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Purpose: Early language and speech acquisition can be delayed in twin children, a twinning effect that diminishes between 4 and 6 years of age in a population-based sample. The purposes of this study were to examine how twinning effects influence the identification of children with language impairments at 4 and 6 years of age, comparing children with specific language impairment (SLI) and nonspecific language impairment (NLI); the likelihood that affectedness will be shared within monozygotic versus dizygotic twin pairs; and estimated levels of heritability for SLI and NLI. Twinning effects are predicted to result in elevated rates of language impairments in twins. Method: The population-based twin sample included 1,354 children from 677 twin pairs, 214 monozygotic and 463 dizygotic, enrolled in a longitudinal study. Nine phenotypes from the same comprehensive direct behavioral assessment protocol were investigated at 4 and 6 years of age. Twinning effects were estimated for each phenotype at each age using structural equation models estimated via diagonally weighted least squares. Heritabilities were calculated for SLI and NLI. Results: As predicted, the twinning effect increased the percentage of affected children in both groups across multiple language phenotypes, an effect that diminished with age yet was still not aligned to singleton age peers. Substantial heritability estimates replicated across language phenotypes and increased with age, even with the most lenient definition of affectedness, at −1 SD. Patterns of outcomes differed between SLI and NLI groups. Conclusions: Nonverbal IQ is not on the same causal pathway as language impairments. Twinning effects on language acquisition affect classification of 4- and 6-yearold children as SLI and NLI, and heritability is most consistent in the SLI group. Clinical practice requires monitoring language acquisition of twins to avoid misdiagnosis when young or a missed diagnosis of language impairments at school entry. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to investigate the language outcomes of 7-year-old children with and without a history of late language emergence at 24 months. Method: One hundred twenty-eight children with a history of late language emergence (LLE) at 24 months and 109 children with a history of normal language emergence (NLE) at 24 months participated in direct behavioral assessment of multiple dimensions of language at 7 years. The children were recruited from a prospective cohort study of 1,766 epidemiologically ascertained 24-month-old singleton children. Results: The group mean for the LLE children was within the typical range on an omnibus measure of general language ability and measures of specific dimensions of language. However, a greater percentage of LLE children, relative to NLE children, performed below normative expectations on a measure of general language ability (20% versus 11%), speech (7% versus 2%), syntax (18% versus 8%), and morphosyntax (9%-23% versus 2%-14%), but not vocabulary or semantics. Conclusion: The results provide support for growth models of language impairment that predict that late onset of language foretells a protracted growth difference for some LLE children relative to NLE children, particularly for syntax and morphosyntax. [ABSTRACT FROM AUTHOR]

Purpose: The primary objectives of this study were to determine the prevalence of late language emergence (LLE) and to investigate the predictive status of maternal, family, and child variables. Method: This is a prospective cohort study of 1,766 epidemiologically ascertained 24-month-old singleton children. The framework was an ecological model of child development encompassing a wide range of maternal, family, and child variables. Data were obtained using a postal questionnaire. Item analyses of the 6-item Communication scale of the Ages and Stages Questionnaire (ASQ; D. Bricker & J. Squires, 1999; J. Squires & D. Bricker, 1993; J. Squires, D. Bricker, & L. Potter, 1997; J. Squires, L. Potter, & D. Bricker, 1999) yielded a composite score encompassing comprehension as well as production items. One SD below the mean yielded good separation of affected from unaffected children. Analyses of bivariate relationships with maternal, family, and child variables were carried out, followed by multivariate logistic regression to predict LLE group membership. Results: 13.4% of the sample showed LLE via the ASQ criterion, with 19.1% using the single item of "combining words." Risk for LLE at 24 months was not associated with particular strata of parental educational levels, socioeconomic resources, parental mental health, parenting practices, or family functioning. Significant predictors included familial history of LLE, male gender, and early neurobiological growth. Covariates included psychosocial indicators. Conclusion: Results are congruent with models of language emergence and impairment that posit a strong role for neurobiological and genetic mechanisms of onset that operate across a wide variation in maternal and family characteristics. [ABSTRACT FROM AUTHOR]

