When British actress Emily Blunt hits the big screen as Mary Poppins in the December release "Mary Poppins Returns," few will guess that she stuttered as a child.

She told an interviewer in 2008: "I was a smart kid, and had a lot to say, but I just couldn't say it ... I never thought I'd be able to sit and talk to someone like I'm talking to you right now."

What changed everything? "One of my teachers at school had a brilliant idea and said, 'Why don't you speak in an accent in our school play?'... It was really a miracle," says Blount.

Well, it turns out there's a scientific explanation for the brain activity that triggers — or avoids — stuttering.

Whether it's initiated by genetics, a head trauma, premature birth, a birth complication, or some unknown factor, it's a disruption in the motion or muscle movement involved in speaking that causes the speaker to "get stuck."

In a stutterer's brain, hyperactivity in regions of the right hemisphere causes other brain areas involved in the initiation and termination of motor movements to malfunction.

What does this mean for those who stutter? One day soon, there will be ways of restoring normal function to those brain areas, so motion related to speech starts and stops normally.

But until then, the best options are speech therapy, cognitive behavioral therapy and using electronic devices that can improve fluency. It also may be smart to consider a future on the stage.

Just ask Emily Blunt, or Ed Sheeran.