We investigated developmental changes during the transition from one-word to two-word production, focusing on strategies to lengthen utterances phonologically and to control utterances suprasegmentally. We hypothesized that there is a period of reorganization at the onset of word combinations indicated by decreases in both filler syllables (Fillers) and final syllable lengthening (FSL). The data are from a visually impaired child (Seth) between 1 ; 6.21 and 1 ; 10.26. Seth produced many Fillers until 1 ; 9 when their number decreased for about two weeks after which they changed in nature. FSL was observed until 1 ; 8, but diminished at 1 ; 9. These two regressions coincide with the onset of word combination.

Infants struggle to understand familiar words spoken in unfamiliar accents. Here, we examine whether accent exposure facilitates accent-specific adaptation. Two types of pre-exposure were examined: video-based (i.e., listening to pre-recorded stories; Experiment 1) and live interaction (reading books with an experimenter; Experiments 2 and 3). After video-based exposure, Canadian English-learning 15- to 18-month-olds failed to recognize familiar words spoken in an unfamiliar accent. However, after face-to-face interaction with a Mandarin-accented talker, infants showed enhanced recognition for words produced in Mandarin English compared to Australian English. Infants with live exposure to an Australian talker were not similarly facilitated, perhaps due to the lower vocabulary scores of the infants assigned to the Australian exposure condition. Thus, live exposure can facilitate accent adaptation, but this ability is fragile in young infants and is likely influenced by vocabulary size and the specific mapping between the speaker and the listener's phonological system.

Is noun dominance in early lexical acquisition a widespread or a language-specific phenomenon? Thirty Singaporean bilingual English–Mandarin learning toddlers and their mothers were observed in a mother-child play interaction. For both English and Mandarin, toddlers’ speech and reported vocabulary contained more nouns than verbs across book reading and toy playing. In contrast, their mothers’ speech contained more verbs than nouns in both English and Mandarin but differed depending on the context of the interaction. Although toddlers demonstrated a noun bias for both languages, the noun bias was more pronounced in English than in Mandarin. Together, these findings support early noun dominance as a widespread phenomenon in the lexical acquisition debate but also provide evidence that language specificity also plays a minor role in children's early lexical development.

The key aim of this special issue is to make developmental theory proposals concrete enough to evaluate with empirical data. With this in mind, I discuss proposals from the “Universal Grammar + statistics” (UG+stats) perspective for learning several morphology and syntax phenomena. I briefly review why UG has traditionally been part of many developmental theories of language, as well as common statistical learning approaches that are part of UG+stats proposals. I then discuss each morphology or syntax phenomenon in turn, giving an overview of relevant UG+stats proposals for that phenomenon, specific predictions made by each proposal, and what we currently know about how those predictions hold up. I conclude by briefly discussing where we seem to be when it comes to how well UG+stats proposals help us understand the development of morphology and syntax knowledge.

Multi-accent environments offer rich but inconsistent language input, as words are produced differently across accents. The current study examined, in two experiments, whether multi-accent variability affects infants’ ability to learn words and whether toddlers’ prior experience with accents modulates learning. In Experiment 1, two-and-a-half-year-old Norwegian toddlers were exposed, in their kindergarten, twice per day for one week, to a child-friendly audiovisual tablet-based e-book containing four novel pseudowords. Half of the toddlers heard the story in three Norwegian accents, whereas the other half heard it in one Norwegian accent. The results revealed no differences between conditions, suggesting that multi-accent variability did not hinder toddlers’ word learning. In experiment 2, two-and-a-half-year-old Norwegian toddlers were exposed, in their homes, for one week, to the e-book featuring three Norwegian accents. The results revealed overall better learning in toddlers raised in bi-dialectal households, as compared to mono-dialectal peers – suggesting that accent exposure benefits learning in multi-accent environments.

In a longitudinal study concerned to assess Verb Phrase (VP) development in three Trinidadian children, adverbials were found to be crucial in delineating specific areas of semantic intent, and to develop early (between ages 2;3 and 3;0). The children were studied over a two-year period, from the onset of morphological marking on the verb, and were recorded two to four hours per month, in their home environments, with a variety of addressees. Two of the children were exposed to, and acquired, both TC and SE verb categories and the third, TC, but the existence of TC past-completive zero 0 as a prominent verbal marker in all their systems made for reliance on adverbial and extralinguistic context in delineating meaning intentions at an early stage;the use which they made of adverbial specification, in particular for marking perfect aspect, indicates how useful these elements may be for precise specification of the development of tense-aspect categories. When they are considered alongside other VP features a clearer overall assessment of tense–aspect development may be made.

