Twenty-four years ago, 60 Minutes introduced viewers to George Finn, whose talent was immortalized in the movie "Rainman." George has a condition known as savant syndrome, a mysterious disorder of the brain where someone has a spectacular skill, even genius, in a mind that is otherwise extremely limited.

Morley Safer met another savant, Daniel Tammet, who is called "Brain Man" in Britain. But unlike most savants, he has no obvious mental disability, and most important to scientists, he can describe his own thought process. He may very well be a scientific Rosetta stone, a key to understanding the brain.

Back in 1983, George Finn, blessed or obsessed with calendar calculation, could give you the day if you gave him the date.

"What day of the week was August 13th, 1911?" Safer quizzed Finn.

"A Sunday," Finn replied.

"What day of the week was May 20th, 1921?" Safer asked.

"Friday," Finn answered.

George Finn is a savant. In more politically incorrect times he would have been called an "idiot savant" - a mentally handicapped or autistic person whose brain somehow possesses an island of brilliance.

Asked if he knew how he does it, Finn told Safer, "I don't know, but it's just that, that's fantastic I can do that."

If this all seems familiar, there's a reason: five years after the 60 Minutes broadcast, Dustin Hoffman immortalized savants like George in the movie "Rainman.""

Which brings us to that other savant we mentioned: Daniel Tammet. He is an Englishman, who is a 27-year-old math and memory wizard.

"I was born November 8th, 1931," Safer remarks.

"Uh-huh. That's a prime number. 1931. And you were born on a Sunday. And this year, your birthday will be on a Wednesday. And you'll be 75," Tammet tells Safer.

It is estimated there are only 50 true savants living in the world today, and yet none are like Daniel. He is articulate, self-sufficient, blessed with all of the spectacular ability of a savant, but with very little of the disability. Take his math skill, for example.

Asked to multiply 31 by 31 by 31 by 31, Tammet quickly - and accurately - responded with "923,521."

And it's not just calculating. His gift of memory is stunning. Briefly show him a long numerical sequence and he'll recite it right back to you. And he can do it backwards, to boot.

That feat is just a warm-up for Daniel Tammet. He first made headlines at Oxford, when he publicly recited the endless sequence of numbers embodied by the Greek letter "Pi." Pi, the numbers we use to calculate the dimensions of a circle, are usually rounded off to 3.14. but its numbers actually go on to infinity.

Daniel studied the sequence - a thousand numbers to a page.

"And I would sit and I would gorge on them. And I would just absorb hundreds and hundreds at a time," he tells Safer.

It took him several weeks to prepare and then Daniel headed to Oxford, where with number crunchers checking every digit, he opened the floodgates of his extraordinary memory.

Tammet says he was able to recite, in a proper order, 22,514 numbers. It took him over five hours and he did it without a single mistake.

Scientists say a memory feat like this is truly extraordinary. Dr. V.S. Ramachandran and his team at the California Center for Brain Study tested Daniel extensively after his Pi achievement.

What did he make of him?

"I was surprised at how articulate and intelligent he was, and was able to interact socially and introspect on his own - abilities," says Dr. Ramachandran.

And while that introspection is extremely rare among savants, Daniel's ability to describe how his mind works could be invaluable to scientists studying the brain, our least understood organ.

"Even how you and I do 17 minus nine is a big mystery. You know, how are these little wisps of jelly in your brain doing that computation? We don't know that," Dr. Ramachandran explains.

It may seem to defy logic, but Ramachandran believes that a savant's genius could actually result from brain injury. "One possibility is that many other parts of the brain are functioning abnormally or sub-normally. And this allows the patient to allocate all his attentional resources to the one remaining part," he explains. "And there's a lot of clinical evidence for this. Some patients have a stroke and suddenly, their artistic skills improve."

That theory fits well with Daniel. At the age of four, he suffered a massive epileptic seizure. He believes that seizure contributed to his condition. Numbers were no longer simply numbers and he had developed a rare crossing of the senses known as synesthesia.

"I see numbers in my head as colors and shapes and textures. So when I see a long sequence, the sequence forms landscapes in my mind," Tammet explains. "Every number up to 10,000, I can visualize in this way, has it's own color, has it's own shape, has it's own texture."

