Pi master relates secrets of recall: record holder turned digits to images for use in stories.
All it took was intensive practice and a knack for storytelling for a Chinese man to figure out how to have his pi and recite it, too--beyond 60,000 decimals.
The man who set a world's record in 2005 by reciting 67,890 decimals of pi learned to associate number pairs with images of people and objects, scientists report in the June Cognitive Psychology. From those images, 23-year-old Chao Lu concocted stories that corresponded to blocks of 500 to 1,o0o numbers, say Yi Hu of East China Normal University in Shanghai and K. Anders Ericsson of Florida State University in Tallahassee.
As Chao Lu delivered a heaping slice of pi to Guinness World Record judges for 24 hours and four minutes, a tale containing more than 60 chapters ran through his head. "That's up there with the Bible," Ericsson says.
Several thousand hours of practice over seven years with an efficient memory strategy enabled Chao Lu's achievement, says psychologist Elizabeth Valentine of Royal Holloway University of London. No special mental or memory abilities were required, in her view, although scientists disagree about the extent to which practice makes perfect.
In the new study, Hu and Ericsson asked the pi master to describe his thinking as he memorized 100- and 300-digit lists. His recall immediately afterward ranged from 95 percent to 100 percent.
Chao Lu described generating mental images for number pairs from 00 to 99, such as a classroom for 94 and stones for 17. From these cues he created stories.
The ultimate pi guy said that different stories containing common image sequences became confusing once he surpassed 10,000 decimals of pi. He then generated images for combinations of digit pairs. The second pair in a sequence was primary. So 1514 became a key (14) shaped like a parrot (15), whereas 1415 became a parrot with a key in its mouth.
Chao Lu's memory feat was short-lived. Five years after his pi-rotechnics, he could recall only 39 decimals.