The Working Memory Model

The working memory model (WMM), proposed by __Baddeley and Hitch (1974)__, proposes a dynamic view of short-term memory.

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The working memory model (WMM), proposed by Baddeley and Hitch (1974), proposes a dynamic view of short-term memory.

Baddeley and Hitch (1974) proposed a multi-component model of memory, initially consisting of:
- The central executive (CE).
- The phonological loop (PL).
- The visuo-spatial sketchpad (VSS).
A fourth component, called the episodic buffer (EB), was added in 2000.

The working memory model (WMM) attempts to rectify some of the criticisms of the multi-store model by proposing a more dynamic view of short-term memory.
The WMM thinks of short-term memory as working memory, a dynamic construct that allows for the manipulation of information within the short-term store.
This is different from the proposal of Atkinson and Shiffrin that short-term memory is a static structure that just temporarily stores information.

Working memory is used when performing certain cognitive functions, such as mental arithmetic.
Information in long-term memory is accessed and transferred to working memory where it is combined with new information and manipulated.
If a person is asked to count the number of windows in their house using only their memory, the required information about their house stored in long-term memory would combine with current task requirements. The counting would take place in working memory.

The Central Executive

The central executive (CE) is an attentional system that processes all sensory information.

The CE is an attentional system. This means that it filters information to determine what is attended to.
The CE processes information in all sensory forms and directs this information to the appropriate component. The CE collects responses.
The CE has a limited unknown capacity and can only effectively cope with one strand of information at a time.
When attention needs to be divided (for example, when driving and engaging in conversation), the CE decides how resources are shared, switching attention between different inputs of information.

Baddeley (1996) asked participants to generate lists of random numbers while simultaneously switching between number and letters on a keyboard.
Participants found the task difficult because the two tasks appeared to be competing for the same CE resources.
Because the CE only has a limited capacity, it is difficult to cope with more than one type of information at a time.

D’Esposito et al. (1995) used fMRI scans and identified that the pre-frontal cortex is activated when verbal and spatial tasks are performed at the same time. This suggests that the PFC is involved in CE.

Little is known about the CE at present and it isn’t clear how it works or what it does precisely.
This vagueness means that it can be used to explain a variety of experimental results.
- E.g. if two tasks cannot be performed together, is it because the two components are conflicting or because they exceed the CE capacity?
The CE is perhaps better understood as a component that controls the focus of attention, rather than being a memory store.

The phonological loop (PL) deals with auditory information and consists of the inner ear and inner voice.

The PL deals with auditory information (information in the form of sound) and the order of information (e.g. which words happen before or after each other).
The acoustic nature of the store also means that confusion can occur with similar sounding words.

Baddeley (1986) divided the PL into two sub-systems:
- The primary acoustic store (or inner ear) - stores words recently heard.
- The articulatory process (or inner voice) - keeps information in the PL through sub-vocalised repetition of information and is linked to speech production.

Trojani and Grossi (1995) conducted a case study of an individual known as SC, who suffered brain damage affecting the functioning of the PL but not the visuo-spatial sketchpad (VSS).
This suggests that the PL and VSS are separate systems.

Baddeley at al. (1975) investigated what is known as the word length effect, where participants recalled more short words in serial order than longer words.
Baddeley concluded that the capacity of the PL is set by the duration of words and not the number of words.

PET scans show that different areas are activated when doing verbal and visual tasks. This adds further support that the PL and VSS exist as separate systems within the brain infrastructure.
The PL is associated with the evolution of human vocal language.
The development of the PL is seen to convey an evolutionary advantage. This is because of short-term ability to remember vocalisations which help in the learning of more complex language abilities, such as grammar and meaning.