Tongue shape variations in laughter and speech: Exploring movement patterns

Laughter is a common non-verbal communicative function of the vocal tract [Krepsz et al., 2024, CognitiveProcessing, 25(1)]. Previous studies using real-time magnetic resonance imaging (rtMRI) of the vocal tract found spontaneous (natural) laughter to be less speech-like compared to volitional (induced) laughter [Belyk & McGettigan, 2022, Phil. Trans. Royal Soc. B, 377(1863)]. Expanding on prior research on laughter production [Belyk & McGettigan, 2022] and ultrasound imaging comparing the production of spoken vowels to trombone notes [Heyne & Derrick, 2019, Frontiers in Psych., 10(2597)], the present study employs ultrasound imaging to analyze tongue shape variations between spontaneous and induced laughter, to ascertain whether laughter draws on the speech movement inventory. Video stimuli were presented to elicit spontaneous laughter, and vowels [i, ɪ, e, ɛ, æ, ʌ, ə, ʊ, u, o, ɔ, ɑ] were produced to compare articulatory postures. Acoustic analyses using Praat [Boersma & Weenink, 2024] and ultrasound data will be presented comparing spontaneous vs. natural laughter and their similarity to vowels in the speech inventory. Induced laughter is predicted to draw on speech-like behaviour, exhibiting similar tongue postures to speech compared to natural laughter. Implications will be discussed regarding similarities and differences in tongue positioning between spontaneous, volitional laughter, and speech.