Working Memory (Baddeley and Hitch, 1974)
Atkinson’s and Shiffrin’s (1968) multi-store model was extremely successful in terms of the amount of research it generated. However, as a result of this research, it became apparent that there were a number of problems with their ideas concerning the characteristics of short-term memory.
Building on this research, Baddeley and Hitch (1974) developed an alternative model of short-term memory which they called working memory (see fig 1).
Fig 1. The Working Memory Model (Baddeley and Hitch, 1974)
Baddeley and Hitch (1974) argue that the picture of short-term memory (STM) provided by the Multi-Store Model is far too simple. According to the Multi-Store Model, STM holds limited amounts of information for short periods of time with relatively little processing. It is a unitary system. This means it is a single system (or store) without any subsystems. Working Memory is not a unitary store.
Working memory is STM. Instead of all information going into one single store, there are different systems for different types of information. Working memory consists of a central executive which controls and co-ordinates the operation of two subsystems: the phonological loop and the visuo-spatial sketchpad.
Central Executive: Drives the whole system (e.g. the boss of working memory) and allocates data to the subsystems (VSS & PL). It also deals with cognitive tasks such as mental arithmetic and problem solving.
Visuo-Spatial Sketch Pad (inner eye): Stores and processes information in a visual or spatial form. The VSS is used for navigation.
The phonological loop is the part of working memory that deals with spoken and written material. It can be used to remember a phone number. It consists of two parts
o Phonological Store (inner ear) – Linked to speech perception Holds information in speech-based form (i.e. spoken words) for 1-2 seconds.
o Articulatory control process (inner voice) – Linked to speech production. Used to rehearse and store verbal information from the phonological store.
Fig 2. The Working Memory Model Components (Baddeley and Hitch, 1974)
The labels given to the components (see fig 2) of the working memory reflect their function and the type of information they process and manipulate. The phonological loop is assumed to be responsible for the manipulation of speech based information, whereas the visuo-spatial sketchpad is assumed to by responsible for manipulating visual images. The model proposes that every component of working memory has a limited capacity, and also that the components are relatively independent of each other.
Empirical Evidence for the Working Memory Model
What evidence is there that working memory exists, that it is made up of a number of parts, that it performs a number of different tasks?
The working memory model makes the following two predictions:
1. If two tasks make use of the same component (of working memory), they cannot be performed successfully together.
2. If two tasks make use of different components, it should be possible to perform them as well as together as separately.
Key Study: Baddeley and Hitch (1976)
Aim: To investigate if participants can use different parts of working memory at the same time.
Method: Conducted an experiment in which participants were asked to perform two tasks at the same time (dual task technique) - a digit span task which required them to repeat a list of numbers, and a verbal reasoning task which required them to answer true or false to various questions (e.g. B is followed by A?).
Results: As the number of digits increased in the digit span tasks, participants took longer to answer the reasoning questions, but not much longer - only fractions of a second. And, they didn't make any more errors in the verbal reasoning tasks as the number of digits increased.
Conclusion: The verbal reasoning task made use of the central executive and the digit span task made use of the phonological loop.
The Central Executive
The central executive is the most important component of the model, although little is known about how it functions. It is responsible for monitoring and coordinating the operation of the slave systems (i.e. visuo-spatial sketch pad and phonological loop) and relates them to LTM. The central executive decides which information is attended to and which parts of the working memory to send that information to be dealt with.
The central executive decides what working memory pays attention to. For example, two activities sometimes come into conflict such as driving a car and talking. Rather than hitting a cyclist who is wobbling all over the road, it is preferable to stop talking and concentrate on driving. The central executive directs attention and gives priority to particular activities.
The central executive is the most versatile and important component of the working memory system. However, despite its importance in the working-memory model, we know considerably less about this component than the two subsystems it controls.
Baddeley suggests that the central executive acts more like a system which controls attentional processes rather than as a memory store. This is unlike the phonological loop and the visuo-spatial sketchpad, which are specialized storage systems. The central executive enables the working memory system to selectively attend to some stimuli and ignore others.
Baddeley (1986, 1999) uses the metaphor of a company boss to describe the way in which the central executive operates. The company boss makes decisions about which issues deserve attention and which should be ignored. They also select strategies for dealing with problems, but like any person in the company, the boss can only do a limited number of things at the same time. The boss of a company will collect information from a number of different sources. If we continue applying this metaphor, then we can see the central executive in working memory integrating (i.e. combining) information from two assistants (the phonological loop and the visuo-spatial sketchpad) and also drawing on information held in a large database (long-term memory).
