Summary: Study identifies key factors in peoples’ voices that show when they are lying.
Faster speech rate, greater intensity in the middle of the word, and falling pitch at the end of the word: that is the prosody to adopt if one wants to come across as reliable and honest to one’s listeners.
Scientists from the Science and Technology for Music and Sound laboratory (CNRS/Ircam/Sorbonne Université/Ministère de la Culture) and the Perceptual Systems Laboratory (CNRS/ENS PSL) have conducted a series of experiments to understand how we decide, based on the voice, whether a speaker is honest and confident, or on the contrary dishonest and uncertain.
They have also shown that this signature was perceived similarly in a number of languages (French, English, Spanish), and that it is registered “automatically” by the brain: even when participants were not judging the speaker’s certainty or honesty, this characteristic sound impacted how they memorized the words.
Prosody consequently conveys information on the truth-value or certainty of a proposition.
Scientists are now trying to understand how speakers produce such prosody based on their intentions.
This research was published on 8 February in Nature Communications.
Note: Scientists used vocal signal processing techniques to create random pronunciations of words (rising pitch, falling pitch, etc.), and then asked multiple groups of participants whether these words were pronounced with certainty or honesty. The software they developed as part of this effort, CLEESE, is open source: https://forum.ircam.fr/projects/detail/cleese/
Listeners’ perceptions of the certainty and honesty of a speaker are associated with a common prosodic signature
The success of human cooperation crucially depends on mechanisms enabling individuals to detect unreliability in their conspecifics. Yet, how such epistemic vigilance is achieved from naturalistic sensory inputs remains unclear. Here we show that listeners’ perceptions of the certainty and honesty of other speakers from their speech are based on a common prosodic signature. Using a data-driven method, we separately decode the prosodic features driving listeners’ perceptions of a speaker’s certainty and honesty across pitch, duration and loudness. We find that these two kinds of judgments rely on a common prosodic signature that is perceived independently from individuals’ conceptual knowledge and native language. Finally, we show that listeners extract this prosodic signature automatically, and that this impacts the way they memorize spoken words. These findings shed light on a unique auditory adaptation that enables human listeners to quickly detect and react to unreliability during linguistic interactions.