A widely held practice in many studies of child language development and disorders has been to employ an easily calculated numerical metric, mean length of utterance measured in morphemes (MLU), as a ‘general index of grammatical development’. While this practice seems to have found acceptance among many students of child language, the usefulness of MLU past Stage II has been assumed but never empirically tested. This study evaluated the grammatical performance and MLU of 18 normally developing 2- and 3-year-old children and found that MLU did not correlate significantly with age (r = 0·26), nor did it discriminate children's profiles of grammatical development.

Mother–infant interactions were recorded for five dyads in a home environment. This report describes the vocalizations produced when the infants were 13 months old. Data are reported on syllable structure, phonetic properties of vowel-like and consonant-like segments, intonation contours and peak f0 values for individual syllables. In general, the acoustic–phonetic properties of the 13-month-olds' vocalizations were consistent with data reported in other studies for younger and older children. Hence, the results are seen as evidence for an overall continuity in early phonetic development.

The study of language acquisition underwent a major revolution in the late 1950s as a result of the dissemination of technology permitting high-quality tape-recording of children in the family setting. This new technology led to major breakthroughs in the quality of both data and theory. The field is now at the threshold of a possible second major breakthrough stimulated by the dissemination of personal computing. Researchers are now able to transcribe tape-recorded data into computer files. With this new medium it is easy to conduct global searches for word combinations across collections of files. It is also possible to enter new codings of the basic text line. Because of the speed and accuracy with which computer files can be copied, it is now much easier to share data between researchers. To foster this sharing of computerized data, a group of child language researchers has established the Child Language Data Exchange System (CHILDES). This article details the formation of the CHILDES, the governance of the system, the nature of the database, the shape of the coding conventions, and the types of computer programs being developed.

The role of agent priority in event perception in word acquisition was investigated using 24 infants at the one-word stage of language production. Nonsense words were presented in narrations referring to agent, recipient or stationary nonsense puppet-actors in filmed events. The nonsense stimuli along with a sense word referring to a sense puppet were presented in a habituation series. Word acquisition was measured by the extent of response recovery to an incorrect pairing of a nonsense word with a sense referent, and by the number of infants accurately choosing named puppets. Both measures were significantly greater for puppets in agent roles than for other puppets. A speech modification condition (exaggerated intonation with repetition) held attention longer but did not facilitate acquisition.

We undertook a detailed computer-implemented acoustic analysis of the speech of a child from 46 to 149 weeks. We measured overall word duration and pitch perturbation (a measure of task-induced stress), in addition to measuring within-word phonetic segments. Results revealed that (1) there were strong age-dependent decreases in word duration but only at a relatively late stage (75–149 weeks); (2) degree of fluency was not correlated with vocal stress; (3) certain segments (i.e. /k/ and /æ/) increased greatly in duration, contributing to the absence of an overall word-duration decrease at an earlier stage (46–79 weeks) and revealing the child's ability to approximate adult-like phonetic norms. Relevance to theories of phonetic development and language change are discussed.

The effect of an adult–child discourse structure on children's production of word combinations was examined. Seventeen children at the singleword utterance level (1; 5–2; 1) served as subjects. An experimental group of six children were engaged in vertical structures over 10 sessions, while the remaining children served as a control group. Pre-tests and post-tests revealed a significant difference in the number of spontaneous and elicited multiword productions for the experimental group, but no difference for the control group.

This paper traces the process involved in the bilingual infant's gradual differentiation of his two languages, beginning with the acquisition of a dual lexicon. Word combination is at first based indiscriminately on this dual language source; function words account for a disproportionately large number of tokens used in mixed-language utterances. Universal principles of child syntax are at first applied; later, rules specific to each of the languages are developed separately. The development of self-awareness and sensitivity to standards in the second year provides the essential cognitive underpinning for the child to begin to avoid mixed-language utterances and to choose his language according to his interlocutor. At a still later point the bilingual older child may begin to make use of code-switching strategies appropriate to his or her bilingual community.

A case study is presented of the babbling monologues produced by a Dutch child in the six weeks following acquisition of the first word. The relationship between word and babbling development is investigated. There appears to be a continuous interplay between both aspects of speech development: new words may influence the character and the course of babbling, whereas babbling in turn may give rise to phonological preferences for selecting other new words. It is concluded that the analysis of concurrent babbling may provide clues for explaining the highly variable phenomena of early word production.

The relationship between affix processing and linguistic systems was evaluated through an analysis of prefixation and suffixation in the tense-aspect and locative systems of child Polish. For six children ranging in age from 1; 7 to 2; 6, the distinction between imperfective and perfective aspect was made more frequently by prefixation than by suffixation. Prefixation was found to be just as productive in the specification of locative distinctions as aspectual distinctions. We found no bias in affix processing which might have favoured suffixation, and no interaction of linguistic systems with affix processing. Furthermore, an inter-language comparison confirmed these intralanguage findings. Finally, we argued that affix processing involves a parallel analysis of patterns of stored information providing the motivation for selective attention.

