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Neighborhood is a key context where children learn to process social information; however, the field has largely overlooked the ways children's individual characteristics might be moderated by neighborhood effects. We examined 1,030 six- to 11-year-olds (48.7% female; 82% White) twin pairs oversampled for neighborhood disadvantage from the Twin Study of Behavioral and Emotional Development in Children. We evaluated neighbor reports (N = 1,880) of neighborhood structural and social characteristics as moderators of genetic and environmental influences on children's social processing. Although there was no evidence of moderation for children's hostile attributions, there was robust evidence that the social and structural characteristics of the neighborhood moderated the genetic and environmental origins of children's positive expectations of aggressive behavior. Specifically, we found that genetic influences on aggressive expectations increased in the presence of neighborhood deprivation and decreased in the presence of protective social processes and availability of resources. Such findings suggest that protective neighborhood social processes may buffer against the development of aggressive expectations during middle childhood by suppressing the expression of genetic influences on those outcomes. In doing so, they suggest that neighborhood social processes may be able to promote youth resilience to neighborhood deprivation "under the skin."

Emerging literature links neighborhood disadvantage to altered neural function in regions supporting socioemotional and threat processing. Few studies, however, have examined the proximal mechanisms through which neighborhood disadvantage is associated with neural functioning. In a sample of 7- to 19-year-old twins recruited from disadvantaged neighborhoods (354 families, 708 twins; 54.5% boys; 78.5% White, 13.0% Black, 8.5% other racial/ethnic group membership), we found that exposure to community violence was related to increased amygdala reactivity during socioemotional processing and may be one mechanism linking neighborhood disadvantage to amygdala functioning. Importantly, parenting behavior appeared to modulate these effects, such that high parental nurturance buffered the effect of exposure to community violence on amygdala reactivity. These findings elucidate the potential impact of exposure to community violence on brain function and highlight the role parents can play in protecting youth from the neural effects of exposure to adversity.

The role of parental literacy skills in cross-linguistic transfer, the phenomenon of the sharing of skills and competence from one language to another, is under-researched. The present study tested 147 Hong Kong Chinese children and their parents (76 boys; mean age = 7.16). Parental literacy skills significantly explained children's reading and spelling in English after controlling for socioeconomic status, highlighting the role of parental skills in facilitating children's second language development. Cross-linguistic transfers between Chinese and English were found between reading and writing after controlling for age, grade, non-verbal intelligence, and socioeconomic status. The results were replicated with another twin sample.

This study explored whether high autistic traits, high attention deficit hyperactivity disorder (ADHD) traits and their interaction were associated with quality of life (QoL) in a sample of 556 of young-adult twins (Mean age 22 years 5 months, 52% Female). Four participant groups were created: high autistic traits, high ADHD traits, high autistic/ADHD traits, and low ADHD/autistic traits. High autistic traits were associated with lower QoL across domains (physical, psychological, social, and environmental). High ADHD traits associated with lower physical, psychological, and environmental QoL. The interaction of autistic and ADHD traits was not significant in any domain. While mental health difficulties were associated with lower QoL, after accounting for mental health, most relationships between autistic traits, ADHD traits and QoL remained.

Behavior genetic methods are useful for examining mechanisms underlying the interaction between genetic and family environmental factors of internalizing problem behavior (INT). Previous twin studies, however, have shown little consistency in interaction patterns, depending on type and operationalization of measured environments. The aim of the current study was to explore different gene-by-environment interaction patterns among different family-level environmental risk factors and resources known to correlate with INT. Using an empirical-based approach, we combined various indicators of the family environment to derive four dimensions: "positive parenting," "negative parenting," "lack of parental resources," and "socioeconomic status." We then used a genetically informed design of twins raised in the same family to test whether interaction patterns followed a diathesis stress or vantage sensitivity model formulation. The sample consisted of 2,089 twin pairs and their families from two twin birth cohorts (ages 11 and 17) participating in Wave 1 of the German TwinLife study of social inequalities. In line with a vantage sensitivity pattern of interaction and with the bioecological model of development (Bronfenbrenner & Ceci, 1994), evidence for a general mechanism of gene-environment interaction with increasing nonshared environmental variance for more adverse and less propitious family conditions was found. In preadolescence, parenting behavior had a greater moderating influence on INT compared to general family conditions like socioeconomic status. Interventions for INT that directly involve parents, thus, may be more important in preadolescent populations whereas individual interventions for adolescents may be more successful if they are adapted to different levels of socioeconomic status.

The ability to perceive approximate numerosity is present in many animal species, and emerges early in human infants. Later in life, it is moderately heritable and associated with mathematical abilities, but the etiology of the Approximate Number System (ANS) and its degree of independence from other cognitive abilities in infancy is unknown. Here, we assessed the phenotypic specificity as well as the influence of genetic and environmental factors on the ANS in a sample of 5-month-old twins (N = 514). We found a small-to-moderate but statistically significant effect of genetic factors on ANS acuity (heritability = 0.18, 95% CI: 0.02, 0.33), but only when differences in numerosity were relatively large (1:4 ratio). Non-verbal ability assessed with the Mullen Scales of Early Learning (MSEL) was found to be heritable (0.47; 95% CI: 0.34, 0.57) and the phenotypic association between ANS acuity and non-verbal ability performance was close to zero. Similarly, we found no association between ANS acuity and general attention during the task. An unexpected weak but statistically significant negative association between ANS acuity and scores on the receptive language scale of the MSEL was found. These results suggest that early ANS function may be largely independent from other aspects of non-verbal development. Further, variability in ANS in infancy seems to, to some extent, reflect genotypic differences in the population.

