Three models of memory (multi-store, working memory, levels of processing) and the brain structures of memory (QCE Psychology Unit 3)
“Compare three models of memory, specifically the multi-store model of memory, including sensory, short-term and long-term memory; the working memory model, including the central executive, phonological loop, visuospatial sketchpad, and episodic buffer; the levels of processing (LOP) model of memory, including the role of encoding in long-term memory; State the duration and capacity of sensory memory (including iconic and echoic), and short-term and long-term memory; Describe the role of the hippocampus, the neo-cortex and the amygdala in forming and storing explicit memories; Describe the role of the cerebellum in forming implicit memories”
The Atkinson-Shiffrin multi-store model describes memory as a sequence of stores (sensory, short-term, long-term) that differ in capacity and duration. Baddeley and Hitch's working memory model replaces the single short-term store with an active workspace: central executive, phonological loop, visuospatial sketchpad and episodic buffer. The levels of processing model drops fixed stores and argues that how deeply information is encoded (structural, phonemic or semantic) determines how well it is remembered. Explicit memories are formed by the hippocampus, stored across the neo-cortex and given emotional strength by the amygdala; implicit procedural memories are formed with the cerebellum.
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What this dot point is asking
The 2025 syllabus asks you to compare three models of memory (the multi-store model, the working memory model and the levels of processing model), state the duration and capacity of sensory memory (iconic and echoic), short-term and long-term memory, and describe the roles of the hippocampus, neo-cortex and amygdala in forming and storing explicit memories and the cerebellum in forming implicit memories. Recall, recognition and relearning, forgetting, and strategies to improve memory are on our forgetting and improving memory page.
The answer
The three processes
All memory models rest on three processes. Encoding is converting information into a usable form (acoustic, visual or semantic). Storage is retaining that information over time. Retrieval is recovering stored information when it is needed, either by recall (producing it) or recognition (identifying it). A failure can occur at any of these three stages.
The multi-store model (Atkinson and Shiffrin, 1968)
This model proposes three separate stores through which information flows in sequence.
- Sensory memory. Holds raw sensory input very briefly (iconic visual memory for under a second, echoic auditory memory for a few seconds). Sperling's (1960) partial-report experiment showed iconic memory has a large capacity that fades almost instantly.
- Short-term memory (STM). Limited capacity, around 7 plus or minus 2 items (Miller, 1956), and limited duration. Peterson and Peterson (1959) showed that without rehearsal, STM decays within about 18 seconds, because preventing rehearsal with a counting task caused recall to drop sharply.
- Long-term memory (LTM). Potentially unlimited capacity and duration. Information enters LTM through rehearsal and is divided into explicit (declarative) and implicit (procedural) memory.
The model's strength is its clear structure; its weakness is treating STM as a single passive store, which the working memory model corrects.
The working memory model (Baddeley and Hitch, 1974)
This model reconceives short-term memory as an active workspace with multiple components.
- Central executive. The attentional controller that directs resources and coordinates the subsystems.
- Phonological loop. Handles verbal and auditory information (an inner voice and inner ear).
- Visuospatial sketchpad. Handles visual and spatial information (an inner eye).
- Episodic buffer (added by Baddeley in 2000). Integrates information across the subsystems and links to long-term memory.
Evidence comes from dual-task studies: people can do a verbal task and a visual task at once with little interference, but two verbal tasks compete, showing separate subsystems.
The levels of processing model (Craik and Lockhart, 1972)
The levels of processing (LOP) model takes a different approach. Instead of separate stores, it proposes that how well something is remembered depends on how deeply it is processed at encoding:
- Shallow processing: structural (what the word looks like, such as whether it is in capital letters) and phonemic (what it sounds like, such as what it rhymes with).
- Deep processing: semantic (what it means, such as whether it fits in a sentence).
Deeper, more meaningful encoding produces more durable long-term memories. In Craik and Tulving's (1975) experiments, participants answered structural, phonemic or semantic questions about words and were then given a surprise recognition test; words processed semantically were recognised best. The model explains why elaborative rehearsal (linking information to meaning) works better than repetition. Its main criticism is that "depth" is hard to measure independently of the memory it is meant to explain, so the argument can become circular.
