Key Concept

In their efforts to persuade and influence others, leaders pay close attention to the words they choose. Listeners, however, often doubt the sincerity of those trying hard to persuade them. Research into how leaders modulate their voices — by adjusting the volume of their speech, for example — reveals that such ‘paralinguistic cues’ can enhance their persuasiveness, and even increase their perceived sincerity. 

Idea Summary

Most attempts at persuasion are met by wary resistance. People are naturally suspicious of the motives of persuaders, ready to believe that persuaders will use devious means to achieve their goal of persuasion. 

Previous research has focused on linguistic cues—that is, the words that persuaders can use to overcome this natural resistance. However, in their attempts to persuade, people can also modulate how they express their words—speaking more loudly or more softly, using a higher or lower pitch, or speaker faster or slower. 

Through a series of experiments, Alex B. Van Zant of Rutgers University Business School and Jonah Berger of The Wharton School explore whether paralinguistic cues such as volume, pitch and speech rate, are more effective in persuasion than linguistic cues—and if so, why.

In one experiment, for example, one set of volunteers recorded two reviews of a television, one with and one without paralinguistic cues. Another set of volunteers listened to one of the two recordings, and then answered questions on whether or not they were likely to buy the TV. They also answered questions on whether the reader of the review seemed confident in what he or she was saying. 

Half of the listeners were also given a statement that disclosed the fact that the TV manufacturer had paid the reader of the review (telling the listener, in essence, that the reviewer is attempting to persuade them to buy the TV). 

The results of the experiment showed, as expected, that the listeners who heard the recording with the paralinguistic cues were more likely to be persuaded to buy the TV than listeners who heard no paralinguistic cues. 

The results also showed that listeners who read the disclosure statement — that is, listeners who were aware of the speaker’s intent to persuade them — were less likely to buy the TV.

However, the disclosure statements (and in a follow-up experiment, an even more explicit statement of persuasion intent) did not, as expected, neutralize the impact of the paralinguistic cues. That is, among the listeners who read the disclosure statement, those who heard the paralinguistic cues were still more likely to buy the TV than those who had not heard the cues. Paralinguistic cues remained effective tools of persuasion, whether or not the listeners knew the reader of the review was trying to persuade them.

This result indicates that the power of the paralinguistic cues does not depend on the fact that they are undetectable—since the disclosure statement “blowing their cover” did not impact their effectiveness. Instead, the researchers found that the appearance of confidence was the key differentiator: Listeners believed speakers who used paralinguistic cues in their readings of the review were more confident about what they were saying than speakers who did not use paralinguistic cues. 

Further experiments confirmed the higher effectiveness of paralanguage over language in persuasion attempts. In addition, the research showed the following: 

• The most effective paralinguistic cues for persuasion were speaking louder and varying the volume of speech.
• Confidence enhances persuasion because of what psychologists call ‘attitude extremity’, manifested as follows: listeners who hear a confident speaker assume the speaker strongly believes in the task (e.g., in the review of the TV in the experiment above), which makes the speakers’ words more persuasive.
• Not only did paralinguistic cues not make listeners suspicious (as linguistic cues tend to do), but actually made listeners more convinced of the sincerity of the speakers.

Business Application

With the era of strict command and control in the past, the best leaders today are effective communicators, adept at inspiring, influencing and persuading their people and organizations. This research explores paralinguistic options that leaders may not have previously considered when verbally communicating their message.

Specifically, leaders want to project confidence, knowing that the appearance of confidence is vital to gaining trust and support. Persuaders struggle to project confidence through linguistic cues, and this can raise listeners’ suspicions about the sincerity of the speaker. Paralinguistic cues — notably, a generally higher volume with variations — that project confidence, on the other hand, raise no such suspicions, even when listeners know the speaker is trying to convince them.