Purpose: This study examines the effect of sibling size on children's educational attainment in Indonesia. Design/Approach/Methods: To establish causality, it exploits the exogenous variation of sibling size caused by twin birth in families. Findings: Results of instrumental variable (IV) estimation support a traditional wisdom of quantity-quality trade-off, where sibling size is negatively correlated with the completed years of schooling, educational levels, and likelihood of school attendance. Building on this, the subsample analysis reveals that the negative effect is larger for Muslim children, children with less educated mothers, and children belonging to earlier birth cohorts. Originality/Value: These findings provide insights into both population and education policymaking in developing countries.

Background: Children's academic achievement is considerably influenced by genetic factors, which rarely operate independently of environmental influences such as teachers' behaviour. Praise and punitive discipline are commonly used management strategies by teachers. However, their effects on the genetic expression of children's academic achievement are still unclear. Aims: This study examined potential gene-environment interactions in the associations between children's estimated genetic disposition for academic achievement and teachers' use of praise and punitive discipline in predicting academic achievement. Sample: The participants were 165 twin pairs in sixth grade (M = 12.1 years). Methods: Teachers reported on children's academic achievement, as well as on their own behaviour. Results: Multilevel regression analyses showed significant interactions between children's estimated genetic disposition for academic achievement and teachers' use of praise and punitive discipline, respectively, in predicting academic achievement. These interactions indicated an enhancement process, suggesting that genetically advantaged children are those most likely to benefit from regular praise and infrequent punishments from their teacher. Moreover, genetically advantaged children were not more (nor less) likely to receive praise or punishments than other students. However, students from underprivileged backgrounds were less likely to receive praise from their teachers. Conclusions: The results emphasize the importance of teachers' regular use of praise and infrequent punitive discipline to help genetically advantaged children reach their full potential. Future studies should investigate other protective factors of the school environment that might reduce the role of genetic influences that undermine disadvantaged youth's academic achievement.

Transposable elements (TEs) have been implicated in autism spectrum disorder (ASD). However, our understanding of their roles is far from complete. Herein, we explored de novo TE insertions (dnTEIs) and de novo variants (DNVs) across the genomes of dizygotic twins with ASD and their parents. The neuronal regulatory elements had a tendency to harbor dnTEIs that were shared between twins, but ASD-risk genes had dnTEIs that were unique to each twin. The dnTEIs were 4.6-fold enriched in enhancers that are active in embryonic stem cell (ESC)-neurons (p < 0.001), but DNVs were 1.5-fold enriched in active enhancers of astrocytes (p = 0.0051). Our findings suggest that dnTEIs and DNVs play a role in ASD etiology by disrupting enhancers of neurons and astrocytes.

Empathy and executive functions (EFs) are multimodal constructs that enable individuals to cope with their environment. Both abilities develop throughout childhood and are known to contribute to social behavior and academic performance in young adolescents. Notably, mentalizing and EF activate shared frontotemporal brain areas, which in previous studies of adults led researchers to suggest that at least some aspects of empathy depend on intact EF mechanisms. Despite the substantial development that empathy and EF undergo during adolescence, no study to date has systematically examined the associations between components of empathy and EF in this age group. Here, we explore these associations using data from an online battery of tasks, collected as part of a longitudinal twin study (N = 593; M[subscript age] 11.09 ± 0.2; 53.46% female, Israeli adolescents from Jewish decent). Using a confirmatory factor analysis, we quantified the associations between the main components of empathy (mentalizing and interpersonal concern) and of EF (working memory [WM], inhibition and shifting [IaS]). We found that WM was related to both mentalizing and interpersonal concern, whereas IaS were related to mentalizing but not to interpersonal concern. We also discuss the genetic and environmental contributions to individual differences in each factor. Our findings show both similarities and differences from previous findings in adults, suggesting that the ongoing brain maturation processes and environmental age-dependent experiences in adolescence may affect the developing relation between cognitive and emotional development. These results have implications for better understanding and treating clinical populations demonstrating executive or emotional deficits, specifically during adolescence.

This study investigated the relationship between mathematics difficulties and psychopathology in a large community sample (N = 881) of youth (8-18 years of age) in the United States. The primary aims of the study were to (a) test the associations between mathematics difficulties and specific components of internalizing, externalizing, attention, and social problems; (b) examine potential age and gender differences; and (c) investigate the longitudinal relationship between mathematics and psychopathology using 5-year follow-up data. Results indicated that individuals with mathematics difficulties exhibited elevations in most dimensions of psychopathology, including anxiety, depression, externalizing behaviors, attention problems, and social problems. Furthermore, mathematics impairment was associated with internalizing problems, rule-breaking behaviors, inattention, and social problems even after controlling for comorbid reading difficulties. Results suggested that the associations between mathematics and psychopathology are generally similar in males and females. Finally, preliminary longitudinal evidence suggested that initial mathematics difficulties predicted elevations of conduct disorder, rule-breaking behavior, inattention, hyperactivity, and social problems at follow-up, with several of these associations remaining significant even after controlling for initial reading. In contrast, there was no significant association between initial mathematics ability and internalizing symptoms at follow-up, demonstrating some amelioration of internalizing symptoms over time.

