On this page you will find some information on the theoretical background of our simulation. It is based on a simplified version of Baddeley's working memory model.

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A Short History of Working Memory

In cognitive psychology, the human working memory has gained a lot of interest and a great deal of research during the last decades. Since the beginnings of cognitive psychology, researchers have been searching for a cognitive concept that is able to describe how all the different aspects of the human mind interact with each other.

Nowadays, we refer to this major workplace of human cognition as working memory. The working memory is a store where conscious mental work takes place on information brought in from sensory memory and long-term memory. Working memory makes use of external and internal information to compute, reason and combine. It is the place where we become aware of our perceptions and feelings (Gray, 2006).

One of the most influential researchers on working memory has been the British psychologist Alan Baddeley. In contrast to models which describe working memory (or short-term memory) as a single system in which just one task at a time can be performed, Baddeley and Graham Hitch proposed a more precise model in 1974 (Baddeley & Hitch, 1974).

In various experiments Baddeley showed that the working memory was able to perform different tasks at once. The most important finding was that tasks of two different types (e.g. a visual and a phonological task) could be performed in parallel with a good performance, while two tasks of the same type could only be performed in parallel with a rather bad performance or not at all. This led Baddeley to propose a model of working memory consisting of three different components that interact with each other: the visuo-spatial sketchpad, the phonological loop and the central executive (Baddeley, 2002).

A simplified model of working memory (adapted from Groome et al., 2008)

Baddeley's Multicomponent Model

In 1974, Baddeley and Hitch proposed a multicomponent model that consists of an attentional control system the central executive and two subsidiary control systems the phonological loop and the visuospatial sketchpad. The phonological loop was thought to hold speech-based information and auditory information which would fade away if not rehearsed by either overt or covert rehearsal. The visuospatial sketchpad was assumed to hold visual and spatial information. In a similar way, rehearsal should prevent the component from losing its information, possibly by eye movements. The central executive has been described as a rather vague concept of general processing capacity.

Several experiments lead Baddeley to the conclusion that the phonological loop consist of two mechanisms: One mechanism stores auditory information - the phonological store - and one rehearses the auditory information - the articulatory rehearsal mechanism - by means of subvocalization. It is good to think of the phonological store as a mechanism that converts the auditory information into a memory trace that always tends to fade away (pp. 8-10). For example, imagine you were supposed to listen to a sequence of words, to keep them in mind and to reproduce them after a certain time. What could you do to prevent yourself from forgetting the words? You could say the words to yourself and repeat them over and over again until you have to reproduce them. This way of holding the information in mind is exactly what Baddeley called the articulatory rehearsal mechanism.

What determines the memory span a person has? Or referring to the just mentioned example, how many words is a certain person able to reproduce. According to Baddeley, this depends on two factors: The rate at which the trace fades away and the speed at which items can be rehearsed (p. 9).

The visuospatial sketchpad is assumed to do the same but for visual and spatial information (p. 10). Baddeley divided the visuospatial sketchpad into three mechanisms. The first mechanism stores where a certain stimuli has occurred, while the second mechanism stores what kind of stimuli has occurred. The third mechanism is thought to store the temporal order of stimuli (pp. 64-65).

In 1996, Baddeley tried to describe the central executive in more detail. This approach described the central executive as a mechanism that consists of four components: the capacity to focus attention, to divide attention, to switch attention and to provide a link between working memory and long-term memory (pp. 171-181). According to this view, the central executive represents a capacity limited provider of attention that coordinates the two capacity limited subsystems (Baddeley, 2002).

In 1996, Baddeley proposed a further subsystem that he called the episodic buffer. The episodic buffer was assumed to be the interface between the phonological loop, the visuospatial sketchpad and the long term memory (Baddeley, 2002).


Baddeley, A. D. & Hitch, G. J. L (1974). Working Memory, In G.A. Bower (Ed.). The psychology of learning and motivation: advances in research and theory (Vol. 8, pp. 47-89), New York: Academic Press.

Baddeley, A. D. (2002). Is working memory still working?. European Psychologist, 7, 8597.

Baddeley, A. D. (2007). Working memory, thought, and action. Oxford, UK: Oxford University Press.

Gray, P. (2006). Psychology. New York: Worth Publishers.

Groome, D. et al. (2008). An introduction to cognitive psychology: processes and disorders (2nd edition). NY: Psychology Press.

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