In three studies, two-year-old children communicated to a parent which of two out-of-reach objects contained a sticker. Across trials, the objects were positioned in different configurations so that it was possible or impossible for a child's pointing gesture to unambiguously specify one object. In Study 1, the objects used were two boxes distinguished by a different picture of a vehicle on the front, and children (n = 16; mean age 2;8) were significantly more likely to name the box's picture on trials where pointing alone could not unambiguously specify the box than on trials where it could. In Studies 2 and 3, the stickers were hidden inside different animal figures. Older two-year-olds (n = 16, mean age 2;9), but not younger two-year-olds (n = 16, mean age 2;4), showed an ability to recognize the referential (in)efficacy of their pointing gestures and to adapt their communication accordingly.

Verbal/vocal interactions of three Japanese mother–child dyads were examined when the children were 1;0, 1;2 to 1;3, 1;6 to 1;7, and 1;8 to 1;9 to determine whether mothers provide information which may facilitate the elaboration of child lexical forms during the transition from the prelinguistic to the linguistic period. Mothers were likely to reproduce only the child's word-like utterances, both well- and ill-formed. This provided an opportunity for the child's ill-formed word-like utterance to be contrasted with an immediate maternal response. This finding, along with results showing within-child variability of lexical forms, suggested that maternal contrastive replies 1) signal errors to the child (cf. Saxton, 1997), and 2) may promote the child's selection and stabilization of production alternatives which are more accurate. Maternal reproductive responding presumably originated in their tendency to seek content-oriented communication, as was reflected in mother's growing inclination to continue verbal interactions following the child's non-word-like vocalizations.

This paper investigates the relationship between a child's degree of bilingualism and features of parental input. It seeks to demonstrate that parental discourse strategies have a direct bearing on the levels of mixing present in the child's utterances in his weaker language, English. It is based on the longitudinal study of a Catalan/English bilingual child from 1;3 to 4;2 years old. The strategies adopted by both parents in response to their child's mixing are examined following Lanza's (1992, 1997) categorization of parental discourse strategies. Whereas the Catalan-speaking mother negotiates a bilingual context of interaction with her son, as of the child's third year, the English-speaking father endeavours to impose a monolingual context. Such a change of strategy clearly favours the child's increasing use of the minority language, which entails a sharp decline in rates of mixing. It appears that parents' pragmatic choices may have an impact on the development of productive family bilingualism.

Four experiments examine the child's ability to draw on functional information to predict the similarity of function across exemplars and to extend new words from an initial exemplar to one of two others. Experiments 1 and 2 tested 16 three- and four-year-olds each (mean ages: 4;5 and 4;4, in Experiments 1 and 2, respectively) and reveal that three- and four-year-olds are able to predict similarity of function and to extend new words on the basis of function if the function is based on shape, but not if the function is based on material makeup. Experiment 3 tested 53 older children, at three age groups (mean ages: 7;2, 8;3, 9;10) and suggests that seven-year-olds have more difficulty in judging similarity of function on the basis of material makeup than eight- and nine-year-olds, and that nine-year-olds are more likely than seven- and eight-year-olds to use functional information to extend new words. Experiment 4 tested 108 children in two age groups (with mean ages of 7;9 and 9;8) and reveals that when function is pitted against syntax as criteria for categorization under a new name, seven-year-olds are more attentive to syntax than nine-year-olds, while nine-year-olds are more attentive to function than seven-year-olds. The cognitive difficulties associated with judgements concerning material function are discussed in relation to additional factors that could lead children under age nine to perform in a non-adult-like fashion in the extension of new names.

This study investigates the role of performance limitations in children's early acquisition of verb-argument structure. Valian (1991) claims that intransitive frames are easier for children to produce early in development than transitive frames because they do not require a direct object argument. Children who understand this distinction are expected to produce a lower proportion of transitive verb utterances early in development in comparison with later stages of development and to omit direct objects much more frequently with mixed verbs (where direct objects are optional) than with transitive verbs. To test these claims, data from nine children aged between 1;10.7 and 2;0.25 matched with Valian's subjects on MLU were examined. When analysed in terms of abstract syntactic structures Valian's findings are supported. However, a detailed lexical analysis of the data suggests that the children were not selecting argument structure on the basis of syntactic complexity. Instead, a clear predictor of the frames used by the children with specific verbs was the frames used by the children's mothers with those same verbs, regardless of whether they were transitive or intransitive. This suggests that the most important determinant of the children's use of verb frame was the specific patterns of verb use in the input rather than abstract grammatical knowledge constrained by performance limitations. The implications of these findings for performance-based explanations for children's early errors and early patterns of language use are discussed.

