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 en-ergy) in word production. Multiple regression analyses showed that word frequency exhibits significantly higher correlation with articulatory and acoustic factors for content words com-pared to function words. A Granger causality analysis uncov-ered a causal relationship from articulatory speed to F0/energy for low-frequency content words. We further observed, us-ing functional canonical correlation analysis, a tight coupling of articulatory and acoustic characteristics for low-frequency content words. These results support the view that word fre-quency distinctly influences the production of function and con-tent words as manifested in their articulation and acoustics, as well as the dynamic coupling of these temporal streams. Index Terms: word frequency, function words, content words, articulatory-acoustic coupling, real-time MRI, speech produc-tion. 1