This study examined whether domain-general cognitive weaknesses in processing speed (PS) or executive functioning (EF) moderate the relation between word reading scores and anxiety such that lower word reading scores in combination with lower cognitive scores are associated with higher anxiety symptoms. The sample consisted of 755 youth ages 8-16 who were recruited as part of the Colorado Learning Disabilities Research Center twins study. Lower scores on PS (R[superscript 2] = 0.007, p = 0.014), EF (R[superscript 2] = 0.009, p = 0.006), and word reading (R[superscript 2] = 0.006-0.008, p = 0.010-0.032) were associated with higher anxiety scores. In addition, the word reading × cognitive interactions were significant such that lower scores on PS (R[superscript 2] = 0.010, p = 0.005) or EF (R[superscript 2] = 0.013, p = 0.010) "combined" with lower word reading were associated with higher-than-expected anxiety symptoms. Results suggest that weaknesses in PS, EF, and word reading are modestly associated with higher anxiety symptoms, and these anxiety symptoms may be compounded in youth with both PS or EF weaknesses and word reading difficulties. These findings can guide assessment approaches for identifying youth with word reading challenges who may be at increased risk for anxiety.

We compared maternal speech in interactions of mothers with their firstborn dizygotic twin and singleton infants. Nine twins and nine singletons were video-recorded at home in spontaneous face-to-face interactions with their mothers, from the 2nd to the 6th month. Continuous micro-analysis revealed that there are more quantitative and qualitative similarities than differences between singleton and twin mothers' speech. Singleton and twin mothers are similar in the frequency of thematic sequences though duration of maternal speech favours singletons. Singleton mothers' speech favours infant emotion and attention thematic sequences. However, singleton and twin mothers responded similarly to the rest infant internal states. Twin, but not singleton, mothers' infant attention utterances differed at times when there are marked advances in the infants' attentiveness. These results are discussed in relation to the theory of innate intersubjectivity and the sensitivity that twin mothers, similarly to singleton mothers, express to the young infants' expressions.

Objective: The effectiveness of the Social Anxiety Program on Adolescent Twins investigated in this study. Method: The study is a mixed-method study using a one-group pretest-posttest design, together with the qualitative method. First, Intraclass Correlation Coefficient used to find out the concordance and differentiation level of the twins' social anxiety. Because monozygotic twins' concordance rate is higher than dizygotic twins, four pair female monozygotic twins aged 17-18 participated in the group. Wilcoxon Single Ranks Test used to analyze the experimental part of the research. Three sessions of focus groups held after the program. Content analysis techniques used as a qualitative analysis. Result: As a result, there was a statistically significant difference between pre/post-program. Since this difference was in favor of initial measurement, the program interpreted as being effective. Themes also supported the quantitative results. Conclusion: Findings obtained from both experimental and qualitative parts discussed. Suggestions provided for future researcher.

Classroom placement of twins is an ongoing issue for educational policy. Many educational jurisdictions have standard policy most commonly founded in the belief that separation supports individual identity, personal development and academic opportunity. This study examined the effects of classroom placement in a sample of 560 twin pairs whose behaviors were assessed from ages 5 to 12 years. We found no detrimental effect of classroom sharing on twins' social development. In contrast, this study provides evidence that educating twins together is associated with modest positive twins' behaviors and social functioning at school. Implications for educational policies are further discussed.

Turkish-speaking dyzygotic twins (n = 21) and singletons (n = 23) were tested through a standard articulation test to observe whether their consonant articulations were related to their vocabulary sizes, recorded through CDI forms, at age 3;0. Twins were observed to lag behind their singleton peers and performed below the norm level in their production. Vocabulary size failed to predict twins' articulation scores although it predicted the scores of the singleton group. The results suggested that articulation was not related to vocabulary size in twins. Exposure to sibling language was discussed as an alternative risk factor.

Noncognitive factors have gained attention in recent years as potential intervention targets for academic achievement improvement in students. Two notable facets, intelligence mindset and grit, have been of particular interest. Both have been shown to consistently improve educational outcomes, although little work has focused on reading ability. As such, we examined the relation between both grit and mindset on current, future, and change in reading comprehension ability in a twin sample. We used data from 422 twin pairs (171 monozygotic pairs, 251 dizygotic pairs) drawn from the Florida Twin Project on Reading, Behavior and Environment (Taylor et al., 2019). The racial composition of the sample included 1.00% American Indian or Alaska Native, 2.25% Asian, 13.25% Black or African American, 22.63% Hispanic, 1.00% Native Hawaiian or Other Pacific Islander, 56.13% White, and 3.75% more than 1 race. The household income of the sample at time 1 was 16.15% below $25,000, 18.06% $25,000-49,999, 36.34% $50,000-99,999, and 29.45% $100,000 or more and closely align with the overall composition reported for the state of Florida (United States Census Bureau, 2021). Twins were on average 13 years old when the questionnaire and first reading ability measure were collected, and on average 15 years old when the second reading ability measure was collected. Weak and moderate positive correlations were found between both mindset and grit and with each reading ability score and neither were significantly related to change in reading ability. Twin modeling suggested little to no common genetic or environmental influences between mindset and grit to reading ability. In total, our results do not lend support to the notion of mindset or grit being a mechanism of change for reading ability.

