Phonetic learning as a pathway to language: new data and native language magnet theory expanded (NLM-e)

TLDR

Infants’ speech perception undergoes a dual change near the end of the first year, raising theoretical interest in the mechanisms linking native and non‑native perception. The study reviews phonetic perception models, presents new ERP data linking 7.5‑month perception to two‑year language growth, and expands the native language magnet model (NLM‑e) with testable predictions. NLM‑e introduces five new principles to explain how native and non‑native phonetic perception influence language development. New data show that while native‑language perception improves, non‑native perception declines, and that at 7.5 months native‑language skill predicts faster language growth whereas non‑native skill predicts slower growth, suggesting native performance reflects neural commitment and non‑native performance reflects uncommitted circuitry.

Abstract

Infants' speech perception skills show a dual change towards the end of the first year of life. Not only does non-native speech perception decline, as often shown, but native language speech perception skills show improvement, reflecting a facilitative effect of experience with native language. The mechanism underlying change at this point in development, and the relationship between the change in native and non-native speech perception, is of theoretical interest. As shown in new data presented here, at the cusp of this developmental change, infants' native and non-native phonetic perception skills predict later language ability, but in opposite directions. Better native language skill at 7.5 months of age predicts faster language advancement, whereas better non-native language skill predicts slower advancement. We suggest that native language phonetic performance is indicative of neural commitment to the native language, while non-native phonetic performance reveals un committed neural circuitry. This paper has three goals: (i) to review existing models of phonetic perception development, (ii) to present new event-related potential data showing that native and non-native phonetic perception at 7.5 months of age predicts language growth over the next 2 years, and (iii) to describe a revised version of our previous model, the native language magnet model, expanded (NLM-e). NLM-e incorporates five new principles. Specific testable predictions for future research programmes are described.