MNEMONISTS

The Guinness Book of World Records reports that in 1981 Rajan Srinavasen Mahadevan (known as Rajan) recited the first 31,811 digits of pi from memory and that in 1987 Hideaki Tomoyori broke that record by reciting the first 40,000 digits. People performing such feats of memory are called mnemonists or memorists. Although feats like these are rare, since the 1890s there have been several scientific accounts of people with prodigious memories. Starting with the pioneering work of Alfred Binet, the scientific literature describes over a dozen people showing exceptional memory for verbal materials. Brown and Deffenbacher (1975) give a comprehensive review of these studies. Studies of exceptional memory performance contribute to our understanding of memory by describing the processes memorists use and by comparing them with processes used by people with ordinary memories.

Representative Case Studies

The studies on memorists have shown that they use a variety of techniques to remember material. Four memorists are presented here to demonstrate that variety: Shereshevskii, Alexander Craig Aitken, VP, and Rajan.

Shereshevskii

A. R. Luria (1968) has made Shereshevskii (S) the most famous mnemonist. (Luria referred to him only as S, but his real name later became known.) S was almost thirty when Luria began his studies, and the research continued for almost thirty years. Somewhat surprisingly, S was unaware that his memory was unusual until Luria began his investigations.

S used three basic processes, usually in combination, for remembering verbal material. The first was to generate rich visual images to represent information. When he became a stage performer, he trained himself to convert senseless words into meaningful images so that he could remember nonsense words or words from unfamiliar languages. The second process was to use familiar locations, such as stops on an ofttraveled street, to place the images mentally for later retrieval. This procedure is the method of locations (or loci) developed by the ancient Greek poet Simonides of Ceos in about 500 B. C. The method of locations has been discussed by authors as diverse as Aristotle and Thomas Aquinas. S apparently developed the technique independently. The third process was to create a story with appropriate images to retrieve the information.

With these techniques, S was able to remember any information presented. Luria was unable to find any limit to the amount of material S could recall in this fashion. More surprisingly, there appeared to be no limit to the duration of S's memory. Luria reports a request for recall of a fifty-word list given without warning sixteen years after presentation of the list. That request, like all the others Luria reports, resulted in successful retrieval of the list.

S had strong synesthesia, which appears to be unique among the memorists who have been investigated. Synesthesia is said to occur when information coming into one sensory system (e.g., audition) produces an effect in another sensory system (e.g., vision). S once said to the Russian psychologist Vygotsky, "What a crumbly, yellow voice you have" (Luria, 1968, p. 24). On another occasion, Luria was concerned that S might not remember his way in an unfamiliar location. S replied that he couldn't possibly forget because "here's this fence. It has such a salty taste and feels so rough; furthermore, it has such a sharp, piercing sound. …" (Luria, 1968, p. 38). Synesthesia interfered with the images S produced and presented an enduring problem for him. For example, S once noted that "Other times smoke or fog appears … and the more people talk, the harder it gets, until … I can't make anything out" (Luria, 1968, p. 39).

Professor Aitken

Many psychologists think that Professor Aitken, who lived from 1895 to 1967, was the best all-around mnemonist. In a summary of the work on Aitken, Hunter (1977) points out that he was a brilliant mathematician, an excellent mental calculator, and an accomplished violinist with an extraordinary memory. His primary method for learning was to search out meaningful relationships within the material and with previously learned information. Hunter provides a quote from Aitken that best captures his approach:

Musical memory can … be developed to a more remarkable degree than any other, for we have a metre and a rhythm, a tune, or more than one, the harmony, the instrumental color, a particular emotion or sequence of emotion, a meaning, … in the executant an auditory, a rhythmic and a muscular and functional memory; and secondarily in my case, a visual image of the page … perhaps also a human interest in the composer, with whom one may identify oneself … and an esthetic interest in the form of the piece. They are so many, and they are so cumulative, that the development of musical memory, and appreciation, has a multitude of supports. (1977, p. 157)

Although Aitken's memory was prodigious, it was not infallible. For example, in 1936 he correctly recalled sixteen three-digit numbers after four presentations. Two days later, he recalled all but one of the numbers and, after an additional presentation, he recalled them all. In 1960, without further study, he recalled twelve of the numbers but also produced eight incorrect numbers.

