The English modal system is complex, exhibiting many-to-one, and one-to-many, form-function mappings. Usage-based approaches emphasise the role of the input in acquisition but rarely address the impact of form-function mappings on acquisition. To test whether consistent form-function mappings facilitate acquisition, we analysed two dense mother-child corpora at age 3 and 4. We examined the influence on acquisition of input features including form-function mapping frequency and the number of functions a modal signifies, using innovative methodological controls for other aspects of the input (e.g., form frequency) and child characteristics (e.g., age as a proxy for socio-cognitive development). The children were more likely to produce the frequent modals and form-function mappings of their input but modals with fewer functions in caregiver speech did not promote acquisition of these forms. Our findings support usage-based approaches to language acquisition and demonstrate the importance of applying appropriate controls when investigating relationships between input and development.

We analysed both structural and functional aspects of sentences containing the four adverbials “after”, “before”, “because”, and “if” in two dense corpora of parent-child interactions from two British English-acquiring children (2;00–4;07). In comparing mothers’ and children's usage we separate out the effects of frequency, cognitive complexity and pragmatics in explaining the course of acquisition of adverbial sentences. We also compare these usage patterns to stimuli used in a range of experimental studies and show how differences may account for some of the difficulties that children have shown in experiments. In addition, we report descriptive data on various aspects of adverbial sentences that have not yet been studied as a resource for future investigations.

Inflection impairments are commonly noted in aphasia, particularly non-fluent variants, where descriptions of such difficulties often focus on inflection omission. This aligns with rule-based theory, in which inflected forms should be more difficult to produce than their uninflected counterparts. Recent studies address noun inflection for number and potential effects of the relative frequency of singular and plural forms (dominance effects). However, none examine number errors qualitatively or in spontaneous speech. We present quantitative and qualitative analyses of such errors in nouns produced by twelve people with aphasia in spoken Cinderella narratives, examining: error rate; error types and nouns involved; relationship between error production and dominance; and speakers’ consistency with error production and flexibility in varying the noun forms concerned. Twelve unimpaired speakers provide comparison data. While error rates were low, arguably more important is error type. Singularisation and pluralisation errors were observed, all on regular nouns and involving production of the dominant form. The pluralisation errors, all occurring on references to Cinderella’s glass slipper, arguably challenge rule-based predictions that the singular is easier to retrieve than the plural. We suggest constructivist, usage-based theory as a promising framework to characterise such productions. Implications for aphasiology and clinical practice are also discussed.

The positive effects of shared book reading on vocabulary and reading development are well attested (e.g., Bus, van Ijzendoorn, & Pellegrini, 1995). However, the role of shared book reading in grammatical development remains unclear. In this study, we conducted a construction-based analysis of caregivers’ child-directed speech during shared book reading and toy play and compared the grammatical profile of the child-directed speech generated during the two activities. The findings indicate that (a) the child-directed speech generated by shared book reading contains significantly more grammatically rich constructions than child-directed speech generated by toy play, and (b) the grammatical profile of the book itself affects the grammatical profile of the child-directed speech generated by shared book reading.