The physical basis of gesture-speech synchrony: Exploratory study and pre-registration

Hand gestures during speech move in a common rhythm, as exemplified by the synchrony between prosodic contrasts in gesture movement (e.g., peak velocity) and speech (e.g., peaks in Fundamental Frequency). This joined rhythmic activity is hypothesized to have a variable set of functions, ranging from self-serving cognitive benefits for the gesturer, to communicational advantages that support listeners’ understanding. However, gesture-speech synchrony has been invariably understood as a “neural-cognitive” achievement; i.e., gesture and speech are coupled through neural-cognitive mediation. Yet, it is possible that gesture-speech synchrony emerges out of resonating forces that travel through a common physical medium – the body. The current paper presents an exploratory study together with a pre-registration of a larger scale confirmatory study. We provide preliminary evidence that upper limb motions with greater momentum (i.e., physical impetus) affects Fundamental Frequency and the Amplitude Envelope of phonation in a way that accommodates research on gesture-speech synchrony. We speculate that anticipatory postural adjustments and related physical effects of upper limb movements on the musculoskeletal connective system could lead to changes in alveolar (lung) pressure that can impart (prosodic) contrasts in phonation. Here we pre-registered a confirmatory study to more comprehensively address this hypothesis.