Cowan, N. (1999). An
Embedded-Processes Model of Working Memory. In: A. Miyake & P. Shah. Models of Working Memory: Mechanisms of
Active Maintenance and Executive Control. Cambridge: Cambridge University
Press. pp. 62-101. doi: http://dx.doi.org/10.1017/CBO9781139174909.006.
This chapter presents Nelson Cowan’s model of Working Memory (WM). According
to Cowan, WM is a functional system that retains both old and new information
in a state suitable for manipulating and carrying out mental operations. Initially,
a stimulus is stored for a brief moment (hundreds of milliseconds) in a sensory
storage mechanism, which then activates representations in long-term memory
(LTM). In this model, these activated representations constitute Short Term Storage
(or Short Term Memory—STM). STM is responsible for holding information relevant
to the task at hand. A subset of these activations (and novel stimuli) are held
within our focus of attention. The Central Executive, then, gathers those
mental representations for processing or manipulating.
According to this account, individual differences in WM tasks can be
explained by limitations in both attention and LTM. Attention is limited by the
amount of information that can be held in the focus of attention at a given
time. LTM contributions, on the other hand, are limited by how long
representations can remain activated in STM. If activations are lost (decay)
over time, those representations will not be available in an easily accessible
state for processing by the central executive. Cowan reviews considerable
evidence that activated LTM indeed decays through time—in 10 to 20 seconds, and
that without chunking or rehearsal participants tend to retain about 4±1 items in working memory tasks.
Cowan’s model provides an excellent
rationale for the use of warm up activities to activate related knowledge prior
to the teaching of new skills. By activating LTM for familiar and related
concepts, these concepts will be easier for children to access and connect to
new information.
Blogger: Alberto Filgueiras is a visiting
doctoral student at the LWM lab from the Pontifical Catholic University of Rio
de Janeiro, Brazil.
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