Developmental trajectory for production of prosody: lexical stress contrastivity in children ages 3 to 7 years and in adults

Abstract

PURPOSE: Accurate production of lexical stress within English polysyllabic words is critical for intelligibility and is affected in many speech-language disorders. However, models of speech production remain underspecified with regard to lexical stress. In this study, the authors report a large-scale acoustic investigation of lexical stress production in typically developing Australian English–speaking children ages 3–7 years(n = 73)compared with young adults (n = 24). METHOD: Participants named pictures of highly familiar strong–weak and weak–strong polysyllabic words. Of 388 productions, 325 met criteria for acoustic measurement. Relative vowel duration, peak intensity, and peak f 0 over the first two syllables were measured. RESULT: Lexical stress was marked consistently by duration and intensity but not f 0. Lexical stress on strong–weak words was adultlike by 3 years. All 3 measures showed significant differences between adults and children for weak–strong words still present at 7 years. CONCLUSION: Our findings suggest that protracted development of weak–strong stress production reflects physiological constraints on producing short articulatory durations and rising intensity contours. Findings validate treatment that is centered on strong–weak stress production for children 3 years with dysprosody. Although intervention for the production of weak–strong words may be initiated before age 7 years, reference to normative acoustic data is preferable to relying on perceptual judgments of accuracy.