Early life stress, daily life experiences, and the stress responsive hypothalamic-pituitary-adrenal (HPA) axis have each been examined as predictors of the development of psychopathology. Rarely have researchers attempted to understand the covariation or interaction among these stress domains using a longitudinal design in the prediction of symptoms of internalizing psychopathology, particularly during childhood. This study examined early family stress, daily interpersonal stress, indicators of diurnal cortisol, and internalizing symptoms in a racially/ethnically and socioeconomically diverse sample of twins (N = 970 children; M[subscript age at outcome] = 9.73; 52% female; 23.7% Hispanic/Latino, 58.8% White; 30% below middle class; Lemery-Chalfant et al., 2019). An additive model of stress, a stress mediation model, and a stress sensitization framework model each delineated potential pathways linking stress and internalizing symptoms. Supporting additive pathways, multilevel models showed that all 3 stress indicators uniquely predicted internalizing symptoms. There was a significant indirect path from early family stress to 9 year internalizing symptoms through interpersonal stress, supporting stress mediation. Family stress moderated the association between interpersonal stress and internalizing symptoms, though not in the direction that would support stress sensitization. Child stress, including daily interpersonal stress and HPA axis activity, and internalizing symptoms are prevalent and family stress is a significant precursor to child internalizing symptoms across child development.

Dysregulation of biological stress response, as measured by cortisol output, has been a primary candidate mechanism for how social experiences become biologically embedded. Cortisol is the primary output of the hypothalamic pituitary adrenal (HPA) axis. Cortisol levels vary systematically across the day and change in response to both sudden, acute stress experiences as well as prolonged exposure to environmental stress. Using data from 8- to 15-year-old twins in the Texas Twin Project, we investigate the extent to which genetic influences are shared across different measures of cortisol output: chronic cortisol accumulations in hair (n = 1,104), diurnal variation in salivary output (n = 488), and salivary response to a standardized, acute in-laboratory stressor (n = 537). Multivariate twin models indicate that genetic factors regulating cortisol response to the in-laboratory stressor are separable from those regulating baseline cortisol levels, naturally occurring diurnal variation in cortisol, and hair cortisol levels. These findings illustrate that novel environments can reveal unique genetic variation, reordering people in terms of their observed phenotype rather than only magnifying or mitigating preexisting differences.

Background: Educational attainment is connected to many important life outcomes, and the previous research has already focused on identifying its genetic and environmental components. However, most of these studies used twin data only and did not incorporate information from other family members. Twin studies typically decompose the phenotypic variance into genetic, shared, and unique environment components. In this study design, the shared environment component encompasses the influence of parents and the shared environments of twins and siblings independent of parents (e.g., teachers, schools, and peers). The classical twin design (CTD) conflates these influences as part of the shared environment. This shortcoming can be overcome using the nuclear twin family design (NTFD), which enables separation of the parental and shared twin/sibling environmental components. Aims: The aim of this study was to broaden the understanding of the aetiology of educational attainment using the nuclear twin family design to provide a detailed account of the genetic and environmental effects on the type of school leaving certificate. Sample: The data of 1,048 monozygotic and 916 dizygotic same-sex twins, their biological parents, and non-twin full biological siblings of the German project TwinLife were used in the nuclear twin family design. Methods: Structural equation modelling (SEM) techniques were used to analyse the variance-covariance patterns of the ordinal outcome variable. Results: Genetic influences were found to make up around 60% of variance, whilst environmental influences shared by all siblings, educational influences shared by the twins only, and non-shared environmental influences explained the remaining variance in equal amounts. Environmental transmission from parent to offspring was found to be negligible. Conclusion: Through its advanced design, our study extends the previous work enabling more detailed and robust estimations of sources of variance and contributes to a better understanding of the complex aetiology of educational attainment.

Feeling inhibited and socially not at ease is reflected in the trait social inhibition (SI). SI is associated with psychopathology that arises in young adulthood, such as anxiety. We aim for a better insight into the genetic and environmental contributions to SI across the life span, and as such examine their contributions to SI stability and change across adolescent and adult life span. We analyzed cohort-sequential longitudinal data from the Netherlands Twin Register (NTR), spanning a period of 25 years (Men (N, %): 17855, 37.4%; Age (Median, IQR): 19 years, 16-26 years; 7474 complete MZ twins and 8799 complete DZ twins). The data were organized into 7 age groups: <14 (preadolescence), 15-16 (early adolescence), 17-18 (mid adolescence), 19-20 (late adolescence), 21-30 (young adulthood), 31-40 (adulthood), 41+ (middle-age-older adulthood). SI was assessed with the ASEBA-based proxy questionnaire. Phenotypic stability was established across the entire age range. Next, a longitudinal genetic simplex model was fitted to estimate the genetic and environmental contributions to the observed phenotypic stability. Results showed SI correlated well across follow-up of a single decade (0.44 [greater than or equal to] r [greater than or equal to] 0.59) and moderately across the 25 years (0.23 - 0.32) from adolescence to middle-age and older. Broad-sense heritability (h2) was between 40 and 48% across the 7 age groups. Additive and nonadditive genetic effects together explained most of the stability of SI across the life span (about 60-90% of the phenotypic correlation between ages), whereas environmental effects played a lesser role (about 10-40%). Concluding, SI, known to increase the risk of internalizing psychopathology, is phenotypically stable across the life span, which is largely attributable to genetic contributions to individual differences in SI.

