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.

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.

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.

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.

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.

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 validity of MLU and a measure of syntactic complexity were tested against LARSP on spontaneous speech samples from 87 children, ranging in age from 1;6 to 4;9. Change in some LARSP clausal measures was found across MLU stages up to MLU 4.5. For the measure of syntactic complexity, no such ceiling was found for the clausal connectivity score in LARSP or for average clausal complexity in LARSP. Neither MLU nor the measure of syntactic complexity indexed LARSP phrasal complexity. It is concluded that MLU is a valid measure of clausal complexity up to 4·5 and that our measure of syntactic complexity is more valid at more advanced stages.

This study examined the development of children's comprehension of the use of intonation and belief verbs to mark the relative certainty with which a speaker makes a statement. Subjects were presented with a task in which they had to guess the location of an object hidden in one of two boxes over a series of trials. As clues to location, the children were presented with contrasting pairs of statements by two puppets. In the first experiment with 30 children at each of three, four, five and six years of age, statements in each pair differed either with respect to the belief term included – know, think or guess – or with respect to terminal pitch contour – rising or falling. Results showed that three-year-olds did not use any information reliably to determine the location of the object, four-year-olds treated falling pitch as a more reliable indicator of location than rising pitch, and older children responded on the basis of the belief terms but not on the basis of prosody. In Experiment 2, 40 children at each of three, four and five years heard statements which differed with respect to both belief verbs and prosody. In one condition falling intonation was paired with the more certain belief term in each pair, and rising intonation with the less certain pair. In a second condition, the pairings were reversed. Results showed that, while four-year-olds could tell the difference between know and think, they could not use intonation information to determine the location. Five-year-olds used both lexical and prosodic information, with prosodic eues modulating the effects of lexical. Taken together, these experiments show that prosodic and lexical cues start to be used by children to interpret relative speaker certainty at about the same time developmentally, but that lexical cues initially appear to dominate while prosodic ones modulate their effects. Finally, it is argued that children's understanding of prosody will be best revealed in contexts in which they are required to respond to the pragmatic function of verbal stimuli rather than to the lexical content.

As shown by Bowerman (1986), it has proved remarkably difficult to find clear-cut interpretations of why children face problems with conditionals. The present study reassesses a part of this puzzle by analysing four- to eight-year-old French children's acquisition of conditional verb forms. Relevant data in the literature and results of an experiment designed to gain information on the temporal meaning of young children's past conditional verb forms are presented and discussed. Among others, they are shown to provide weak support for interpretations stressing the role of conceptual problems and related mapping problems. Meeting one of Slobin's (1985) proposals, an interpretation is suggested that views the lateness of the past conditional verb form as due to an unexpected juxtaposition of ‘possibility’ and ‘non-possibility’ in its semantic representation. It is argued that such a juxtaposition cannot be achieved on the sole basis of cognitive development and that it requires the preliminary mastery of the conditional verb form.

An infant girl's unusual phonological behaviour was evaluated in the light of a maternai model which appeared to exaggerate features of normal conversational speech. It is suggested that parental responses to immature speech patterns may account for selected case study behaviours which have been reported in both the child phonology and child fluency literatures. It appears that evaluation of phonological development within an interactive framework may allow a more accurate picture of the conditions under which children learn speech skills. To this end, further study of the phonetic characteristics of input language and patterns of parental feedback to early articulatory attempts is desirable.

Do infants and young children (two-year-olds) possess an implicit theory of mind which is revealed through their communicative interactions or are they simply treating their interlocutors as objects to manipulate in service to their own material ends? Shatz & O'Reilly (1990) criticized a paper by Golinkoff (1986) for claiming that infants were attempting to communicate as opposed to simply manipulate their listeners. This paper takes exception to that argument. It reviews additional evidence which indicates that infants in the second year of life are capable of communicating for the sake of the ‘meeting of minds’. The alternative – treating young children's communications as only the firing off of conversational routines for the purpose of attaining material ends – seriously underestimates infants' knowledge of the communicative process.

Edwards (1992c) concerns data and data use rather than manuals. It presents principles to facilitate reliable archive research in an imperfect world. MacWhinney & Snow (1992) endorse the principles but disagree on important details, discussed in this response. M&S underrate the impact of corpus inconsistencies on substantive conclusions. Since acquisition research concerns events which often trickle in a few at a time, main findings often involve a handful of examples, so overlooking a single early variant can seriously skew results. Until archives become perfect, if they do, type-token listings can help in identifying variants before computer search and avoiding this hazard.