Through an analysis of chimpanzee–human discourse, we show that two Pan troglodytes chimpanzees and two Pan paniscus chimpanzees (bonobos) exposed to a humanly devised symbol system use partial or complete repetition of others' symbols, as children do: they do not produce rote imitations, but instead use repetition to fulfil a variety of pragmatic functions in discourse. These functions include agreement, request, promise, excitement, and selection from alternatives. In so doing, the chimpanzees demonstrate contingent turn-taking and the use of simple devices for lexical cohesion. In short, they demonstrate conversational competence. Because of the presence of this conversational competence in three sibling species, chimpanzees, bonobos, and humans, it is concluded that the potential to express pragmatic functions through repetition was part of the evolutionary history of human language, present in our common ancestor before the phylogenetic divergence of hominids and chimpanzees. In the context of these similarities, two interesting differences appeared: (1) Human children sometimes used repetition to stimulate more talk in their conversational partner; the chimpanzees, in contrast, use repetition exclusively to forward the non-verbal action. This difference may illuminate a unique feature of human linguistic communication, or it may simply reflect a modality difference (visual symbols used by the chimpanzees, speech used by the children) in the symbol systems considered in this research. A second difference seems likely to reflect a true species difference: utterance length. The one- and two-symbol repetitions used by the chimpanzees to fulfil a variety of pragmatic functions were less than half the maximum length found in either the visual symbol combinations addressed to them by their adult human caregivers or the oral repetitions of two-year-old children. This species difference probably reflects the evolution of increased brain size and consequent increased memory capacity that has occurred since the phylogenetic divergence of hominids and chimpanzees four to seven million years ago.

This diary study describes early phonological and lexical development in a child with chronic otitis media with effusion. Equipped with the tools of a referential/analytic language-learner, the child solved the problem of reduced and fluctuating auditory input with phonological selection and avoidance strategies that capitalized on prosodie cues. This ‘tone-language’ approach resulted in a lexical inventory that would be categorized as an extreme expressive style. Having ‘boot-strapped’ her lexical learning, the child continued to rely on phonological constraints and selection strategies to fuel lexical and syntactic growth, i.e. cross-domain interactions leading to a vocabulary spurt and the onset of two-word utterances. These findings illustrate the need to consider interactions among performance, input and linguistic constraints in order to explain individual variation in language learning.

In ‘Nouns in early lexicons: evidence, explanations and implications’ (Vol. 20, No. 1, February 1993) by Nelson, Hampson & Kessler Shaw, the following statement on p. 70 contains an error: ‘children learned 73% of the BLOCS’. It should read: ‘children learned 37% of the BLOCS’, as reported in Table 1 on p. 70.

When children produce regularizations like comed, not all verbs are equally likely to be regularized. Several variables (e.g. lexical frequency) have been shown to be relevant, but not all the variability between verbs is understood. It is argued here that one predictor is which vowels are present in the base form vs. the past tense form. Using a notion of recessive vs. dominant vowel (where recessive vowels are more likely to be replaced by dominant vowels than vice versa) based on adult phonological processing, it is predicted that regularizations should be likely when the base vowel is dominant and unlikely when the past tense vowel is dominant. Data from 17 children reported in the literature, aged 1;6–5;6, show that this prediction is correct. Implications for the role of phonological variables in the processing of irregular past tense forms are discussed.

With the increase in interest in formulas, or apparently non-productive utterances in children's speech, a range of definitions has emerged and sometimes conflicting criteria have been proposed for their identification. These definitions of formulas are compared, and the criteria of Brown (1973), Wong Fillmore (1976), Peters (1983) and Plunkett (1990) for the recognition of formulas are reviewed. A preference rule System is proposed, which distinguishes necessary, typical and graded conditions for the recognition of formulas. Using these conditions, some of the formulas found in the data of one child acquiring Irish between 1;4 and 2;1 are examined. Issues such as length of units, frequency of occurrence and appropriateness of use are discussed. The methods developed in this study could be used to assess the importance of formulas in the language acquisition of other children.

