Input and development in Cantonese-speaking monolingual, bilingual and trilingual three-year-olds

Abstract

Infants and toddlers acquire language(s) mainly based on the language input during naturalistic interactions with their caretakers. Both the amount and the quality of input are strongly associated with developmental outcomes. This thesis examines the complex input-outcome relations in Cantonese monolingual, Cantonese-English bilingual and Cantonese-Mandarin-English trilingual toddlers (3;0) through three independent and interrelated studies. The studies are based on data drawn from the Early Additive Child Multilingual Corpus (EACMC) and its accompanying dataset, jointly constructed by the author of the thesis and collaborators. Input characteristics and outcomes were derived from parental reports and caretaker-child standard interactions.

The first study examines individual differences in input and outcomes, and their sources of variation in 25 monolingual Cantonese caretaker-child dyads. Input was investigated through the lens of well-established linguistic features (e.g., lexical diversity, grammatical complexity) and a number of understudied interactive features (e.g., number of conversational turns). The results reveal substantial variation in both input and outcomes, consistent with previous Western studies. Nevertheless, the variation was conditioned by factors that differ from those identified in the Western population. Our findings highlight the important role of the broader social context in shaping input and outcomes in early language acquisition.

In the second study, 34 bilingual children were compared with their monolingual peers (participants in Study 1) in terms of vocabulary, grammatical complexity and 18 specific grammatical structures in Cantonese. This study also investigates the extent to which input quality accounts for individual differences in bilingual children after the proportion of input. The bilingual children showed reduced complexity in their Cantonese utterances, compared to the monolingual baseline. The results show that the bilingual children were below the monolingual group on grammatical complexity and structures specific to Cantonese but were comparable on structures shared by both Cantonese and English. The grammatical complexity of input explained an additional 17% of the variance in bilingual children’s Cantonese vocabulary size after input proportion, SES and cognition.

The third study investigated the extent to which proportional measures of input in a language predict outcomes in the same language in Cantonese-Mandarin-English bilingual children. Crosslinguistic influences between the two closely-related Chinese languages (Cantonese and Mandarin) are also examined. The results reveal that Cantonese and Mandarin developed in tandem despite a large gap in the proportion of input. The children were more productive with Cantonese-Mandarin translation equivalents with similar phonological forms than those with distinct forms. The findings of this study and those of the second study suggest that multilingual children might develop early sensitivity to linguistic similarities and strategically leverage such overlaps to support the buildup of multiple systems, tackling the challenge of input reduction.

Taken together, the three studies illuminate how factors at different levels (social context, caregiving structures) interact to shape input and outcomes and demonstrate that input-outcome relations in multilingual development are moderated by language distance and similarity as well as children's ability to utilize crosslinguistic overlaps.

Date of Award	3 Mar 2026
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Yuet Hung Cecilia CHAN (Supervisor) & Ziyin Maggie MAI (External Co-Supervisor)