The 'Sherlock' actor (47 years old) has revealed he had a lisp when he was younger, but he managed to shake it off after his parents signed him up for acting classes to help with his shyness, as well as elocution lessons.
He told Variety: "I used to go to these drama classes on a Saturday, and I would be fully shaking before you go in. And then you'd have to get up in front of your other seven, eight-year-olds, and do an improvisation, or say a poem or something.
"I don't feel like it's an overstatement to say that I think it's completely changed my life - not just my career. I had a really bad lisp when I was a kid, so I had to do elocution lessons. I had to go, 'He sees seashells by the seashore,' and I just completely got rid of it."
He added: "Just to wrap that shyness thing up, somebody said a really brilliant thing to me, which was, like, 'There's nothing wrong with being shy. Be shy. It's a nice thing you go a little bit red'."
Andrew made the revelation in a joint interview with Brie Larson, who revealed she also used acting to become more confident as a shy child.
Brie explained: "My parents were chiropractors, and I was super shy. I wouldn't let it go. Of course, it's changed the course of my life in so many ways.
"But at a time when I was so shy and had such a hard time expressing myself, at six years old, I was basically given, like, 'OK, here's a script for how you have a conversation'.
"The actual fibre of how I understand how to have pleasant conversations with people is based upon weekly acting sessions."
Brie added that shyness still affects her as an adult, adding: "I blush very easily. It's horrible".