Vocal development during the prelinguistic period

Abstract

The vocal developmental process during the prelinguistic period in Japanese infants has not yet been clarified in detail. The purpose of this study was to clarify the characteristics of vocal development during the prelinguistic period in Japanese infants. The subjects were five Japanese infants. Vocalizations were collected monthly from four to ten months of age, and auditory evaluation was performed by two experienced listeners. We examined the following points regarding Japanese- and English-speaking infants: (i) the correspondence between developmental stage and stage model, (ii) the degree of overlap in cases where staging is possible, (iii) the degree of difference in developmental stage between individuals, and (iv) the relationship between feeding and vocalization. The results showed that canonical babbling appeared prior to vowel-like sounds and vocal play sounds, indicating that developmental stages exist, though there is an overlap between stages. Furthermore, the types and frequency of vocalizations also varied among the infants. Raspberry sounds (RSP) increased in association with the start of feeding with baby food, suggesting that there is a relationship between the appearance of RSP and feeding function.