In November 2005, Chinese businessman Chao Lu became a world record holder by reciting pi to 67,890 places. It took him a year to memorise the stream of digits and over 24 hours to reel them off. Like most extraordinary memorists, Chao Lu used a set of formal memory aids, or mnemonics (Journal of Experimental Psychology: Learning, Memory, and Cognition, vol 35, p 1426). To memorise a long list of numbers, for example, a mnemonist might assign consonants to each number from 0 to 9, then group the stream into four-digit chunks and convert these into words by judiciously adding vowels – a mnemonic known as the phonetic system. They might then create an image for each word and weave these into a familiar journey or arrange them in the rooms of a mental “memory palace”. This creation of a narrative or mental map in which to place memories is called the “method of loci”. Later, retracing the journey or walking through the rooms brings back the images, which can
then be decoded into the string of digits. A similar approach can help you to remember a list of random words, even the order of a pack of cards in one viewing.
Some memory champions have talents that most of us cannot emulate, however. A century ago, Russian journalist Solomon Shereshevsky was studied extensively for his amazing ability to remember long lists of numbers and words. This apparently required very little effort: he could recite a list of 50 numbers, forwards and backwards, after just 3 minutes of study. It turned out that as well as using mnemonics, Shereshevsky was aided by his synaesthesia. For him, each number had a different personality – 1 was a proud, well-built man, 2 a high-spirited woman, and so on – while the sounds of other words would produce vivid colours and tastes, making them more memorable.
The oldest known memory aid is the method of loci, invented by the ancient Greeks at least 2000 years ago. These days there are any number of mnemonics, but while memory champions may swear by them, how useful are they in day-to-day life? Two psychologists, James B. Worthen and R. Reed Hunt, attempt to answer this question in their recently published book Mnemonology (Psychology Press, 2010). “We tried to cover everything that’s out there,” says Worthen, of Southeastern Louisiana University in Hammond.
So what did they find? Disappointingly, many mnemonics fail to live up to their reputation. Take the keyword method, which is often taught to language students. To help remember an unfamiliar word, the student creates an elaborate image based on the sound – the Spanish word for moustache, bigote, might be visualised as a big goat with a handlebar moustache, for example. Although widely used, several studies suggest that this method is of little value to experienced language learners, and even beginners reap minimal benefits. While it slightly improves the accuracy of their memory compared to rote repetition, it also slows down the speed at which they can recall a word.
The phonetic system, in which numbers are encoded as letters, fared little better. Developed in the Renaissance, it is often touted in books on memory improvement, which suggest using it to create memorable phrases from strings of numbers. While there is good evidence that it improves recall, the difficulties of applying the technique led Worthen and Hunt to conclude that it would often be impractical in everyday situations.