For example, when Daniel says he sees Pi, he does those instant computations, he is not calculating, but says the answer simply appears to him as a landscape of colorful shapes.

"The shapes aren't static. They're full of color. They're full of texture. In a sense, they're full of life," he says.

Asked if they're beautiful, Tammet says, "Not all of them. Some of them are ugly. 289 is an ugly number. I don't like it very much. Whereas 333, for example, is beautiful to me. It's round. It's...."

"Chubby," Safer remarks.

'It's - yes. It's chubby,' Tammet agrees.

Yet even with the development of these extraordinary abilities as a child, nobody sensed that Daniel was a prodigy, including his mother, Jennifer. But he was different.

"He was constantly counting things," Jennifer remembers. "I think, what first attracted him to books, was the actual numbers on each page. And he just loved counting."

Asked if she thinks there's a connection between his epilepsy and his rare talent, she tells Safer, "He was always different from - when he was really a few weeks old, I noticed he was different. So I'm not sure that it's entirely that, but I think it might have escalated it."

Daniel was also diagnosed with Asperger's Syndrome - a mild form of autism. It made for a painful childhood.

"I would flap my hands sometimes when I was excited, or pull at my fingers, and pull at my lips," Tammet remembers. "And of course, the children saw these things and would repeat them back to me, and tease me about them. And I would put my fingers in my ears and count very quickly in powers of two. Two, four, eight, 16, 32, 64."

"Numbers were my friends. And they never changed. So, they were reliable. I could trust them," he says.

And yet, Daniel did not retreat fully into that mysterious prison of autism, as many savants do. He believes his large family may have actually forced him to adapt.

"Because my parents, having nine children, had so much to do, so much to cope with, I realized I had to do for myself," he says.

He now runs his own online educational business. He and his partner Neil try to keep a low profile, despite his growing fame.

Yet the limits of his autism are always there. "I find it difficult to walk in the street sometimes if there are lots of people around me. If there's lots of noise, I put my fingers in my ears to block it out,' he says.

That anxiety keeps him close to home. He can't drive, rarely goes shopping, and finds the beach a difficult place because of his compulsion to count the grains of sand. And it manifests itself in other ways, like making a very precise measurement of his cereal each morning: it must be exactly 45 grams of porridge, no more, no less.

Daniel was recently profiled in a British documentary called "Brainman." The producers posed a challenge that he could not pass up: Learn a foreign language in a week - and not just any foreign language, but Icelandic, considered to be one of the most difficult languages to learn.

In Iceland, he studied and practiced with a tutor. When the moment of truth came and he appeared on TV live with a host, the host said, "I was amazed. He was responding to our questions. He did understand them very well and I thought that his grammar was very good. We are very proud of our language and that someone is able to speak it after only one week, that's just great."

"Do you think that Daniel, in a certain way, represents a real pathway to further understanding the brain?" Safer asks Dr. Ramachandran.

"I think one could say that time and again in science, something that looks like a curiosity initially often leads to a completely new direction of research," Ramachandran replies. "Sometimes, they provide the golden key. Doesn't always happen. Sometimes it's just mumbo-jumbo. But that may well be true with savants."

Daniel continues to volunteer for scientists who want to understand his amazing brain. But he is reluctant to become what he calls "a performing seal" and has refused most offers to cash in on his remarkable skills.

"People all the time asking me to choose numbers for the lottery. Or to invent a time machine. Or to come up with some great discovery," he explains. "But my abilities are not those that mean that I can do at everything."

But he has written a book about his experiences, entitled "Born on a Blue Day."

He also does motivational speeches for parents of autistic children - yet one more gift of his remarkable brain.

But at the end of the day - genius or not - that brain does work a little differently.

"One hour after we leave today, and I will not remember what you look like. And I will find it difficult to recognize you, if I see you again. I will remember your handkerchief. And I will remember you have four buttons on your sleeve. And I'll remember the type of tie you're wearing. It's the details that I remember," Tammet tells Safer.

And it's the details that make us all so different. One man may see numbers as a tedious necessity of modern life, another sees them as the essence of life.

"Pi is one of the most beautiful things in all the world and if I can share that joy in numbers, if I can share that in some small measure with the world through my writing and through my speaking, then I feel that I will have done something useful," he says.