Rules for interpreting empty category (EC) subjects of complement clauses vary crosslinguistically across structural and lexical dimensions. In adult Greek, a distinction is made between the verbs meaning WANT and TRY, the former but not the latter permitting the EC subject of its subjunctive complement to refer outside the sentence. The EC is pro for WANT and PRO for TRY. In adult Spanish, both the verbs meaning WANT and TRY require the EC subject (pro) to refer outside when the complement is in the subjunctive, and require the EC subject (PRO) to refer to the main clause subject when the complement is in the infinitive. Twenty-three Greek-speaking four- to five-year-olds and 10 adults, 29 Spanish-speaking four- to five-year-olds, 18 six- to seven-year-olds and eight adults took part in act-out experiments. The results indicate an awareness of language-particular distinctions governing the interpretation of EC complement subjects. However, child speakers of both languages experience difficulty in giving sentence external reference, leading to error in the case of subjunctive sentences for Spanish-speaking children. We argue that the data overall is most compatible with children having access to the empty category PRO by age four, and that failure to give external reference of an EC when required can plausibly be treated as performance error. A picture verification task produced less clear results, but points to the need for data from younger children to establish whether there is an early stage in which lexical semantics dominates children's interpretation of ECs.

Three studies, designed to examine use of word order and animacy for interpretation of sentences by 21 typically-developing two-year-old, 23 typically-developing two-and-one-half-year-old, 16 typically-developing three-year-old, 17 language-delayed two-and-one-half-year-old and 19 language-delayed three-year-old children were carried out. Results indicated that typically-developing two-year olds used neither cue consistently to interpret sentences. Typically-developing two-and-one-half-year olds, on the other hand used a coalition of word order and animacy cues and language-delayed two-and-one-half-year olds used neither cue. At three years of age both groups of children used word order exclusively to interpret sentences.

Descriptions of the development of prosodic and segmental tiers of children's phonological systems have been derived from investigations of the development of English. This paper provides a preliminary description of phonological tier development in Cantonese-speaking children. Eight children, (two each at 1;7, 2;6, 3;5, and 4;2 years) named 95 pictures. The data were analysed for word, syllable, onset-rime, skeletal, and segmental tiers. The results suggested a developmental order in the acquisition of hierarchical features. Decreasing order of accuracy of the tiers was word = syllable > onset-rime = skeletal > segmental. A model of feature geometry was adopted to describe the acquisition of features. An interesting finding is the way the laryngeal feature (aspiration) was combined with place contrasts one at a time rather than all at once.

Although it has long been observed that some children incorporate unglossable syllables into their early utterances, it has been difficult to integrate these ‘fillers’ into theories of language acquisition. Because they straddle boundaries between phonology and morphosyntax, and between pragmatics and lexicon, they do not fit neatly into linguists' notions about ‘modules’ of language. Fillers have been reported in quite an array of languages, and yet they seem to be more common among learners of some languages than others. Even when language is held constant, children seem to vary immensely as to whether they produce fillers at all. With more researchers reporting fillers in more languages, it seems time to (1) review what we now know about fillers; (2) propose a reasonably unified set of criteria for identifying them; and (3) suggest an approach that will promote their further study.

In her note, Ann Peters distinguishes between two types of fillers: (1) premorphological, whose presence in the utterance is motivated by purely phonological considerations (the child attempts to produce an adult utterance at the prosodic level, or approximates the prevalent rhythmic pattern in the language); and (2) protomorphological, which function as place-holders for grammatical morphemes and eventually differentiate into various grammatical morphemes. I would like to suggest that there may also be a third type which sometimes appears when the child begins to generalize over a set of related words. Just as protomorphological fillers can provide valuable information about how children acquire function words, these ‘generalized’ fillers may offer insights into how children form categories of function words. I will illustrate this phenomenon with data from the Naomi corpus in the CHILDES database (Sachs, 1983).

