In Study 1 we analyzed Italian child-directed-speech (CDS) and selected the three most frequent active transitive sentence frames used with overt subjects. In Study 2 we experimentally investigated how Italian-speaking children aged 2;6, 3;6, and 4;6 comprehended these orders with novel verbs when the cues of animacy, gender, and subject–verb agreement were neutralized. For each trial, children chose between two videos (e.g., horse acting on cat versus cat acting on horse), both involving the same action. The children aged 2;6 comprehended S + object-pronoun + V (soprov) significantly better than S + V + object-noun (svonoun). We explain this in terms of cue collaboration between a low cost cue (case) and the firstargument = agent cue which we found to be reliable 76% of the time. The most difficult word order for all age groups was the object-pronoun + V + S (oprovs). We ascribe this difficulty to cue conflict between the two most frequent transitive frames found in CDS, namely V + object-noun and object-pronoun + V.

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.

We investigated longitudinal relations among gaze following and face scanning in infancy and later language development. At 12 months, infants watched videos of a woman describing an object while their passive viewing was measured with an eye-tracker. We examined the relation between infants' face scanning behavior and their tendency to follow the speaker's attentional shift to the object she was describing. We also collected language outcome measures on the same infants at 18 and 24 months. Attention to the mouth and gaze following at 12 months both predicted later productive vocabulary. The results are discussed in terms of social engagement, which may account for both attentional distribution and language onset. We argue that an infant's inherent interest in engaging with others (in addition to creating more opportunities for communication) leads infants to attend to the most relevant information in a social scene and that this information facilitates language learning.

Famously, dog bites man is trivia whereas man bites dog is news. This illustrates not just a fact about the world but about language: to know who did what to whom, we must correctly identify the mapping between semantic role and syntactic position. These mappings are typically predictable, and previous work demonstrates that young children are sensitive to these patterns and so could use them in acquisition. However, there is only limited and mixed evidence that children do use this information to guide acquisition outside of the laboratory. We find that children understand emotion verbs which follow the canonical CAUSE–VERB–PATIENT pattern (Mary frightened/delighted John) earlier than those which do not (Mary feared/liked John), despite the latter's higher frequency, suggesting children's generalization of the mapping between causativity and transitivity is broad and active in acquisition.

Within the first year of life, infants learn to segment words from fluent speech. Previous research has shown that infants at 0;7·5 can segment consonant-initial words, yet the ability to segment vowel-initial words does not emerge until the age of 1;1–1;4 (0;11 in some restricted cases). In five experiments, we show that infants aged 0;11 but not 0;8 are able to segment vowel-initial words that immediately follow the function word the [ði], while ruling out a bottom-up, phonotactic account of these results. Thus, function words facilitate the segmentation of vowel-initial words that appear sentence-medially for infants aged 0;11.

This paper investigates six- to nine-year-old children's acquisition of evidentiality. In two minimally different tasks we assess whether children can be made to use a particular source of information by presenting them with a specific evidential term. That is, we assess whether children have an explicit awareness of the source requirement of the evidential terms. The results demonstrate that children explicitly understand the direct evidential term, but not the indirect evidential terms. Interestingly, the direct evidential term tested (Dutch lijken) does not encode high speaker certainty. Hence, even though the child cannot rely on speaker certainty to provide an answer, the results still show that direct evidentiality is acquired before indirect evidentiality.

This study investigates the development of plural morphology in Jordanian Arab children, and explores the role of the predictability, transparency, productivity, and frequency of different plural forms in determining the trajectory that children follow in acquiring this complex inflectional system. The study also re-examines the development of the notion of default over several years. Sixty Jordanian children, equally divided among six age groups (three to eight years), completed an oral real-word pluralization task and a nonsense-word pluralization task. The findings indicate that feminine sound plurals are acquired before and extended to the other plural forms. Productivity and frequency seem to shape the acquisition patterns among younger children, but predictability becomes more critical at a later age. Younger children use the most productive plural as the default form, but older children tend to use two default forms based on frequency distributions in the adult language. The theoretical implications of the findings are discussed.

