But it's this kinetic thought process that serves his acting so well. He used to walk from one end of Manhattan to another, talking to himself, trying to absorb his character. His latest character is controversial Dr. Jack Kevorkian.
In the film he looked and acted eerily similar to the real Dr. Kevorkian. How did he do it?
"What I did with Jack Kevorkian is I worked. I went into my little bunker by the house. A lot of acting is private time," he explained. "I'm watching the pieces. I'm reading the script. I'm listening to the sound of him. It's like work."
When he took on the role of New York cop Frank Serpico nearly 40 years ago, he became so immersed in the part he had trouble getting out of character.
"I was in a cab once, and I was Serpico. I was playing Serpico. And there was this truck, and for years, it's been a pet peeve of mine when they blow out that carbon monoxide from the back and it's all black. It pisses me off, really. So I saw that thing and I just rolled down my window and I just, 'Pull over!' 'Pull over!' I was going to pull him over and put him under a citizen's arrest, I guess," Pacino recalled.
Pacino was raised on the rough streets of the South Bronx by a single mother and his grandparents.
He dropped out of high school at 16 and eventually headed to Greenwich Village to act in small plays. His only money came from tips; he was broke and homeless.
"You learn to go without food," Pacino recalled.
"But, you were sleeping in, under storefronts and…stages," Couric remarked.
"I remember at one point I would sleep there at night on the stage. They had a lovely couch. It was very comfortable," Pacino replied.
But he got his first break when he was accepted at the Actor's Studio in midtown Manhattan, where Marlon Brando, James Dean and Paul Newman were trained in method acting, which teaches actors to draw on their own life experiences.
Asked if he thinks he'd be successful today if the studio hadn't been in New York, Pacino said, "Well, it think it had a lot to do with my success because when I was younger they weren't hiring people like me to play in Shakespeare, or anything else, or Moliere or Noel Coward. You could do everything here."
On the streets of Greenwich Village today, walking with Al Pacino feels like old home week, where he is stopped by passersby.
Asked if it happens wherever he goes, Pacino said, "If I go with a big camera and you, I think then it might happen."
His mother never lived to see moments like these. She died when he was 21.
"Was it hard that she never saw you attain success?" Couric asked.
"Yeah. It was. And my grandfather too who raised me. Those are the two most important people in my life. But they never saw it, no," he replied.