited. Unlike STM, there appears to be no upper limit on the amount of information that LTM can hold.

Duration: The duration of LTM can be potentially lifelong. Many memories in LTM last for years or even a lifetime, although they may fade or weaken over time if not retrieved frequently.

Bahrick et al. (1975) studied high school graduates’ recall of classmates after several decades and found that participants could remember names and faces with significant accuracy even after 48 years, supporting the idea of LTM's long duration.

Evaluation of the Multi-Store Model of Memory

Strengths of the MSM

• Empirical Support: The MSM is supported by research evidence, such as studies on coding, capacity, and duration in each store (e.g., Peterson & Peterson, Miller, and Bahrick). These studies validate the separate characteristics of STM and LTM.
• Clear Structure: The model provides a clear and intuitive structure, distinguishing different types of memory storage, which has helped guide further research and development in memory theories.
• Influence on Memory Research: The MSM has been foundational in memory psychology, influencing subsequent models and theories, such as the Working Memory Model by Baddeley and Hitch.

Limitations of the MSM

• Over-Simplified: The MSM is criticised for oversimplifying memory processes by assuming that STM and LTM are unitary stores. Research has since shown that there are multiple types of STM (e.g., Working Memory Model) and LTM (e.g., episodic, semantic, and procedural memory), each with distinct functions.
• Role of Rehearsal: The MSM emphasises rehearsal as a key process for transferring information from STM to LTM. However, research shows that meaningful information can enter LTM without rehearsal, and not all rehearsed information is retained long-term.
• Focus on Structure over Process: The model focuses more on the structure of memory rather than the processes involved in encoding and retrieval, limiting its ability to explain more complex aspects of memory, such as how emotions and attention impact memory formation and recall.

Summary of the Multi-Store Model of Memory

The Multi-Store Model of Memory provides a foundational understanding of memory as a series of distinct stores:

Sensory Register: Large capacity, brief duration, modality-specific coding.

Short-Term Memory (STM): Limited capacity, short duration, acoustic coding.

Long-Term Memory (LTM): Potentially unlimited capacity and duration, semantic coding.

The model's strengths lie in its clear structure and foundational contribution to memory research. However, it is also critiqued for oversimplifying memory processes, particularly the role of rehearsal, and for treating memory stores as unitary rather than multi-faceted. Despite its limitations, the MSM remains an influential model that has shaped our understanding of how memory functions.