The use of mental techniques for assisting improving and expanding memory

Mr Memory, Hitchcock's master of facts, earned his living by performing feats of trivia pursuit in night clubs, while in parallel trusting to memory information for the sake of the notorious spy organization '39 Steps' (Hitchcock 1935). Most mnemonists, both in fiction and in real life, are engaged in much more innocent activities. In modern times mnemonists are either regarded as curiosities or at most as interesting "subjects for research. But only a few centuries ago, mnemonists were still masters of an important and respectable art.

Mneme is 'memory' in Greek (Mnemosyne was the mother of the muses; Hesiod 8C bc). Before writing became widespread (and surely before recording devices became inexpensive), the ability to trust data to memory was highly valuable, and mnemotechniques were extensively developed. From its early days, writing could have turned these mental techniques obsolete for most practical purposes. This was clearly appreciated by philosophers and teachers. Socrates tells us that when the God Theuth praised the newly invented art of writing, claiming that it will make people wiser, the Egyptian King Thamus responded: 'O man full of arts, to one it is given to create the things of art, and to another to judge what measure of harm and of profit they have for those that shall employ them... If men learn this, it will implant forgetfulness in their souls; they will cease to exercise memory because they rely on that which is written' (Plato, Phaedrus 274-275). Well, King Thamus panicked prematurely. In practice, for a very long period after its introduction, writing was used mostly for administrative purposes, and most of the population, being illiterate, could not make use of it anyway. Thousands of years after Socrates, in medieval

Europe, it was still common practice to regard written documents with suspicion because texts could not be challenged to defend their statements whereas people could (false memory was clearly not on the mind of people as it is now). In societies all around the globe, epics and ballads continued to rely for many generations on oral traditions. Even after the invention of printing, printed bibles and books of prayers were considered primarily as aids to memorization by heart (Clanchy 1979; Ong 1982; Rubin 1995). Mnemonics, therefore, was not abandoned for a long while. On the contrary, great intellects devoted their energy to the development and improvement of 'artificial memory systems' composed of mnemonic techniques and procedures (Yates 1966; Carruthers 1990).

In a popular type of artificial memory systems, images of physical items or loci (e.g. rooms in palaces, 'memory theaters'; Figure 48), were associated in memory with specific items or meanings, and later used as a code to "retrieve them. Some expert mnemonists became legends in exploiting these techniques. For example, Peter of Ravena (fifteenth century) was said to have memorized no less than 100000 loci, and that '... on his travels, he does not cease to make new places in some monastery or church, remembering through them histories, or fables, or Lenten sermons. ... He can repeat from memory the whole of the canon law, text and gloss ... two hundred speeches or sayings of Cicero; three hundred sayings of the philosophers; twenty thousands legal points.' (Yates 1966). Superb memory and mnemotechniques were considered highly useful in church and government, and therefore, in "classic education, Memoria (trained memory) was part of the curriculum of language arts, side by side with grammar, logic, and rhetoric. It was told of Thomas Aquinas, the scholastic philosopher and theologian of the thirteenth century, that he was able to dictate simultaneously to four secretaries on four different subjects, and even go on dictating while asleep; in that he excelled Julius Caesar, who, fourteen centuries earlier, was said to be capable of dictating to four people while writing a fifth letter in his own hand, but no mention was made of his ability to keep on dictating from memory after falling asleep (Carruthers 1990).

Fig.48 A popular type of mental 'artificial memory systems' was based on the allocation of items in memory to spatial maps of familiar locations. In this one, items are associated with buildings, rooms, and items in an abbey. (Johannes Rombrach, Congestium artificiosememorie, Venice 1533; reprinted in Yates 1966.)

Fig.48 A popular type of mental 'artificial memory systems' was based on the allocation of items in memory to spatial maps of familiar locations. In this one, items are associated with buildings, rooms, and items in an abbey. (Johannes Rombrach, Congestium artificiosememorie, Venice 1533; reprinted in Yates 1966.)

