The types of gesture+speech combinations children produce during the early stages of language development change over time. This change, in turn, predicts the onset of two-word speech and thus might reflect a cognitive transition that the child is undergoing. An alternative, however, is that the change merely reflects changes in the types of gesture+speech combinations that their caregivers produce. To explore this possibility, we videotaped 40 American child–caregiver dyads in their homes for 90 minutes when the children were 1;2, 1;6, and 1;10. Each gesture was classified according to type (deictic, conventional, representational) and the relation it held to speech (reinforcing, disambiguating, supplementary). Children and their caregivers produced the same types of gestures and in approximately the same distribution. However, the children differed from their caregivers in the way they used gesture in relation to speech. Over time, children produced many more REINFORCING (bike+point at bike), DISAMBIGUATING (that one+point at bike), and SUPPLEMENTARY combinations (ride+point at bike). In contrast, the frequency and distribution of caregivers' gesture+speech combinations remained constant over time. Thus, the changing relation between gesture and speech observed in the children cannot be traced back to the gestural input the children receive. Rather, it appears to reflect changes in the children's own skills, illustrating once again gesture's ability to shed light on developing cognitive and linguistic processes.

Most studies on CV co-occurrence patterns in early phonetic development have been based on Indo-European languages. Data from infants learning Mandarin, which has a substantially different phonological system from Indo-European languages, can confirm or refute the findings of previous studies, thus shedding further light on the theoretical bases of CV association. Spontaneous vocalizations were recorded in 45-minute sessions for each of 24 Mandarin-learning infants aged 0;7 to 1;6. In addition, the speech production of 24 caregivers was audio-recorded during their natural daily interactions with the infants at home. Both infants' vocalizations and adults' speech were transcribed and analysed for consonant–vowel co-occurrence patterns. These patterns were similar to those in other language groups, but language-specific patterns were evident by 1;0. Combinations of alveolars+front vowels and velars+back vowels confirm Davis & MacNeilage's (1990, 1995) frame-then-content theory and Clements's (1991) model of unified features for consonants and vowels. However, our finding of a language-specific pattern (labials+back vowels) suggests the need to reexamine the ‘pure frame’ of Davis & MacNeilage and Clements's grouping of labials and rounded vowels.

Properties of the input, such as raw frequency and syntactic diversity, have been shown to play a role, to different extents, in the acquisition of nouns and verbs. This study investigated the relationship between three properties of the input (input frequency, syntactic diversity, and variety in noun-type co-occurrence) and age of acquisition of English adjectives. In addition, this study explored the relationship between adjectival semantic typology and order of acquisition. The data are 7262 child utterances and 6318 maternal utterances containing one of 272 adjective in the language samples of two children, Sarah and Adam, from age 2;3 to 5;0 (Brown, 1973) available in CHILDES (MacWhinney, 2000). Statistical analyses revealed that all three properties of the input were significantly correlated with age of acquisition, but variety in noun-type co-occurrence was not a significant predictor once input frequency and syntactic diversity were taken into account. Semantic analyses revealed that the distribution of adjective types and tokens differed between the children and the mothers (to an extent) when the data were examined in terms of adjectival semantic types. The results suggest that both properties of the input and the semantic properties of the English adjective class play a role in its acquisition.

This is a study of the lexical and grammatical abilities of 16 lexically precocious talkers. These children, aged 2;0 were compared to their age-matched peers, 22 typical talkers aged 2;0, and their expressive vocabulary-matched peers, 22 typical talkers aged 2;6. Individual differences in children's lexical knowledge at 2;0 were stable – evident in parent report, laboratory observation, and an experimental fast-mapping paradigm. In accordance with the continuity hypothesis, the lexically precocious children were also grammatically precocious, having a greater representation of grammatical types and tokens and more advanced combinatorial language than their typical age-matches. Their grammatical development was very similar to that of their older vocabulary-matched peers. Limits on continuity were highly constrained with no true dissociation between the lexicon and the grammar in 33 cases examined. We conclude that, among two-year-olds, grammatical development is more tightly associated with the size of the lexicon than with chronological age.

Auxiliary syntax is recognized to be one of the more complex aspects of language that children must acquire. However, there is much disagreement among researchers concerning children's early understanding of auxiliaries, with some researchers advocating a relatively abstract grammar as the basis for auxiliary syntax, while others view the acquisition of auxiliary syntax as the gradual accumulation of linguistic knowledge, initially tied to individual lexical items. To investigate the status of children's early knowledge of auxiliary syntax, two studies were carried out. In study 1, 28 children (M=3;1) were tested for their use of the auxiliaries BE and HAVE in declaratives, while in study 2, 19 children (M=3;3) were tested for their use of these auxiliaries in questions. Although overall error rates were low, there were differences between BE and HAVE in the proportion and types of errors observed in declaratives and questions, and some individual children showed very high error rates. The implications of these findings for different models of auxiliary syntax in children's early utterances are discussed.

Why are young children's utterances short? This elicited imitation study used a new task – double imitation – to investigate the factors that contribute to children's failure to lexicalize sentence subjects. Two-year-olds heard a triad of sentences singly and attempted to imitate each; they then again heard the same triad singly and again attempted to imitate each. Comparisons between the two attempts showed that children's second passes were more accurate than their first. In addition, independent of sentence length, children increased their inclusion of pronominal and expletive but not lexical subjects. Children included verbs more often from sentences with pronominal than lexical subjects, suggesting a trade-off. Children included subjects more often in short sentences than long ones, and increased subject inclusion only in short sentences. The results suggest that children's language production is similar to adults': a complex interaction of syntactic knowledge, limited cognitive resources, communicative goals, and conversational structure.

Effects of negative input for 13 categories of grammatical error were assessed in a longitudinal study of naturalistic adult–child discourse. Two-hour samples of conversational interaction were obtained at two points in time, separated by a lag of 12 weeks, for 12 children (mean age 2;0 at the start). The data were interpreted within the framework offered by Saxton's (1997, 2000) contrast theory of negative input. Corrective input was associated with subsequent improvements in the grammaticality of child speech for three of the target structures. No effects were found for two forms of positive input: non-contingent models, where the adult produces target structures in non-error-contingent contexts; and contingent models, where grammatical forms follow grammatical child usages. The findings lend support to the view that, in some cases at least, the structure of adult–child discourse yields information on the bounds of grammaticality for the language-learning child.

This study focuses on parent–child book reading and its connection to the development of a theory of mind. First, parents were asked to report about frequency of parent–child storybook reading at home. Second, mothers were asked to read four picture-books to thirty-four children between 4;0 and 5;0. Both frequency of parent–child storybook reading at home, and mother's use of mental state terms in picture-books reading tasks were significantly associated with success on false belief tasks, after partialling out a number of potential mediators such as age of children, verbal IQ, paternal education, and words used by mothers in joint picture-book reading. Among the different mental state references (cognitive terms, desires, emotions and perceptions), it was found that the frequency and variety of cognitive terms, but also the frequency of emotional terms correlated positively with children's false belief performance. Relationships between mental state language and theory of mind are discussed.