Previous work has suggested that infants may segment continuous speech by a BRACKETING STRATEGY that segregates portions of the speech stream based on prosodic cues to their endpoints. The two present studies were designed to assess whether infants also can deploy a CLUSTERING STRATEGY that exploits asymmetries in transitional probabilities between successive elements, aggregating elements with high transitional probabilities and identifying points of low transitional probabilities as boundaries between units. These studies examined effects of the structure and redundancy of speech context on infants' discrimination of two target syllables using an operant head-turning procedure. After discrimination training on the target syllables in isolation, discrimination maintenance was tested when the target syllables were embedded in one of three contexts. Invariant Order contexts were structured to promote clustering, whereas the Redundant and Variable Order contexts were not. Thirty-six seven-month-olds were tested in Experiment I, in which stimuli were produced with varying intonation contours; 36 eight-month-olds were tested in Experiment 2, in which stimuli were produced with comparable flat pitch contours. In both experiments, performance of the three groups was equivalent in an initial 20-trial test. However, in a second 20-trial test, significant improvements in performance were shown by infants in the Invariant Order condition. No such gains were shown by infants in the other two conditions. These studies suggest that clustering may complement bracketing in infants' discovery of units of language.

The identification of appropriate lexical segmentations of the speech signal constitutes a problem for the language learner and the child language researcher alike. Articulatory precision and fluency criteria for identifying formulaic expressions, sub-lexical forms and target lexemes in linguistic productions are defined and applied to the analysis of two Danish children's language development between the ages of 1;0 and 2;0. The results of this analysis are compared to the results of applying standard distributional and frequency criteria in the tabulation of mean length of utterance and vocabulary profiles for both standard and nonstandard lexical segmentations. It is argued that although the two methods yield converging profiles of development during the latter part of the period studied, articulatory precision and fluency criteria offer a more powerful tool for identifying alternative segmentation strategies in early language acquisition. Profiles of vocabulary development for these two children suggest that the solution to the segmentation problem may be an important trigger for their vocabulary spurts.

This paper describes the early lexical development of a group of 328 normal Spanish-speaking children aged 0;8 to 2;7. First the development and structure of a new parent report instrument, Inventario del Desarollo de Habilidades Communcativas is described. Then five studies carried out with the instrument are presented. In the first study vocabulary development of Spanish-speaking infants and toddlers is compared to that of English-speaking infants and toddlers. The English data were gathered using a comparable parental report, the MacArthur Communicative Development Inventories. In the second study the general characteristics of Spanish language acquisition, and the effects of various demographic factors on that process, are examined. Study 3 examines the differential effects of three methods of collecting the data (mail-in, personal interview, and clinic waiting room administration). Studies 4 and 5 document the reliability and validity of the instrument. Results show that the trajectories of development are very similar for Spanish-and English-speaking children in this age range, that children from varying social groups develop similarly, and that mail-in and personal interview administration techniques produce comparable results. Inventories administered in a medical clinic waiting room, on the otherhand, produced lower estimates of toddler vocabulary than the other two models.

Many theories of grammatical and lexical acquisition assume that children learn predominantly nouns, and specifically names of objects, when they first begin to acquire words in the second year. We show that the noun bias in early vocabularies is far from universal, and that it rests only in part on the acquisition of object names. An analysis of vocabulary composition from 45 children at 1;8 indicates that more nouns are acquired than all other word classes, but that of the nouns acquired only about half are the names of basic level object classes (BLOCS). An examination of the use of nouns in mother-child discourse shows that non-object words referencing locations, actions and events, for example, are used in distinctive pragmatic and grammatical contexts which might enable a child to grasp the word's use and eventually its meaning. It is concluded that a theory of lexical acquisition in discourse context is required to explain word learning at all levels and for all word types. Implications for semantic bootstrapping theories are considered.