Whether Aquinas was indeed capable of dictating something legible from sleep is questionable; he could have appeared as if in sleep at a state of extreme concentration. This is at least an explanation that would be favoured nowadays by those scientists who doze off in research seminars and then wake up to the applause to ask a question. Naturally, information about past memory feats and mnemonists is mostly anecdotal. However, we do have data on more recent cases (Stratton 1917; Luria 1969; Hunter 1977, 1978; Thompson et al. 1993; Brown and Deffenbacher 1995). From this information, based on only a small number of mnemonists, one could draw a conclusion that there are different mnemonic strategies. Compare, for example, the patient Shereshevskii of Luria (1969), and Professor Aitken, a mathematician, mental calculator, and mnemonist (Hunter 1977). Whereas Shereshevskii's mnemonics was of the classical type (see above), using imagery and forming a rich perceptual chain to link and retrieve information, Aitken formed a rich conceptual map to encode and retain his memory (ibid.).1 Another conclusion is that some exceptional mnemonists display pathological traits, even to the degree of becoming 'idiot savants',2 whereas others are apparently normal. For example, Shereshevskii led a rather miserable life and couldn't adjust to any profession (Luria 1969). Aitken was a professor of mathematics and it is left for the reader to judge whether this is entirely normal. And Rajan Srinivasan Mahadevan, who in 1981 recited from memory the first 31811 digits of n and entered the Guinness Book of World Records, was described as a 'decently normal', 'average to above-average student' of cognitive psychology (Thompson et al. 1993). It would be of great interest to find out which brain systems subserve the performance of mnemonic feats like these of Shereshevskii, Aitken or Mahadevan. Do they use the same brain systems as do individuals with an average memory on the same task? "Functional neuroimaging of mnemonists could provide the answer (Pesenti et al. 2001).

Can ordinary individuals with an average memory become memory experts? It is useful to remember that practice and the perfection of "skill are bound to improve the skill-related aspects of memory. Experts do usually have a markedly larger task-related memory than novices in their field of expertise. Take chess as an extreme example. Master chess players clearly outperform novices or middle-range players, and some chess experts can remember as many chess positions as the above mentioned number of loci in the memory of the legendary Peter of Ravena (Chase and Simon 1973). What is it that turns the expert's memory, or the use of memory, so good? The elementary "capacity of memory probably remains the same, but the use of "metamemory, the chunking of information, the retrieval from long-term stores, and the switching from short-term to long-term stores and back, could improve tremendously (Chase and Simon 1973; Hirst 1988; Pesenti et al. 2001; "working memory). An improvement in chunking and retrieval rather than in capacity was also detected in controlled laboratory experiments, in which subjects succeeded in improving 10-fold their performance on digit span tests (Chase and Ericsson 1982).

All this suggests that practice, combined with personal mnemonic strategies for chunking, tagging, and association, could improve an average memory (Loisette 1899; Rawles 1978; Hirst 1988; Hertzog 1992). Here are some hints. "Spaced training could be useful. Test-type rehearsals instead of straightforward repetitions could be useful as well, for example, in assigning names to faces and thus preventing social embarrassment in parties (Landauer 1988). In the future, memory enhancing chemicals ("nootropics) and bionic gadgets might become available as well, but this is not really bona fide mnemonics any more.

Do we really wish to expand our memory, and if so, to what extent? A modest memory improvement is likely to be beneficial. But remembering too much could mean a decline in the ability to "generalize and to focus on important data. This is another manifestation of the general maxim of "performance, which states that moderation is the key to success. The sad life of Shereshevskii, who was overwhelmed by details and could not generalize, hints at the potential disadvantage of remembering much too much (Luria 1969; Dudai 1997a).

Selected associations: Capacity, Metamemory, Nootrop-ics, Performance, Real-life memory

1Borges, in the marvellous story about Ireneo Funes who lost the ability to forget after being thrown off a horse (1944), endowed the fictitious hero with a mnemonic system in between that of Aitken and that of Shereshevskii: a mental idiosyncratic vocabulary of all the mental images ever encoded in the brain.

2Idiot savant (French for 'learned idiot') is a mentally impaired individual who exhibits genius in a highly specialized area, such as calculation or painting (Treffert 2000).

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