This longitudinal study involving 101 Dutch four- and five-year-olds charts indirect request (IR) and mental state term (MST) understanding and investigates the role that Theory of Mind (ToM) and general linguistic ability (vocabulary, syntax, and spatial language) play in this development. The results showed basic understanding of IR and MST in four-year-olds, but full understanding had not been reached even at five years old. Furthermore, although ToM predicted both IR and MST when linguistic ability was not taken into account, this relationship was no longer significant once the language measures were added. Linguistic ability thus seems to play an important role in the development of both IR and MST. Additional analyses revealed that whereas syntactic ability was the primary predictor of IR, spatial language was the best predictor of MST, suggesting that IR relies primarily on general linguistic skills, but that more specific aspects of language may bootstrap MST.

In this paper we report a large-scale developmental study of early productive vocabulary acquisition by 928 Chinese-speaking children aged between 1;0 and 2;6, using the Early Vocabulary Inventory for Mandarin Chinese (Hao, Shu, Xing & Li, 2008). The results show that: (i) social words, especially words for people, are the predominant type of words in Chinese-speaking children's earliest productive vocabulary; (ii) overall, Chinese-speaking children's vocabulary contains greater proportions of nouns than other word categories, especially at the earliest vocabulary stage; and (iii) verbs tend to appear earlier for Chinese-speaking children as compared with English-speaking children at the same levels of vocabulary development. In addition, our study has identified the underlying variables that influence the age of acquisition of words, specifically, the interplay between the conceptual (imageability) and linguistic properties (word frequency, word length, and grammatical category) that jointly shape the development of Mandarin-speaking children's early vocabulary.

Social deficits have been implicated in the language delays and deficits of children with autism (ASD); thus, the extent to which these children use language input in social contexts similarly to typically developing (TD) children is unknown. The current study investigated how caregiver input influenced the development of wh-question comprehension in TD children and language-matched preschoolers with ASD. Children were visited at four-month intervals over 1.5 years; mother–child play sessions at visits 1–2 were coded for maternal wh-question use. At visits 3–5 children watched videos in the Intermodal Preferential Looking paradigm, to assess their comprehension of subject and object wh-questions. Mothers' use of wh-questions with verbs and complex wh-questions positively predicted wh-question comprehension in the TD group; in contrast, mothers' use of wh-questions with ‘be’ as the main verb negatively predicted wh-question comprehension in the ASD group. Thus, TD children and children with ASD appear to use their linguistic input differently.

This study examined (a) the relationship between gesture and speech produced by children with specific language impairment (SLI) and typically developing (TD) children, and their mothers, during shared book-reading, and (b) the potential effectiveness of gestures accompanying maternal speech on the conversational responsiveness of children. Fifteen preschoolers with expressive SLI were compared with fifteen age-matched and fifteen language-matched TD children. Child and maternal utterances were coded for modality, gesture type, gesture–speech informational relationship, and communicative function. Relative to TD peers, children with SLI used more bimodal utterances and gestures adding unique information to co-occurring speech. Some differences were mirrored in maternal communication. Sequential analysis revealed that only in the SLI group maternal reading accompanied by gestures was significantly followed by child's initiatives, and when maternal non-informative repairs were accompanied by gestures, they were more likely to elicit adequate answers from children. These findings support the ‘gesture advantage’ hypothesis in children with SLI, and have implications for educational and clinical practice.

Existing studies have observed a robust relationship between infants' pointing gestures and language outcomes. By contrast, infants' overall vocal production is not related to language outcomes. One possible explanation for the association between pointing and language is that pointing gestures, as compared to vocalizations, may elicit more verbal responses from social partners that are facilitative for language learning. To test this, we observed forty-seven infants aged 1;0 during free play with their mothers and fathers separately to compare parents' verbal responses to infants' pointing gestures and object-directed vocalizations. Results showed that, compared to object-directed vocalizations, infants' pointing elicited more verbal responses from parents, particularly object labels. Moreover, mothers were more likely than fathers to provide labels. These results may help explain why pointing is associated with indices of language acquisition, but the production of vocalizations is not.

This paper examines the production of word-initial stops by two simultaneous trilingual sisters, aged 6;8 and 8;1, who receive regular input in Italian and English from multiple speakers, but in Spanish from only one person. The children's productions in each language were analyzed acoustically and compared to those of their main input providers. The results revealed consistent cross-linguistic differences by both children, including between Italian and Spanish stops, although these have identical properties in the speech of Italian- and Spanish-speaking adults. While the children's English stops were largely target-like, their Italian stops exhibited non-target-like realizations in the direction of English, suggesting interactions. Interestingly, their Spanish productions were largely unaffected by cross-linguistic interactions, with target-like voiceless stops, and voiced stops predominantly realized as spirants. These findings raise interesting questions about phonological development in multilingual settings and demonstrate that the number and type of input providers may crucially affect cross-linguistic interactions.

