Working memory

Baddeley & Hitch (1974) developed an alternative model of short-term memory which they named working memory. It aimed at building on the research already done by Atkinson & Shiffrin on their multi-store model of memory.

Baddeley and Hitch argued that the short-term memory store as described in the multi-store model of memory was too simple. According to the multi-store model of memory, STM holds a limited amount of information for short periods of time, with relatively little processing. It is a unitary system, with no subsystems. In comparison, working memory has several subsystems

Working memory is short-term memory. Instead of all information going into one single store, there are different systems for different types of information.

Baddeley (2001) updated his original version to add an extra component: the episodic buffer. Working memory is now made up of 4 components: central executive, phonological loop, visual-spatial sketchpad, and episodic buffer.

The phonological loop manages spoken and written information, the latter of which must first be converted to speech in the mind. The phonological loop involves 2 processes, the phonological store and the articulatory control process

The phonological store is thought of as an "inner ear", as it receives and holds spoken words for 1-2 seconds. The information must be refreshed to prevent it from decaying and being lost. This is handled by the articulatory control process.

The articulatory control process acts as an "inner voice" to rehearse information from the phonological store. Another function of the articulatory control process is to convert written information into speech and move it to the phonological store.

Phonological similarity effect (Larsen, Baddeley, & Andrade (2000)

• "Fee, he, knee, lee, me, she" - phonologically similar. "bay, it, odd, shy, up" - phonologically disimilar. Serial recall was worse with the phonologically similar list. Provides convincing evidence that we use the phonological loop on STM tasks.

The visuo-spatial sketchpad acts as an "inner eye" and deals with visual and spatial information. It's likely that the visuo-spatial sketchpad plays an integral role in helping us keep track of where we are in relation to other objects as we move through our environment (Baddeley, 1997). Vogel et al (2001) stated that visual short-term memory has a span of approximately 4 items. The sketchpad also displays and manipulates visual and spatial information held in the long-term memory store. 

Logie (1995) proposed that like the phonological loop, the visuo-spatial sketchpad is comprised of two components. This involves the visual cache, which holds information about form and colour, and the inner scribe, which manages movement and spatial information. The inner scribe can also rehearse information which is in the visual cache, and move it to the central executive.

The central executive plays a major role in the organisation and management of the other two systems, the visuo-spatial sketchpad and the phonological loop, and it relays information to the long-term memory. The central executive determines which information needs to be attended to, and coordinates where than information should be sent. Nearly all actions which occur in the working memory theory are coordinated by the central executive.

A small amount of research has been conducted on the central executive, and it proves difficult to study. The capacity and precise functions remain largely unknown.

Baddeley suggests that the central executive acts more like a system which controls attentional processes rather than a memory store. The central executive enables the working memory system to selectively attend to some stimuli and ignore others.

Evidence

• Collette & Van der Linden (2002) reviewed brain-imaging studies involving several central executive function: some prefrontal areas are systematically activated by a large range of various executive taks, suggesting their involvement in rather general executive processes

The original model was updated by Baddeley (2000) after the model failed to explain the results of various experiments. An additional component called the episodic buffer was added. The episodic buffer acts as a backup store which communicates with both long-term memory and the other components of working memory.

It stores information as well as being fed information by the other two subsystems and perception, and links to the central executive. Its name as a buffer refers to how it holds information temporarily, storing visual and verbal items, and combining them. Episodic refers to how it binds items into chunks, or episodes.

• Researchers generally agree that short-term memory is made up of a number of components or subsystems. The working memory model has replaced the idea of a unitary STM.
• The working memory model explains a lot more than the multistore model. It makes sense of a range of tasks - verbal reasoning, comprehension, reading, problem solving, and visual and spatial processing.
• The KF case study supports the working memory model. KF suffered brain damage from a motorcycle accident that damaged his short-term memory. KF's impairment was mainly for verbal information, his memory for visual information was largely unaffected. This shows there are separate STM components for visual information and verbal information
• Baddeley & Hitch (1976): dual-task design. One task was to track a point of light as it moved around a screen and the other task was the F task. When doing the tasks simultaneously, performance suffered. When asked to do one of the tasks together with a verbal task, performance was as good at the visual task than when it was done alone. This study suggests that execution of two visual tasks forces a competition for limited resources of the visuo-spatial sketchpad.
• However, working memory only encompasses short-term memory. It is not a complete picture as it doesn't involve long-term memory