This study investigates forms and functions of the perfect in 22 preschool children. Children retold and re-enacted two-sentence stories which modelled the perfect. Although the perfect appeared to be emerging in imitative speech, including certain ungrammatical forms, children varied in the extent to which they used it and appreciated its meaning of current relevance. Three factors were found to influence children's selective imitation and paraphrasing of the perfect: form of the verb (present perfect versus perfect progressive), semantic sense of the perfect, and duration of the lexical verb. Children's performance demonstrates the need to consider not only the developmental frequency of advanced, optional verb forms but the generality of their use and their relation to the child's lexicon.

Macken & Barton (1980) noted an asymmetry in their young Spanish-learning children's word-initial stop productions, as compared with English-learning children's, namely, ‘the Spanish-learning children acquire “lead” voicing…after age four’, whereas ‘English-learning children acquire “long lag” stops…by about 2;6’. ‘One possible explanation’, they propose, ‘is that lead voicing is inherently difficult to produce or at least more difficult to learn than long lag…’. The purpose of this Note is to present data suggesting that young children learning French, which also employs phonetically pre-voiced stops for its phonemically voiced category, also show an asymmetry in their word-initial stop productions. Furthermore, this asymmetry supports the notion, proposed by Macken & Barton, that lead voicing is somehow ‘more difficult’ for these young children to learn to produce. However, the actual ‘strategy’ used by the French-learning children to circumvent this presumed difficulty is different from that used by Macken & Barton's Spanish-learning children. This difference supports the notion that children have a certain degree of latitude in finding their way through the maze of psycholinguistic development (Kiparsky & Menn 1977).

Some word-finding problems (recorded on tape) of a Dutch two-year-old are reported. The child's attempts at retrieving a certain target form show many characteristics which are typical for ‘tip-of-the-tongue’ experiences. During his lexical search the child produces malapropisms and a blend. The speech errors are analysed, and implications for the character of early lexical organization and the order of lexical form/meaning acquisition are discussed.

This paper examines the relationship between context and mothers' speech to prelinguistic infants. In the first phase, videorecordings of a mother talking with her infant were transcribed; in the second phase, 48 mothers were asked to select the utterance most apt for a series of drawings representing different contexts of mother–infant interaction. Data analyzed with respect to syntactic and semantic features revealed that the informational content of mothers' speech is different in relation to various contexts. Furthermore, different syntactic types are chosen in relation to different contents. Results are discussed in relation to a hypothesis assuming that mothers' speech is determined by particular interactive rules operating in the mother–infant dyad.

Samples of spontaneous speech from two young children and their mothers were analysed to examine how children learn some of the inflectional/syntactic possibilities for individual verbs. Multiple regression analyses were performed to establish predictors of the children's range of grammatical use of particular verbs. Maternal variety of use proved to be a highly significant predictor of the children's use of the same verbs, but maternal frequency was not a significant predictor of children's use. Step-wise regression analyses revealed that each child's own mother's use was a significantly better predictor of the child's use than that of the unacquainted mother. It is argued that the children were monitoring the grammatical patterns of use of individual verbs in the input they received. The extent of novel use of verbs by the child cannot be assessed from these data, and awaits further experimental investigation.

This study examined the relationship between mothers' speech and the rate of child syntax growth for 22 2½-year-old children whose speech was sampled at two-month intervals over a six-month period. The relations which appeared suggest that linguistic experience does contribute to syntax development, but that the relation between linguistic input and language growth is different for different domains of language and at different points in the course of development. The results further suggest that there are multiple bases to the benefit of input to language acquisition. One mechanism particularly suggested by the findings is that children analyse the distributional properties of the speech they hear and may induce linguistic structure from the relationship between the structural properties of adjacent utterances in discourse.

A token-placement technique was used to investigate the influence of actor and patient animacy in determining which sentences 48 2-year-olds viewed as prototypical. After training on one of three sentence types that varied in the animacy/inanimacy of actors and patients, all children were tested for generalization on pictures with different animacy/inanimacy patterns. While most children placed actor tokens on generalization sentences correctly, regardless of animacy, half responded randomly in patient token placement. Type of training only affected children who, overall, were random responders. The results suggest that the actor category is usually acquired first for prototypical sentences with animate actors and inanimate patients.

Children's production of case-marked pronouns in Hebrew was studied with respect to possessive marking, direct-object marking, and ‘on’- locative marking. In each of these three instances the preposition appears in a bound form with a suffixal pronominal. One hundred and five children between 2;0 and 5:5 were tested in a game-like procedure designed to elicit each of the three prepositions with 1st, 2nd and 3rd personal pronouns. Results indicate that general cross-linguistic principles are operating in the acquisition process, while language specific morphophonological complexity affects relative order of acquisition. A developmental sequence may be seen in the five response patterns identified.

Comprehension test results from children acquiring Warlpiri as a first language in the Yuendumu community indicate that the canonical transitive sentence is one with an ergative-absolutive verb. We hypoth- esize that the acquisition process is influenced by a number of properties of the language, properties including the presence of homophonous forms for some of the case endings, the use of three different case frames, the optional ellipsis of core arguments, and the optionality of case markings in certain conditions.