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Digit Span

Test type: Memory

Are you a budding mnemonist?

How many numbers can you remember? Try this test to find out.

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About this test

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.

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We have been studying how the brain remembers verbal information for nearly ten years (Owen et al 2000, Bor et at al 2004, 2007). Our research has revealed that, while you are performing the digit span task, areas of your frontal cortex become activated.



In one study (Owen et al, 2000), participants either had to recall digits in the order presented ('forward recall'), or in reverse order ('backward recall'), a much more demanding task. We found that both of these tasks engaged the mid-ventrolateral frontal cortex, but only when participants were recalling in reverse order did the mid-dorsalateral frontal cortex become activated. Both of these tasks required verbal working memory, yet different activation patterns were observed in the brain. On this basis, we concluded that frontal-lobe activty in this task relates to the type of memory process being performed (i.e. storage, reordering) and is not specific to the type of information that is being remembered (i.e. verbal memory).

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).

References
-Baddeley, A. D., & Hitch, G. (1974). Working Memory. In GA Bower (Ed.), Recent Advances in learning and motivation, Vol. 8. New York: Academic Press.
-Bor., D., Cumming, N., Scott, C. E. M., Owen, A. M. (2004). Prefrontal cortical involvement in verbal encoding strategies. European Journal of Neuroscience, 19(12), 3365-3370. Read Abstract
-Bor, D., Owen, A. M. (2007). A Common Prefrontal-parietal Network for Mnemonic and Mathematical Recoding Strategies within Working Memory. Cerebral Cortex. 17: 778-786. Download PDF
-Owen, A. M., Lee, A. C. H., Williams. (2000). Dissociating Aspects of Verbal Working Memory Within The Human Frontal Lobe: Further Evidence for a 'Process-Specific' Model of Lateral Frontal Organization. Psychobiology, 28(2), 146-155.Read Abstract
-Miller, G. A. (1956), The Magical Number Seven, Plus or Minus Two: Some Limits on our Capacity for Processing Information. Psychological Review, 63, 81-97.
-Ericcson, K. A., Chase, W. G., Falloon, S. (1980). Acquisition of a memory skill. Science 208:1181-1182

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