Comparing the three models
| Feature | Multi-store model | Working memory model | Levels of processing model |
|---|---|---|---|
| View of memory | A sequence of separate stores | Short-term memory as an active workspace with components | A by-product of how deeply information is processed |
| Short-term memory | One passive store (limited capacity and duration) | Central executive, phonological loop, visuospatial sketchpad, episodic buffer | Not a separate store; the focus is encoding |
| How information reaches long-term memory | Rehearsal transfers it | Via the episodic buffer and the central executive's control | Deep (semantic) processing makes it durable |
| Key evidence | Capacity and duration studies (Miller, 1956; Peterson and Peterson, 1959) | Dual-task studies | Craik and Tulving (1975) |
| Main limitation | Treats short-term memory as a single, passive store | Central executive is vaguely defined | Depth is hard to measure independently |
The syllabus also notes that the working memory model has greater explanatory power than earlier models, and that models are refined or replaced as new evidence appears (the episodic buffer was added to the working memory model in 2000).
Brain structures of memory
Memory is not stored in one place; different structures support different memory types.
- Hippocampus. Essential for forming new long-term explicit memories. The case of patient HM (Henry Molaison), who had his hippocampi removed to treat epilepsy, is the landmark evidence: he could no longer form new long-term memories (anterograde amnesia) but retained older memories and could learn new motor skills, showing the hippocampus is needed for forming, not storing, explicit memory.
- Neo-cortex. Once consolidated, explicit memories (episodic and semantic) are stored in a distributed way across the neo-cortex, which also helps retrieve them.
- Amygdala. Attaches emotional significance to explicit memories and strengthens their consolidation, which is why emotionally charged events are often vividly remembered.
- Cerebellum and basal ganglia. Support procedural (implicit) memory and motor skills, which is why HM could still learn the mirror-drawing task despite his amnesia.
Patient HM could learn and improve at a mirror-drawing task across days yet had no memory of ever having done it before. This dissociation is powerful evidence that procedural memory (cerebellum and basal ganglia) is separate from explicit memory (hippocampus).
Putting it together for an exam
A strong response names the model, describes its components, then links a process or store to a brain structure and a study. For example: forming a new long-term memory depends on the hippocampus, as shown by HM's anterograde amnesia after its removal. Connecting model, process, structure and evidence is what earns top marks.
- Treating levels of processing as a store model
- It is about the depth of encoding, not about where information is held.
- Confusing the store models
- The multi-store model has a single STM store; the working memory model breaks STM into the central executive, phonological loop and visuospatial sketchpad.
- Saying the hippocampus stores long-term memories
- It is needed to form and consolidate them; long-term storage is distributed across the cortex.
- Mixing up encoding, storage and retrieval
- Forgetting where you parked is usually a retrieval failure, not a storage failure.
- Treating STM capacity as fixed at exactly seven items
- Miller's figure is 7 plus or minus 2, and chunking can dramatically increase effective capacity.
Exam-style questions
Questions in the style of QCAA exam questions on this dot point, each with a worked answer. They are written by ExamExplained unless tagged "Past paper"; the year shows the paper a question is modelled on.
Practice5 marksa) Identify the capacity and duration of short-term memory without the use of strategies. [2 marks] b) Describe chunking and discuss one argument for using chunking and one argument against using it to increase the capacity of short-term memory. [3 marks]
Show worked answer →
a) Capacity is about 7 plus or minus 2 items (Miller, 1956); duration is roughly 18 to 30 seconds without rehearsal (Peterson and Peterson, 1959). 1 mark each.
b) Chunking is grouping separate items into larger meaningful units, so a string of digits becomes a few chunks that each count as one item in short-term memory (1 mark).
For chunking (1 mark): it increases the effective amount held because capacity is measured in chunks, not individual items, so more raw information fits within the 7 plus or minus 2 limit.
Against chunking (1 mark): it relies on existing long-term knowledge to form meaningful chunks, so unfamiliar material cannot be chunked, and forming chunks takes effort and time that can disrupt rehearsal.
Practice2 marksDescribe two roles of the hippocampus in memory formation.Show worked answer →
Two distinct roles are required, 1 mark each.
The hippocampus encodes and forms new explicit (declarative) long-term memories, binding the elements of an experience into a single memory trace.
It consolidates these memories, gradually transferring them for long-term storage in the cortex.
Evidence: patient HM, whose hippocampi were removed, could no longer form new long-term memories (anterograde amnesia), confirming the hippocampus is needed to form, not permanently store, explicit memory.
Practice2 marksDescribe the role of the hippocampus in memory formation and storage.Show worked answer →
For 2 marks, address both formation and storage.
Formation (1 mark): the hippocampus is essential for encoding and forming new explicit long-term memories, integrating sensory and contextual details into a coherent memory.
Storage (1 mark): the hippocampus consolidates new memories and gradually transfers them to the cerebral cortex for permanent storage, so it is required to form and consolidate long-term memories rather than to store them indefinitely itself. Damage to the hippocampus (as in patient HM) prevents new long-term explicit memories from forming.