What is the working memory model?

The working memory model (Baddeley, 1986) contrasts to the modal model of memory (Atkinson & Shiffrin, 1971) in that it states that there are multiple components of short-term memory, as opposed to being it being a unitary store. This model states that working memory consists of two slave systems: the phonological loop and the visuospatial sketchpad, which are responsible for spoken/written material and visual/spatial material respectively. Furthermore, the phonological loop can be split into two parts. The phonological store holds information in a speech based form, and the articulatory control process rehearses the information in the phonological store. The slave system are monitored and controlled by the central executive, a component which is also involved in processes such as controlling attention.
There is evidence to support the theory of working memory and multiple short-term components. Logie et al (1990) found that participants' percentage recall decreased when remembering both letters and arithmetic or both patterns and a spatial matrix, as these would utilise the same store. However, participants still showed good recall for remembering arithmetic and spatial matrices or patterns and letters. This could be accounted for by the information being processed in different components of working memory, but could not be explained by a single short-term memory store.