The working memory model

Specification: The working memory model: central executive, phonological loop, visuo-spatial sketchpad and episodic buffer. Features of the model: coding and capacity.

The Working Memory Model (WMM) was proposed by Baddeley & Hitch (1974) as a way of explaining some of the research findings that could not be accounted for by the multi‐store model (MSM), for example dual‐task studies. 

The WMM focuses on short‐term memory (STM) and Baddeley and Hitch put forward a multi‐component system, which consists of a central executive, phonological loop and visuo‐spatial sketchpad. 

The central executive is the ‘boss’ of the WMM. It controls attention and directs information to the two slave systems, the phonological loop and visuo‐spatial sketchpad. The central executive can process information from any sensory modality.

The phonological loop is a temporary storage system for verbal information (held in a speech‐based form) which has two components, the articulatory control process (the ‘inner voice’) and the phonological store (the ‘inner ear’). The articulatory control process allows for subvocal repetition of acoustic information and the phonological store is a temporary storage space for coding acoustic information, which has a limited capacity. 

The visuo‐spatial sketchpad is a temporary storage system for visual and spatial information which also has two components, the inner scribe and the visual cache. The inner scribe deals with the manipulation of mental images and the visual cache has a limited capacity for coding visual and spatial information. 

The episodic buffer binds and integrates information from all of the components and passes the information to long‐term memory (LTM). It therefore codes both visual and acoustic information, but also has a limited capacity.

Evaluating the working memory model

Support for the WMM comes from the case study of Patient KF, who was injured in a motorcycle accident. Following his accident, KF was able to recall stored information from his LTM; however, he had issues with his STM. He was able to remember visual images, including faces, but was unable to remember sounds (acoustic information). This suggests that there are at least two components within STM, one component for visual information and one for acoustic information. The research into KF supports the WMM and the idea of two slave systems, the phonological loop and the visuo‐spatial sketchpad, therefore providing support to the WMM and the idea of a multi‐component STM system. 

Further support for the WMM comes from dual‐task studies by Baddeley and Hitch (1976). Dual‐task studies require participants to complete two tasks at the same time. In one condition, participants may be required to complete two acoustic‐based tasks, such as simultaneously remembering a series of digits and completing a verbal reasoning task. In another condition, participants may be required to complete one acoustic based task and one visual based task, for example, remember a series of digits and copying a drawing. When both tasks require the participants to use their phonological loop, their ability to perform the tasks is impaired. However, when one task requires the participant to simultaneously use their phonological loop (remembering a series of numbers) and the other requires their visuo‐spatial sketchpad (copying a drawing) then their performance is not impaired. Dual‐task studies provide evidence for the existence of multiple components within our STM and support the idea of a separate phonological loop and visuo‐spatial sketchpad.

However, one issue with the WMM is that it only focuses on STM, and the link between the WMM and LTM is not fully explained. The WMM provides a detailed description of our STM, but no information on how information is processed and transferred from STM to LTM and back again. Therefore, the WMM is an incomplete model of memory and other theories/models are required to gain a complete picture of this complex cognitive phenomenon.Â