Atkinson and Shiffrin’s multistore model (MSM) of memory. Revision Notes

The multistore model of memory, developed by Atkinson and Shiffrin in 1968, proposes that memory is composed of three separate stores arranged in a linear sequence: sensory memory, short-term memory (STM), and long-term memory (LTM). Information enters the system through sensory memory, passes to STM if attended to, and can be encoded into LTM through rehearsal. Each store differs in capacity, duration, and function, which explains how we process and retain information over time.

• Memory is not a single unit but a system of stores.
• Information flows sequentially from sensory memory to STM to LTM.
• Each store has unique characteristics affecting memory performance.

Sensory memory acts as a brief buffer for incoming sensory information from the environment. It holds raw data from the senses (e.g., sights, sounds) for a very short time—typically less than a second for visual information (iconic memory) and a few seconds for auditory information (echoic memory). Because of its fleeting nature, most sensory information is lost unless attention is directed towards it, which allows the information to pass into short-term memory.

For example, when you glance at a word on a page, the image is held momentarily in sensory memory before you consciously process it.

• Duration: milliseconds to a few seconds.
• Capacity: very large, as it briefly holds all sensory input.
• Role of attention: selects information to transfer to STM.

Short-term memory temporarily holds information that we are consciously aware of. It has a limited capacity, often described as 7 ± 2 items, and a short duration of about 15 to 30 seconds without rehearsal. Information in STM is mainly encoded acoustically (by sound).

Rehearsal, such as repeating a phone number aloud, helps maintain information in STM and can lead to its transfer into long-term memory. Without rehearsal, information in STM is quickly lost due to decay or displacement by new incoming information.

For instance, when trying to remember a new colleague’s name, you might repeat it silently to yourself to keep it active in STM.

• Capacity: approximately 5 to 9 items.
• Duration: up to 30 seconds without rehearsal.
• Encoding: mainly acoustic.
• Rehearsal is key for retention and transfer to LTM.

Long-term memory stores information for extended periods, potentially for a lifetime. It has an effectively unlimited capacity and stores information mainly in semantic form (by meaning), although visual and acoustic encoding also occur.

Information reaches LTM through processes like rehearsal and meaningful encoding. Retrieval from LTM back to STM is necessary for conscious recall.

An example is remembering your first day at school years later, which involves retrieving stored information from LTM.

• Capacity: unlimited.
• Duration: from minutes to a lifetime.
• Encoding: mainly semantic, but also visual and acoustic.
• Retrieval is required to bring information back to STM for use.

The model emphasises the flow of information: sensory input → sensory memory → attention → short-term memory → rehearsal → long-term memory → retrieval back to STM.

Attention acts as a gatekeeper, determining which sensory information moves into STM. Rehearsal maintains information in STM and facilitates encoding into LTM. Retrieval allows stored information to be accessed when needed.

For example, when studying, focusing attention on the material moves it from sensory memory to STM, rehearsing it helps encode it into LTM, and recalling it during an exam involves retrieval.

• Attention controls transfer from sensory memory to STM.
• Rehearsal enables transfer from STM to LTM.
• Retrieval brings information from LTM back to STM for use.

The sensory register is the first stage of memory where sensory information from the environment is briefly held. It receives input directly from the senses—such as sights, sounds, and smells—and stores this information for a very short time, typically less than one second.

The capacity of the sensory register is very large because it can hold a vast amount of sensory data at once. However, this information fades quickly unless attention is paid to it.

Attention acts as a filter that selects which sensory information moves into short-term memory. For example, when you glance at a colourful poster, the image enters your sensory register, but only if you focus on it does it transfer to short-term memory for further processing.

• Input: raw sensory data from the environment (e.g., visual, auditory).
• Capacity: very large, can hold many sensory impressions.
• Duration: less than 1 second, information fades rapidly.
• Retrieval: information is not consciously retrieved; it either decays or is attended to for transfer.

Short-term memory holds information that you are currently aware of or thinking about. It acts as a workspace for processing information and has a limited capacity and duration.

The capacity of STM is about 7 ± 2 items (Miller’s magic number), meaning most people can hold between 5 and 9 chunks of information at once. For example, remembering a phone number briefly before dialling it.

The duration of STM is approximately 20 to 30 seconds without rehearsal. If information is rehearsed (repeated mentally), it can be maintained longer. Without rehearsal, information decays or is displaced by new incoming data.

• Input: information attended to from the sensory register or retrieved from long-term memory.
• Capacity: limited to about 7 ± 2 items.
• Duration: around 20–30 seconds without rehearsal.
• Retrieval: information can be recalled or encoded into long-term memory through rehearsal.

Long-term memory stores information for extended periods, potentially for a lifetime. It has a very large or unlimited capacity and stores information semantically (by meaning), visually, or acoustically.

