Memory span
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In psychology and neuroscience, memory span is the longest list of items that a person can repeat back in correct order immediately after presentation on 50% of all trials. Items may include words, numbers, or letters. The task is known as digit span when numbers are used. Memory span is a common measure of short-term memory. It is also a component of cognitive ability tests such as the WAIS.Backward memory span is a more challenging variation which involves recalling items in reverse order.
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[edit] The memory span procedure
In a typical test of memory span, a list of random numbers or letters is read out loud or presented on a computer screen at the rate of one per second. The test begins with two to three numbers, increasing until the person commits errors. Recognizable patterns (for example 2, 4, 6, 8) should be avoided. At the end of a sequence, the person being tested is asked to recall the items in order. The average digit span for normal adults without error is seven plus or minus two.[1]. However, memory span can be expanded dramatically - in one case to 80 digits - by learning a sophisticated system of recoding rules by which substrings of 5 to 10 digits are translated into one new chunk [2].
[edit] From simple span to complex span
Research in the 1970s has shown that memory span with digits and words is only weakly related to performance in complex cognitive tasks such as text comprehension, which are assumed to depend on short-term memory [3]. This questioned the interpretation of memory span as a measure of the capacity of a a central short-term memory or working memory. Daneman and Carpenter introduced an extended version of the memory span task which they called reading span [4]. In the reading span task, lists of sentences are presented instead of lists of words. The person is asked to read each sentence (in some versions silently, in other versions aloud), make a judgment about the sentence (e.g., whether it is true or whether it is grammatically correct), and remember the last word of each sentence. After a number of sentences, all the last words must be recalled in correct order. Daneman and Carpenter found that reading span was much more strongly related to reading comprehension than word span. Later research corroborated the finding that reading span is more closely related to language comprehension than word span [5]
The reading span task was the first instance of the family of complex span tasks, which differ from the traditional simple span tasks by adding a processing demand to the requirement to remember a list of items. In complex span tasks encoding of the memory items (e.g., words) alternates with brief processing episodes (e.g., reading sentences). For example, the operation span task [6], for example, combines verification of brief mathematical equations such as "2+6/2 = 5?" with memory for a word or a letter that follows immediately after each equation. Complex-span tasks have also been shown to be closely related to many other aspects of complex cognitive performance besides language comprehension, among other things to measures of fluid intelligence [7][8].
[edit] See also
[edit] References
- ^ Miller, G. (1956). The Magical Number Seven, Plus or Minus Two: Some Limits on Our Capacity for Processing Information, Psychological Review, 63, 81–97.
- ^ Ericsson, K. A., Delaney, P. F., Weaver, G., & Mahadevan, R. (2004). Uncovering the structure of a memorist's superior "basic" memory capacity. Cognitive Psychology, 49, 191-237
- ^ Perfetti, C. A., & Goldman, S. R. (1976). Discourse memory and reading comprehension skill. Journal of Verbal Learning & Verbal Behavior, 15, 33-42
- ^ Daneman, M., & Carpenter, P. A. (1980). Individual differences in working memory and reading. Journal of Verbal Learning and Verbal Behavior, 19, 450-466
- ^ Daneman, M., & Merikle, P. M. (1996). Working memory and language comprehension: a meta-analysis. Psychonomic Bulletin & Review, 3, 422-433.
- ^ Turner, M. L., & Engle, R. W. (1989). Is working memory capacity task dependent? Journal of Memory and Language, 28, 127-154
- ^ Kane, M. J., Hambrick, D. Z., Tuholski, S. W., Wilhelm, O., Payne, T. W., & Engle, R. W. (2004). The generality of working-memory capacity: A latent-variable approach to verbal and visuo-spatial memory span and reasoning. Journal of Experimental Psychology: General, 133, 189-217
- ^ Conway, A. R. A., Kane, M. J., Bunting, M. F., Hambrick, D. Z., Wilhelm, O., & Engle, R. W. (2005). Working memory span tasks: A methodological review and user’s guide. Psychonomic Bulletin & Review, 12, 769-786
