Articulatory variability is a phonological characteristic that can be observed
frequently from young children in early stage of phonological acquisition process.
It is also a characteristic that gradually disappear through progress of phoneme
learning by age (Sosa & Stoel Gammon, 2006). If it occurs with high ratio of undevelopmental
error pattern during long periods prominently, not appearing
during developmental error acquisition process, children can be diagnosed as
speech sound disorder such as childhood apraxia of speech(CAS; American
Speech Language Hearing Association[ASHA], 2007) and inconsistent disorder
(Dodd, 2005). Therefore, classifying characteristic of variability on normal children and inconsistency of disorder diagnosis sign and studying about
characteristic of articulatory variability on normal children will help on
understanding of articulatory variability.
According to many researches about variability, it is reported that children
before 50-word stage, early stage of phonological acquisition process, have high
variability in speech sound production. Also variability from normal children
during that period can be found in phonological system elements like consonant
and word structure, but this occurs due to incompletion of the process. Children
from 18 months to 36 months are reported to show extreme variability for
approaching adult phonological model as much as they can. In other word, it has
been reported that pronunciation from around 2 years old children in early stage
of phonological development has high variability.
Pervious domestic articulatory variability research was conducted mainly not
on spontaneous conversation of children but on word level. Most of researches
evaluated variability only on word level without reflection of information about
phonological variability. It is pretty rare to find research about 2 years old
children predicted to have the most variability. Therefore this research is going
to study on word variability and phonological variability of 24-36 months
children thought to have high variability due to incompletion of phonological
acquisition.
This study targets were 22 children whose ages are 24-36 months and
confirmed as normal development. The grout was divided into 24-30 months
group and 31-36 months group to compare about their development. Data was
gathered by visiting target children''s family and collecting of spontaneous utterances for 30 minutes. During data collection, parents and inspector
interacted with children freely using the same toy. Through recording data and
video data, sample of spontaneous utterances of children was phonetic
transcripted. Based on the transcripted data, percentage of correct consonant,
consonant inventory, phonological variability and word variability were analyzed.
Analysis, based on 30 minutes of sample of spontaneous utterances data
from children, to measure word variability was conducted by Eojeol. Sample of
spontaneous utterances of children was categorized omission, substitution,
addition and distortion error as articulation error. Measured value of articulatory
variability was designed based on measuring method from Dodd(1995) to find out
overall variability including correct articulation and articulation error of normal
children on spontaneous conversation. To find out differences of word variability
and phonological variability due to age, t-test was conducted on independent
sample and Pearson correlation analysis was conducted to find out correlation
among percentage of correct consonant, consonant inventory, word variability
and phonological variability.
As a result of independent sample t-test, word variability and phonological
variability in both groups are different significantly. Both word variability and
phonological variability seemed to appear more in 24-36 months children than
31-36 months children. Children seemed to have consistent articulation in word
and phonemes by age increase. From the result of Pearson correlation analysis,
word variability and phonological variability seemed have negative correlation
with percentage of correct consonant and consonant inventory. In other word, it
seemed that the lower the word variability and phonological variability, the higher the speech development measures such as percentage of correct
consonant and number of consonant inventory.
It appeared that word variability and phonological variability in case of 31-
36 months children are lower significantly than of 24-30 months children, with
gradually consistent articulation, which seems to be because of maturation of
phonological system and articulation organ''s movement control ability. Also
general development pattern of articulatory variability seems to decrease by
increasing percentage of correct consonant and number of consonant inventory.
This research suggested phonological characteristic that children around 2
years old show stable and consistent articulation pattern due to rapid
advancement of phonological acquisition. This result can be used to compare and
evaluate degree of articulatory variability on children who have inconsistent
phonological disorder or childhood apraxia of speech more objectively.