Information enters LTM through processes such as rehearsal, meaningful association, or emotional impact. For example, learning facts for an exam or remembering a childhood event.

Retrieval from LTM can be slower and requires cues or prompts. Sometimes information is temporarily inaccessible, which explains forgetting.

• Input: rehearsed or meaningful information from STM.
• Capacity: effectively unlimited.
• Duration: from minutes to a lifetime.
• Retrieval: requires cues; can be conscious or unconscious.

When people try to recall a list of items, they tend to remember items at the beginning and end better than those in the middle. This phenomenon is called the serial position effect.

The primacy effect refers to better recall of items at the start of the list. This happens because these items are rehearsed more and transferred into long-term memory.

The recency effect refers to better recall of items at the end of the list. These items remain in short-term memory at the time of recall, making them easier to retrieve.

• Primacy effect: enhanced recall of early items due to rehearsal and LTM encoding.
• Recency effect: enhanced recall of recent items still in STM.
• Items in the middle are less well recalled due to less rehearsal and displacement.

The serial position effect provides evidence for the existence of separate memory stores. Early items benefit from transfer to long-term memory (primacy), while recent items remain in short-term memory (recency).

If a delay or distraction occurs before recall, the recency effect often disappears because short-term memory contents decay or are displaced, but the primacy effect remains.

For example, if you hear a list of words and immediately recall them, you will likely remember the last few words well (recency). However, if you count backwards for 30 seconds before recalling, the recency effect reduces because STM is cleared.

• Primacy effect relies on LTM encoding through rehearsal.
• Recency effect depends on STM retention at recall time.
• Distraction before recall reduces recency but not primacy effect.

Atkinson and Shiffrin’s multistore model proposes that memory consists of three distinct stores: the sensory register (SR), short-term memory (STM), and long-term memory (LTM). Information flows sequentially through these stores, each with different characteristics of capacity, duration, and encoding. Forgetting can occur at any stage due to different mechanisms specific to each store. Understanding these mechanisms helps explain why we sometimes fail to remember information.

The sensory register briefly holds sensory information from the environment for a very short time, typically less than a second. If attention is paid, information passes into STM, which holds information for about 15–30 seconds with limited capacity (around 7±2 items). Rehearsal in STM can transfer information into LTM, which has a potentially unlimited capacity and duration. However, forgetting can occur in all three stores due to different causes.

• Memory consists of three stores: SR, STM, and LTM.
• Information flows from SR to STM to LTM.
• Each store has unique forgetting mechanisms.

Displacement is a key cause of forgetting in STM. Because STM has a limited capacity (about 7 items), when new information enters STM and it is already full, the oldest information is pushed out or displaced to make room for the new. This means the displaced information is lost and cannot be recalled from STM.

For example, if you try to remember a phone number and someone interrupts by giving you a new number, the first number may be forgotten because the new digits displace the old ones in STM. This explains why STM forgetting is often rapid and related to the amount of information held rather than the passage of time alone.

Displacement differs from decay because it involves active replacement of information rather than fading over time. It highlights the importance of capacity limits in STM as a cause of forgetting.

• STM has limited capacity (~7 items).
• New information can push out old information (displacement).
• Displacement causes loss of old information in STM.
• Example: Forgetting a phone number when interrupted by new digits.

Decay refers to the fading or loss of information over time when it is not rehearsed or attended to. In the sensory register, information lasts only milliseconds to a second before it decays if not transferred to STM. For example, the brief afterimage of a sparkler fades quickly because it is stored only in the sensory register and decays rapidly.

Similarly, in STM, if information is not rehearsed (repeated mentally or aloud), it will decay within about 15–30 seconds. This means the memory trace weakens and is lost. For instance, if you hear a new word but do not repeat it or use it, you may forget it quickly due to decay in STM.

Decay differs from displacement because it is a passive fading process rather than active replacement. Both decay and displacement contribute to forgetting in STM, but decay is time-dependent while displacement depends on capacity limits.

• Decay is fading of memory trace over time without rehearsal.
• Sensory register information decays within milliseconds to a second.
• STM information decays within 15–30 seconds without rehearsal.
• Example: Forgetting a phone number if not repeated.

Forgetting in LTM is often due to problems accessing stored information rather than loss of the information itself. Although LTM has a large capacity and long duration, retrieval can fail if cues are absent or if interference occurs.

For example, you may know a person’s name but fail to recall it temporarily (a ‘tip of the tongue’ experience). The information is stored but inaccessible at that moment. This is an access problem rather than decay or displacement.

Access problems can arise from interference, where similar memories compete, or from insufficient retrieval cues. This explains why some memories seem lost but can be recalled later with the right prompt.

