Introduction

This chapter outlines an approach to the development of expressive and communicative behavior of Japanese infants until the onset of single-word utterances. It will be argued that expressive and communicative actions are organized as a complex and cooperative system with other elements of the infant's physiology, behavior, and the social environment.

Although children do not produce linguistically meaningful sounds or signs until they are approximately one year old, the ability to produce them begins to develop in early infancy, and important developments in the production of language occur throughout the first year of life. Unless they are hearing-impaired, infants acquire phonology during their first year. In spoken language, the acquisition of phonology consists of learning to distinguish and produce the sound pattern of the adult language. At birth, the newborn has the ability to distinguish virtually all sounds used in all languages, at least when the sounds are presented in isolation. The newborn produces no speech sounds, however. During the first year of life, speech-like sounds gradually emerge, beginning with vowel-like coos at 6 to 8 weeks of age, followed by some consonant sounds, then followed by true babbling. By the end of the first year, children are typically babbling sequences of syllables that have the intonation contour of their target languages. Finally, meaningful words are produced; that is, the onset of speech occurs. In this chapter, papers related to this process in Japan are to be reviewed (see Masataka, 2003 for more detail).