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

https://doi.org/10.23641/asha.12291074