Given the importance of writing for academic achievement, this study aimed to understand how early oral language contributes to later writing skills. The first objective was to determine if preschool language skills were associated with high school writing, and if so, whether they contributed directly or indirectly through school age language. The second aim was to explore the extent to which genetic and environmental factors explained these potential associations. The sample was drawn from the Quebec Newborn Twin Study, a longitudinal follow-up of twins born in the greater Montreal area, Quebec, Canada. Language skills were assessed when children were 1.5, 2.5, 6, 7, 10, and 12 years old. Writing skills were measured at 15 years old. Participants who completed the writing task in French were included in the study (n = 316 twin pairs: 46% males). Mothers of these participants self-identified mostly as White. About 74% of them had a postsecondary diploma or certificate, and 27% further had a university degree. Most families had an income higher than 30,000 CND. Results indicate that preschool language was modestly associated with high school writing (r = 0.25) and that school age language fully mediated this association. Genes explained 53% of the association between preschool language and school age language and 64% of the association between school age language and high school writing. These results highlight the developmental continuity from oral to written language from preschool to high school and show that genetic factors largely account for this continuity.

This study investigated the association between autism and self-reported eating problems and the influence of gender on the association, in a sample of adolescent and adult twins (N = 192). Autistic traits and autism diagnosis were associated with both total and specific eating problems, including selective eating and sensory sensitivity during mealtimes. Interaction effects indicated a stronger association between autistic traits and total eating problems in females, as well as more difficulties with eating in social contexts among autistic females. In within-pair analyses, where unmeasured confounders including genes and shared environment are implicitly controlled for, the association was lost within monozygotic pairs, which might further indicate a genetic influence on the relationship between autism and eating problems.

Parents are known to provide a lasting basis for their children's social development. Understanding parent-driven socialization is particularly relevant in adolescence, as an increasing social independence is developed. However, the relationship between key parenting styles of care and control and the microlevel expression of daily-life social interactions has been insufficiently studied. Adolescent and young adult twins and their nontwin siblings (N = 635; mean age = 16.6; age range = 14.2-21.9; 58.6% female; 79.5% in or having completed higher secondary/tertiary education; 2.8% speaking language other than Dutch at home) completed the Parental Bonding Instrument (PBI) on parental care and control. Participants also completed a 6-day experience sampling period (10 daily beeps, mean compliance = 68.0%) to assess daily-life social interactions. Higher overall parental bonding quality (of both parents) related to more positive social experiences in daily life (e.g., belonging in company), but not to more social behaviors (e.g., being with others). Factor analysis indicated a three-factor structure of the PBI, with care, denial of psychological autonomy, and encouragement of behavioral freedom. Paternal care was uniquely predictive of better social experiences. These findings demonstrate how parenting styles may be uniquely associated with how adolescents experience their social world, with a potentially important role for fathers in particular. This complements the long-held idea of socialization through parenting by bringing it into the context of daily life and implies how both conceptualizations of social functioning and interventions aimed at alleviating social dysfunction might benefit from a stronger consideration of day-to-day social experiences.

There is increasing concern regarding additional psychiatric problems that co-occur with Autism Spectrum Disorder (ASD), as reflected in recent changes to diagnostic schemes. However, there remains little research with population-based samples across childhood. We report on additional problems, as measured by the Strengths and Difficulties Questionnaire, in a population-based sample of 135 twins with ASD, 55 non-ASD co-twins, and 144 comparison twins low in ASD traits. Frequencies, associated demographic factors, and changes in mental health difficulties from age 4 to 13 years are presented. Our data confirm the high rates of additional difficulties reported in previous studies, and suggest that the profile, associated risk factors and longitudinal course of additional difficulties in ASD may differ from those in typically-developing populations.

Twins regularly score nearly a standard deviation below the population mean on standardized measures of cognitive development in infancy but recover to the population mean by early childhood, making rapid gains through the toddler years. To date, only polynomial growth models have been fit to model cognitive recovery across childhood, limiting the applicability of the growth parameters to later developmental periods. We fit a nonlinear asymptotic Gompertz growth model to prospective cognitive scores from 1,153 individual twins from 578 families (47.9% male, 91.5% White, 61.6% monozygotic) measured at 16 time points between 3 months and 15 years. Twins displayed a lower asymptote of 86.47 (0.90 SD below the population mean) and gained on average 17.01 points, achieving an upper asymptote of 103.48. Growth was observed to be most rapid at 3.26 years, highlighting the importance of the toddler years in cognitive development. Biometric analyses revealed that shared environmental factors accounted for the majority of the variance in initial cognitive ability as well as asymptotic growth in cognitive ability. Gestational age and family socioeconomic status (SES) were robust predictors of cognitive growth. Results from the present study provide insight into the growth processes underlying the recovery of cognitive ability to the population mean for children evincing slight delays in their initial cognitive ability. In particular, findings highlight prenatal factors and family economic resources as important aspects of the environment in the recovery of cognitive ability.

