Listeners can reliably determine a speaker's sincerity through prosodic cues, since sincere compliments are spoken faster and with a higher pitch

The sound of (in)sincerity. Karyn Fish, Kathrin Rothermich, Marc D.Pella. Journal of Pragmatics, Volume 121, November 2017, Pages 147-161. https://doi.org/10.1016/j.pragma.2017.10.008

Highlights
•    Sincere compliments and prosocial lies occur frequently in communication.
•    Listeners can reliably determine a speaker's sincerity through prosodic cues.
•    Sincere compliments are spoken faster and with a higher pitch.
•    Social context biases impressions of sincerity in compliments.
•    Prosody and speaker attitude are both important for understanding speaker intentions.

Abstract: In social life, humans do not always communicate their sincere feelings, and speakers often tell ‘prosocial lies’ to prevent others from being hurt by negative truths. Data illuminating how a speaker's voice carries sincere or insincere attitudes in speech, and how social context shapes the expression and perception of (in)sincere utterances, are scarce. Here, we studied the communication of social, other-oriented lies occurring in short dialogues. We recorded paired questions (So, what do you think of my new hairdo?) and responses (I think it looks really amazing!) using a paradigm that elicited compliments which reflected the true positive opinion of the speaker (sincere) or were meant to hide their negative opinion (insincere/prosocial lie). These Question–Response pairs were then presented to 30 listeners, who rated the sincerity of the person uttering the compliment on a 5-point scale. Results showed that participants could successfully differentiate sincere compliments from prosocial lies based largely on vocal speech cues. Moreover, sincerity impressions were biased by how the preceding question was phrased (confident or uncertain). Acoustic analyses on a subset of utterances that promoted strong impressions of sincerity versus insincerity revealed that compliments perceived as being sincere were spoken faster and began with a higher pitch than those that sounded insincere, while compliments rated as insincere tended to get louder as the utterance unfolded. These data supply new evidence of the importance of vocal cues in evaluating sincerity, while emphasizing that motivations of both the speaker and hearer contribute to impressions of speaker sincerity.