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 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.

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.

We tested four predictions based on the assumption that optional infinitives can be attributed to properties of the input whereby children inappropriately extract non-finite subject–verb sequences (e.g. the girl run) from larger input utterances (e.g. Does the girl run? Let's watch the girl run). Thirty children with specific language impairment (SLI) and thirty typically developing children heard novel and familiar verbs that appeared exclusively either in utterances containing non-finite subject–verb sequences or in simple sentences with the verb inflected for third person singular -s. Subsequent testing showed strong input effects, especially for the SLI group. The results provide support for input-based factors as significant contributors not only to the optional infinitive period in typical development, but also to the especially protracted optional infinitive period seen in SLI.

Previous studies have shown that infant-directed speech (IDS) differs from adult-directed speech (ADS) on a variety of dimensions. The aim of the current study was to investigate whether acoustic differences between IDS and ADS in English are modulated by prosodic structure. We compared vowels across the two registers (IDS, ADS) in both stressed and unstressed syllables, and in both utterance-medial and -final positions. Vowels in target bisyllabic trochees in the speech of twenty mothers of 4- and 11-month-olds were analyzed. While stressed and unstressed vowels differed between IDS and ADS for a measure of F0, and trended in similar directions for vowel peripherality, neither set differed in duration. These profiles held for both utterance-medial and -final words.

Research with adults has shown that spoken language processing is improved when listeners are familiar with talkers' voices, known as the familiar talker advantage. The current study explored whether this ability extends to school-age children, who are still acquiring language. Children were familiarized with the voices of three German–English bilingual talkers and were tested on the speech of six bilinguals, three of whom were familiar. Results revealed that children do show improved spoken language processing when they are familiar with the talkers, but this improvement was limited to highly familiar lexical items. This restriction of the familiar talker advantage is attributed to differences in the representation of highly familiar and less familiar lexical items. In addition, children did not exhibit accent-general learning; despite having been exposed to German-accented talkers during training, there was no improvement for novel German-accented talkers.

To achieve language proficiency, infants must find the building blocks of speech and master the rules governing their legal combinations. However, these problems are linked: words are also built according to rules. Here, we explored early morphosyntactic sensitivity by testing when and how infants could find either words or within-word structure in artificial speech snippets embodying properties of morphological constructions. We show that 12-month-olds use statistical relationships between syllables to extract words from continuous streams, but find word-internal regularities only if the streams are segmented. Seven-month-olds fail both tasks. Thus, 12-month-olds infants possess the resources to analyze the internal composition of words if the speech contains segmentation information. However, 7-month-old infants may not possess them, although they can track several statistical relations. This developmental difference suggests that morphosyntactic sensitivity may require computational resources extending beyond the detection of simple statistics.

Cross-linguistic influence (CLI) refers to the linguistic influence of one of a bilingual's languages while processing the other. Researchers have debated whether CLI is better explained by the structure of bilinguals' two languages or by a combination of processing demands and structure. In this study, we test if Welsh–English bilingual children manifest CLI when producing adjectival constructions. Welsh adjectives typically appear postnominally, English adjectives typically appear prenominally. Since these structures do not overlap, there may be no CLI. If, however, CLI is a result of competition between languages, children's adjectival constructions may be reversed in both languages. We elicited adjectival constructions from Welsh–English bilingual children and English monolingual children between three and six years of age. The bilingual children produced more reversals than monolinguals and equivalent rates of reversals in both languages. In other words, the results support an interpretation of CLI resulting, at least in part, from processing demands.

The gender and number of a direct object clitic pronoun are based on the gender and number of the noun to which it refers. Grammatical gender is an intrinsic property of the lexical item that is independent from the natural sex of referents, whereas number is a non-intrinsic feature of nouns based on the conceptual level of quantity. The aim of this paper is to investigate children's ability in matching Italian direct object clitic pronouns to an inanimate visual referent on the basis of number or gender information. The dependent variables are accuracy and response time. A total of sixty-nine children aged from 4;6 to 7;5 participated. The results show that children are more accurate and faster in selecting the referent when they use number information compared to the condition in which this matching operation is led by gender.

This study examines whether lexical repetition, syntactic skills, and working memory (WM) affect children's syntactic-priming behavior, i.e. their tendency to adopt previously encountered syntactic structures. Children with Specific Language Impairment (SLI) and typically developing (TD) children were primed with prenominal (e.g. the yellow cup) or relative clause (RC; e.g. the cup that is yellow) structures with or without lexical overlap and performed additional tests of productive syntactic skills and WM capacity. Results revealed a reliable syntactic-priming effect without lexical boost in both groups: SLI and TD children produced more RCs following RC primes than following prenominal primes. Grammaticality requirements influenced RC productions in that SLI children produced fewer grammatical RCs than TD children. Of the additional measures, WM positively affected how frequently children produced dispreferred RC structures, but productive syntactic skills had no effect. The results support an implicit-learning account of syntactic priming and emphasize the importance of WM in syntactic priming tasks.