Idioms (e.g., go by the book, keep a straight face) are figurative expressions that frequently occur in the English language. Given the pervasiveness of these expressions, it is important that young people can understand their meanings. Developmental studies have shown that idioms that are higher in familiarity and transparency (e.g., blow off some steam) are generally easier for children and adolescents to understand than those that are less familiar and more opaque (e.g., pull up one's socks). In those studies, judgments of idiom familiarity and transparency were based on the perceptions of individuals who were older than the study participants. In the present study, 11-year-old children (n = 50) and 16-year-old adolescents (n = 50) were asked to judge the familiarity and transparency of a set of 20 idioms. Their comprehension of the same expressions was also examined. The results indicated that the children were less familiar with the idioms and had greater difficulty comprehending them than did the adolescents. However, the children's transparency judgments did not differ from those of the adolescents. For the children, the easiest idioms were also more familiar and transparent than the most difficult expressions. For the adolescents, the easiest idioms were more transparent than the most difficult ones, but the two types did not differ in familiarity. Suggestions are offered for conducting future studies of the development of idiom understanding in youth. [ABSTRACT FROM AUTHOR]

Purpose: This study investigates the heritability of language, speech, and nonverbal cognitive development of twins at 4 and 6 years of age. Possible confounding effects of twinning and zygosity, evident at 2 years, were investigated among other possible predictors of outcomes. Method: The population-based twin sample included 627 twin pairs and 1 twin without a co-twin (197 monozygotic and 431 dizygotic), 610 boys and 645 girls, 1,255 children in total. Nine phenotypes from the same comprehensive direct behavioral assessment protocol were investigated at 4 and 6 years of age. Twinning effects were estimated for each phenotype at each age using general linear mixed models using maximum likelihood. Results: Twinning effects decreased from 4 to 6 years; zygosity effects disappeared by 6 years. Heritability increased from 4 to 6 years across all 9 phenotypes, and the heritability estimates were higher than reported previously, in the range of .44-.92 at 6 years. The highest estimate, .92, was for the clinical grammar marker. Conclusions: Across multiple dimensions of speech, language, and nonverbal cognition, heritability estimates are robust. A finiteness marker of grammar shows the highest inherited influences in this early period of children's language acquisition. [ABSTRACT FROM AUTHOR]

Purpose: This study investigated the etiology of late language emergence (LLE) in 24-month-old twins, considering possible twinning, zygosity, gender, and heritability effects for vocabulary and grammar phenotypes. Method: A population-based sample of 473 twin pairs participated. Multilevel modeling estimated means and variances of vocabulary and grammar phenotypes, controlling for familiality. Heritability was estimated with DeFries–Fulker regression and variance components models to determine effects of heritability, shared environment, and nonshared environment. Results: Twins had lower average language scores than norms for single-born children, with lower average performance for monozygotic than dizygotic twins and for boys than girls, although gender and zygosity did not interact. Gender did not predict LLE. Significant heritability was detected for vocabulary (0.26) and grammar phenotypes (0.52 and 0.43 for boys and girls, respectively) in the full sample and in the sample selected for LLE (0.42 and 0.44). LLE and the appearance of Word Combinations were also significantly heritable (0.22–0.23). Conclusions: The findings revealed an increased likelihood of LLE in twin toddlers compared with single-born children that is modulated by zygosity and gender differences. Heritability estimates are consistent with previous research for vocabulary and add further suggestion of heritable differences in early grammar acquisition. [ABSTRACT FROM AUTHOR]

Purpose: This study investigated the etiology of late language emergence (LLE) in 24-month-old twins, considering possible twinning, zygosity, gender, and heritability effects for vocabulary and grammar phenotypes. Method: A population-based sample of 473 twin pairs participated. Multilevel modeling estimated means and variances of vocabulary and grammar phenotypes, controlling for familiality. Heritability was estimated with DeFries–Fulker regression and variance components models to determine effects of heritability, shared environment, and nonshared environment. Results: Twins had lower average language scores than norms for single-born children, with lower average performance for monozygotic than dizygotic twins and for boys than girls, although gender and zygosity did not interact. Gender did not predict LLE. Significant heritability was detected for vocabulary (0.26) and grammar phenotypes (0.52 and 0.43 for boys and girls, respectively) in the full sample and in the sample selected for LLE (0.42 and 0.44). LLE and the appearance of Word Combinations were also significantly heritable (0.22–0.23). Conclusions: The findings revealed an increased likelihood of LLE in twin toddlers compared with single-born children that is modulated by zygosity and gender differences. Heritability estimates are consistent with previous research for vocabulary and add further suggestion of heritable differences in early grammar acquisition. [ABSTRACT FROM AUTHOR]