The Working Memory Model

The working memory model (WMM) was proposed by Baddeley and Hitch (1974) as an alternative to the multi-store model's view of short-term memory as a single, unitary store. The WMM suggests that STM is not one simple store but an active system made up of several components that work together to process information.

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Why Was the Working Memory Model Needed?

Atkinson and Shiffrin's multi-store model described STM as a single store. However, research showed that people can carry out two tasks simultaneously if they use different types of information (e.g. a verbal task and a visual task) but struggle to perform two tasks that use the same type of information. This suggested that STM must have separate components for processing different types of information, not just one single store.

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Components of the Working Memory Model

The WMM has four components:

flowchart TD
    CE["Central Executive<br/>directs attention,<br/>limited capacity"]
    CE --> PL["Phonological Loop<br/>verbal/auditory"]
    CE --> VSS["Visuospatial Sketchpad<br/>visual/spatial"]
    CE --> EB["Episodic Buffer<br/>integrates info<br/>added 2000"]
    PL --> PS["Phonological Store<br/>inner ear"]
    PL --> ACP["Articulatory Control<br/>inner voice"]
    EB --> LTM[Long-Term Memory]

1. The Central Executive

The central executive is the most important component. It acts as a control centre that:

• Directs attention to particular tasks
• Allocates resources to the other components (called "slave systems")
• Monitors and coordinates the work of the other components

The central executive has limited capacity but does not have a specific coding system — it can process information from any sense. It decides which information to attend to and which to ignore.

2. The Phonological Loop

The phonological loop deals with auditory and verbal information (spoken and written words). It has two sub-components:

Sub-component	Function
Phonological store (the "inner ear")	Holds speech-based information for 1–2 seconds
Articulatory control process (the "inner voice")	Rehearses verbal information through silent repetition (like talking to yourself in your head)

The phonological loop explains why it is difficult to remember long words — they take longer to rehearse using the articulatory control process. This is known as the word length effect.

3. The Visuospatial Sketchpad

The visuospatial sketchpad (the "inner eye") deals with visual and spatial information. It is used when you:

• Picture something in your mind
• Plan a spatial task (e.g. navigating a route)
• Think about the size, shape, or position of objects

Like the phonological loop, the visuospatial sketchpad has limited capacity. It processes visual information (what things look like) and spatial information (where things are in relation to each other).

4. The Episodic Buffer

The episodic buffer was added by Baddeley in 2000. It acts as a temporary store that:

• Integrates information from the phonological loop, visuospatial sketchpad, and long-term memory
• Combines information from different sources into a single, coherent episode or experience
• Has limited capacity (approximately 4 chunks of information)
• Is controlled by the central executive

Baddeley added this component because the original model could not explain how information from different components was combined, or how working memory interacted with long-term memory.

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How the Components Work Together

Imagine you are reading a book and trying to picture the scene:

1. The central executive directs your attention to the text
2. The phonological loop processes the words you read (or subvocalise)
3. The visuospatial sketchpad creates a mental image of the scene
4. The episodic buffer combines the verbal and visual information with your existing knowledge from LTM into a coherent experience

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Evidence Supporting the WMM

Dual-Task Studies

Baddeley and Hitch (1974) conducted experiments where participants performed two tasks simultaneously:

• When both tasks used the same component (e.g. two verbal tasks), performance was poor — the tasks competed for the same limited resource
• When the tasks used different components (e.g. one verbal, one visual), performance was good — the tasks used separate resources

This supports the idea that working memory has separate components with independent resources.

The Word Length Effect

People find it harder to remember lists of long words (e.g. "refrigerator", "encyclopaedia") than short words (e.g. "cat", "pen"). This is because long words take longer to rehearse in the articulatory control process of the phonological loop.

Case Study: KF

A patient known as KF suffered brain damage that impaired his ability to process verbal information but left his visual processing intact. This supports the WMM's view that verbal and visual information are processed by separate components.

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Evaluation of the Working Memory Model

Strengths

• It explains how we can multitask — performing two tasks that use different components is easier than performing two tasks that use the same component
• It is supported by dual-task studies and brain-damaged patients (e.g. KF)
• It provides a more detailed and accurate account of STM than the multi-store model
• The addition of the episodic buffer addresses earlier criticisms about how information is integrated

Weaknesses

• The central executive is not well understood — it is described as an "attentional control system" but its exact function is vague
• Most research supporting the model uses lab experiments, which may lack ecological validity
• The model focuses only on STM and does not explain how information is transferred to and from LTM in detail
• The role of the episodic buffer is still not fully established through research

Exam Tip: When comparing the MSM and WMM, focus on how the WMM addresses the weaknesses of the MSM. The MSM treats STM as one store; the WMM shows it has multiple components. Use evidence (e.g. KF, dual-task studies) to support your answer.

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Key Points