Eng and Chang Bunker (1811--1874) were conjoined twins of Chinese ethnicity born in Siam (today, Thailand). Before the Civil War, they toured the United States to exhibit themselves as a "human curiosity," a wonder of nature, their conjoined state documented by local doctors at each stop on their tours, and their exhibition touted as edifying and educational. The American public was amazed, therefore, or, rather, aghast to learn in 1840 that these racialized "freaks of nature" had bought land in North Carolina's Piedmont, built a house, taken US citizenship and the last name Bunker, married two farmer's daughters, Sarah (Sally Ann) and Adelaide Yates, and were fathering with them what would become, respectively, eleven and ten children. Two of Chang and Adelaide's children, Louisa and Jesse, were born deaf in 1855 and 1861, respectively, and would attend school at the North Carolina Institution for the Deaf and Dumb and the Blind (NCIDDB) during its chaotic Reconstruction years of partial racial integration, where Louisa would marry a deaf teacher of semi-segregated "colored" deaf pupils. Meanwhile, the twins had returned to the freak show touring circuit, now as conjoined Southern gentlemen and fathers of growing families, exhibiting, along with their own anomalous bodies, sample well-dressed offspring who bore marked resemblances to themselves. Naturally, the two deaf children were never selected as co-exhibits, the point of exhibiting sample children, after all, being to show that the offspring of these "curiosities" were healthy, handsome, and acceptably "normal." The lives of Chang and his daughter Louisa thus provide a two-generation immigrant story of negotiating the culturally constructed intersections of race and physical anomaly both before and after the Civil War. Louisa's life was largely determined by the choices that her father made in his efforts to negotiate those intersections.

Future orientation tends to prevent engagement in risk behaviours and results in good academic performance among adolescents. Our study aimed to establish whether genetic factors contributed to future orientation among Chinese adolescents. We recruited 988 pairs of twins from Beijing. By constructing a high-order A (additive genetic variance) C (common environmental variance) E (unique environmental variance) model, we found that heritability and a common environment contributed significantly to the development of future orientation among adolescents. Moreover, this study did not detect significant heritability differences in future orientation between girls and boys. In addition, there was a negative relationship between age and heritability of future orientation but a positive relationship between age and non-shared environmental effect on the development of future orientation. Our findings provide empirical evidence for the heritability of future orientation, suggesting that both genetics and common environment influence its development.

The present study used quantitative and qualitative methods to explore how lonely young people are seen from others' perspectives, in terms of their personality, behavior, and life circumstances. Data were drawn from the Environmental Risk Longitudinal Twin Study, a cohort of 2,232 individuals born in the U.K. in the mid-1990s. When participants were aged 18, they provided self-reports of loneliness, and informant ratings of loneliness were provided by interviewers, as well as participants' parents and siblings. Interviewers further provided Big Five personality ratings and detailed written notes in which they documented their perceptions of the participants and their reflections on the content of the interview. In the quantitative section of the article, regression analyses were used to examine the perceptibility of loneliness and how participants' loneliness related to their perceived personality traits. The informant ratings of participants' loneliness showed good agreement with self-reports. Furthermore, loneliness was associated with lower perceived conscientiousness, agreeableness, and extroversion and higher perceived neuroticism. Within-twin pair analyses indicated that these associations were partly explained by common underlying genetic influences. In the qualitative section of the study, the loneliest 5% of study participants (N = 108) were selected, and thematic analysis was applied to the study interviewers' notes about those participants. Three themes were identified and named: "uncomfortable in own skin," "clustering of risk," and "difficulties accessing social resources." These results add depth to the current conceptualization of loneliness and emphasize the complexity and intersectional nature of the circumstances severely lonely young adults live in.

Executive functions (EFs) and intelligence (IQ) are phenotypically correlated. In twin studies, latent variables for EFs and IQ display moderate to high heritability estimates; however, they show variable genetic correlations in twin studies spanning childhood to middle age. We analyzed data from over 11,000 children (9- to 10-year-olds, including 749 twin pairs) in the Adolescent Brain Cognitive Development (ABCD) Study to examine the phenotypic and genetic relations between EFs and IQ in childhood. We identified two EF factors--Common EF and Updating-Specific--which were both related to IQ (rs = 0.64-0.81). Common EF and IQ were heritable (53%-67%), and their genetic correlation (rG = 0.86) was not significantly different than 1. These results suggest that EFs and IQ are phenotypically but not genetically separable in middle childhood, meaning that this phenotypic separability may be influenced by environmental factors.

There is considerable variability in the extent to which young people with developmental language disorder (DLD) experience mental health difficulties. What drives these individual differences remains unclear. In the current article, data from the Twin Early Development Study were used to investigate the genetic and environmental influences on psychopathology in children and adolescents with DLD (n = 325) and those without DLD (n = 865). Trivariate models were fitted to investigate etiological influences on DLD and psychopathology, and bivariate heterogeneity and homogeneity models were fitted and compared to investigate quantitative differences in etiological influences on psychopathology between those with and without DLD. The genetic correlation between DLD and internalizing problems in childhood was significant, suggesting that their co-occurrence is due to common genetic influences. Similar, but nonsignificant effects were observed for externalizing problems. In addition, genetic influences on internalizing problems, but not externalizing problems, appeared to be higher in young people with DLD than those without DLD, suggesting that the presence of DLD may exacerbate genetic risk for internalizing problems. These findings indicate that genetic influences on internalizing problems may also confer susceptibility to DLD (or vice versa) and that DLD serves as an additional risk factor for those with a genetic predisposition for internalizing problems.