• LTM has large capacity and long duration.
• Forgetting in LTM often due to retrieval/access failure.
• Example: ‘Tip of the tongue’ phenomenon.
• Access problems differ from decay and displacement.

Atkinson and Shiffrin’s model explains forgetting through different mechanisms in each memory store: displacement and decay in STM and SR, and access problems in LTM. Understanding these helps explain everyday forgetting.

For example, forgetting a phone number shortly after hearing it can be due to displacement or decay in STM. Forgetting a visual image seconds after seeing it is likely decay in the sensory register. Difficulty recalling a childhood event may be due to access problems in LTM rather than loss of the memory itself.

This model highlights the importance of rehearsal to prevent decay and the limits of STM capacity that cause displacement. It also shows that forgetting is not always permanent but can be due to retrieval failure in LTM.

• Displacement and decay cause forgetting in STM and SR.
• Access problems cause forgetting in LTM.
• Rehearsal helps prevent decay and transfer to LTM.
• Forgetting can be temporary or permanent depending on the store.

The multistore model of memory, proposed by Atkinson and Shiffrin, suggests that memory consists of three distinct stores: the sensory register, short-term memory (STM), and long-term memory (LTM). Information flows sequentially through these stores, with attention and rehearsal playing key roles in transferring information from one store to the next.

Short-term memory has a limited capacity and duration, typically holding information for around 15-30 seconds unless rehearsed. Long-term memory, in contrast, has a potentially unlimited capacity and duration. The model predicts that different types of information are processed and stored differently depending on these characteristics.

• Memory consists of sensory register, STM, and LTM.
• Information moves sequentially through these stores.
• STM has limited capacity and duration; LTM has large capacity and long duration.

The serial position effect is a phenomenon observed when people are asked to recall items from a list. It shows that recall accuracy is higher for items at the beginning and end of the list compared to those in the middle.

This effect is divided into two components: the primacy effect and the recency effect. The primacy effect refers to better recall of the first items, while the recency effect refers to better recall of the last items.

These effects suggest that different cognitive processes or memory stores are involved in recalling items depending on their position in the list.

• Primacy effect: enhanced recall of first items.
• Recency effect: enhanced recall of last items.
• Middle items are recalled less well.

Murdock conducted an experiment where participants were presented with lists of words and then asked to recall as many as possible in any order. The words were presented one at a time at a steady pace.

The results showed a characteristic U-shaped curve when recall accuracy was plotted against word position. Participants recalled the first few words (primacy effect) and the last few words (recency effect) better than those in the middle.

This pattern supports the idea that the first words were rehearsed and transferred to long-term memory, while the last words remained in short-term memory at the time of recall.

• Participants recalled first and last words better than middle words.
• Primacy effect linked to rehearsal and LTM encoding.
• Recency effect linked to STM retention.

The primacy effect supports the multistore model’s claim that rehearsal in STM leads to transfer into LTM. Early items receive more rehearsal time, increasing their chance of long-term storage.

The recency effect supports the existence of STM as a separate store because the last items are still active in STM at recall, allowing better immediate recall.

The poorer recall of middle items occurs because they receive less rehearsal and have likely left STM without being encoded into LTM, demonstrating the limited capacity and duration of STM.

• Primacy effect shows rehearsal transfers info from STM to LTM.
• Recency effect shows STM holds recent info temporarily.
• Middle items forgotten due to STM limits and lack of rehearsal.

Murdock’s findings provide strong experimental support for the multistore model by demonstrating behavioural evidence of separate memory stores with distinct properties.

However, the model does not explain all aspects of memory, such as the depth of processing or the influence of meaning on recall, which later models address.

Despite limitations, the serial position effect remains a key piece of evidence justifying the distinction between STM and LTM in the multistore model.

• Supports separate STM and LTM stores.
• Highlights role of rehearsal in memory transfer.
• Does not account for all memory phenomena, e.g., depth of processing.

The multistore model (MSM) proposed by Atkinson and Shiffrin describes memory as consisting of three separate stores: the sensory register, short-term memory (STM), and long-term memory (LTM). Information flows sequentially through these stores, starting with sensory input, moving to STM through attention, and then to LTM via rehearsal. Each store differs in capacity, duration, and function. This model was influential in shaping early understanding of memory structure.

• Sensory register briefly holds raw sensory information.
• Short-term memory holds limited information for a short time.
• Long-term memory stores information more permanently.

Depth of processing refers to the level at which information is cognitively analysed during encoding. Shallow processing involves surface features such as the appearance or sound of words, while deep processing involves semantic analysis, such as meaning and associations. Research shows that deeper processing leads to stronger, more durable memory traces and better recall. For example, linking new information to personal experiences typically improves retention compared to simply repeating it.

