Stabilizing the production of nonnative consonant clusters with acoustic variability.

Previous research on the perception, recognition, and learning of sounds and words has identified diverse effects of phonetic variation. The present study examined how variation affects cross-language production of consonant clusters. American English speakers shadowed words beginning with nonnative clusters in low- and high-variability conditions. Shadowing responses in the low-variability condition were quite sensitive to fine-grained phonetic properties that were manipulated across the stimuli. Notably, longer stop bursts led to increased rates of epenthesis, lower burst amplitudes resulted in more feature change and deletion, and intense periods of voicing at cluster onset elicited prothetic responses. Sensitivity to the acoustic manipulations was substantially attenuated in the high-variability condition, which combined stimuli from the first condition with baseline productions of the same items from two additional talkers. Detailed analyses of the response patterns indicate that more stable production targets in the high-variability condition resulted from integration, or blending, of the multiple talker stimuli. Implications of these findings for language-specific speech processing and the role of phonetic variability in second language acquisition are discussed.