VP

VP (identified only by these initials in the published report) is an excellent chess player whose memory has been investigated by Hunt and Love (1972). VP has an exceptional memory but, like Aitken's, it is not infallible. For example, Hunt and Love reproduced VP's recall of an Indian story after intervals of 1 hour and 6 weeks. Although there were small changes in both recalls, his overall accuracy was remarkable.

VP learned material by relating it to prior information. For example, he knew several languages and could associate any three-letter string with a word. He learned number matrices by rows and sometimes recoded the row as a date. It is also clear that he spent a great deal of time practicing memorizing so that he became very adept at recoding information.

Rajan

Rajan has an exceptional memory for digits but not for other material. A group of researchers from Kansas State University (Thompson, Cowan, and Frieman, 1993) performed extensive tests on his memory. Their studies showed that Rajan learned sets of digits more rapidly than VP or S. He used a procedure pairing locations and digits to learn the material. He also encoded the digits in chunks (such as a row in a matrix). Thus, he learned that the fifth digit in the fourth row was 3 rather than using preexisting knowledge to encode the information. He explicitly attached cues to the chunks for retrieval. For example, he learned the first column in a matrix as a cue for retrieving each row of the matrix.

Once the material was learned, Rajan's procedure allowed for extremely effective retrieval of information. Working in the first 10,000 decimal digits of pi, he could retrieve a digit at a specified location (e.g., digit 4,765) in an average time of twelve seconds. He had the digits of pi chunked in groups of 10 digits. When he was given the first five digits of a ten-digit group in the first 10,000 digits of pi, he could give the next five digits in an average time of seven seconds.

The Memorists and a Theory of Skilled Memory

In several papers, Ericsson and his colleagues (e.g., Ericsson and Chase, 1982) suggest three general principles for skilled memory and illustrate these principles with people skilled at some aspect of memory. The three principles they propose are meaningful encoding (the use of preexisting knowledge to store the presented information in memory), retrieval structure (explicitly attaching cues to the encoded material to allow efficient retrieval), and speedup (a reduction in study time with further practice). They claim that ordinary subjects, as well as skilled memorists, show these principles.

Consistent with this theory, all four mnemonists described here attach retrieval cues when learning material to ensure accurate and fast retrieval. Further, three of them show a reduction in study time with practice. There is no clear evidence available on this point for Professor Aitken. However, it seems likely that he would show a similar effect.

The data from these memorists suggest that the skilled-memory theory founders on the third principle. All four memorists use procedures for encoding the material that are available to and used by people with ordinary memories. But, contrary to the theory, not all of them encode the material by relating it to preexisting knowledge. VP fits the theory because he encodes material by relating it to prior information.

Aitken uses that technique and also searches for relationships within the material to be learned. S uses imagery and the classic method of locations as his primary means for learning material. Because Ericsson and his colleagues clearly refer to relating the material to preexisting verbal knowledge, S's procedures do not conform to their theory. Rajan also does not fit the theory at all. His procedure, pairing locations and digits, cannot be construed as encoding by relation to preexisting knowledge.

Conclusion

The four memorists use quite different techniques to remember information, some of which call into question a portion of the theory of skilled memory. Their memories are unusually good, but the processes they use to remember can all be used by people with ordinary memories. In short, their memories are unusual in the amount they can remember but not in the processes they use to remember.

See also:MNEMONIC DEVICES

Bibliography

Brown, E. (1988). Superior memory performance and mnemonic encoding. In L. K. Obler and D. Fein, eds., The exceptional brain. New York: Guilford Press.

Brown, E., and Deffenbacher, K. (1975). Forgotten mnemonists. Journal of the History of the Behavioral Sciences 11, 342-349.

Ericsson, K. A., and Chase, W. G. (1982). Exceptional memory. American Scientist 70, 607-615.

Hunt, E., and Love, T. (1972). How good can memory be? In A. W. Melton and E. Martin, eds., Coding processes in human memory. Washington, DC: John Wiley.

Hunter, I. M. L. (1977). An exceptional memory. British Journal of Psychology 68, 155-164.

Luria, A. R. (1968). The mind of a mnemonist. New York: Basic Books.

Obler, L. K., and Fein, D. (1988). The exceptional brain. New York: Guilford Press.

Thompson, C. P., Cowan, T. M., and Frieman, J. (1993). Memory search by a memorist. Hillsdale, NJ: Erlbaum.

Charles P.Thompson