Wednesday, March 7, 2012

Working memory - Part 2 - How does chunking help?

What is working memory and how does it function?

As mentioned in part 1, working memory is where most of the thought processes take place moment by moment. Working memory temporarily stores information while it makes decisions or solves a problem. For example, while reading, the word "bow" is stored in verbal short-term memory while the reader decides if it is part of a boat, something that one ties, or a weapon that fires arrows.

This diagram is a simple model of working memory showing the three main parts. The central executive is the decision maker that directs attention, selects and sends information to the two storage components. The two storage components are referred to as the visuo-spatial short-term memory and the verbal short-term memory. The visuo-spatial short-term memory stores information in the form of pictures such as objects, people and places whereas the verbal short-term memory stores speech information such as letter sounds, words, phrases, or sentences. Both parts have limited storage and work quite differently. They are connected to the central executive where the two types of information can be linked in some way.

We will now focus on verbal short-term memory in part 2 of this series.

Verbal working memory is quite limited in that it can store approximately 5 items (give or take 2). During reading this can become a problem when large words are sounded out letter-by-letter. For example, when a reader attempts to store each letter of a 7 letter word as separate bits of information the reader's working memory may be overloaded and some of the letters may be lost, thereby making word decoding quite difficult. This strategy may work, to some degree, with smaller words but readers will find it increasingly frustrating when words become longer.

This problem can be overcome by chunking as many of the word elements together in the form of syllables or even whole words. Chunking groups of words in the form of phrases or whole sentences is even less demanding on storage space.  For example, a single letter can be stored as one item in verbal short-term memory and a whole sentence may take up the same amount of space.  Chunking is also important for reading comprehension because words, phrases, and sentences carry more meaning than single letters. Thus, the bigger the chunk the more meaningful it will be and the less space it will use in verbal short-term memory.

To overcome these storage problems readers should be encouraged to go beyond letter-by-letter sounding out to recognising whole words, then to whole phrases (see the earlier blog on highlighting phrases) to recognising whole sentences (see the earlier blog on repeated readings). This will free up working memory space to allow other thinking and problem solving to take place.

Alan Baddeley on the development of the working memory model

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