• Shallow processing: focusing on physical features (e.g., font style).
• Deep processing: focusing on meaning and connections.
• Deeper processing enhances memory retention.

The MSM emphasises rehearsal as the main mechanism for transferring information from STM to LTM but treats rehearsal as a uniform process. It does not differentiate between types or quality of rehearsal. This means it overlooks how the nature of processing—whether shallow or deep—affects memory strength. For example, simply repeating a phone number (maintenance rehearsal) may not lead to long-term retention, whereas elaborating on the meaning of a concept (elaborative rehearsal) does. The MSM’s linear and structural focus misses these qualitative differences in encoding.

• Rehearsal is treated as a single process in MSM.
• No distinction between shallow and deep processing.
• Ignores how meaning-based encoding improves memory.

Because the MSM does not incorporate depth of processing, it cannot fully explain why some information is remembered better than other information despite similar rehearsal time. This limits its explanatory power and practical application. For instance, students who use meaningful study techniques (e.g., making connections) often remember material better than those who rely on rote repetition, a phenomenon the MSM cannot adequately explain. This gap led to alternative models, such as Craik and Lockhart’s levels of processing framework, which emphasises processing quality over memory stores.

• MSM cannot explain differences in retention based on processing quality.
• Limits understanding of effective learning strategies.
• Encouraged development of alternative memory theories.

Imagine two students learning a list of words. Student A repeats the words aloud several times (maintenance rehearsal), while Student B thinks about the meaning of each word and how it relates to their life (elaborative rehearsal). According to the MSM, both students rehearse the information, so both should transfer it to LTM equally. However, Student B typically recalls more words later because deeper processing creates stronger memory traces. This example shows the MSM’s failure to account for the depth of processing effect.

• Maintenance rehearsal: repeating words aloud.
• Elaborative rehearsal: linking words to personal meaning.
• Deeper processing leads to better recall, not explained by MSM.

The MSM proposes that memory consists of three distinct stores: sensory memory, short-term memory (STM), and long-term memory (LTM). Information first enters sensory memory through the senses, where it is held very briefly. If attention is paid, this information passes into STM, which has limited capacity and duration. Through rehearsal, information in STM can be encoded into LTM, which has a potentially unlimited capacity and duration. Retrieval allows information to move back from LTM to STM for use.

• Sensory memory holds raw sensory input for milliseconds to seconds.
• STM holds information temporarily (about 15-30 seconds) with limited capacity (around 7±2 items).
• LTM stores information more permanently with large capacity.

Information transfer depends on attention and rehearsal. Without attention, sensory memory fades quickly. Without rehearsal, STM contents decay or are displaced by new information. Forgetting in STM can occur by displacement, where new incoming information pushes out older items, or by decay over time. In LTM, forgetting is often due to retrieval failure, where the information is stored but cannot be accessed.

• Attention moves information from sensory memory to STM.
• Rehearsal maintains STM information and encodes it into LTM.
• Displacement in STM occurs when new information replaces old information due to limited capacity.
• Decay happens when information fades over time without rehearsal.
• Retrieval failure in LTM means stored information cannot be recalled.

Motivated forgetting refers to the process where individuals forget information intentionally or unconsciously because it is emotionally distressing or unwanted. Within the MSM framework, motivated forgetting can be seen as a retrieval failure in LTM, where emotional factors inhibit access to certain memories. For example, a person may be unable to recall a traumatic event because their mind suppresses the memory to protect their emotional wellbeing. This shows that forgetting is not always accidental but can be influenced by motivation and emotion.

• Motivated forgetting involves intentional or unconscious blocking of memories.
• It is explained as retrieval failure in LTM influenced by emotional factors.
• This type of forgetting serves as a coping mechanism to avoid distress.

Imagine a student who performed poorly on an exam and feels embarrassed. According to the MSM, the memory of the exam experience is stored in LTM. However, due to motivated forgetting, the student may unconsciously avoid recalling details of the exam to reduce emotional discomfort. This retrieval failure is not due to decay or displacement but an active psychological process.

• Memory of the exam is encoded into LTM through rehearsal.
• Emotional distress triggers motivated forgetting, blocking retrieval.
• The student may recall other memories easily but not the stressful exam details.

The MSM provides a clear structure for understanding how information is processed and forgotten. It highlights the importance of attention and rehearsal in memory retention. Incorporating motivated forgetting expands the model by recognising that forgetting can be influenced by psychological factors, not just mechanical processes like decay or displacement. This application helps explain why some memories are inaccessible despite being stored, especially when they are emotionally charged.

• Memory retention depends on attention and rehearsal.
• Forgetting can be mechanical (decay, displacement) or psychological (motivated forgetting).
• Understanding motivated forgetting aids in explaining selective memory loss.