Leher Singh

Vocabulary Growth in Late Talkers: Lexical Development from 2;0 to 3;0

Vocabulary growth from 2;0 to 3;0 was studied in 28 late talkers using expressive vocabulary inventories reported bimonthly on the Language Development Survey (LDS). Group milestones were 18 words at 2;0, 89 words at 2;6, and 195 words at 3;0. A sub-group of 11 children (Group 1) showed a rapid vocabulary spurt between 2;2 and 2;8, reached the 150-180 word mark by 2;6, and attained the LDS ceiling of about 300 words by 2;10. In contrast, the 17 children in Group 2 still had a mean vocabulary of fewer than 30 words at 2;6, had less of a vocabulary spurt when they did start acquiring words, and attained the 150-180 vocabulary mark at 3;0. All 3;0 language outcome measures were significantly predicted by LDS vocabulary size from 2;2 to 2;4.

Infant word segmentation and childhood vocabulary development: a longitudinal analysis

Infants begin to segment novel words from speech by 7.5 months, demonstrating an ability to track, encode and retrieve words in the context of larger units. Although it is presumed that word recognition at this stage is a prerequisite to constructing a vocabulary, the continuity between these stages of development has not yet been empirically demonstrated. The goal of the present study is to investigate whether infant word segmentation skills are indeed related to later lexical development. Two word segmentation tasks, varying in complexity, were administered in infancy and related to childhood outcome measures. Outcome measures consisted of age-normed productive vocabulary percentiles and a measure of cognitive development. Results demonstrated a strong degree of association between infant word segmentation abilities at 7 months and productive vocabulary size at 24 months. In addition, outcome groups, as defined by median vocabulary size and growth trajectories at 24 months, showed distinct word segmentation abilities as infants. These findings provide the first prospective evidence supporting the predictive validity of infant word segmentation tasks and suggest that they are indeed associated with mature word knowledge. A video abstract of this article can be viewed at http://www.youtube.com/watch?v=jxzLi5oLZQ8.

Back to Basics: A Bilingual Advantage in Infant Visual Habituation

Comparisons of cognitive processing in monolinguals and bilinguals have revealed a bilingual advantage in inhibitory control. Recent studies have demonstrated advantages associated with exposure to two languages in infancy. However, the domain specificity and scope of the infant bilingual advantage in infancy remains unclear. In the present study, 114 monolingual and bilingual infants were compared in a very basic task of information processing-visual habituation-at 6 months of age. Bilingual infants demonstrated greater efficiency in stimulus encoding as well as in improved recognition memory for familiar stimuli as compared to monolinguals. Findings reveal a generalized cognitive advantage in bilingual infants that is broad in scope, early to emerge, and not specific to language.

Infant feeding effects on early neurocognitive development in Asian children

BACKGROUND Breastfeeding has been shown to enhance global measures of intelligence in children. However, few studies have examined associations between breastfeeding and specific cognitive task performance in the first 2 y of life, particularly in an Asian population. OBJECTIVE We assessed associations between early infant feeding and detailed measures of cognitive development in the first 2 y of life in healthy Asian children born at term. DESIGN In a prospective cohort study, neurocognitive testing was performed in 408 healthy children (aged 6, 18, and 24 mo) from uncomplicated pregnancies (i.e., birth weight >2500 and <4000 g, gestational age ≥37 wk, and 5-min Apgar score ≥9). Tests included memory (deferred imitation, relational binding, habituation) and attention tasks (visual expectation, auditory oddball) as well as the Bayley Scales of Infant and Toddler Development, Third Edition (BSID-III). Children were stratified into 3 groups (low, intermediate, and high) on the basis of breastfeeding duration and exclusivity. RESULTS After potential confounding variables were controlled for, significant associations and dose-response relations were observed for 4 of the 15 tests. Higher breastfeeding exposure was associated with better memory at 6 mo, demonstrated by greater preferential looking toward correctly matched items during early portions of a relational memory task (i.e., relational binding task: P-trend = 0.015 and 0.050 for the first two 1000-ms time bins, respectively). No effects of breastfeeding were observed at 18 mo. At 24 mo, breastfed children were more likely to display sequential memory during a deferred imitation memory task (P-trend = 0.048), and toddlers with more exposure to breastfeeding scored higher in receptive language [+0.93 (0.23, 1.63) and +1.08 (0.10, 2.07) for intermediate- and high-breastfeeding groups, respectively, compared with the low-breastfeeding group], as well as expressive language [+0.58 (-0.06, 1.23) and +1.22 (0.32, 2.12) for intermediate- and high-breastfeeding groups, respectively] assessed via the BSID-III. CONCLUSIONS Our findings suggest small but significant benefits of breastfeeding for some aspects of memory and language development in the first 2 y of life, with significant improvements in only 4 of 15 indicators. Whether the implicated processes confer developmental advantages is unknown and represents an important area for future research. This trial was registered at www.clinicaltrials.gov as NCT01174875.

