Vocabulary development of three children (aged 1;6–1;8 at the start of the study) who had not begun to evidence a vocabulary spurt even though their productive vocabularies already included well over 50 words was followed to determine if these children eventually would have a vocabulary spurt. All three children evidenced a spurt, beginning at a mean productive vocabulary size of 112 words. The vocabulary spurt occurred at about the same time as the children first demonstrated the ability to sort objects exhaustively and to fast map new object names. Results are discussed in the context of Goldfield & Reznick's (1990; Reznick & Goldfield, 1992) argument that a substantial proportion of children never evidence a vocabulary spurt.

There are numerous models of how speech segmentation may proceed in infants acquiring their first language. We present a framework for considering the relative merits and limitations of these various approaches. We then present a model of speech segmentation that aims to reveal important sources of information for speech segmentation, and to capture psycholinguistic constraints on children's language perception. The model constructs a lexicon based on information about utterance boundaries and deduces phonotactic constraints from the discovered lexicon. Compared to other models of speech segmentation, our model performs well in terms of accuracy, computational tractability and the number of components of the model. Finally, our model also reflects the psycholinguistic effects of language learning, in terms of the early advantage for segmentation provided by the child's name, and by revealing the overlap in usefulness of information for segmentation and for grammatical categorization of the language.

What is the function of babbling in language learning? We examined the structure of parental speech as a function of contingency on infants’ non-cry prelinguistic vocalizations. We analyzed several acoustic and linguistic measures of caregivers’ speech. Contingent speech was less lexically diverse and shorter in utterance length than non-contingent speech. We also found that the lexical diversity of contingent parental speech only predicted infant vocal maturity. These findings illustrate a new form of influence infants have over their ambient language in everyday learning environments. By vocalizing, infants catalyze the production of simplified, more easily learnable language from caregivers.

We investigated infant precursors of low language scores in early childhood. The sample included 373 probands in 130 monozygotic (MZ) and 109 same-sex dizygotic (DZ) twin pairs in which at least one member of the pair scored in the lowest 15th percentile of a control sample on a general language factor derived from tester-administered tests at 4;6. From data at 2;0, 3;0 and 4;0 the antecedents of poor language performance at 4;6 for these probands were compared to 290 control children. As early as 2;0, language measures substantially predicted low-language status at 4;6, with predictions increasing at 3;0 and 4;0. Nonverbal cognitive development at 3;0 and 4;0 was nearly as predictive of low language at 4;6 as were the language measures. Behaviour problems were also significant predictors of low language status although the associations were only about half as strong. Bivariate genetic analyses indicated that these predictions are mediated by both genetic and shared environmental links.

The present study investigated the universality of the early development of young children's understanding and representation of false beliefs, and specifically, the effect of language on Chinese-speaking children's performance in false belief tasks under three between-subjects conditions. The three conditions differed only in the belief verb that was used in probe questions regarding one's own or another person's beliefs, namely the Chinese verbs, xiang, yiwei, and dang. While the three words are all appropriate to false beliefs, they have different connotations regarding the likelihood of a belief being false, with xiang being more neutral than either yiwei or dang. Experiment i involved thirty-five Chinese-speaking adults who responded to false belief tasks to be used in Experiment 2 in order both to establish an adult comparison and to obtain empirical evidence regarding how Chinese-speaking adults use the three belief verbs to describe different false belief situations. In Experiment 2, 188 three-, four-, and five-year-old Chinese-speaking children participated in three false belief tasks. They were asked to report about an individual's false belief when either xiang, yiwei, or dang was used in the probe question. Results revealed a rapid developmental pattern in Chinese-speaking children's understanding of false belief, which is similar to that found with Western children. In addition, children performed significantly better when yiwei and dang, which connote that the belief referred to may be false, were used in belief questions than when xiang, the more neutral verb, was used. This finding suggests an important role of language in assessing children's understanding of belief and false belief.

To evaluate Brown's assertion that frequency of input is not a significant variable in language acquisition, some of Brown's data were reanalysed. The data pertaining to Adam, Eve, Sarah and their parents were predominantly obtained from Brown's (1973) book and were supplemented from the transcripts. Parental input frequency and the children's age at mastery were highly related for each of the three triads. Then Sarah's input and rate of language acquisition were compared with that of the other two children. The correlation between Sarah's relative input deprivation and her relative linguistic delay was 0·66. Finally, an analysis of Eve's acquisition of specific prepositional phrases involving the preposition in were made. Again it was found that frequency of input was highly related to frequency of production. Detailed analyses of parent-child interactions provided evidence also for short-term effects of input frequency.

This study investigates preschoolers’ ability to understand and produce novel metonyms. We gave forty-seven children (aged 2;9–5;9) and twenty-seven adults one comprehension task and two elicitation tasks. The first elicitation task investigated their ability to use metonyms as referential shorthands, and the second their willingness to name animates metonymically on the basis of a salient property. Although children were outperformed by adults, even three-year-olds could understand and produce metonyms in certain circumstances. Our results suggest that young children may find it easier to produce a metonym than a more elaborate referential description in certain contexts, and that metonymy may serve as a useful strategy in referring to entities that lack a conventional label. However, metonymy comprehension appeared to decrease with age, with older children tending to choose literal interpretations of some metonyms. This could be a result of growing metalinguistic awareness, which leads children to overemphasize literal meanings.

