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.

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 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.

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 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.

A recurring result from studies which relate the frequency of input variables to rate of language development, is the link between auxiliary verb growth and yes—no questions addressed to children. Explanations for this relationship usually concentrate on the advantages of hearing stressed and non-contracted auxiliary forms in sentence-initial position over hearing unstressed, contracted forms in medial position in declaratives. If such accounts are correct, then it can be predicted that yes—no questions which place forms of COPULA be in initial position will also increase the rate of growth of children's COPULA verb development. This prediction was tested using a sample of 33 children, carefully matched for stage of language development at 1;9 and 2;0 years; rate of copula verb growth was then measured over the succeeding nine months. Analyses include an examination of the contribution of sub-categories of yes—no question, tag questions, and utterances containing sentence-final copulas to the growth of contracted and full copulas. Results confirm that the frequency of inverted copulas in yes—no questions predicts children's copula development. Nevertheless, caution is urged before interpreting the relationship in terms of a direct causal model.

Mothers have been found to respond differently to grammatical and ungrammatical utterances in young children's language. However, parents indicate that they are conscious only of responding to communicative aspects of their children's speech, not grammar. Further, researchers have looked to the understandability of utterances to explain the effects of grammaticality on maternal responses. The present study addressed the question of whether it is actually grammatical form that mothers respond to, or whether it is ambiguity in the communicative functions of children's utterances. Three mother-child dyads were videotaped in a free play setting when the children were 2;0 and 3;0. Children's spontaneous comprehensible utterances were rated for grammaticality and ambiguity of function, and mothers' responses to them were noted. Results indicated that mothers responded differentially to both the ambiguity and grammaticality of children's utterances, and that these two factors had some degree of independence in their effects on mothers' responses.

The use of Italian morphology was examined in 34 children ranging in age from 2;6 to 5;0. By the age of 3;6–4;0, high percentages of use in obligatory contexts were seen for a number of grammatical morphemes. Children age 2;6–3;0 showed percentages of use that were somewhat lower than those seen for the older children. In this age range, singular forms were used with higher percentages in obligatory contexts than plural forms, for several different types of grammatical morphemes. Greater control over singular forms in these younger children was corroborated by data from a comprehension task. Even at the younger ages studied, use of grammatical morphemes did not seem influenced by whether phonological eues to agreement were present, or whether the grammatical morphemes were homonymous. Percentages for grammatical morphemes in the form of free-standing morphemes were somewhat lower than percentages for morphemes taking the form of inflections, suggesting that the obligatory nature of inflections in Italian may be a more influential factor than the amount of morphological information contained in a grammatical morpheme.

This research examines whether infants actively seek information from a speaker regarding the referent of the speaker's utterance. Forty-eight infants (in three age groups: 1;2–1;3, 1;4–1;5, and 1;6–1;7) heard novel labels for novel objects in two situations: follow-in labelling (the experimenter looked at and labelled the toy of the infant's focus) vs. discrepant labelling (the experimenter looked at and labelled a different toy than that of the infant's focus). Subsequently, half of the infants were asked comprehension questions (e.g. ‘Where's the peri?’). The other half were asked preference questions (e.g. ‘Where's the one you like?’), to ensure that their comprehension performance was not merely the result of preferential responding. The comprehension results revealed developmental change in both (a) infants' ability to establish new word-object mappings (infants aged 1;2–1;3 failed to establish stable word-object links even in follow-in labelling), and (b) infants' ability to pinpoint the correct referent during discrepant labelling (only infants aged 1;6–1;7 succeeded). Thus the period between 1;2 and 1;7 represents a time of change in infants' ability to establish new word-object mappings: infants are becoming increasingly adept at acquiring new labels under minimal learning conditions.

We examined whether children rely on linguistic information (i.e. mass vs. count nouns) or object category information (i.e. objects vs. substances) when they name things. A grinder test was used, in which substances (e.g. water) maintain identity through transformation but objects (e.g. a cup) do not. Thirty children aged three through six were asked if the same name could be used for the same item after transformation. The items included pairs of amorphous substances and discrete objects (e.g. water – a cup), perceptually similar discrete objects (e.g. chalk – a crayon), and food items (e.g. corn – a bean). Children accepted the same name for food, ignoring linguistic information, and for objects, relying on linguistic information. In Experiment 2, 32 children aged five through eight were asked if the same name could be used for unfamiliar hardware and food items after transformation when they were labelled by nonsense mass and count nouns. Children tended to use the same name for food, relying on perceptual information. These results are discussed in terms of the active conceptualization about names of objects in relation to object characteristics.

Twenty-two normally developing five-year-olds were asked to judge, identify, repair and explain phonological and morphological errors. All of the errors involved the addition, substitution or omission of a single phoneme, which in the morphological task, was also an inflectional morpheme. Stimuli were controlled for type of error (omission, addition, substitution), location of the error (word final) and word status of the resulting error (word, non-word). Children performed significantly better on the phonological task than on the morphological task. It is proposed that the results are due to differences in the type and location of linguistic information to be analysed and to differences in memory demands in the tasks.

The purpose of this study was to explore the relation between joint picture-book-reading experiences provided in the home and children's early oral language skills. Subjects were 41 two-year-old children and their mothers. Measures included maternal report of the age at which she began to read to the child, the frequency of home reading sessions, the number of stories read per week, and the frequency of visits by the child to the local library. Measures of language skill used were the child's receptive and expressive scores on the revised Reynell Developmental Language Scales. Multiple regression analyses indicated that picture-book reading exposure was more strongly related to receptive than to expressive language. Age of onset of home reading routines was the most important predictor of oral language skills. Directions of effect, the importance of parental beliefs as determinants of home reading practices, and the possible existence of a threshold level for reading frequency are discussed.