The study of bilingualism has often focused on two contradictory possibilities: that the learning of two languages may produce deficits of performance in each language by comparison with performance of monolingual individuals, or on the contrary, that the learning of two languages may produce linguistic or cognitive advantages with regard to the monolingual learning experience. The work reported here addressed the possibility that the very early bilingual experience of infancy may affect the unfolding of vocal precursors to speech. The results of longitudinal research with 73 infants aged 0;4 to 1;6 in monolingual and bilingual environments provided no support for either a bilingual deficit hypothesis nor for its opposite, a bilingual advantage hypothesis. Infants reared in bilingual and monolingual environments manifested similar ages of onset for canonical babbling (production of well-formed syllables), an event known to be fundamentally related to speech development. Further, quantitative measures of vocal performance (proportion of usage of well-formed syllables and vowel-like sounds) showed additional similarities between monolingual and bilingual infants. The similarities applied to infants of middle and low socio-economic status and to infants that were born at term or prematurely. The results suggest that vocal development in the first year of life is robust with respect to conditions of rearing. The biological foundations of speech appear to be such as to resist modifications in the natural schedule of vocal development.

Beliefs about whether or not children receive corrective input for grammatical errors depend crucially on how one defines the concept of correction. Arguably, previous conceptualizations do not provide a viable basis for empirical research (Gold, 1967; Brown & Hanlon, 1970; Hirsh-Pasek, Treiman & Schneiderman, 1984). Within the Contrast Theory of negative input, an alternative definition of negative evidence is offered, based on the idea that the unique discourse structure created in the juxtaposition of child error and adult correct form can reveal to the child the contrast, or conflict, between the two forms, and hence provide a basis for rejecting the erroneous form. A within-subjects experimental design was implemented for 36 children (mean age 5;0), in order to compare the immediate effects of negative evidence with those of positive input, on the acquisition of six novel irregular past tense forms. Children reproduced the correct irregular model more often, and persisted with fewer errors, following negative evidence rather than positive input.

Mothers' provision of names for novel and familiar toy animals was examined during play interactions with 20 infants observed at ages 0;10, 1;1, 1;5, and 1;9. Of particular interest were characteristics of mothers' speech which might bear on children's development of lexical principles or constraints. Analyses demonstrated that mothers facilitated their children's determination of reference and differentially adjusted their naming practices to novel, comprehended, and familiar animals. They virtually always named the whole object first. More important, the first mention of novel, but not comprehended or familiar animals involved both maternal naming and physical designation of the object 92% or more of the time. Thus, although a novel word's referent may be indeterminate logically, mothers specify it practically. These results support the position that maternal labelling practices may assist children in acquiring lexical principles and that lexical acquisition, perhaps even the vocabulary spurt, can proceed during natural conversational interactions before infants master lexical principles.

This study investigated whether and when children establish various semantic relations between old and new words. Fifty two-year-olds were taught labels for objects previously referred to by an overextended term. We found that children were more likely to learn a new label when (a) it referred to a new object that was perceptually dissimilar, rather than similar, to a known one, and (b) when linguistic information indicated it had an inclusion, rather than a mutually exclusive, relation to a known label. Children were more likely to interpret a new label as mutually exclusive to a known one when their referents were perceptually dissimilar. These findings are discussed in light of theories of lexical development, particularly with regard to conceptualizations of constraints on the acquisition of word meaning.

Reports that infants imitate the vocal pitch characteristics of adult caregivers (e.g. Lewis, 1936/1951) include Lieberman's (1967; Lieberman, Ryalls & Rabson, 1982) claim that infants differentially adjust their vocal pitch or fundamental frequency (f0) towards that of their caregivers, resulting in higher mean pitch when interacting with mothers than when interacting with fathers. However, a recent cross-sectional study of infants at ages 0;8 to 0;9 and 1;0 failed to find evidence of differential pitch adjustment toward male and female caregivers (Siegel, Cooper, Morgan & Brennesie-Sarshad, 1990). A more sensitive test of Lieberman's claims would be to use a longitudinal design, with spontaneous recording sessions repeated over many months. The current study presents data from a longitudinal case study of an infant recorded at ages 0;3, 0;7, 0;10, 1;3 and 1;5 interacting with each of her parents in spontaneous play sessions and in isolated play. The infant in our study did not demonstrate significant adjustment of her vocal pitch in the direction of either parent. However, we did find evidence for consistent adjustment by the parents, in accord with the literature on infant-directed speech and mother–infant dyadic interactions, which suggest that the parents adjusted their behaviour to suit the infant more than vice versa.

