Monday, May 5, 2014
An Embedded-Processes Model of Working Memory
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.