The current analysis investigates genetic and environmental influences on the bidirectional relationships between temperament and general cognitive ability (GCA). Measures of GCA and three temperament factors (persistence, approach, and reactivity) were collected from 486 children ages 4-9 years (80% white, 50% female) from the Louisville Twin Study from 1976 to 1998. The results indicated a bidirectional dynamic model of temperament influencing subsequent GCA and GCA influencing subsequent temperament. The dynamic relationship between temperament and GCA arose primarily from shared genetic variance, particularly in families with higher socioeconomic status, where input from temperament contributed on average 20% to genetic variance in GCA versus 0% in lower SES families.

This study examined whether typically developing (TD) twins of non-TD children demonstrate enhanced empathy and prosociality. Of 778 Hebrew-speaking Israeli families who participated in a twin study, 63 were identified to have a non-TD child with a TD twin, and 404 as having both twins TD. TD twins of non-TD children (27% males) were compared to the rest of the cohort of TD children (46% males) on measures of empathy and prosociality. Participants were 11 years old. TD twins of non-TD children scored significantly higher than TD twins of TD children in a measure of cognitive empathy (d = 0.43). No differences were found in emotional empathy and prosociality. The specificity of the positive effect on cognitive empathy is discussed.

Background: Creativity is linked with educationally relevant constructs such as achievement, intelligence, and motivation. However, very few studies have explored longitudinal links between the constructs or the aetiology of individual differences in childhood creativity. Aims: The study addresses the gap in the literature of developmental studies on the relationship of creativity with other educationally relevant measures. Additionally, the present study is the first adequately powered genetically informative analysis of childhood creativity. Sample(s): The present study utilized data from 1,306 twins, a subsample from a longitudinal, representative twin sample in the UK. Methods: Creativity was operationalised as a "Creative Expressiveness" score, using the Consensual Assessment Technique on stories written by 9-year-olds. Intelligence and writing motivation were assessed at age 9. Academic achievement was collected at ages 9, 12, and 16. Results: "Creative Expressiveness" was associated with intelligence and motivation, all measured at age 9. It also predicted variance in English grades at ages 9 and 16. The associations were weak, but significant, over and above intelligence, motivation, and earlier English grades. The variance in "Creative Expressiveness" was explained by genetic (35%), shared environmental (21%), and non-shared environmental (45%) influences. The phenotypic correlations with other study variables were mainly mediated genetically. Conclusions: The results provide information that can be used for planning educational content. First, creativity can be detected in childhood writing. Second, childhood creativity may be overlooked in early educational assessments. Third, the results from the genetic analyses are important indications on the role of environments in the development of creativity.

In this article, it is argued that it makes sense to define and distinguish three levels of human intelligence: intelligence as genotypical potential, intelligence as actualised in environmental interaction, and intelligence as measured by tests (IQ). This raises the questions of what is meant by the term "intelligence as potential", and how and in what sense does a child's cognitive potential express the parents' potential and genetics? The larger the number of genes involved in a certain trait, the more possibilities emerge for the formation of new combinations for that trait. The degree of similarity between a child and their parents depends on the "unique" combination of innate genes in each newborn child. The more genes are connected with a human trait or ability, the more refined or intricate the structure of the distribution for that trait in a population will be. The question of how a parents' genes relate to their children's genes has been studied, among other things, in 'twin studies'. Another relevant, but complicated question concerns the relation between genetics (nature) and environment (nurture). Nature appears to be at work in nurture, while nurture influences processes of nature. In psychological research, some DNA differences can be used to predict psychological differences, called polygenic scores. In this context, it is argued that individual cognitive growth comes about by all kinds of influences; psychologists call such influences 'bidirectional' influences. It is also argued that, ultimately, it is the individual human explorative "activity" that is responsible and a strong catalyst for the development and mastery of human traits and for the cognitive qualifications of all newborn children.

The goal of the present study was to replicate Burt et al. (2009) and Hou et al. (2013) findings by determining the contribution of peers' deviance to changes in participants' (monozygotic [MZ] twins') self-reported delinquency from mid- to late adolescence while controlling for possible gene-environment correlations (rGE) through the use of the cotwin method in the context of a cross-lagged design. Two separate samples were used to this purpose. The first sample included 289 MZ-twin pairs (48.42% female; 65.5% of European descent, 21.7% of African descent, 12.8% other; average age at first assessment = 16.20 years) and relied on perceived measures of peer deviance, as in the two original studies. The second sample comprised 181 MZ-twin pairs (50.67% female; 84% of European descent, 3% of African descent, 2% of Asian descent, 2% Native North Americans, and 9% unspecified; average age at first assessment = 13.05 years) and used direct measures to assess peers' deviance. Participants in the first sample were part of a large representative sample of American adolescents, whereas the second sample included families with twins born in a large Canadian city. Results showed that within-pair differences in self-reported delinquency were stable from midadolescence to late adolescence in both samples. As in Burt et al. (2009) and Hou et al. (2013) within-pair differences in peer deviance did not predict changes in within-pair differences in self-reported delinquency in both samples (i.e., no socialization effect). In contrast to Burt et al. (2009) and Hou et al. (2013), however, we found no predictive link from twins' self-reported delinquency to peers' deviance (i.e., no selection effect). Finally, as in Burt et al. (2009) we found that peers' deviance was stable from middle to late adolescence and that peers' deviance and participants' delinquency were cross-sectionally correlated in the first sample, but not in the second sample. These results are interpreted in the context of the ongoing debate in regard to peers' socialization vs selection effects.

