Short answer: The multi-store model of memory says information flows in one direction through three stores: the sensory register, short-term memory (STM) and long-term memory (LTM). Attention moves it to STM, rehearsal moves it to LTM, and retrieval brings it back. Each store differs in coding, capacity and duration.
What the multi-store model says
Atkinson and Shiffrin proposed the model. They described memory as a flow of information through separate stores, much like items moving along a conveyor belt.
AQA lists the model in the Memory topic of the specification, the document that sets out what you must learn. It names three stores and asks you to know the coding, capacity and duration of each [1].
Define these three terms the moment you use them in an answer:
- Coding: the format in which information is held, such as sound or meaning.
- Capacity: how much a store can hold.
- Duration: how long information lasts in the store.
Examiners reward this precision as AO1, which is knowledge and understanding.
How information moves between stores
The model has three processes that move information. Describing them clearly is the quickest way to pick up AO1 marks.
- Attention: information from the environment enters the sensory register. Only what you pay attention to passes into STM. The rest is lost.
- Rehearsal: repeating information, for example saying a phone number aloud. Enough rehearsal transfers it from STM to LTM. Without it, information in STM is lost.
- Retrieval: bringing information back from LTM into STM so you can use it.
The model is linear. Information moves in a fixed order, so it must pass through STM to reach LTM.
The multi-store model of memory: coding, capacity and duration
This table is the core of your AO1 knowledge. Learn each row, including the study that supports it.
| Store | Coding | Capacity | Duration | Key study |
|---|---|---|---|---|
| Sensory register | Specific to each sense, such as images for sight and sounds for hearing | Very large | Very brief, a fraction of a second | None needed for AQA |
| Short-term memory | Mainly acoustic (by sound) [5] | About 7 plus or minus 2 items [2]. Closer to about 4 chunks on later evidence [3] | A matter of seconds without rehearsal [4] | Miller (1956); Cowan (2001); Peterson and Peterson (1959); Baddeley (1966) |
| Long-term memory | Mainly semantic (by meaning) [5] | Potentially unlimited | Potentially a lifetime [6] | Baddeley (1966); Bahrick et al. (1975) |
Here is what each study shows:
- Miller (1956): STM span is about 7 plus or minus 2 items. Chunking, which means grouping items into meaningful units, increases what you can hold [2].
- Cowan (2001): argued the true capacity is closer to 4 chunks than 7 [3].
- Peterson and Peterson (1959): 24 students recalled consonant trigrams (three-letter nonsense strings) after 3 to 18 seconds while counting backwards. Recall fell sharply, to under 10% after 18 seconds. This suggests STM has a short duration without rehearsal [4].
- Baddeley (1966): acoustically similar word lists were harder to recall straight away, so STM coding is mainly acoustic. Semantically similar lists were harder after a delay, so LTM coding is mainly semantic [5].
- Bahrick et al. (1975): 392 American ex-high-school students recognised former classmates from yearbook photos. They were about 90% accurate within 15 years of leaving school and around 70% after 48 years. LTM can last a lifetime [6].
A real-world example of chunking
An NHS number has 10 digits and is written in groups of 3-3-4, such as 111 111 1111 [8]. That is chunking in everyday life.
Ten separate digits would stretch a span of about 7 plus or minus 2 [2]. Three chunks sit comfortably within even Cowan's lower estimate of about 4 [3]. In an exam, use an example like this for AO2 when a question gives you a scenario.
How the assessment objectives reward this topic
An assessment objective (AO) is a skill the exam board tests. AQA's overall A-level weightings are approximate percentages [9].
| AO | What it asks you to do | Approx. weighting |
|---|---|---|
| AO1 | Show knowledge and understanding of scientific ideas, processes, techniques and procedures [9] | 30–33% |
| AO2 | Apply that knowledge in a theoretical or practical context, including data [9] | 30–33% |
| AO3 | Analyse, interpret and evaluate evidence, make judgements and reach conclusions [9] | 36–38% |
AO3 carries the largest weighting across the whole assessment, so evaluation skills matter in every topic, including this one. The split differs by paper. For example, Paper 1 uses AO1 11–14, AO2 6–9 and AO3 12–14 [9].
You need both halves. Accurate description earns AO1 marks, and a developed evaluation point earns AO3 marks.
Evaluating the model for AO3
Strength: support for separate stores. Different studies show STM and LTM differ in coding, duration and capacity [2][4][5][6]. This supports the claim that memory is not one single store. It gives the model good evidence for its basic structure.