The effect of homonymity on children's use of semantic context to derive word meaning was examined in two studies. Participants were presented with stories that included three types of key words: nonsense words, familiar words used accurately, and homonymous words. Thirty-two preschoolers aged 3;7 to 5;4, 32 second graders aged 7;1 to 8;8, and 16 college students in Study 1 indicated the keys words' meaning by selecting one of six possible illustrations per key word. In Study 2, 16 toddlers aged 2;9 to 3;3, 32 preschoolers aged 4;0 to 4;11, 32 second graders aged 7;0 to 8;11, and 32 fifth graders aged 10;1 to 11;8 indicated key word meanings either by enacting each story with paper dolls or by selecting one of six possible illustrations. Word type and age, but not response mode, affected children's interpretations. Children from all four age groups made fewer contextually based interpretations of homonymous words than of nonsense words. Fifth graders and adults made more contextually based (rather than literal) interpretations of homonymous words than did younger children. The results suggest that homonymity is a powerful inhibitor of children's tendency to derive a meaning for a new word from context.

Previous studies of children's comprehension of compound nouns show that three-year-olds can identify the appropriate referent for a compound when shown picture arrays that include salient distractors. The four studies presented here investigate comprehension of one kind of compound, metaphoric compounds (i.e. noun–noun compounds in which one noun expresses similarity to another object, as in catfish). Forty-four three-year-olds, 45 five-year-olds and 22 adults were shown a series of picture arrays and were asked to identify referents of various types of metaphoric compounds. The arrays included target pictures that had metaphoric resemblances based on shape (e.g. bug shaped like a stick) or on colour/pattern (e.g. shells with black and white stripes, like a zebra). Results showed that three- and five-year-olds can comprehend shape-based metaphoric compounds such as stick-bug, even when faced with salient distractors (e.g. a stick, a bug next to a stick). The younger children had some difficulty with colour-based compounds, such as zebra-shells. Overall, five-year-olds outperformed three-year-olds but performed significantly less well than adults. However, even at age 3, children did not show a general expectation to interpret the compounds literally.

Williams syndrome (WS), a rare neurodevelopmental disorder, is of special interest to developmental psycholinguists because of its uneven linguistico-cognitive profile of abilities and deficits. One proficiency manifest in WS adolescents and adults is an unusually large vocabulary despite serious deficits in other domains. In this paper, rather than focus on vocabulary size, we explore the processes underlying vocabulary acquisition, i.e. how new words are learned. A WS group was compared to groups of normal MA-matched controls in the range 3–9 years in four different experiments testing for constraints on word learning. We show that in construing the meaning of new words, normal children at all ages display fast mapping and abide by the constraints tested: mutual exclusivity, whole object and taxonomic. By contrast, while the WS group showed fast mapping and the mutual exclusivity constraint, they did not abide by the whole object or taxonomic constraints. This suggests that measuring only the size of WS vocabulary can distort conclusions about the normalcy of WS language. Our study shows that despite equivalent behaviour (i.e. vocabulary test age), the processes underlying how vocabulary is acquired in WS follow a somewhat different path from that of normal children and that the atypically developing brain is not necessarily a window on normal development.

The communicative interactions of 15 dyads of four- to five-year-olds during pretend play involving routine, or scripted, events were investigated as a function of the children's knowledge of the scripts. Measures of the quantity and quality of interaction and the strategies that the children used to establish mutual knowledge (i.e. assess and adapt to their discourse partner's level of expertise), which is essential to good communication, were examined. Each dyad participated in a MATCHED condition (both members had extensive knowledge of the script) and a MISMATCHED condition (one member had extensive script knowledge and the other did not). Shared script knowledge facilitated communicative interactions, as indicated by more topic maintenance and fewer requests for clarification in the matched condition than in the mismatched condition. The children attempted to establish mutual knowledge more frequently in the mismatched condition than in the matched condition and, moreover, mutual knowledge establishment was related to the children's communicative effectiveness.

