Consonant-vowel co-occurrence in early speech development of normal Cantonese-speaking children

Research shows that the occurrence of consonants and vowels of CV syllables are not independent. The present study evaluates one of the leading theories in explaining early speech development in the light of motor constraints of young children: the Frame/ Content (F/C) theory. The notion of frame dominance" proposed by the F/C theory in prespeech babbling and in babbling concurring with words was investigated. Results show that the F/C theory was able to predict the predominant CV patterns in prespeech babbling, but not in babbling concurring with words: "frame dominance" was concluded in prespeech babbling only The effect of lexical development with respect to Cantonese on the production of CV patterns of the older children was also evaluated. Older children tended to target at CV patterns of words according to predominant CV pattern distribution in Cantonese lexicon, instead of targeting at the predicted patterns of the F/C theory. Results of error analysis also indicate a tendency for target words to be produced as syllables with phonological characteristics of the target forms. This study shows that prespeech babbling is frame-dominated, with the effect of lexicon of ambient language retains a strong influence on first words. Introduction Various research suggests that the acquisition of vowels and consonants is not unrelated. Piske (1997) describes consonants and vowels as "cohesive units" in which individual segments are not independent. Tyler & Langsdale (1996) stated that consonants are context dependent, and their development depends on neighboring sounds, that is, vowels. Indeed, Kent (1982) proposed that "facilitative phonetic contexts", determined by physiological and acoustic factors, benefit the production of some consonants. For example, the assimilatory effect of vowels on neighboring consonants is reported by Stoel-Gammon (1983). The study showed that a labial consonant is replaced by an alveolar consonant when followed by a front vowel, which gives evidence of a constraint on "labial consonant-front vowel sequences". Thus, patterns of early vowel acquisition are important in the studies of consonant acquisition. Conversely, Stoel-Gammon (1992) showed that certain vowels would be "misarticulated" in some consonant contexts but not in others. Kent (1992) stated that vowel is the nucleus of most words, and a consonant-vowel (CV) syllable is the earliest recognizable production unit". Kent's (1992) claim and Stoel-Gammon's (1983) findings lend support to a model of consonant-vowel co-articulation proposed by MacNeilage and Davis. The Frame/ Content Theory MacNeilage & Davis (1990a, 1990b) proposed "Frames, then Content" as a description of babbling forms and types of changes noticed in early speech development of children across languages. The theory depicts the "spatio-temporal and biomechanical" features of early speech. As suggested by the theory, early speech production is a combination of "rhythmic mandibular oscillation" and "syllable-like cycles under mandible-independent control" (Davis & MacNeilage, 1995, p. 1199). Also, early speech development shows 'frame dominance' in which speech patterns are the direct result of production of syllabic frames. The Frame/ Content (F/C) theory suggests that the production of babbling in infants is a result of "an alternating depression and elevation of the mandible". The alternating motions result in an alternate production of consonants and vowels, in which consonants are produced with an elevated mandible while vowels with a depressed mandible. Three types of frames were suggested: pure frames (that is, labial consonants and central vowels), fronted frames (that is, alveolar consonants and front vowels), and backed frames (that is, velar consonants and back vowels). The three types of frames were differentiated by local modifications which result from the movement of the tongue in particular. Based on the results of a transcription-based longitudinal study with subjects aged 14 to 20 months old, Davis & MacNeilage (1990) reported patterns of consonant-vowel co-occurrences. Alveolar consonants were found to co-occur with front vowels (that is, front frames), labial consonants with central vowels (that is, pure frames), and velar consonants with back vowels (that is, back frames). The strong co-occurrence patterns of alveolar consonants with front vowels and labial consonants with central vowels were also reported in later longitudinal studies (e.g. Davis & MacNeilage, 1994; MacNeilage, Davis & Matyear, 1997). Davis & MacNeilage (1994) suggested that pure frames are the "simplest frames", and should be observed as a preference in early speech development Not all transcription-based studies favoured the F/C theory. Tyler & Langsdale (1996) showed, with subjects aged 18 to 24 months, that the association between velars and back vowels was evident, but the bilabial-central vowel and the alveolar-front vowel associations were not supported. Vihman (1992) studied the first 50 words of 23 children across four different languages. The study showed that the co-occurrence of 4 labial consonants and central vowels, and velar consonants and back vowels was strongly supported, while that of alveolar consonants and front vowels were not supported. Oiler & Steffans (1993) showed that CV associations were strong for children aged 10 to 12 months, but weakened by 16 to 24 months, which was consistent with the development of more segmental functions. Levelt (1996) proposed different CV co-occurrence patterns using the phonological approach. The results of a longitudinal study, with children aged 12 to 35 months, showed that coronal consonants were associated with coronal vowels, labial consonants with labial vowels, and dorsal consonants with dorsal vowels. The observed patterns are interpreted as "phonological frames" which determines the amount of consonant-vowel co-articulation, in contrast with the "motor frames" in the F/C theory. In phonological approaches, "children learn to bring the domain of specification for Place of Articulation features down to individual segments" (Levelt, 1995, p.22). In particular, phonological theories stress that coronal is the "universally unmarked place of articulation". Under the principle of underspecification, combinations of coronal consonants with any vowels are favoured. While the motor constraints limit CV patterns production in early speech is proposed by the F/C theory, phonological theories stress the importance of places of articulation and the acquisition of individual segments. Some acoustic studies supported the notion that there may be minimal changes in the articulators across CV sequences" (Davis & MacNeilage, 1995, p. 1120). Nittrouer (1995) showed that children aged 3,5 and 7 moved away from consonant closure more slowly and initiated the vowel gesture sooner than adults for stop-vowel sequences. Sussman, Duder, Dalson & Cacciatore (1999) reported that, with the most limited range of variation, d-words yielded the most fronted vowels. The study also showed that vowels following 5 initial velars stops were modally the most back, and vowels follow initial labials were slightly more fronted. The authors also claimed that the production of [dV] syllables in words maintained a highly restricted occlusion location which was an example of maintenance and extension of articulatory patterns rooted in prelingual babbling to production of word in real speech.