Weakness: STM is not one unitary store. Shallice and Warrington (1970) studied KF, who had a brain injury. He had poor STM for verbal (heard) information but better STM for visual information. He could still form new long-term memories [7].
This suggests STM has more than one part. It also challenges the idea that all information must pass through one STM before reaching LTM. The working memory model addresses this weakness by splitting STM into several components [1][7].
Weakness: artificial stimuli. Peterson and Peterson used consonant trigrams, which have little meaning in daily life. This means low ecological validity, which is how well findings apply to real life. Counting backwards may also have caused interference, so forgetting may not be due to duration alone [4].
Counterpoint: real-life support. Bahrick et al. used real yearbook photos, so their study has higher ecological validity than lab studies [6]. It strengthens the claim that LTM has a very long duration.
You can also argue the model treats rehearsal as the main route to LTM. Many everyday memories form without deliberate repetition. This is a general point, so support it with reasoning rather than a statistic.
A worked 6-mark plan and AO3 paragraph
Below is a CC practice question, written in our own words, which mirrors the command word 'outline' and a 6-mark tariff.
Outline the multi-store model of memory. [6 marks]
Plan: three stores, then transfer, then one detail per store. Aim for six clear, accurate points.
The multi-store model describes memory as three separate stores: the sensory register, short-term memory and long-term memory. Information enters the sensory register from the senses. This store has a very large capacity but a very brief duration. Information is lost unless attention is paid to it.
Attended information passes to STM. STM codes mainly acoustically, has a limited capacity of about 7 plus or minus 2 items, and lasts seconds unless rehearsed. Rehearsal, which means repetition, transfers information to LTM. LTM codes mainly by meaning, has potentially unlimited capacity and can last a lifetime. Retrieval brings information back from LTM to STM so it can be used.
Now an AO3 paragraph in PEEL form (Point, Evidence, Explain, Link).
A weakness of the multi-store model is that it presents STM as one unitary store. Evidence comes from the case of KF, studied by Shallice and Warrington. After a brain injury, KF had poor STM for verbal information but better STM for visual information, and he could still form new long-term memories. This suggests STM has separate parts for different types of information, so a single store cannot explain his pattern. It also challenges the idea that all information must pass through one STM to reach LTM. Therefore the model is too simple, which is why the working memory model replaced the single STM with several components.
Notice that the outline uses accurate terms and gives one detail per store, so each sentence earns an AO1 mark. Notice also that the PEEL paragraph names the study, states what it found, explains why that matters and ends with a judgement, which is what AO3 rewards.
Common mistakes
- Mixing up the codes. STM is mainly acoustic and LTM is mainly semantic. Reversing them loses easy marks.
- Stating a figure with no label. Write 'about 7 plus or minus 2 items', not just 'seven'. Name Miller if the question allows.
- Describing studies in the evaluation. AO3 needs a judgement about what the evidence means for the model, not a retelling of the procedure.
- Calling the sensory register the same as STM. It is a separate store with a larger capacity and a far shorter duration.
- Forgetting the processes. Name attention, rehearsal and retrieval. Without them you have listed stores but not described a model.
- Teaching old content. Types of long-term memory were removed from the updated specification, so do not spend revision time on them [1].
Practise the multi-store model
Practise this skill topic by topic on the CC Psychology revision platform, which follows the AQA specification.
See the CC Psychology revision platformNext, read How to write AO3 evaluation in A-level Psychology.
Sources
- AQA (2026). A-level Psychology 7182: subject content, 3.1 Introductory topics in Psychology (3.1.2 Memory).
- Miller, G. A. (1956). The magical number seven, plus or minus two. Psychological Review, 63(2), 81–97.
- Cowan, N. (2001). The magical number 4 in short-term memory. Behavioral and Brain Sciences, 24(1), 87–114.
- Peterson, L. R. and Peterson, M. J. (1959). Short-term retention of individual verbal items. Journal of Experimental Psychology, 58(3), 193–198.
- Baddeley, A. D. (1966). Short-term memory for word sequences as a function of acoustic, semantic and formal similarity. Quarterly Journal of Experimental Psychology, 18(4), 362–365.
- Bahrick, H. P., Bahrick, P. O. and Wittlinger, R. P. (1975). Fifty years of memory for names and faces. Journal of Experimental Psychology: General, 104(1), 54–75.
- Shallice, T. and Warrington, E. K. (1970). Independent functioning of verbal memory stores: a neuropsychological study. Quarterly Journal of Experimental Psychology, 22(2), 261–273.
- University Hospitals Birmingham NHS Foundation Trust. Your NHS number.
- AQA (2026). A-level Psychology 7182: scheme of assessment (assessment objectives and weightings).