This study examines pragmatic factors that bias English-speaking children to produce more of the nouns and fewer of the verbs that they know. If nouns are favoured for production, parents should elicit more nouns than verbs in child speech. If verb comprehension is favoured over verb production, parents should more often prompt children to produce an action than to produce a verb. Data from 44 parent–child (age 1;8) dyads in the New England directory of the CHILDES data base were analysed. Children produced more nouns than verbs but mothers produced more verbs than nouns. Speech act analyses indicate that mothers elicited noun production but rarely prompted children to produce verbs. Mothers more often prompted children to produce an action than to produce a verb, and verbs occurred most often in maternal speech acts used to elicit children's actions. Moreover, children comprehended many more verbs than they produced. These data suggest that production measures underestimate the frequency and significance of verb-learning in early lexical development.

Two suprasegmental characteristics of three children's single-word, successive single-word and multiple-word utterances were examined spectrographically. The location of terminal pitch contour and the duration of words were compared across the three utterance types. It was found that successive single-word utterances shared suprasegmental patterns, on these dimensions, with multiple-word forms but not with single words. It is argued that successive single-word utterances are not simply single words uttered in close temporal proximity. Further, an account of the underlying organization of successive utterances is proposed.

Measures of pragmatic development for children in the second year of life were developed, based on a brief (30 minute) language sample and on structured elicitation conditions. When age is partialled out, number of pragmatic functions expressed is not statistically related to MLU, due to the fact that the number of functions grows steadily during the one-word and very early two-word phases. Performance on the structured imperative tasks also reflects development during this period, though performance on the declarative tasks does not. We conclude that the range of pragmatic functions in the second year is measurable and contributes information not provided by a measure of syntactic development such as MLU. Such information should prove useful for research on language and cognition in normal and language-impaired children.

Modal auxiliaries have an epistemic and deontic sense and range in strength, e.g. must propositions are stronger than may propositions. Children (ages 3; 0–6; 6) heard two contradictory modal propositions of varying strength. In the epistemic condition, the propositions concerned the location of a peanut. In the deontic condition, they were commands by two teachers about what room a puppet should go to. The child was to indicate which command should be followed. The general acquisitional rule was: the greater the difference in the strength of the two modal propositions the earlier the difference was appreciated. Since the acquisitional history was similar across conditions, the two senses probably arose from a single lexical entry.

Research on categorization suggests that information conveyed by language may be a guide for children performing classification tasks. In our study we asked whether differences between languages in linguistic form influence this performance. Thirty-five three- and four-year-old monolingual speakers of Spanish and English, languages differing in the way they encode gender, were tested in their native countries on a classification task of familiar objects. This task assessed strategies used in (1) a free sort, (2) a sort with instructions to use natural gender, and (3) one (for the Spanish speakers) with specific instructions to use grammatical gender. Half of both the Spanish and the English groups used animacy as a sorting strategy in the first sort, whereas the majority of both groups sorted by natural gender in the second sort. Most Spanish speakers also used grammatical gender as a categorizing strategy in at least one of the sorts. Results suggest that both instructional context and language-specific experience can influence the ways children classify familiar referents.

Prior empirical work in semantic development has produced an impressive finding showing that children can reliably detect a modal's relative force (e.g. that must is stronger sounding than may) by five-and-a-half years of age. We investigate the extent to which a representation of relative force can account for an understanding of epistemic modals when their logical meaning is considered (i.e. when modals are interpretable as expressions of necessary and possible conclusions). Experiment 1 presents a replication of Hirst & Weil's hidden-object task, which originally included the supremely forceful indicative is. Thirty-two five-year-olds were required to find a peanut hidden under one of two containers based on a pair of statements that contrasted is with has to, has to with might, or is with might. Half the children were entitled to search for the peanut upon hearing the two statements and half were required to indicate only where they would look. Results largely confirmed the influence of relative force in this paradigm. Both groups of children usually searched under the container associated with the stronger-sounding term. Experiment 2 employed a modified version of the hidden-object task in which contrasts presented one true and one false modal statement and 32 five-year-olds, 20 seven-year-olds, 16 nine-year-olds and 20 adults were asked to determine which of two statements was correct. Half the contrasts presented a relatively weaker-sounding modal term in the true statement and the other half presented equally forceful modal terms in the two statements. No age group systematically endorsed a false stronger-sounding modal statement over a true weaker-sounding one. The five-year-olds' rate of correct responding overall was above levels predicted by chance. Mature logical modal understanding was found among seven-year-olds who routinely endorsed a contrast's true modal statement. These findings suggest that deductive inference is an early semantic component of modal terms.