As Peters points out in this and other work, the treatment of filler syllables continues to be problematic. To the extent that theoretical linguistic approaches to language acquisition have addressed the problem of morphology at all, this has been almost entirely in the domain of syntax. Thus, the phonological and prosodic characteristics of filler syllables in children's early speech have been largely ignored, the assumption being that the appearance of grammatical morphemes is ‘triggered’ by the maturation of syntactic representations (e.g. Radford, 1990). If this were the case, we would not expect to find crosslinguistic differences in the timing of the acquisition of determiners (Lleó & Demuth, 1999), nor the variable appearance of grammatical morphemes in some contexts and not others (Demuth, 1994, Gerken, 1996). These cases of crosslinguistic and within-language variation call for a more comprehensive account of early morpheme acquisition which can explain their variable presence or absence.

In her new and again significant paper on fillers, Ann Peters does us the honour of referring to our three-stage model of premorphology, proto-morphology and morphology proper (or modularized morphology), especially in regard to fillers (cf. also Kilani-Schoch & Dressler (2000a, b), where ample data analyses are presented).

Peters' note is valuable as an overview of current knowledge about filler syllables, in part because it clarifies how much we do NOT know about these elements. The note also points to the potential value of filler syllables for theoretical accounts of early language development, including contrasting predictions derived from nativist accounts against those that Peters describes as ‘constructivist.’ Characterizing the nature and function of filler elements could be very helpful for distinguishing these accounts, particularly if the focus is on identifying changes that might reflect a transition from phonological to morphological functions. As Peters indicates, differentiating these functions is unlikely to be easy. Indeed, it will be particularly difficult if Peters is correct in believing that the morphological categories are constructed; that position predicts a gradual transition from phonological to morphological functions and thus a period during which filler syllables are neither phonological nor morphological but, instead, somewhere in between.

Peters has made an excellent case for the importance of ‘filler’ syllables during the early stages of children's language development. In this commentary, I discuss some of the implications of filler-syllable use for related areas of child language research. The comments are based on observations made during collaborative cross-linguistic studies of both normally developing children and children with language disorders acquiring Italian (Leonard, Bortolini, Caselli, McGregor & Sabbadini, 1992; Bortolini & Leonard, 1996; Bortolini, Caselli & Leonard, 1997; Leonard & Bortolini, 1998), Hebrew (Dromi, Leonard & Shteiman, 1993; Leonard & Dromi, 1994; Dromi, Leonard, Adam & Zadunaisky-Ehrlich, 1999; Leonard, Dromi, Adam & Zadunaisky-Ehrlich, 2000), and Swedish (Hansson, Nettelbladt & Leonard, 2000).

With great clarity Ann Peters has summarized the way we have been viewing ‘fillers’ from the time they were considered a nuisance for seriously studying the development of language; the different roles they fulfill, depending on the developmental stage; and important open questions that should bring our understanding of fillers ahead. She notes that the reason for having ignored fillers for quite a while is that ‘they do not fit neatly into linguist's notions about ‘modules’ of language because at the very least they straddle preconceived boundaries.’ In fact, it is not a coincidence that researchers began to develop an interest for such neglected entities, as the interfaces of grammar began to play a central role in our understanding of language architecture. Being at the crossroads of phonology, morphology and syntax, fillers resist a rigidly compartmentalized view of language.

Although interest in fillers has grown amazingly, we definitely need more detailed descriptions of filler production and development, in order to be able to distill individual and language specific trends. On this note, I want to emphasize some of the general features of early fillers and argue that they neither support nor justify the assumption of a pregrammatical stage. On the contrary, their very presence argues against it.

Fillers appear during the early grammaticalization process, roughly between the one- or two-word phase and the earliest grammar, in a variety of languages. Peters accurately points out there have been theoretical and methodological difficulties when trying to integrate the filler phenomenon in language acquisition theory, probably because fillers do not fit neatly into linguistic categories, nor a structure of ‘modules’. Her note is a major contribution to the solution of those problems. She gives us a rich review that can guide any reader – specialised or naive – to deep, critical insights and to the relevant research literature. In addition to this valuable contribution, she points the way to future work. The very richness makes it difficult to add any interesting comments. So these remarks will be limited to complementary concepts and data.

Peters sets up a very useful initial structure for classifying elements which are not yet well-defined morphemes, especially those that seem to be modelled phonologically on adult functors. Some of these primitive elements (pre-morphological items) have neither semantic content nor distributional properties that correspond to any adult morpheme, while the more advanced (protomorphological) items have begun to take on some of the syntactic/semantic characteristics of particular classes of adult-language morphemes.