Proficiency and Linguistic Complexity Influence Speech Motor Control and Performance in Spanish Language Learners.

Purpose: Second-language (L2) production requires greater cognitive resources to inhibit the native language and to retrieve less robust lexical representations. The current investigation identifies how proficiency and linguistic complexity, specifically syntactic and lexical factors, influence speech motor control and performance. Method: Speech movements of 29 native English speakers with low or high proficiency in Spanish were recorded while producing simple and syntactically complex sentences in English and Spanish. Sentences were loaded with cognate (e.g., baby-bebe) or noncognate (e.g., dog-perro) words. Effects of proficiency, lexicality (cognate vs. noncognate), and syntactic complexity on maximum speed, range of movement, duration, and speech movement variability were examined. Results: In general, speakers with lower L2 proficiency differed in their speech motor control and performance from speakers with higher L2 proficiency. Speakers with higher L2 proficiency generally had less speech movement variability, shorter phrase durations, greater maximum speeds, and greater ranges of movement. In addition, lexicality and syntactic complexity affected speech motor control and performance. Conclusions: L2 proficiency, lexicality, and syntactic complexity influence speech motor control and performance in adult L2 learners. Information about relationships between speech motor control, language proficiency, and cognitive-linguistic demands may be used to assess and treat bilingual clients and language learners.