Monolingual children sometimes resist learning second labels for familiar objects. One explanation is that they are guided by word learning constraints that lead to the assumption that objects have only one name. It is less clear whether bilingual children observe this constraint. In the current study, we test the hypothesis that bilingual children might be more willing to accept second labels for objects and ask how they are affected by different amounts of information relevant to the second label. Although monolingual and bilingual children benefited from increased levels of information, only bilingual children chose the referent at above chance levels when they were offered increased levels of information. They were also more likely than monolingual children to accept second labels. Differences emerged even when English language vocabulary size was controlled for in the analyses.

Languages typically express semantic components of motion events such as manner (roll) and path (down) in separate lexical items. We explore how these combinatorial possibilities of language arise by focusing on (i) gestures produced by deaf children who lack access to input from a conventional language (homesign); (ii) gestures produced by hearing adults and children while speaking; and (iii) gestures used by hearing adults without speech when asked to do so in elicited descriptions of motion events with simultaneous manner and path. Homesigners tended to conflate manner and path in one gesture, but also used a mixed form, adding a manner and/or path gesture to the conflated form sequentially. Hearing speakers, with or without speech, used the conflated form, gestured manner, or path, but rarely used the mixed form. Mixed form may serve as an intermediate structure on the way to the discrete and sequenced forms found in natural languages.

Communicative Development Inventories (CDIs, parent-completed language development checklists) are a helpful tool to assess language in children who are unused to interaction with unfamiliar adults. Generally, CDIs are completed in written form, but in developing country settings parents may have insufficient literacy to complete them alone. We designed CDIs to assess language development in children aged 0;8 to 2;4 in two languages used in Coastal communities in Kenya. Measures of vocabulary, gestures, and grammatical constructions were developed using both interviews with parents from varying backgrounds, and vocabulary as well as grammatical constructions from recordings of children's spontaneous speech. The CDIs were then administered in interview format to over 300 families. Reliability and validity ranged from acceptable to excellent, supporting the use of CDIs when direct language testing is impractical, even when children have multiple caregivers and where respondents have low literacy levels.

There is a noted advantage of dense neighborhoods in language acquisition, but the learning mechanism that drives the effect is not well understood. Two hypotheses – long-term auditory word priming and phonological working memory – have been advanced in the literature as viable accounts. These were evaluated in two treatment studies enrolling twelve children with phonological delay. Study 1 exposed children to dense neighbors versus non-neighbors before training sound production in evaluation of the priming hypothesis. Study 2 exposed children to the same stimuli after training sound production as a test of the phonological working memory hypothesis. Results showed that neighbors led to greater phonological generalization than non-neighbors, but only when presented prior to training production. There was little generalization and no differential effect of exposure to neighbors or non-neighbors after training production. Priming was thus supported as a possible mechanism of learning behind the dense neighborhood advantage in phonological acquisition.

When learning their first language, children develop strategies for assigning semantic roles to sentence structures, depending on morphosyntactic cues such as case and word order. Traditionally, comprehension experiments have presented transitive clauses in isolation, and cross-linguistically children have been found to misinterpret object-first constructions by following a word-order strategy (Chan, Lieven & Tomasello, 2009; Dittmar, Abbot-Smith, Lieven & Tomasello, 2008; Hakuta, 1982; McDonald, 1989; Slobin & Bever, 1982). In an act-out study, we replicated this finding with Danish preschoolers. However, object-first clauses may be context-sensitive structures, which are infelicitous in isolation. In a second act-out study we presented OVS clauses in supportive and unsupportive discourse contexts and in isolation and found that five- to six-year-olds' OVS comprehension was enhanced in discourse-pragmatically felicitous contexts. Our results extend previous findings of preschoolers' sensitivity to discourse-contextual cues in sentence comprehension (Hurewitz, 2001; Song & Fisher, 2005) to the basic task of assigning agent and patient roles.