Spoken word recognition in early childhood: Comparative effects of vowel, consonant and lexical tone variation

The majority of the worlds languages exploit consonants, vowels and lexical tones to contrast the meanings of individual words. However, the majority of experimental research on early language development focuses on consonant-vowel languages. In the present study, the role of consonants, vowels and lexical tones in emergent word knowledge are directly compared in toddlers (2.5-3.5 years) and preschoolers (4-5 years) who were bilingual native learners of a consonant-vowel-tone language (Mandarin Chinese). Using a preferential looking paradigm, participants were presented with correct pronunciations and consonantal, vowel, and tonal variations of known words. Responses to each type of variation were assessed via gaze fixations to a visual target. When their labels were correctly pronounced, visual targets were reliably identified at both age groups. However, in toddlers, there was a high degree of sensitivity to mispronunciations due to variation in lexical tones relative to those due to consonants and vowels. This pattern was reversed in preschoolers, who were more sensitive to consonant and vowel variation than to tone variation. Findings are discussed in terms of properties of tones, vowels and consonants and the respective role of each source of variation in tone languages.

One world, two languages: cross-language semantic priming in bilingual toddlers.

The interconnectedness of bilingual memory remains a topic of great debate. Semantic priming provides a powerful methodological tool with which to investigate this issue in early bilingual toddlers. Semantic priming effects were investigated in 21 bilingual toddlers (2.5 years) within and across each of their languages. Results revealed the first evidence of cross-language and within-language semantic priming in bilingual toddlers. However, priming effects were only observed when the prime was presented in the dominant language and were comparable in magnitude within and across languages. Findings point to high interconnectivity across languages; however, there appear to be strong influences of language dominance on semantic facilitation. Findings serve to inform and refine developmental models of bilingual memory.

Rise and fall: Effects of tone and intonation on spoken word recognition in early childhood

Abstract A crucial component of word learning is the ability to recognize words in spite of the varying forms they assume. This may be particularly challenging in tone languages as learners have to develop tone representations in the face of intonational variation in order to accurately recognize words. The effects of intonational variation on word recognition of tone-marked words in Mandarin Chinese were investigated in toddlers and preschoolers using a cross-sectional design. Participants were presented with known words where intonation (question/statement) and tone (rising/falling) were independently manipulated. Results demonstrated that word recognition in toddlers was heavily influenced by changes in the pitch contour of a tone due to intonational variation. In contrast, preschool were able to recognize tone-marked words regardless of simultaneous intonational variation, demonstrating a comparatively robust representation of lexical tone. Results chart an evolution in integrating pitch cues to tone and intonation over the first few years of life.

A New View of Language Development: The Acquisition of Lexical Tone.

Research in first language development draws disproportionately from nontone languages. Such research is often presumed to reveal developmental universals in spite of the fact that most languages are tone languages. Recent research in the acquisition of tone languages points to a distinct course of development as compared to nontone languages. Our purpose is to provide an integrated review of research on lexical tone acquisition. First, the linguistic properties and origins of tone languages are described. Following this, research on the acquisition of tones in perception and production is reviewed and integrated. Possible reasons for the uniqueness of tone in language acquisition are discussed. Finally, theoretical advances promised by further research on tone acquisition and specific research directions are proposed.

Limits on Monolingualism? A Comparison of Monolingual and Bilingual Infants’ Abilities to Integrate Lexical Tone in Novel Word Learning

To construct their first lexicon, infants must determine the relationship between native phonological variation and the meanings of words. This process is arguably more complex for bilingual learners who are often confronted with phonological conflict: phonological variation that is lexically relevant in one language may be lexically irrelevant in the other. In a series of four experiments, the present study investigated English–Mandarin bilingual infants’ abilities to negotiate phonological conflict introduced by learning both a tone and a non-tone language. In a novel word learning task, bilingual children were tested on their sensitivity to tone variation in English and Mandarin contexts. Their abilities to interpret tone variation in a language-dependent manner were compared to those of monolingual Mandarin learning infants. Results demonstrated that at 12–13 months, bilingual infants demonstrated the ability to bind tone to word meanings in Mandarin, but to disregard tone variation when learning new words in English. In contrast, monolingual learners of Mandarin did not show evidence of integrating tones into word meanings in Mandarin at the same age even though they were learning a tone language. However, a tone discrimination paradigm confirmed that monolingual Mandarin learning infants were able to tell these tones apart at 12–13 months under a different set of conditions. Later, at 17–18 months, monolingual Mandarin learners were able to bind tone variation to word meanings when learning new words. Our findings are discussed in terms of cognitive adaptations associated with bilingualism that may ease the negotiation of phonological conflict and facilitate precocious uptake of certain properties of each language.

Can bilingual children turn one language off? Evidence from perceptual switching.

Bilinguals have the sole option of conversing in one language in spite of knowing two languages. The question of how bilinguals alternate between their two languages, activating and deactivating one language, is not well understood. In the current study, we investigated the development of this process by researching bilingual childrens abilities to selectively integrate lexical tone based on its relevance in the language being used. In particular, the current study sought to determine the effects of global conversation-level cues versus local (within-word phonotactic) cues on childrens tone integration in newly learned words. Words were taught to children via a conversational narrative, and word recognition was investigated using the intermodal preferential-looking paradigm. Children were tested on recognition of words with stimuli that were either matched or mismatched in tone in both English and Mandarin conversations. Results demonstrated that 3- to 4-year-olds did not adapt their interpretation of lexical tone changes to the language being spoken. In contrast, 4- to 5-year-olds were able to do so when supported by informative within-word cues. Results suggest that preschool children are capable of selectively activating a single language given word-internal cues to language.