A coincidence of senses
There are, however, ways in which Tammet may inherently have a different approach to numbers than most pi memorizers.
Tammet has high-functioning autism, a developmental condition associated with impaired social communication and repetitive behaviors or fixated interests. On top of that, he has synesthesia, meaning he experiences a mixing of senses and perceptions -- specifically, he sees words and numbers as colors and shapes.
In an analysis of Tammet's case, published by Simon Baron-Cohen and colleagues in the Journal of Consciousness Studies in 2007, researchers wrote that both autism and synesthesia, while different, are associated with an excess of neural connections; it's possible they have a "common neural abnormality." They also proposed the idea that autism and synesthesia together may have increased the likelihood of Tammet's savant memory. More research is needed to support both these ideas.
Foer's book questions whether Tammet has used mnemonic methods to memorize digits of pi and other information, just like everyone else without synesthesia. But Julian Asher at the Autism Research Centre at the University of Cambridge, who studied Tammet, said synesthesia is "fundamental to his feats of memory." Recalling pi for Tammet is like "walking through a synaesthetic landscape in which different numbers are represented by geographical features, and 'reading' them off as he goes," Asher said in an e-mail.
Tammet grew up as the oldest of nine children. The stimulation he received from his large family probably helped him develop social skills, he said.
"If I hadn't had that love and that patience and that support from an early age, I might not be where I am today, certainly," he said.
As a child, he was called "private," "shy" and "timid." He also had epileptic seizures, and took medication until he grew out of them.
"When he sat on the carpet during story time, with his eyes tight shut and his fingers in his ears, picturing numbers in his mind and their shapes and colors, whilst the other children looked at each other or at the teacher and listened to the story, (Tammet) was in some sense in a world of his own," Baron-Cohen and colleagues wrote.
In high school, Tammet learned about pi and thought it was beautiful. But when he talked about it with his classmates, they didn't understand. For them, pi was just a number. It didn't have any color or beauty or emotion.
"That's when I had a perception of the world, of words, of numbers, that was different," he said. Secretly, he started memorizing digits of pi.
Finding life through pi
At age 25, Tammet finally felt confident enough to "share all those years of loneliness, all those years of battling with this condition, with my autism, all the years of also experiencing this tremendous beauty, this emotion."
He spent about three months learning thousands of digits of pi, which he saw as an emotional experience, being transported into another world.
Tammet's achievement of the European record for pi recitation wasn't about showing off, he said. First and foremost, he wanted to accomplish something that meant something to him personally. He was able to reach out to people without autism, without synesthesia, and communicate to them in a new way. The event also benefited an epilepsy charity.
"When the digits darken in my mouth --- heavy eights and nines packed together --- the tense distant faces grow tenser still. When a sudden three emerges from a series of zeroes and sevens, I hear something like a faint collective pant. Silent nods greet my accelerations; warm smiles welcome my slowdowns," he wrote in his book "Thinking in Numbers," which comes out in the United States in July.
At the pi recitation, Tammet realized he had a gift of communicating, and that set him on the path to becoming a full-time writer.
The pi memorization event also led Tammet to Baron-Cohen and colleagues, who made the diagnosis of high-functioning autism. It explained the difficulties he had with communication and social skills as a child.
He has not recited pi since the 2004 event, but still appreciates the beauty and wonder of the number enough to promote Pi Day in France.
"You can find a lover's telephone number. Your date of birth. Your Social Security code. You can find everything in pi," he said. "It's big enough to have all of life inside of it."
Want to memorize pi? Here are 10,000 digits.