By their second birthday, children are beginning to map meaning to form with relative ease. One challenge for these developing abilities is separating information relevant to word identity (i.e. phonemic information) from irrelevant information (e.g. voice and foreign accent). Nevertheless, little is known about toddlers' abilities to ignore irrelevant phonetic detail when faced with the demanding task of word learning. In an experiment with English-learning toddlers, we examined the impact of foreign accent on word learning. Findings revealed that while toddlers aged 2 ; 6 successfully generalized newly learned words spoken by a Spanish-accented speaker and a native English speaker, success of those aged 2 ; 0 was restricted. Specifically, toddlers aged 2 ; 0 failed to generalize words when trained by the native English speaker and tested by the Spanish-accented speaker. Data suggest that exposure to foreign accent in training may promote generalization of newly learned forms. These findings are considered in the context of developmental changes in early word representations.

This study investigated different accounts of early argument structure acquisition and verb paradigm building through the detailed examination of the acquisition of the verb Go. Data from 11 children followed longitudinally between the ages of 2;0 and 3;0 were examined. Children's uses of the different forms of Go were compared with respect to syntactic structure and the semantics encoded. The data are compatible with the suggestion that the children were not operating with a single verb representation that differentiated between different forms of Go but rather that their knowledge of the relationship between the different forms of Go varied depending on the structure produced and the meaning encoded. However, a good predictor of the children's use of different forms of Go in particular structures and to express particular meanings was the frequency of use of those structures and meanings with particular forms of Go in the input. The implications of these findings for theories of syntactic category formation and abstract rule-based descriptions of grammar are discussed.

Given the nature of Hebrew as a highly synthetic language with rich bound morphology, an attempt was made to establish a measure corresponding to the MLU for a language such as English. The method of calculating MPU (morpheme-per-utterance) which is described here was tried out on 38 Hebrew-speaking children aged 2;0 to 3;0, and measured for internal consistency against different types of elicitation procedures, and for validity by comparison with the subjects' performance on a specially-devised measure of syntactic–semantic development. The results clearly indicate that the MPU is a useful developmental index of the linguistic proficiency of two- to three-year-old Hebrew speakers. Implications of this finding for intra-linguistic and cross-linguistic evaluation are then discussed.

Various measures for identifying the onset of babbling have been proposed in the literature, but a formal definition of the exact procedure and a thorough validation of the sample size required for reliably establishing babbling onset is lacking. In this paper the reliability of five commonly used measures is assessed using a large longitudinal corpus of spontaneous speech from forty infants (age 0 ; 6−2 ; 0). In a first experiment it is shown that establishing the onset of babbling with reasonable (95%) confidence is impossible when the measures are computed only once, and when the number of vocalizations are not equal for all children at all ages. In addition, each measure requires a different minimal sample size. In the second experiment a robust procedure is proposed and formally defined that permits the identification of the onset of babbling with 95% confidence. The bootstrapping procedure involves extensive resampling and requires relatively few data.

Japanese provides a valuable contrast for crosslinguistic studies of noun and verb dominance in early child language, and the effect of input on the early lexicon. In this study, 31 Japanese children between 1;0 and 2;0 and their caregivers were recorded in two contexts: joint bookreading and play with toys. Context had the largest effect, as nouns were much more frequent in the book context. Noun dominance was constant across development in the book context, but in the toy context there was a shift away as children developed from single words through the presyntactic stage to the syntactic stage. Caregiver language was verb dominant in a number of respects across development in the toy context, and thus was not closely related to child lexical balance. We conclude that in early lexical development, all children have a conceptual disposition to learn nouns. With vocabulary growth and the emergence of grammar, the proportion of verbs increases substantially, and at this stage properties of the input language may influence development.

Twelve one-word-stage children (aged 1; 4 to 2; 0) were given minimally contrasting two-word instructions, e.g. kiss duck, kiss car, bang duck and bang car. Since non-linguistic cues were eliminated, comprehension involved making non-syntactic inferences from the word combinations. The children could respond correctly to some of the instructions, and even carried out some unfamiliar activities such as tickle book. Observations of mother–child interactions revealed play routines that may help the child learn to understand more than one word at a time.

Two experiments compared how French vs. English adults and children (three to seven years) described motion events. Given typological properties (Talmy, 2000) and previous results (Choi & Bowerman, 1991; Hickmann, 2003; Slobin, 2003), the main prediction was that Manner should be more salient and therefore more frequently combined with Path (MP) in English than in French, particularly with four types of ‘target’ events, as compared to manner-oriented ‘controls’: motion up/down (Experiment I, N=200) and across (Experiment II, N=120), arrivals and departures (both experiments). Results showed that MP-responses (a) varied with events and increased with age in both languages, but (b) were more frequent in English at all ages with all events, and (c) were age- and event-specific among French speakers, who also frequently expressed Path or Manner alone. The discussion highlights several factors accounting for responses, with particular attention to the interplay between cognitive factors that drive language acquisition and typological properties that constrain this process from early on.