The interaction between lexical acquisition and acquisition of initial voiceless stops was studied in two normally developing children, aged 1;9 and 1;10, by acoustically examining the token-by-token accuracy of initial voiceless stop targets in different lexical items. Production accuracy was also examined as it related to the frequency of usage of different words, as well as the time when they entered the children's lexicons. Fewer than half of the words in the children's lexicons had tokens representing the emergence of accurate voiceless stop production prior to the session at which the voicing contrast was achieved. These words were primarily ‘old’ words that had been in the children's lexicons from the beginning of data collection, as opposed to ‘new’ words, first produced in later recording sessions. Findings are discussed in reference to the ‘lexical diffusion’ model of sound change and within the framework of nonlinear underspecification theory.

The present study investigates the possibility that the previously documented relationship between referential–expressive and nominal–pronominal styles (Nelson, 1975) may be best explained not so much in terms of ‘object-orientation’ or ‘noun-preference’, as in terms of the direction from which different children break into structure, with some children tending to construct patterns by combining two or more items from their single-word vocabularies and others tending to develop patterns by gaining productive control over ‘slots’ in previously unanalysed phrases. In order to do so it makes use of a methodology for distinguishing between productive and unanalysed multi-word speech proposed in Lieven, Pine & Dresner-Barnes (1992) which is applied to observational and maternal-report data from a longitudinal study of seven children between the ages of 0; 11 and 1; 8. The results suggest not only that variation in children's early word combinations can indeed be explained in terms of different routes to multi-word speech, but also that, far from being atypical, a strategy involving the breaking down of originally unanalysed phrases may be used by all children, though to varying degrees.

This study examines the distribution of nouns and verbs in maternal speech to one-year-olds. Mothers and children were videotaped during toy play and non-toy play. Nouns and verbs in maternal speech were coded for frequency, sentence position and occurrence with grammatical inflections. maternal speech was also coded for utterances that prompted the child to produce a noun or a verb. Frequency of nouns and verbs varied with context. There were more noun types and tokens during toy play, and more verb types and tokens during non-toy play. Nouns occurred more often than verbs in shorter maternal sentences, in sentence-final position, and with fewer grammatical inflections. Mothers also more often prompted their children to produce nouns. There was a significant positive correlation between frequency of noun types and tokens during toy play, and the proportion of nouns in children's first 50 words.

Seventeen of a sample of 30 precocious talkers aged 1;8 produced at least one pronoun reversal (I/you) during unstructured play. This finding led to an examination of the role of cognitive and linguistic individual differences as well as contextual factors and processing complexity as determinants of pronoun reversal. Contrary to predictions derived from previous hypotheses, there were few differences between reversers and non-reversers, other than higher use of second person forms by reversers. Reversals were more likely to occur in certain contexts: semantically reversible predicates with two noun phrases, and in imitations (though the rate of imitation was lower overall in reversers). We propose that pronoun reversals commonly result from a failure to perform a deictic shift, which is especially likely when children's psycholinguistic processing resources are taxed. Children who did not produce any pronoun reversals tended to avoid pronoun use, especially second person forms. Overt reversal may thus reflect a risk-taking approach to language acquisition, which may be particularly characteristic of precocious children.

This paper examines the acquisition of the grammatical tone system of Sesotho, a southern Bantu language where tone sandhi is rich, and where surface and underlying representations are often quite distinct. Results of the longitudinal case study show that rule-assigned tone on subject markers is generally marked appropriately by age two. In contrast, underlying tonal representations on verb roots are learned gradually over time, showing an early Default High tone pattern. The study also finds that, while some tone sandhi rules are in the process of being acquired between 2;6 and 3;0, problems in the mapping between tonal representations and segments persist. The paper raises methodological and theoretical issues not only for the acquisition of tonal systems, but for the acquisition of phonology in general.

