Talking and walking works fairly well, but new research from the University of South Carolina suggests the urge to speak and the act of speaking are way more taxing on the brain than just listening.

So much for hands-free cellphones.

“It’s really an attention problem, not really about holding the phone in your hand” said Dr. Armit Almor, an associate professor of psychology. Almor and his colleague Tim Boiteau, who measured attention levels in 94 people, found that talking was four times more distracting than listening.

“People can tune in or out as needed when listening,” said Almor.

How about talking to a passenger?

“When you have someone sitting next to you they are acting as an extra set of eyes, something that a remote person can’t alert you to.”