The effect of word frequency and lexical class on articulatory-acoustic coupling

Word frequency and lexical class distinction between function and content words have been shown to significantly influence word production. In this paper, we use real-time magnetic resonance imaging to investigate the effect of word frequency and lexical class on articulatory characteristics (the articulator speed) as well as acoustic characteristics (F0 and short-term energy) in word production. Multiple regression analyses showed that word frequency exhibits significantly higher correlation with articulatory and acoustic factors for content words compared to function words. A Granger causality analysis uncovered a causal relationship from articulatory speed to F0/energy for low-frequency content words. We further observed, using functional canonical correlation analysis, a tight coupling of articulatory and acoustic characteristics for low-frequency content words. These results support the view that word frequency distinctly influences the production of function and content words as manifested in their articulation and acoustics, as well as the dynamic coupling of these temporal streams.