In a typical test of memory span, a list of random numbers is read out at about the rate of one per second. The test begins with two to three numbers, increasing until the person commits errors. Recognisable 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.
Reverse repetition is more difficult and requires more processes besides immediate recall.
Individuals with larger memory spans can keep in mind more different stimuli, and this seems to give them an advantage for a wide variety of cognitive tasks. Memory span has been linked to performance on intelligence tests, reading skills, problem solving, and a variety of other cognitive tasks.
The World Record is 198 by former World Memory Champion Clemens Mayer. People taking part in memory competitions achieve far higher results in this test because the mnemonic techniques they use skip short-term memory and give direct access to the long-term memory. Using the method of loci and the "master-system" (to code digits into mental images), most people can achieve a score of 40 or higher in the "memory span" test as described above.