Why confidence is key to persuasion

In persuasive communications, vocal cues affect a speaker's ability to persuade others.

Wharton marketing professor Jonah Berger conducted four experiments on use of nonverbal communication in persuasion, finding that speakers who modulate their voices appear more confident, which makes them more likely to succeed in convincing their listeners to take action. His paper, co-writtern with Alex Van Zant, management professor at Rutgers Business School, is "How the Voice Persuades," published in the Journal of Personality and Social Psychology.

"Often, when we try to persuade others, they're less likely to do what we suggest," says Berger. "We wondered how might the voice that someone uses—the way they talk, in addition to the words they use—affects what other people do, affects whether other people listen? ... In this project, we wanted to begin to ask, 'What about paralanguage? What about vocal features, and how might those aspects impact persuasion?'"

"There's a concept in behavioral science called reactance," he adds. "When we try to push someone to do something ... they often don't do what we want. They often do the opposite."