By Dr. Ken Broda Bahm:
Trial lawyers are used to persuading with their arguments and with their evidence. But what about the voice? It stands to reason that tone matters, but does it matter enough to influence persuasion? Some attorneys, even while understanding that they need to be heard and need to keep an active and pleasant-yet-serious voice, are still wary of going too far with their intonation. After all, they want to sound like lawyers, not like salespeople or preachers.
But is that wariness warranted? Or, alternately, is it possible that clear attempts to put passion into your voice are persuasive, even when people recognize what you are doing? That is the question addressed in a recent research study (Van Zant & Berger, 2019): How persuasive are people when they are using their voice to persuade? The study focused on voice modulation as “paralinguistic cue,” including the role of pitch, volume, and rate of speech in creating more effective communication. What they found is that when speakers tried to persuade, they adopted certain vocal features, and these features made speakers more persuasive by making them seem more confident. And even when this tone is detectable and the targets become aware of persuasive attempts, it is still more persuasive. “Speakers’ confident vocal demeanor,” the researchers noted, “persuades others by serving as a signal that they more strongly endorse the stance they take in their message.” This has implications for presenters and persuaders in and out of court. In this post, I will share a bit more about the research and break down the vocal features that work.
The Research: Paralinguistic Cues Work
The researchers from Wharton and Rutgers began with the descriptive question of how people use their voice when trying to persuade, as well as the prescriptive question comparing two rival hypotheses about whether it works. The first hypothesis focuses on confidence and posits that strong vocal traits increase perceived confidence and that boosts persuasion. But the second hypothesis is that obvious attempts to use one’s voice to persuade are detected, and that causes resistance to kick in, which hampers persuasion.
They had a naturalistic way of testing it. Research participants were first asked to read reviews for a Smart TV, either as they normally would, or how they would when trying to persuade a listener, and incentivized with a chance to win a gift card if they were successful. “You cannot change the words you say,” participants were told, “but you can choose to say them in whatever style you think is best.” This approach was also applied to personally relevant messages that the participants generated on their own.
Next the researchers used specialized software to analyze what the participants did with their voices when they tried to persuade. As noted below, they found that their volume was louder and more varied, their pitch was a bit higher and more varied, and their rate was a little faster.
Looking at the results, the study showed that the confidence based hypothesis was supported: The use of these vocal cues did in fact boost both perceived confidence and persuasion. Furthermore, the hypothesis focusing on detectability was not supported: Even when recipients noted the persuasive intent behind the tone, it still improved effectiveness to adapt those vocal cues. So, even when persuasive targets know they’re being pitched to, it still helps to pitch.
The Implications: The Sound of Persuasion
The strategy for vocal persuasion boils down to this advice: Do more. You want to avoid any sound that is close to monotone and that means adding both emphasis and overall variety to your volume, pitch, and rate.
A Little Bit Louder and More Variable Volume
The researchers found that when you persuade, it pays to have more variety in your volume – more frequent changes in low and high volume – and that, overall, your average volume should be higher than you would use in conversational speech. In other words, project. It is not just a matter of being heard, it is a matter of conveying power, certainty, and confidence.
A Little Higher and More Variable Pitch
The researchers also found that persuasive use of vocal communication means more variety in pitch, and a slightly higher average pitch as well. We are not talking about speaking in falsetto, of course, but instead talking about the subtle shift that occurs when you are eager and engaged, making a good point or telling a good story. That energy and enthusiasm is conveyed in a slightly higher pitch.
A Little Faster and More Variable Rate
Finally, the researchers found that persuaders adopt a slightly faster rate, and in my view, that faster average should also include greater variability, shifting frequently from faster speech to convey information to slower speech to emphasize a point.
The study highlights the fact that good communication, and persuasion in particular, is heightened. Don’t just use your voice to describe, drone, or narrate. Instead sell your point by putting some personality, passion, and variety into it.
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Other Posts on Your Voice:
Van Zant, A. B., & Berger, J. (2019). How the voice persuades. Journal of personality and social psychology.