Articulatory Variability in 24- to 36-Month-Old Typically Developing Children

Abstract

Objectives:This study aims to investigate the articulatory variability of word and phoneme production on spontaneous utterance samples in typically developing children age 24 to 36 months. Methods: Speech samples were collected from 11 children age 24 to 30 months and 11 children age 31 to 36 months. Word variability, phoneme variability, percentage of consonants correct (PCC), and consonant inventory were measured. Eojeol was a basic unit for analysis of word variability. Both correct articulations and error productions were included for the variability analysis. Statistical analyses were conducted to investigate whether word and phoneme variability measures were different between the two age groups and if there were relationships between articulatory variability measures and PCC and consonant inventory. Results: For the children age 24 to 30 months, 51.55% of Eojeols which were produced more than twice showed variable productions and 69% of consonants in the consonant inventory showed variability. For children age 31 to 36 months, word variability and phoneme variability were 36.45% and 52.45%, respectively. Both variability measures showed significantly negative correlation with PCC and consonant inventory. Conclusion: This study suggests that 2-year-old children show progressively stable and consistent articulation patterns along with phonological acquisition. The results of this study have implications for evaluating the degree of articulatory variability in children who have inconsistent phonological disorders or childhood apraxia of speech.이 시기에 변이성이 나타나는 것은 자음이나 낱말 구 조와 같은 음운체계 요소들이 아직 완성되지 못했기 때문이라고 하였다. Dyson과 Paden (1983)은 2세 아동의 음운 습득 전략에 대 한 종단연구에서 18개월에서 36개월 사이의 아동은 성인의 모델에 최대한 도달하기 위해 극심한 변이성을 나타내는 연령대라고 보고 하였다. 또한 Sosa와 Stoel-Gammon (2006)도 1-2세 아동을 대상 으로 종단연구를 실시하였는데 낱말조합이 일어나는 시기에 변이 성이 정점에 달했다고 보고하였다. 전반적으로 많은 연구에서 초기 음운발달 시기인 2세 무렵에 조음 측면에서 높은 변이성이 나타났 다고 하였다. 아동의 조음 변이성을 객관적으로 측정하기 위해 여러 연구자들 이 검사도구와 다양한 측정방법을 제안하였다. 먼저 단어 변이성 측정에 대한 연구로 Dodd, Zhu, Crosbie, Holm 그리고 Ozanne (2002)은 조음음운 진단평가(Diagnostic Evaluation of Articulation and Phonology, DEAP)라는 표준화된 검사도구를 개발하면 서 하위 검사항목으로 비일관성 평가를 포함시켰고 비일관성에 대 한 규준 자료를 제시하였다. 측정방법으로 구조화된 25개의 그림 에 대한 이름대기 과제를 사용하여, 아동의 변이성 산출비율을 구 하였다. Ingram (2002)은 조음 변이성의 측정방법으로 단어 단위 변이성 비율(proportion of whole-word variation, PWV)을 제안하 였는데, 단어당 서로 다른 음운 형태로 산출된 단어의 유형수를 해 당 단어가 산출된 수로 나누어 측정한다. 예를 들어 세 번 산출된 단어의 형태가 모두 동일하면 PWV는 0 (0/3)이 되고 세 번 모두 다 른 형태로 산출되었다면 PWV는 1 (3/3)이 된다. 따라서 수치가 높 을수록 단어를 다양한 음운 형태로 산출함을 의미한다. Betz와 Stoel-Gammon (2005)은 목표단어의 오류 횟수에 대한 오류유형 의 변이성을 측정할 수 있는 조음오류 변이성(overall consistency of error types) 공식을 제안하였다. Ingram (2002)의 PWV는 목표 단어의 정조음과 조음오류를 포함한 전반적인 조음 변이성을 나타 내는 측정치이고 Betz와 Stoel-Gammon (2005)의 조음오류 변이 성은 목표단어의 조음오류만을 포함시킨 측정치이다. 음소 변이성 측정에 대한 연구를 살펴보면, Tyler, Lewis 그리고 Welch (2003)는 음소의 오류 일관성을 측정하기 위해 23개의 음소에서 대치되어 산출된 서로 다른 음소의 총 수를 계산하는 오류 일관성 지수(Error Consistency Index, ECI)를 제시하였다. Isermann (2001)은 단 어 내 음소 위치에서 비일관적 오류 비율로 비일관적인 오류가 나 타난 음소의 총 수를 목표 음소의 총 수로 나누어 계산하는 S IC Total (percent inconsistently correct out of total...

Connected speech of two-year-olds: Test-retest reliability for assessment of phonetic inventory and word shape analysis

“…However, it should be noted that researchers have reported on a lack of articulatory stability across children's speech sound productions and found high variability for children within this study's age group (see McLeod & Hewett [13]). While variability of productions may decrease with age (Holm et al, [11]), it does not entirely dissipate and may continue to limit the reliable use of independent measures across populations of young children as well as populations presenting with speech sound disorders [12].…”

“…However, work with young children presents unique challenges to determining the consistent and reliable use of phonetic analyses due to variable word productions observed. The presence of normal articulatory variability complicates evaluation of speech sound production for young children (for an in-depth discussion see [11][12][13]). As noted above, Ferguson and Farwell [6], suggested that young children do not use phonemes as the minimal unit of lexical representation; rather, they organize with the syllable or word level as the minimal unit.…”

Clinical Challenges: Assessing Toddler Speech Sound Productions

“…46 and has been noted by numerous researchers even for children with typical development. [46][47][48][49][50][51] The presence of intraword variability is particularly noticeable in the speech of 2-and 3-yearolds. 46,[49][50][51] While still observed in the speech of 3-year-olds, intraword variability tends to gradually decrease with age 51 making it a clinical consideration especially relevant to evaluating toddler speech sound productions.…”

A Data-Driven Approach for Perceptually Validated Acoustic Features for Children’s Sibilant Fricative Productions

“…The graph was represented as an adjacency matrix A, such that its value on row i and column j is Ai,j = w(i, j) (see equation (3)) if vertices i and j are adjacent in the graph, and 0 otherwise. The embedding into a low-dimensional space was found by solving the generalized eigenvalue problem…”

“…Accuracy and variability have been measured in multiple ways. For example, accuracy traditionally is assessed using phonetic transcription by trained observers; these transcriptions can then be used to assess variability, by counting the number of different symbols that are used to transcribe multiple productions of the same target sound (e.g., [1], [2], [3]). Accuracy can also be measured in a more granular token-by-token basis by presenting multiple listeners with a word (or an excised syllable, etc.)…”