Expressive moments in communicative hand gesture often align with emphatic stress in speech. It has recently been found that acoustic markers of emphatic stress arise naturally during steady-state phonation when upper-limb movements impart physical impulse on the body, most likely affecting acoustics via respiratory activity. In this confirmatory study, participants (N = 29) repeatedly uttered consonant-vowel CV (/pa/) mono-syllables while moving in particular phase relations with speech, or not moving the upper limbs. We show that respiration-related activity is affected by (especially high-impulse) gesturing when vocalizations occur near peaks in physical impulse. We further show that gesture-induced moments of bodily impulses increase the amplitude envelope of speech, while not similarly affecting the Fundamental Frequency (F0). Finally, tight relations between respiration-related activity and vocalization were observed, even in the absence of movement, but even more so when upper-limb movement is present. The current findings expand a developing line of research showing that speech is modulated by functional biomechanical linkages between hand gesture and the respiratory system. This identification gesture-speech biomechanics promises to provide an alternative phylogenetic, ontogenetic, and mechanistic explanatory route of why communicative upper limb movements co-occur with speech in humans.
Reply to Ravignani and Kotz: Physical impulses from upper-limb movements impact the respiratory-vocal system
