So You Want to Be Persuasive? Start by Sounding Confident

Persuasion is a ubiquitous part of daily life. We’re surrounded by it. Immersed in it. And, in fact, many of us happily peddle our own brand of persuasive tactics for personal profit. Not surprisingly, oftentimes we’re successful in getting what we want from others—after all, practice makes perfect, and we have a lot of experience perfecting the art of persuasion.  

Why Does Our Voice Play Such An Important Role In Persuasion?

Intuitively as well as empirically, we know that the voice can be a powerful source of information because it often provides valuable insight into the emotions and thoughts of the speaker. We can typically very quickly identify and distinguish between different emotions expressed through the voice, even when the speaker is communicating in a language other than our own. Beyond emotions, a person’s voice also gives clues about their traits, social intentions, and even how they are evaluating a particular situation, person, or object. Some of these vocal features include rate of speech (slow or fast), volume (soft or loud), pitch (low or high), and intonation (for example, sentences that end with rising or falling pitch).

If we consider that changes in a person’s voice can affect our inferences about their psychological states, it doesn’t require a herculean stretch of the imagination to realize that how something is said could also influence the success of a persuasive appeal.

Scientists interested in how voice influences persuasion have recently started piecing together a more detailed picture of this relationship. Although many characteristics of voice can influence our willingness to say yes, the position at the top of the persuasive totem pole seems to be occupied by our perceptions of speaker confidence. This probably isn’t all that surprising given the importance we place on confidence when evaluating our own attitudes and thoughts. In fact, it makes a great deal of sense that how confident a person sounds should also be an important basis for deciding whether we heed someone’s advice or seek a second opinion. So what characteristics of voice reflect confidence?

More confident speakers tend to speak faster, louder, use falling intonation at the end of their sentences, and have lower-pitched voices. Furthermore, listeners also perceive these cues as signs of high confidence. In recent years, my colleagues and I have expanded upon this to show that changes in pitch, in particular, can have very profound effects on persuasion. Our initial research found that listeners tend to be more persuaded by a speaker whose voice has a relatively low versus high pitch. Importantly, when a person was carefully thinking about a message, changes in a speaker’s pitch affected the listener’s attitude by biasing their thoughts to be either positive or negative towards the topic. However, when people were distracted and thus not carefully thinking, changes in pitch affected their attitude without influencing their thoughts—illustrating a completing different process of persuasion. Why does it matter how carefully someone thinks about a persuasive message? The attitudes of people who carefully think about a message (versus those who don’t), are longer lasting, more predictive of their future behavior, more resistant to persuasive attempts, and more accessible in memory.

In our most recent studies, conducted at the University Autonoma de Madrid, my colleagues and I demonstrated that changes in one’s own vocal pitch could affect self-persuasion, changing a person’s attitude not only towards things external to themselves (such as a comprehensive exam proposal for university students) but also towards themselves (general academic abilities). What really surprised us was that pitch increased self-persuasion not only when participants were instructed to talk using a lower compared to higher pitched voice, but also when the keyboard on which they typed their thoughts produced a lower versus higher pitched tone with each keystroke, and in response to the same meditation-style music playing in the background in either a lower versus higher pitch. In all three studies, low pitch enhanced the effect of people’s thoughts on their attitudes, whereas high pitch reduced its impact. So for example, in response to low pitch, positive thoughts led to very positive attitudes, and negative thoughts led to very negative attitudes. However, in response to high pitch, positive thoughts produced only mildly positive attitudes, and negative thoughts only mildly negative attitudes. And the explanation behind this? Confidence. Low pitch increased people’s confidence in their thoughts, whereas high pitched decreased confidence.

So, whether you’re interviewing for an important job, trying to convince your friend to go to the movies, or just want to boost your confidence for that upcoming exam, remember that how you deliver your message is often just as important as its content. In the words of the American poet William Carlos Williams, “It is not what you say that matters, but the manner in which you say it; there lies the secret of the ages.”

For Further Reading

Guyer, J. J., Briñol, P., Vaughan-Johnston, T. I., Fabrigar, L. R., Moreno, L., & Petty, R. E. (2021). Paralinguistic features communicated through voice can affect appraisals of confidence and evaluative judgments. Journal of Nonverbal Behavior, 45, 479-504. 10.1007/s10919-021-00374-2

Guyer, J. J., Fabrigar, L. R., & Vaughan-Johnston, T. I. (2018). Speech rate, intonation, and pitch: Investigating the bias and cue effects of vocal confidence on persuasion. Personality and Social Psychology Bulletin, 45(3), 389-405.             https://doi.org/10.1177/0146167218787805

Petty, R. E., & Briñol, P. (2020). A process approach to influencing attitudes and changing behavior: Revisiting classic findings in persuasion and popular interventions. In J. Forgas, W. Crano, & K. Fiedler (Eds.), Applications of social psychology: How social psychology can contribute to real world problems (pp 82-103). Psychology Press.

Joshua Guyer is an assistant professor of psychology at IE University and Saint Louis University (in Madrid). Joshua's research interests include the different roles of vocal qualities (emotions, confidence) in persuasion, and different tactics of social influence.