Decrease of L1–L2 assimilation and its prediction on L2 discrimination: perception of English coronal fricatives by Mandarin speakers

This study examined the perceptual assimilation and discrimination of English coronal fricatives /s, z, θ, ð/ by Mandarin speakers. The focus was on the effect of L2 experience on L1-L2 assimilation and the validity between assimilation patterns and assimilation overlaps in predicting L2 discrimination. The perceptual assimilation task showed that the more experienced group demonstrated weaker L1-L2 assimilation, corroborating the Revised Speech Learning Model (Flege, J. E. & O.-S. Bohn. 2021. The revised speech learning model. In R. Wayland (ed.), <i>Second language speech learning: Theoretical and empirical progress</i>, 3-83. Cambridge University Press). For the discrimination test, both more and less experienced groups performed comparably with moderate accuracy for the place contrasts /s-θ/ and /z-ð/ (assimilated as "Category-goodness") and higher accuracy for the voice contrasts /s-z/ and /θ-ð/ (assimilated as "Two-category"). These results lent support to the predictions made by the Perceptual Assimilation Model-L2 (Best, C. T. & M. D. Tyler. 2007. Nonnative and second-language speech perception: Commonalities and complementarities. In O.-S. Bohn & M. J. Munro (eds.) <i>Language learning & language teaching</i>, vol. 17, 13-34. John Benjamins Publishing Company) based on the assimilation patterns (no group difference) rather than the assimilation overlaps (group difference). The current study suggested that the perceived L1-L2 similarities may decrease with the growth of L2 experience, and the place contrasts /s-θ/, /z-ð/ could render more challenges than the voice contrasts /s-z/, /θ-ð/ for Mandarin speakers. Theoretical implications were brought out through comparing controversial assimilation measurements and the effect of L2 experience on cross-language perception.