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.

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.

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.

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.

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.

H. Clark's hypotheses regarding the acquisition of spatial terms were tested using a task designed to elicit subjects' descriptions of different object arrangements. Children from 3 to 10 years and a group of adults were tested. There was some support for Clark's prediction that the perceptual difficulty of each dimension will affect the order of acquisition of the associated linguistic terms, in that the terms followed the predicted order (1) vertical, (2) horizontal-frontal, (3) horizontal-lateral, in the early years. However, it was concluded that since the horizontal-frontal terms lagged behind the others in later childhood and adulthood, perceptual difficulty alone was not an adequate explanation. In addition, no support was found for Clark's notion that linguistic terms associated with the ‘positive’ end of each spatial dimension will be acquired earlier than those associated with the ‘negative’ end.

This study investigated the development of knowledge about the presuppositions of cognitive verbs that take sentential complements. The verbs included factives, which presuppose the truth of their complements, and nonfactives, which carry no such presupposition. Three tasks assessed children's ability to (a) assign truth values to complements according to the presuppositions of the main verbs; (b) select verbs to describe people's mental states; and (c) state the presuppositions of the verbs in definitions. The results indicated that the presuppositions of the factives know, forget, and remember and the nonfactive think are not learned until age 4. Believe, which has factive and nonfactive properties, is mastered after age 7. The children's performance differed across tasks due to variations in processing requirements.

The comprehension of nine intonational contrasts involving different intonation-groupings, different nucleus placements, and different tones, was examined in 20 ten-year-old children and 20 adults. Fewer ten-year-olds than adults answered correctly on almost all tasks. Initial hypotheses concerning the order of acquisition among the three systems (grouping, nucleus placement, and tone) were in general not confirmed. But the distinction between context-wide and context-limited tonal meanings was predictive of acquisition; and a similar distinction based on local meanings rather than on the intonation patterns themselves is likely to apply to groupings and nucleus placements.