Interview with Hideaki Tomoyori
(September 1988, NHK Radio Japan, with kind permission)

"Of course, I couldn't manage to memorize such a huge, irrational number simply by rote. Instead, I've broken it down into short sequences of just ten numbers at a time. And then I associate the sound of each number with a particular word. With the words made in sentences, I can remember particular images. So, for each group of ten numbers, I think first of a single key word, then that key word reminds me of an image and a sentence, and then the sounds in that sentence remind me of the exact sequence of numbers.

"For example, the number sequence three-nine in Japanese is pronounced san-kyu, and that sounds very like the word sa-kyu, which mens "sand dune". If I picture a sand dune, I easily remember the numbers three and nine. And if I add in other elements, like my wife standing in front of the sand dune by the bright sea, then those words in Japanese can remind me of a whole string of ten numbers.

"No matter how many times you memorize something, you have to start over from the beginning if you let yourself forget it all. To avoid the waste of effort, I realized the need for good timing in reviewing what I'd learned. I review at longer and longer intervals - first, after a minute, then after ten minutes, then after a whole hour. I've found that the very best time for review is when you feel that maybe you've forgotten just about 20 percent of what you've learned.

"As a child, like all other children, I did things like memorizing the names of train stations, or the names of all the emperors in Japan's history. But I don't think I had an especially good memory. In fact, when I reached around the age of 20, I wasn't able to memorize much of anything at all. In my college English class, I was told to memorize some of Shakespeare's Hamlet, but I just couldn't do it. And that bothered me a lot.

"Then I saw a street performer who displayed a special memory trick. He wrote on a blackboard a string of numbers spoken at random by some passers-by. Then, without looking at the blackboard, he was able to recite the numbers perfectly.

"Well, I bought from that street performer a little ten-page booklet on memory skills. And it told about the trick of using images to remember numbers. Based on that idea, I began to work out my own particular approach to memorization.

"One day, a friend who knew about my memory skills left on my desk a page showing the value of pi worked out to many decimal places. He said 'Why don't you memorize the value of pi ?'. Even before that I'd managed to get as far as 40 or 50 decimal places. Then, seeing this page, I decided to go ahead and memorize the value of that eternal number pi up to one thousand places. But it wasn't easy - in fact, it took me three years. To get to 40,000 decimal places it took me about ten years.

"It's part of my life and I've really just started. I feel that human abilities really have no limits. It's often said that we use just about five percent of our brain cells, so I think we have much greater potential - and I want to pursue that potential. So I want to go on with the challenge of memorizing pi, for just the same reason that people climb high mountains. I think it's a wonderful thing to challenge the limits of what we can do.

"In fact, pi is said to be an irrational number, and its decimal places will never reach an end. But the more one memorizes of it, the closer one comes to the real value of the circle - closer to perfection. So, even as I grow old, I'll always face a new challenge; I feel, in some way, as if I'm seeking the ultimate truth. So I plan to go on memorizing more and more, as long as my strenght holds out."