The Working Memory Model (WMM)

The section explores The Working Memory Model. The Working Memory Model (WMM), proposed by Baddeley and Hitch (1974), is an explanation of short-term memory that expands upon the simpler structure outlined in the Multi-Store Model. Unlike the concept of a single, unified short-term memory, the WMM suggests that working memory consists of multiple components, each responsible for handling different types of information. This model highlights active processing in memory and how information is manipulated and temporarily stored for tasks such as problem-solving, comprehension, and reasoning.

Components of the Working Memory Model

Central Executive (CE)

The Central Executive (CE) is the most important component of the WMM, as it directs attention and coordinates the activities of the other systems. It acts as a control centre for working memory, managing resources and allocating tasks to the "slave systems" (the Phonological Loop, Visuo-Spatial Sketchpad, and Episodic Buffer).

Key Features of the Central Executive:

Role: The CE is responsible for focusing attention, dividing it between tasks, and switching attention when needed.

Coding: The coding in the Central Executive is modality-free, meaning it can process information in any form, whether visual, auditory, or otherwise.

Capacity: The Central Executive has a very limited capacity and can only handle a small amount of information at one time. When overloaded, performance on tasks may suffer, as it cannot process large volumes of information simultaneously.

Example:

The Central Executive might direct the Visuo-Spatial Sketchpad to store visual information (e.g., a map) while using the Phonological Loop to rehearse verbal instructions simultaneously.

Phonological Loop (PL)

The Phonological Loop (PL) is a specialised system for dealing with verbal and auditory information. It is often referred to as the "inner ear" and plays a critical role in language comprehension and verbal memory. The PL has two subcomponents: the Phonological Store and the Articulatory Control System.

Key Features of the Phonological Loop:

Subcomponents:

Phonological Store: This is a passive "inner ear" that briefly holds sound-based information, such as spoken words. It has a duration of around 2 seconds.

Articulatory Control System: Known as the "inner voice," this component allows for subvocal rehearsal, or repeating information silently to retain it in working memory.

Coding: Coding in the Phonological Loop is acoustic (sound-based).

Capacity: The capacity of the Phonological Loop is limited and believed to be determined by how much information can be rehearsed in about 2 seconds. This is why the Phonological Loop is better suited to retaining short words compared to long ones.

Example:

The Phonological Loop is used when trying to remember a phone number long enough to dial it, as it involves repeating the numbers internally.

Visuo-Spatial Sketchpad (VSS)

The Visuo-Spatial Sketchpad (VSS) is responsible for handling visual and spatial information. Often referred to as the "inner eye", it helps us to temporarily store and manipulate images, spatial details, and visual information.

Key Features of the Visuo-Spatial Sketchpad:

Subcomponents (proposed by Logie in 1995):

Visual Cache: Stores visual data about form and colour.

Inner Scribe: Processes spatial and movement information and transfers information from the Visual Cache to the Central Executive.

Coding: The coding in the Visuo-Spatial Sketchpad is visual and spatial.

Capacity: The capacity of the VSS is limited, typically handling only a small amount of information at one time. Research by Baddeley (2003) suggests that the capacity is around 3–4 objects.

Example:

The Visuo-Spatial Sketchpad is used when trying to visualise a route on a map or mentally arrange furniture in a room.

Episodic Buffer (EB)

The Episodic Buffer (EB) was added to the model by Baddeley (2000) as a means to address the limitations of the original WMM, particularly the need for a store that could integrate information from different sources. The EB is a temporary store that combines information from the Phonological Loop, Visuo-Spatial Sketchpad, and Long-Term Memory to create a coherent memory episode.

Key Features of the Episodic Buffer:

Role: The Episodic Buffer acts as a backup store that integrates visual, spatial, and verbal information into a single, multi-dimensional representation. It also links working memory to long-term memory.

Coding: Coding in the Episodic Buffer is multi-modal, meaning it can process information in multiple forms (e.g., visual, spatial, and verbal).

Capacity: The Episodic Buffer has a limited capacity, estimated to be around four chunks of information.

Example:

The Episodic Buffer might combine a visual image (from the Visuo-Spatial Sketchpad), a spoken phrase (from the Phonological Loop), and relevant long-term knowledge to create a detailed recollection of an event.

Features of the Working Memory Model: Coding and Capacity

Coding

Each component of the WMM has a unique form of coding:

Central Executive: Modality-free, allowing it to handle information in any form.

Phonological Loop: Acoustic, meaning it encodes and stores information based on sound.

Visuo-Spatial Sketchpad: Visual and spatial, encoding information as images or spatial layouts.

Episodic Buffer: Multi-modal, enabling it to integrate information from various sources and types.

Capacity

Each component also has a limited capacity, with the specific limitations varying according to the nature of each subsystem:

Central Executive: Limited capacity, allowing it to handle only a few items at once.

Phonological Loop: Capacity is constrained by a "time-based" limit, usually around 2 seconds worth of auditory information.

Visuo-Spatial Sketchpad: Limited to about 3–4 objects or images.

Episodic Buffer: Limited to approximately four chunks of information, enabling integration of diverse types of information.

Evaluation of the Working Memory Model

Strengths:

• Empirical Support: The WMM has considerable empirical support. For example, Baddeley et al. (1975) found that participants could not perform two tasks that used the same component (e.g., two visual tasks) as effectively as tasks that used different components, demonstrating the distinct roles of the VSS and PL.
• Application to Real Life: The WMM explains real-life tasks, such as reading, problem-solving, and navigation, where different types of information need to be processed and stored simultaneously.
• Focus on Active Processing: Unlike the simpler view of STM in the Multi-Store Model, the WMM recognises that STM is not just a passive store but an active system for manipulating and using information.

Limitations:

• Central Executive's Lack of Clarity: The Central Executive is poorly defined, and its exact role remains unclear. Researchers argue that it is too simplistic to describe it as a single "control centre," as it likely comprises multiple processes and functions.
• Limited Focus on LTM: The WMM primarily addresses short-term memory processes, providing little detail on how working memory interacts with or contributes to long-term memory processes.
• Neuroimaging Evidence: Some neuroimaging studies suggest that the different components are not always located in distinct brain areas, indicating that the structure of working memory may be more complex than the WMM suggests.

Summary of the Working Memory Model

The Working Memory Model has been influential in understanding the active nature of short-term memory and its role in complex cognitive tasks. It highlights the versatility of memory in processing multiple types of information simultaneously, even if some aspects, particularly the Central Executive, remain open to further clarification.