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

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, which 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, 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.

A limit on behavioral plasticity in speech perception

“…This extends previous studies of second language acquisition which have shown a loss of plasticity with age: the later a language is learnt, the less proficient people are (Oyama, 1976;Flege et al, 1995): it now seems that even early exposure (during the most sensitive period) is not sufficient. After exposure to Spanish leads to the formation of one [e] category, it appears to be difficult for the brain to learn two new phonetic categories which overlap with this one (see also Best et al, 1988). Similarly, Catalan-born subjects who have first learned the two categories of their language apparently did not learn a third category when exposed to Spanish.…”

A unified account of categorical effects in phonetic perception

“…Two classic models that have been widely used to explain these perception effects in second language learning rely on relationships between categories in the first language (L1) and second language (L2) to predict which are easier or harder to acquire: Flege's Speech Learning Model (Flege, 1987) and Best's Perceptual Assimination Model (Best et al, 1988). Flege's model uses equivalence classification to explain why sounds in L2 that are similar to sounds in L1 will be difficult to both perceive and produce, whereas sounds that are considered new, or different from any classes in the L1, will be easier to process.…”

Speech perception skills of deaf infants following cochlear implantation: a first report

“…To assess these skills in infant CI users, we have constructed a new research laboratory within the ENT Clinic at the Indiana University School of Medicine (IUSM) to assess the speech perception and language skills of deaf infants before implantation and at regular intervals following cochlear implantation. One of the procedures we have adapted for this research program is the visual habituation (VH) procedure, which has been used extensively for the past three decades to assess the linguistic skills of NH infants [11,53,54]. Our goals in this initial research were to: (1) validate VH with this population of deaf and hard-of-hearing infants, and (2) use VH to track and assess infants' attention to speech and measure their speech discrimination skills before and after receiving a cochlear implant.…”

“…The VH procedure has been used extensively over the years to assess NH infants' ability to discriminate speech contrasts [11,53]. In the standard implementation of VH, infants are first habituated to several trials of a repeating speech sound presented simultaneously with a visual display (e.g.…”