A total of 48 male infants experienced either conversational turn-taking or random responsiveness of their mothers when aged 0;3 and 0;4. In both periods, the infant's rate of vocalizing was not significantly influenced by the contingency of the mother's response, but contingency altered the temporal parameters of the infant's vocal pattern. Infants tended to produce more bursts or packets of vocalizations when the mother talked to the infant in a random pattern. When the infants were aged 0;3 such bursts occurred most often at intervals of 0·5–1·5 sec whereas when they were aged 0;4 they took place most frequently at significantly longer intervals, of 1·0–2·0. The difference corresponded to the difference between intervals with which the mother responded contingently to vocalizations of the infant at 0;3 and at 0;4. While the intervals (between the onset of the infant's vocalization and the onset of the mother's vocalization) rarely exceeded 0·5 sec when the infant was aged 0;3, they were mostly distributed between 0·5 and 1·0 sec when he was aged 0;4. After vocalizing spontaneously, the infant tended to pause as if to listen for a possible vocal response from the mother. In the absence of a response, he vocalized repeatedly. The intervals between the two consecutive vocalizations were changed flexibly by the infant according to his recent experience of turn-taking with the mother.

The role of event knowledge in early language acquisition was investigated. Thirteen two-year-olds were observed interacting with their mothers over a five-week period. During weekly observational sessions, dyads interacted in both a familiar-event context and an unfamiliar-event context. Events were represented by complex toys (e.g. airport, marina, etc.). In the familiar-event, dyads interacted with the same event-toy during each observation period. In the unfamiliar-event, these same dyads interacted with a different novel toy during each observation period. The results indicated that children's increasing event knowledge facilitated their language development. Specifically, children's lexical type use, action verb use, and MLU increased in the familiar-event, but remained unchanged in the unfamiliar-event. Event knowledge also facilitated children's lexical token use. Results are discussed in terms of the role of event knowledge in language acquisition.

The relative importance of appearance and potential function in children's object naming was examined. Potential function is an object capability that may not be currently realized (e.g. an empty mug has the potential to hold coffee). In Study 1, sixteen children from each of three age groups (3;8, 4;8, and 6;1) were taught novel names for unfamiliar objects; they then had to decide whether these applied to items that resembled the training objects in either appearance or potential function. The youngsters were also shown deceptive objects (e.g., an eraser that looked like a pencil) and had to choose between familiar appearance and function names for them (e.g., pencil or eraser). The frequency of function-based responding in both tasks increased with age. In Study 2, the name training procedure was revised so that equal emphasis was given to both apparent and functional features. The main results of the first study were replicated. Neither study obtained evidence of a strong relation between the appearance—function shift and increased under-standing of the appearance—reality distinction.

The traditional assumptions that novel word compounds fill lexical gaps and allow speakers to convey an intended meaning more precisely were explored. Examples from spontaneous language demonstrated that some novel compounds occur in the absence of a lexical gap and that not all compounds serve a communicative function. The relation between communicative demands and novel noun–noun compound use was explored experimentally also. Twenty-eight five-year-old children and 16 adults participated in referential and non-referential communication tasks in which they were exposed to referents whose elements were inherently and non-inherently related. Both children and adults produced more compounds for inherent than for non-inherent referents. However, although the children demonstrated that they were sensitive to the need for greater communicative precision in the referential compared to the non-referential task, there was no difference in frequency of compound use across tasks. These results suggest that the functions ascribed to novel compounds warrant closer scrutiny.

The main thrust of this paper is to question whether in earlier studies the ‘motherese hypothesis’ has been adequately tested. The present study first explores concurrent relations between maternal and child language at an early age, using the Soyder, Bates & Bretherton (1981) questionnaire to assess vocabulary at 1;1. With a large sample of 45 subjects, videotaped at 1;1 and 1;8, it was possible to analyse earlier talkers separately from later talkers. The results indicate pre-existing differences between the mothers of earlier and later talkers as early as 1;1 – some 5 months before other studies have examined the possible facilitative effects of ‘motherese’. Secondly, and perhaps more importantly, when the sample was divided according to stylistic preference at 1;8, several associations between maternal language at 1;1 and MLU at 1;8 emerged for the non-expressive group which were non-existent for the expressive group. These results imply that earlier studies may have been looking for the effectiveness of maternal input too late. Moreover, it may continue to be difficult to demonstrate consistent effects of child-directed speech as long as researchers continue to ignore individual differences in style of language acquisition.