Working Memory Model

Baddeley and Hitch (1974) developed the Working Memory Model (WMM), which focuses specifically on the workings of short-term memory (STM).

Atkinson and Shiffrin's Multi-Store Model of memory (MSM) was criticised for over-simplifying STM (as well as LTM) as a single storage system, so the WMM alternative proposed that STM is composed of three, limited capacity stores: central executive, articulatory phonological loop, and visuo-spatial sketchpad.

The central executive manages attention, and controls information from the two 'slave stores' (articulatory phonological loop and visuo-spatial sketchpad).

The articulatory phonological loop temporarily retains language-based information, consisting of:

- An articulatory rehearsal process ('inner voice') of language, including any language presented visually to convert to a phonological state, for storage in the phonological store.

- Phonological store ('inner ear'), which holds auditory speech information and the order in which it was heard (or any visually-presented language converted by the articulatory process).

The visuo-spatial sketchpad temporarily retains visual and spatial information.

A later addition was the episodic buffer, which facilitates communication between the central executive and long term memory.

The three-store STM stemmed from research using a 'dual-task technique' (or 'interference tasks'), whereby performance is measured as participants perform two tasks simultaneously. The following observations provided evidence to suggest different, limited-capacity STM stores process different types of memory:

- If one store is utilised for both tasks, then task performance is poorer than when they are completed separately, due to the store's limited capacity. For example, repeating "the the the" aloud and reading some text silently would use the articulatory-phonological loop for both tasks, slowing performance.

- If the tasks require different stores, performance would be unaffected when performing simultaneously. For example, repeating "the the the" aloud whilst performing a reasoning task (requiring attention, i.e. the central executive), or whilst following a mobile stimulus with your eyes (using the visuo-spatial sketchpad).

+ The WMM provides an explanation for parallel processing (i.e. where processes involved in a cognitive task occur at once), unlike Atkinson and Shiffrin's MSM.

+ A Shallice and Warrington (1974) case study reported that the brain-damaged patient KF could recall verbal but not visual information immediately after its presentation, which supports the WMM's claim that separate short-term stores manage short-term phonological and visual memories. 

+ The model was developed based on evidence from laboratory experiments, so confounding variables could be carefully controlled to produce reliable results (that can be replicated).

- Despite providing more detail of STM than the MSM, the WMM has been criticised for being too simplistic and vague, e.g. it is unclear was the central executive is, or its exact role in attention.

- Results from laboratory experiments researching the WMM will often have low ecological validity (i.e. may not relate to will life), as tasks such as repeating 'the the the' are arguably not representative of our everyday activities.