Phonological constraints on children's production of English third person singular -s

Purpose: Children variably produce grammatical morphemes at early stages of development, often omitting inflectional morphemes in obligatory contexts. This has typically been attributed to immature syntactic or semantic representations. In this study, the authors investigated the hypothesis that children's variable production of the 3rd person singular morpheme -s interacts with the phonological complexity of the verb stem to which it is attached. Method: To explore this possibility, the authors examined longitudinal data from the spontaneous speech of 6 English-speaking children between ages 1;3 and 3;6 (years; months) and elicited imitations from a cross-sectional study of 23 two-year-olds (mean age of 2;2). Results: The results showed that children produced third person singular morphemes more accurately in phonologically simple coda contexts (e.g., sees) as compared with complex coda contexts (e.g., needs). In addition, children produced -s more accurately in utterance-final position as compared with utterance-medial position. Conclusions: The results provide strong support for the role of phonological complexity in explaining some of the variability in children's production of third person singular -s. This finding suggests that future research will need to consider multiple factors, including phonological and positional effects, in constructing a comprehensive developmental theory of both grammatical competence and processes of speech planning and production.