Examination of perceptual reorganization for nonnative speech contrasts: Zulu click discrimination by English-speaking adults and infants.

TLDR

Early language experience shapes speech perception, with adults struggling to discriminate many nonnative contrasts that infants can detect, and perceptual reorganization typically occurring by 10–12 months, possibly driven by psychoacoustic experience or phonological development linked to allophonic patterns. We hypothesized that a phonemic process emerges around 10–12 months that assimilates sounds to native categories when possible, otherwise perceiving them auditorily or phonetic‑articulatorily. We tested this hypothesis with English‑speaking listeners using Zulu click contrasts. Adults reliably discriminated Zulu click contrasts, achieving 80 % correct even when the most salient acoustic difference was removed, while infants as young as 12–14 months also discriminated the acoustically modified contrast, supporting a phonological account of language‑specific reorganization.

Abstract

The language environment modifies the speech perception abilities found in early development. In particular, adults have difficulty perceiving many nonnative contrasts that young infants discriminate. The underlying perceptual reorganization apparently occurs by 10-12 months. According to one view, it depends on experiential effects on psychoacoustic mechanisms. Alternatively, phonological development has been held responsible, with perception influenced by whether the nonnative sounds occur allophonically in the native language. We hypothesized that a phonemic process appears around 10-12 months that assimilates speech sounds to native categories whenever possible; otherwise, they are perceived in auditory or phonetic (articulatory) terms. We tested this with English-speaking listeners by using Zulu click contrasts. Adults discriminated the click contrasts; performance on the most difficult (80% correct) was not diminished even when the most obvious acoustic difference was eliminated. Infants showed good discrimination of the acoustically modified contrast even by 12-14 months. Together with earlier reports of developmental change in perception of nonnative contrasts, these findings support a phonological explanation of language-specific reorganization in speech perception.