Ingressive phonation conveys arousal in human nonverbal vocalizations

Animals normally vocalise while exhaling. Ingressive, or inspiratory, voice production occurs in humans and many other species, but its communicative function, if any, remains unknown. To test the perceptual effects of ingressive phonation, naturally occurring ingressive syllables in 109 human nonverbal vocalisations (55 laughs, 21 cries, and 33 moans) were experimentally attenuated or morphed into quiet and unvoiced intakes of breath using voice resynthesis technology. Ratings of the intensity of discrete emotions (amusement, sadness, pleasure) and of general arousal in three perceptual experiments revealed that listeners (N = 283) judged vocalisations with attenuated ingressive syllables to be less emotionally intense compared to the originals. Ingressive vocalisations were not experienced as either unnatural or unpleasant, confirming that they are a familiar part of human vocal repertoire. In sum, ingressive phonation can occur in a wide range of human nonverbal vocalisations and typically conveys intense emotion, presumably because listeners associate heavy breathing, imperfect vocal control, and continuous egressive-ingressive vocalising with the physiological state of high arousal. It remains to be seen whether ingressive phonation is a mere byproduct of high arousal or whether it can be exaggerated, and whether its communicative function extends to vocalisations of non-human animals.