Improve your digit-span performance by 'chunking'.

The digit span task exercises your verbal working memory. Scientists refer to working memory as the cognitive system that allows the temporary storage and manipulation of information. According to one influential cognitive theory, this system has specialised components, one of which, the 'phonological loop', underlies verbal working memory abilities (Baddeley & Hitch 1974). The phonological loop is comprised of a verbal storage system and a rehearsal system. If you do this task, you may find yourself mentally rehearsing the string of digits as they appeared on screen; this is the rehearsal system in action. It allows the visual inputs to be recoded so that they can enter your short term verbal store and it also refreshes decaying representations (that is, any item that is about to be forgotten).

Verbal working memory is involved in many everyday tasks, from remembering your friend's telephone number while you enter it into your phone, to understanding long and difficult sentences. Think about it; how could you understand a whole sentence if you couldn't remember the words at the beginning long enough to connect with the words at the end! Verbal working memory is also thought to be one of the elements underlying intelligence (or 'IQ'); thus, the digit span task is a common component of many IQ tests, including the widely used WAIS (Wechsler Adult Intelligence Scales). Performance on the digit span task is also closely linked to language learning abilities; improving your verbal memory capacities may therefore help you to master a new language or to expand your vocabulary.

An average adult is thought to have a digit span of 7 (plus or minus 2) items. One of the best studied methods for improving verbal memory is through the use of 'chunking' strategies (Miller 1956), in which items are recoded into meaningful units or 'chunks'. For example; 2 6 7 8 9 7 (6 items) is easier to retain when remembered as 26 78 97 (3 items). In one study, by training a volunteer to use complex chunking strategies over the course of 20 months, scientists were able to increase digit span from 7 to a massive 79 items! (Ericcson et al, 1980). We recently studied the underlying brain activity involved in this process. When recoding strategies were used to remember digit sequences, increased activation was oberved in lateral prefrontal and posterior parietal cortex. On this basis, we have hypothesised that this prefrontal-parietal network underlies strategic recoding in working memory (Bor et al, 2004, 2006)




source - http://www.cambridgebrainsciences.com/browse/memory/test/digit-span