This article reviews the proliferation of terms that have been coined to denote the language environment of the young child. It is argued that terms are often deployed by researchers without due consideration of their appropriateness for particular empirical studies. It is further suggested that just three of the dozen or more available terms meet the needs of child language researchers in most instances: child-directed speech, infant-directed speech and exposurelanguage. The phenomena denoted by these terms are then considered. The term register is generally borrowed for this purpose from sociolinguistics. However, close inspection of this concept reveals that the notion of register needs to be constrained, in specified ways, in order to be of any real value within the field of child language research.

Learning to mark for tense in a second language is notoriously difficult for speakers of a tenseless language like Chinese. In this study we test two reasons for these difficulties in Chinese–English sequential bilingual children: (1) morphophonological transfer (i.e., avoidance of complex codas), and (2) interpretation of –ed as an aspect marker of completion, like the Mandarin –le. Mandarin–English bilingual children and age-matched monolinguals did a cartoon retell task. The verbs used in the stories were coded for accuracy in English, telicity, and suppliance of –ed or –le. The results were consistent with morphophonological transfer: the bilingual children were more accurate with irregular past forms in English than regular forms. The results were also consistent with the bilingual children's interpretation of –ed as an aspect marker: most of their production of –ed was on telic verbs. We discuss possible reasons for the children's interpretation of –ed as an aspect marker.

This study presents the first investigation of the development of possessive constructions in Northern East Cree, a polysynthetic language indigenous to Canada. It examines transcripts from naturalistic recording sessions involving one adult and one child, from age 2;01.12 to 3;08.24. Findings reveal that, despite the frequency of possessive inflection in child-directed speech, the child overwhelmingly produces a possessive construction that circumvents this morphology. This construction, named here the equational possessive strategy (EPS), is largely undescribed in existing literature but is the primary mechanism for the child to express possession. These findings have potential implications for the cross-linguistic acquisition of possessive morphology and the connections between child-directed speech and child language production.

Laboratory observations are a mainstay of language development research, but transcription is costly. We test whether speech recognition technology originally designed for day-long contexts can be usefully applied to this use-case. We compared automated adult word and child vocalization counts from Language Environment Analysis (LENATM) to those of transcribers in 20-minute play sessions with Spanish-speaking dyads (n = 104) at 1;7 and 2;2. For adult words, results indicated moderate associations but large absolute differences. Associations for child vocalizations were weaker with larger absolute discrepancies. LENA has moderate potential to ease the burden of transcription in some research and clinical applications.

Several models of language acquisition have emerged in recent years that rely on computational algorithms for simulation and evaluation. Computational models are formal and precise, and can thus provide mathematically well-motivated insights into the process of language acquisition. Such models are amenable to robust computational evaluation, using technology that was developed for Information Retrieval and Computational Linguistics. In this article we advocate the use of such technology for the evaluation of formal models of language acquisition. We focus on the Traceback Method, proposed in several recent studies as a model of early language acquisition, explaining some of the phenomena associated with children's ability to generalize previously heard utterances and generate novel ones. We present a rigorous computational evaluation that reveals some flaws in the method, and suggest directions for improving it.

What are the sources of variation in the input, and how much do they matter for language acquisition? This study examines frequency variation in manner-of-articulation classes in child and adult input. The null hypothesis is that segmental frequency distributions of language varieties are unigram (modelable by stationary, ergodic processes), and that languages are unitary (modelable as a single language variety). Experiment I showed that English segments are not unigram; they exhibit a ‘bursty’ distribution in which the local frequency varies more than expected by chance alone. Experiment II showed the English segments are approximately unitary: the natural background variation in segmental frequencies that arises within a single language variety is much larger than numerical differences across varieties. Variation in segmental frequencies seems to be driven by variation in discourse topic; topic-associated words cause bursts/lulls in local segmental frequencies. The article concludes with some methodological recommendations for comparing language samples.

