This review article presents evidence for the claim that frequency effects are pervasive in children's first language acquisition, and hence constitute a phenomenon that any successful account must explain. The article is organized around four key domains of research: children's acquisition of single words, inflectional morphology, simple syntactic constructions, and more advanced constructions. In presenting this evidence, we develop five theses. (i) There exist different types of frequency effect, from effects at the level of concrete lexical strings to effects at the level of abstract cues to thematic-role assignment, as well as effects of both token and type, and absolute and relative, frequency. High-frequency forms are (ii) early acquired and (iii) prevent errors in contexts where they are the target, but also (iv) cause errors in contexts in which a competing lower-frequency form is the target. (v) Frequency effects interact with other factors (e.g. serial position, utterance length), and the patterning of these interactions is generally informative with regard to the nature of the learning mechanism. We conclude by arguing that any successful account of language acquisition, from whatever theoretical standpoint, must be frequency sensitive to the extent that it can explain the effects documented in this review, and outline some types of account that do and do not meet this criterion.

To fully acquire a language, especially its phonology, children need linguistic input from native speakers early on. When interaction with native speakers is not always possible – e.g. for children learning a second language that is not the societal language – audios are commonly used as an affordable substitute. But does such non-interactive input work? Two experiments evaluated the usefulness of audio storybooks in acquiring a more native-like second-language accent. Young children, first- and second-graders in Hong Kong whose native language was Cantonese Chinese, were given take-home listening assignments in a second language, either English or Putonghua Chinese. Accent ratings of the children's story reading revealed measurable benefits of non-interactive input from native speakers. The benefits were far more robust for Putonghua than English. Implications for second-language accent acquisition are discussed.

This paper investigates the development of discourse referencing in spoken Cantonese of fifteen deaf/hard-of-hearing children studying in a sign bilingual and co-enrolment education programme in a mainstream setting in Hong Kong. A comparison of their elicited narratives with those of the hearing children and adults shows that, despite a delay in acquiring the grammatical markings for (in)definiteness in Cantonese, these d/hh children show sensitivity towards the referential properties of different types of nominal expressions and their corresponding mappings with discourse functions. Specifically, they produced more bare nouns across all discourse contexts but fewer existential constructions, pronouns, demonstratives, and classifier-related constructions. Their choice of nominal expressions and the observed errors show striking similarities to the productions by the younger hearing children in this study, suggesting that the d/hh children's route of development of discourse referencing is likely to be similar to that of hearing children despite a slower rate of development.

This study investigates the developmental trajectory of relative clauses (RCs) in Mandarin-learning children's speech. We analyze the spontaneous production of RCs by four monolingual Mandarin-learning children (0;11 to 3;5) and their input from a longitudinal naturalistic speech corpus (Min, 1994). The results reveal that in terms of the syntactic role of the head noun in the matrix clause, isolated noun phrase RCs dominate, followed by those that modify the subject or object of the matrix clauses and predicate nominal relatives. This pattern differs from those observed in English (Diessel & Tomasello, 2000), German (Brandt, Diessel & Tomasello, 2008), and Japanese (Ozeki & Shirai, 2007). Regarding the syntactic role of the head noun inside the RC (i.e. subject, object, or oblique relatives), the early RCs are dominated by object relatives. This pattern also differs from those observed in English and Japanese. We propose a multifactorial usage-based learning account for the developmental patterns.

In many contexts, pronouns are interpreted as referring to the character mentioned first in the previous sentence, an effect called the ‘first-mention bias’. While adults can rapidly use the first-mention bias to guide pronoun interpretation, it is unclear when this bias emerges during development. Curiously, experiments with children between two and three years old show successful use of order of mention, while experiments with older children (four to five years old) do not. While this could suggest U-shaped development, it could also reflect differences in the methodologies employed. We show that children can indeed use first-mention information, but do so too slowly to have been detected in previous work reporting null results. Comparison across the present and previously published studies suggests that the speed at which children deploy first-mention information increases greatly during the preschool years.

Monolingual infants are typically studied as a homogenous group and compared to bilingual infants. This study looks further into two subgroups of monolingual infants, monodialectal and multidialectal, to identify the effects of dialect-related variation on the phonological representation of words. Using an Intermodal Preferential Looking task, the detection of mispronunciations in familiar words was compared in infants aged 1;8 exposed to consistent (monodialectal) or variable (multidialectal) pronunciations of words in their daily input. Only monodialectal infants detected the mispronunciations whereas multidialectal infants looked longer at the target following naming whether the label was correctly produced or not. This suggests that variable phonological input in the form of dialect variation impacts the degree of specificity of lexical representations in early infancy.