French lexical–phonological development (Kehoe et al., 2020)

Purpose: This study examines the influence of lexical and phonological factors on expressive lexicon size in 40 French-speaking children tested longitudinally from 22 to 48 months. The factors include those based on the lexical and phonological properties of words in the children’s lexicons (phonetic complexity, word length, neighborhood density [ND], and word frequency [WF]) as well as variables measuring phonological production (percent consonants correct and phonetic inventory size). Specifically, we investigate the relative influence of these factors at individual ages, namely, 22, 29, 36, and 48 months, and which factors measured at 22 and 29 months influence lexicon size at 36 and 48 months.
Method: Children were selected based on parent-reported vocabulary size. We included children with low, medium, and high vocabulary scores. The children’s lexicons were coded in terms of phonetic complexity, word length, ND, and WF, and their phonological production skills were based on measures of percent consonants correct and phonetic inventory size extracted from spontaneous speech samples at 29, 36, and 48 months. In the case of ND and WF, we focused on one- and two-syllable nouns.
Results: Across the age range, the most important factor that explained variance in lexicon size was the WF of nouns. Children who selected low-frequency nouns had larger vocabularies across all ages (22–48 months). The WF of two-syllable nouns and phonological production measured at 29 months influenced lexicon size at 36 months, whereas the WF (of one- and two-syllable words) influenced lexicon size at 48 months.
Conclusions: The findings support the role of WF and phonological production in explaining expressive vocabulary development. Children enlarge their vocabularies by adding nouns of increasingly lower frequency. Phonological production plays a role in accounting for vocabulary size up until the age of 36 months.

Supplemental Material S1. Supplemental figures:
-Figure S1. Lexicon size across age in 40 French-speaking children.
-Figure S2. Mean phonetic complexity across age in 40 French-speaking children.
-Figure S3. Mean word length across age in 40 French-speaking children.
-Figure S4. Mean neighborhood density of one-syllable nouns across age in 40 French-speaking children.
-Figure S5. Mean neighborhood density of two-syllable nouns across age in 40 French-speaking children.
-Figure S6. Mean (log) word frequency of one-syllable nouns across age in 40 French-speaking children.
-Figure S7. Mean (log) word frequency of two-syllable nouns across age in 40 French-speaking children.
-Figure S8. Percent consonants correct across age in 40 French-speaking children.
-Figure S9. Syllable-initial phonetic inventory size across age in 40 French-speaking children.

Supplemental Material S2. Supplemental tables:
-Table S1. Correlation coefficients among dependent and predictor variables at 22 months.
-Table S2. Correlation coefficients among dependent and predictor variables at 29 months.
-Table S3. Correlation coefficients among dependent and predictor variables at 36 months.
-Table S4. Correlation coefficients among dependent and predictor variables at 48 months.
-Table S5. Correlation coefficients among predictor variables at ages 22 and 29 months and vocabulary size at 36 and 48 months (i.e., DLPF3tot & DLPF4tot).

Kehoe, M. M., Patrucco-Nanchen, T., Friend, M., & Zesiger, P. (2020). The relationship between lexical and phonological development in French-speaking children: A longitudinal study. Journal of Speech, Language, and Hearing Research. Advance online publication. https://doi.org/10.1044/2020_JSLHR-19-00011