The working memory model - Baddley and Hitch (1974)

The Working Memory Model

Baddley and Hitch (1974) used the term 'working memory' to refer to that bit of memory that you are using when you are working on a complex task which requires you to store information as you go along. They believed that STM was not a single store, but a number of stores because if you do two things at the same time and they are both visual tasks, you perform them less well than if you do them separately. Also because if you do two things at the same time and one is visual whereas the other involves sound, then there is no interference. You do them as well simultaneously as you would do them separately.

The components of the working memory model:

- The central executive 

- The phonological loop

- Visuo-spatial sketchpad

- The episodic buffer 

What the components do:

- The central executive: This is the key component of working memory. It's function is to direct attention to particular tasks, determining at any time how 'resources' are allocated to tasks. It also has a very limited capacity; can't attend to too many things at once.

- The phonological loop: It deals with auditory information and preserves the order of information. Baddley (1986) further subdivided this loop into the phonological store (inner ear) and the articulatory process (inner voice)

- Visuo-spatial sketchpad: This is used when an individual is planning a spatial task. Visual and/or spatial information is temporarily stored here.

- Episodic buffer: Baddley added this in 2000 as he realised the model needed a general store. It is an extra storage system that has a limited capacity. The episodic buffer integrates info from the other stores, including long-term memory.

Evidence supporting the working memory model:

Evidence from brain-damaged patients

Patient SC had generally good learning abilities with the expectation of being unable to learn word pairs that were presented out loud. This suggests damage to the phonological loop (Trojano and Grossi, 1995).

Strengths and weaknesses:

+ The model explains the word-length effect and the partial STM difficulties experienced by individuals with brain damage such as KF and SC.

+ Continuing development of this model reflects the shift from seeing memory as one activity, to being able to distinguish an array of different kings of memory.

+ Includes verbal rehearsal as an optional process rather than the only means by which information is kept in immediate memory

- The central executive is too vague and doesn't really explain anything

- Critics feel the central executive is wrong and that there are probably several components.

- Evidence from brain-damaged patients: there are problems with using such evidence as you can't make before and after comparisons, so it is not clear whether changed in behaviour are caused by the damage.