There have been many studies of infant speech perception over the past few decades which have greatly advanced our understanding of the process of language acquisition. However, there is little research in this field for Japanese infants. In this chapter, several studies of Japanese infants are reported and the results are discussed in relation to universal and language-specific features in language acquisition.

Methodology

In the course of these studies, several methodologies have been developed to measure infant speech perception abilities. Researchers have chosen, from a variety of methodologies, that which best serves the purpose of their study (Werker et al., 1998). For the behavioral measures, the habituation paradigm (e.g. the high-amplitude sucking paradigm and the visual-fixation procedure), the operant conditioned paradigm (e.g. the conditioned headturn procedure), and the auditory preference paradigm (e.g. the headturn preference procedure) are most frequently used in infant speech perception studies. The habituation paradigm and the conditioned paradigm provide information about how infants discriminate a pair of brief sounds, such as a contrast between two syllables. The auditory preference paradigm offers a useful method for studying infants' sensitivity to suprasegmental features in speech signals.

Development of infants' sensitivity to phonetic contrasts

A number of the early studies have indicated that human infants are born with the ability to discriminate a universal set of phonetic contrasts regardless of their language experience, and that this ability declines within the first year of life, as a function of specific linguistic experience.