Young children's skilfulness in conversational interaction is of great importance in understanding pragmatic aspects of language development. The purpose of this investigation was to describe the portion of preschool verbal interaction which could not be considered successful dialogue. Ten dyads of four-year-olds were videotaped during free play. Segments of talk were identified as dialogue or non-dialogue. Non-dialogue was coded when one child did not appear to direct his/her utterances to the other or when an attempted topic failed to capture the interest of the other child. Thirteen types of non-dialogue were identified. Results revealed that all dyads exhibited non-dialogue, but differences were noted in regard to amount and type. Dyads labelled as less co-operative displayed greater amounts of self-directed talk (monologue).

This study examines potential predictors of ‘precocious talking’ (expressive language ⩾90th percentile) at one and two years of age, and of ‘stability’ in precocious talking across both time periods, drawing on data from a prospective community cohort comprising over 1,800 children. Logistic regression was used to examine the relationship between precocious talking and the following potential predictors: gender, birth order, birth weight, non-English speaking background, socioeconomic status, maternal age, maternal mental health scores, and vocabulary and educational attainment of parents. The strongest predictors of precocity (being female and having a younger mother) warrant further exploration. Overall, however, it appears that precocity in early vocabulary development is not strongly influenced by the variables examined, which together explained just 2·6% and 1% of the variation at 1 ; 0 and 2 ; 0 respectively.

We investigated whether manipulating the perceived novelty of nameless objects would influence two-year-olds' tendency to map novel words to these objects. In Experiment 1, children who had been pre-exposed to target nameless objects were more likely to map novel words onto those objects than children who were not pre-exposed to the objects or children who were pre-exposed to non-target members of the nameless object categories. In Experiment 2, children who were pre-exposed to a nameless object were more likely to assign the novel label to that object than to either a familiar object or an unfamiliar object that had not been pre-exposed. The results of these studies suggest that reducing the novelty of nameless objects increases two-year-olds' tendency to map a novel word to a nameless object.

MacWhinney's stimulating discussion suggests that there are many lines of argument that may address concerns raised by theorists who are concerned that there is a logical problem of language acquisition. This commentary argues: (1) that if the ‘logical problem’ applied to language, it would apply, with curious consequences to any learning by experience; (2) that the logical problem does not apply – given sufficient positive data from any reasonable language, language can be learned, in a probabilistic sense, by an ‘ideal learner’ using a simplicity principle; and (3) that a simplicity, or minimum description length, principle may provide a useful methodology for assessing claims concerning learnability of particular linguistic structures.

During communication, hearers try to infer the speaker's intentions to be able to understand what the speaker means. Nevertheless, whether (and how early) preschoolers track their interlocutors' mental states is still a matter of debate. Furthermore, there is disagreement about how children's ability to consult a speaker's belief in communicative contexts relates to their ability to track someone's belief in non-communicative contexts. Here, we study young children's ability to successfully acquire a word from a speaker with a false belief; we also assess the same children's success on a traditional false belief attribution task. We show that the ability to consult the epistemic state of a speaker during word learning develops between the ages of three and five. We also show that false belief understanding in word-learning contexts proceeds similarly to standard belief-attribution contexts when the tasks are equated. Our data offer evidence for the development of mind-reading abilities during language acquisition.

Verbs of agency denote relations between behavioural and mental states. Thus, ‘Jim is looking for X’ goes beyond a behavioural description, to take a mentalistic construal whereby Jim's desire for success, and his beliefs about how to search, explain his observed actions. Greek has two verbs of agency that can be used somewhat interchangeably by adults to mean ‘to look for’. The hypothesis is that young children will obey the principle of contrast to diagnose that one verb is mentalistic and the other verb is to be construed behaviourally. Following a study of mothers' verb-use, two studies with 238 children aged three to five years confirmed that the verb preferred in home use gave below-chance performance on a false-belief test whilst the less-established verb gave above-chance success, with children giving appropriate justifications. Thus, Greek preschoolers seem sometimes to have an adult-type understanding and sometimes fail to match the adult understanding. The proposal is that the children initially convert an adult verb-use pragmatic difference into a semantic contrast.