Pine & Lieven (1993) suggest that a lexically-based positional analysis can account for the structure of a considerable proportion of children's early multiword corpora. The present study tests this claim on a second, larger sample of eleven children aged between 1;0 and 3;0 from a different social background, and extends the analysis to later in development. Results indicate that the positional analysis can account for a mean of 60% of all the children's multiword utterances and that the great majority of all other utterances are defined as frozen by the analysis. Alternative explanations of the data based on hypothesizing underlying syntactic or semantic relations are investigated through analyses of pronoun case marking and of verbs with prototypical agent–patient roles. Neither supports the view that the children's utterances are being produced on the basis of general underlying rules and categories. The implications of widespread distributional learning in early language development are discussed.

This paper provides a further investigation into the linguistic abilities of a subgroup of 12 Grammatical specific language impaired (SLI) children (aged 10;2 to 13;11). The study investigates the use of referential expressions (e.g. pronouns) in a narrative discourse, and provides insight into the underlying nature of Grammatical SLI, thereby contributing to the modularity debate. Previous investigations indicate that Grammatical SLI children have a deficit with dependent structural relationships, i.e. a Representational Deficit for Dependent Relationships (RDDR). Grammatical SLI children's RDDR appears to be a modular language deficit. To test this claim, linguistic representations of dependent structural relationships which are not part of the modular language system are investigated using a narrative discourse based on the picture book Frog where are you? The SLI children's pattern of referential expressions was compared with 36 language ability controls (aged 6;4 to 9;8). The findings indicated that the Grammatical SLI children have relatively mature linguistic development in the use of referential expressions to produce a cohesive, structured narrative discourse. The view of the organisation of the mind in which a modular language system can be differentially impaired from aspects of language which rely on the central system can most easily account for the data. Thus, the data support the hypothesized modular nature of Grammatical SLI children's underlying linguistic deficit. The implications of the findings for language acquisition are discussed.

In a recent note, Marcus (1995) suggests that the rate of overregularization of English irregular plural nouns is not substantively different from that of English irregular past tense verbs. This finding is claimed to be in conflict with the predictions of connectionist models (Plunkett & Marchman, 1991, 1993) which are said to depend solely on the dominance of regular over irregular forms in determining overregulation errors. However, these conclusions may be premature given that Marcus averaged overregulation rates across irregular nominal forms that varied in token frequency and across samples representing a broad range of children's ages. A connectionist view would predict an interplay between type frequency and other item level factors, e.g. token frequency, as well as differences in the developmental trajectories of the acquisition of nouns and verbs. In this response, we briefly review longitudinal parental report data (N=26) which indicate that children are significantly more likely to produce noun overregularizations than verb overregularizations across a prescribed age period (1;5 to 2;6). At the same time, these data also show that children are familiar with proportionately more irregular nouns than irregular verbs. These findings are consistent with the predictions of Plunkett & Marchman (1991, 1993) in that the larger regular class affects the frequency of noun errors but also that familiarity with individual irregular nouns tends to reduce the likelihood of overregularizations. In contrast to the conclusion of Marcus (1995), the connectionist approach to English inflectional morphology provides a plausible explanation of the phenomenon of overregularization in both the English plural and past tense systems.

Kim, Marcus, Pinker, Hollander & Coppola (1994) argue that the preference children and adults show for regular inflection for verbs and nouns with novel meanings (e.g. The batter *flew/flied out to centre field) should be attributed to their grammatically based sensitivity to the derivations of these verbs and nouns. However, it could also be that speakers avoid the use of irregular forms to avoid conveying the conventional meaning associated with the irregular form, such as literally flying to centre field. This paper, in reply to Kim et al. (1994), reinterprets their findings and argues for a semantic/functional account, without resorting to a grammatical account.

This study investigated the general nature of conversational interaction in mother–twin–twin triads. Four sets of firstborn twins (2;3) were videotaped during 15 minutes of free play with their mothers. Analyses revealed that triadic conversations were approximately five times longer, and elicited more turns from all speakers, than dyadic conversations between a mother and a single twin. Twins also responded as often to comments and requests made to another person as to those directed to themselves, but responded more often to questions addressed directly to them than to others, indicating reliable monitoring of language not addressed to them. These results largely parallel those reported for mother–infant–sibling triads and indicate the unique effects of triadic exchanges are not due to the relative linguistic levels of the child partners.