Patterns of vowel and pitch productions at the babbling stage of Hong Kong infants

Abstract

An influential view of early speech development, represented by Jakobson (1941/1968), sees phonological development as unrelated to babbling. For the past three decades, the Jakobsonian hypothesis has been challenged. Various researchers have provided evidence showing the bias of the target language in infant babbling and the relationship between babbling and early lexical development. This thesis evaluates the discontinuity claims of Jakobson with reference to the vowel and pitch productions of infants growing up in Hong Kong, with an aim to ascertaining the degree of continuity between babbling and early words. Longitudinal data from two infants growing up in Hong Kong and acquiring Cantonese as their target language were collected semi-monthly and were analyzed acoustically for formants and fundamental frequencies. Their development revealed a number of patterns of vowel and pitch productions. With respect to vowel production, the acoustic boundary for each vowel was unclear and overlapping patterns were found at the age of eight to nine months. But consistency in vowel formant frequencies slowly emerged at ten months old. The distributions of vowels in the acoustic space were similar in the child and adults, while the absolute formant values of their vowels were different. Phonetic preferences existed in the productions of infants. Low vowels and low-mid vowels dominated. The number of front vowels was higher than that of back vowels and rounded vowels were rarely produced at the babbling stage. Besides, the patterns of vowels at the babbling stage were similar to those at the babbling-and-words stage. The frequencies of vowels in babbling resembled those in early words, with the vowels /a/ and /Œ/ being the most frequent and central vowels occurring more frequently than front and back vowels. In pitch production, level pitch predominated and the number of mid level contours was higher than that of the high and low level contours. With respect to non-level pitch, falling and rising contours far exceeded concave, convex and multiplex contours. Few sharp falls or sharp rises were found among the falling and rising pitches. As in vowel production, the pitch production of Hong Kong infants revealed a trend of continuity. The distribution of pitch contours in the babbling stage resembled that in the babbling-and-words stage, and the profile of pitch contours in babbling paralleled that in words in the babbling-and-words stage, with level pitch contours being predominant, followed by the falling pitch.