Figure 1.
The classification of serial order in articulations in the previous and present studies.
(A) The place of articulations for consonants and vowels, and articulatory organs involved in each consonant. Depending on the horizontal position of the tongue, vowels are categorized into three types including front, center and back. This figure illustrates three places of articulations, including labial, coronal and dorsal. Labial consonants are mainly articulated by the lips and jaw. Coronal consonants are mainly articulated by the tongue apex and jaw. Dorsal consonants are mainly articulated by the tongue dorsum and jaw. (B) Three consonant-vowel patterns preferred by infants in early development. Focusing on three consonantal and vowel categories, theoretically speaking, it is possible to produce nine consonant-vowel sequences. However, infants prefer three out of those nine possible sequences: labial-center, coronal-front, and dorsal-back [11], [12]. (C) Serial order in articulation of consonants in consonant-vowel-consonant(-vowel) sequences. In the present study, focusing on the relationship among articulators producing adjacent consonants, we divided sequences into four categories: (i) Sequences consists of consonants produced at the same place of articulation. (ii) Sequences produced by movements from more anterior place to posterior one. (iii) Sequences consist of coronal and dorsal consonants, which are articulated by the same organ but different places (intra-organ articulations). (iv) Sequences consist of labial and coronal/dorsal consonants, which are articulated by different organs: lips and tongue (inter-organ articulations).
Figure 2.
The developmental changes in serial order in articulation of consonants obtained by the analysis of individual and group data for Japanese.
Middle and right columns show developmental curves obtained by the analysis of individual and group data for Japanese, respectively. Each row indicates (i) repetitions, (ii) fronting, (ii) intra-organ articulations, and (iv) inter-organ articulations. In the middle column, circles, squares and triangles denote relative ratio of each type of CVC patterns produced by child B, child C and child D, respectively. Black, gray and silver curves indicate that developmental curves of child B, child C and child D, respectively. In the right column, circles and lines denotes relative ratio of each type of CVC patterns obtained from pooled data and developmental curves of them, respectively. The shaded areas indicate periods between onset and offset of the developmental changes. We defined the onsets and offsets as months at which a value of curves exceeded 1/3 and 2/3, respectively.
Figure 3.
The developmental changes of durations of CVCV sequences in Japanese children’s speech.
The solid and dash lines denote mean durations of CVCV sequences and ± 1 standard deviations obtained from the group data. The blue, red and gray markers show the individual analysis for the Japanese children denoting means duration of CVCV sequences.
Figure 4.
The developmental curve of each fronting pattern in Japanese.
The black, gray and silver lines show developmental curves of the labial-vowel-coronal, labial-vowel-dorsal, and coronal-vowel-dorsal sequences, respectively. The circles, squares and triangles show raw fronting indices of the labial-vowel-coronal, labial-vowel-dorsal and coronal-vowel-dorsal sequences, respectively.
Figure 5.
The comparison between change in ratios of the repetitions, fronting, intra- and inter-organ articulations in Japanese child-directed and children’s speech.
Changes in the ratio of occurrences of the repetitions, intra- and inter-organ articulations to the total CVC(V) occurrences, and the fronting index were plotted over months of age for Japanese child-directed speech produced by parents (black) and children’s speech (gray).
Figure 6.
The developmental changes in serial order in articulation of consonants obtained by the analysis of individual and group data for English.
The Middle and right columns show developmental curves obtained by the analysis of individual and group data for Japanese, respectively. Each row indicates (i) repetitions, (ii) fronting, (ii) intra-organ articulations, and (iv) inter-organ articulations. In the middle column, circles and squares denote relative ratio of each type of CVC patterns produced by child 1 and child 2, respectively. Black and gray curves indicate that developmental curves of child 1 and child 2, respectively. In the right row, circles and curves denotes that relative ratio of each type of CVC patterns obtained by the analysis of group data and developmental curve of them, respectively. The shaded areas indicate periods between onset and offset of the developmental changes. We defined the onsets and offsets as months at which a value of curves exceeded 1/3 and 2/3, respectively.
Figure 7.
The developmental curve of each fronting pattern in English.
The black, gray and silver lines show developmental curves of the labial-vowel-coronal, labial-vowel-dorsal, and coronal-vowel-dorsal sequences, respectively. The circles, squares and triangles show raw fronting indices of the labial-vowel-coronal, labial-vowel-dorsal and coronal-vowel-dorsal sequences, respectively.