To examine whether implicit social cognition is developmentally stable or variable, this study investigated three primary types of implicit social cognition (self-esteem, the gender-science stereotype, and racial attitude) across 2 years in a sample of Chinese adolescents and emerging adults (N = 608; 56% female; 15- to 27-year-olds). Rank-order stability analyses indicated that implicit self-esteem and implicit racial attitude manifested low stability (r = 0.16, 0.19, respectively), whereas implicit gender-science stereotype was highly stable (r = 0.75). Latent change score model analyses showed that: (a) the mean level of implicit self-esteem decreased across the 2 years, whereas the mean levels of implicit gender-science stereotype and implicit racial attitude manifested no changes; (b) individual changes were heterogeneous for all the three types of implicit social cognition (while some of the participants manifested increasing tendencies, 15%-46%, the others exhibited decreasing tendencies); (c) 30% of participants manifested similar changes across the three types of implicit social cognition (either increasing or decreasing over time on all three), while the remaining participants exhibited distinct changes across them. Together, these findings indicate that, developmentally, implicit social cognition is variable but also stable, though the degree of variability and stability vary across individuals and domains.

Individual differences in music traits are heritable and correlated with the development of cognitive and communication skills, but little is known about whether diverse modes of music engagement (e.g., playing instruments vs. singing) reflect similar underlying genetic/environmental influences. Moreover, the biological etiology underlying the relationship between musicality and childhood language development is poorly understood. Here we explored genetic and environmental associations between music engagement and verbal ability in the Colorado Adoption/Twin Study of Lifespan behavioral development & cognitive aging (CATSLife). Adolescents (N = 1,684) completed measures of music engagement and intelligence at approximately age 12 and/or multiple tests of verbal ability at age 16. Structural equation models revealed that instrument engagement was highly heritable (a[superscript 2] = 0.78), with moderate heritability of singing (a[superscript 2] = 0.43) and dance engagement (a[superscript 2] = 0.66). Adolescent self-reported instrument engagement (but not singing or dance engagement) was genetically correlated with age 12 verbal intelligence and still was associated with age 16 verbal ability, even when controlling for age 12 full-scale intelligence, providing evidence for a longitudinal relationship between music engagement and language beyond shared general cognitive processes. Together, these novel findings suggest that shared genetic influences in part accounts for phenotypic associations between music engagement and language, but there may also be some (weak) direct benefits of music engagement on later language abilities.

Atypical sensory processing is prevalent across neurodevelopmental conditions and a key diagnostic criterion of autism spectrum disorder. It may have cascading effects on the development of adaptive functions. However, its unique contribution to adaptive functioning and the genetic/environmental influences on this link are unclear. In a clinically enriched twin sample (n = 289, 60 diagnosed with autism spectrum disorder), we investigated the associations between the quadrants of the Adult/Adolescent Sensory Profile (low registration, sensory sensitivity, sensation seeking, and sensation avoiding) and adaptive functioning. Associations were modeled across the cohort accounting for the effects of clinical diagnosis, IQ, sex and age, and within-twin pairs, additionally implicitly adjusting for familial factors. Furthermore, we explored interaction effects between atypical sensory processing and autism spectrum disorder diagnosis. Sensory sensitivity and sensation avoiding were associated with reduced adaptive functioning across individuals, but not within-twin pairs. An interaction effect was found between sensation seeking and autism spectrum disorder diagnosis, showing a negative association between sensation seeking and adaptive functioning only in individuals diagnosed with autism spectrum disorder. The results suggest that atypical sensory processing is associated with reduced adaptive functioning and that familial factors influence this link. In addition, sensation seeking behaviors might interfere with adaptive functioning specifically in individuals with autism spectrum disorder.

Children's early vocabulary shows sex differences -- with boys having smaller vocabularies than age-comparable girls -- a pattern that becomes evident in both singletons and twins. Twins also use fewer words than their singleton peers. However, we know relatively less about sex differences in early gesturing in singletons or twins, and also how singletons and twins might differ in their early gesture use. We examine the patterns of speech and gesture production of singleton and twin children, ages 0;10-to-3;4, during structured parent-child play. Boys and girls -- singleton or twin -- were similar in speech and gesture production, but singletons used a greater amount and diversity of speech and gestures than twins. There was no effect of twin dyad type (boy-boy, girl-girl, boy-girl) on either speech or gesture production. These results confirm earlier research showing close integration between gesture and speech in singletons in early language development, and further extend these patterns to twin children.

Children with attention deficit hyperactivity disorder (ADHD) often experience co-occurring emotional problems. ADHD with this comorbidity is associated with poorer outcomes than ADHD without comorbidity. Better understanding of the etiology of comorbidity could improve prevention of negative outcomes for children with ADHD. The sample consisted of 567 twin pairs, 3,632 sibling pairs, and 2,340 cousin pairs from the Norwegian Mother, Father and Child Cohort Study. Mothers rated offspring symptoms of ADHD, anxiety, and depression at 8 years of age. Biometric modeling was performed to examine genetic and environmental contributions to co-occurring symptoms of ADHD and emotional problems in the children. We fitted four variable (inattention, hyperactivity/impulsivity, anxiety, and depression) covariance matrices of additive genetic, common environmental, twin- and individual-specific environmental effects. Genetic, shared environmental, and individual-specific environmental factors contributed to the correlation between ADHD and depression. The pattern was similar for both inattention and hyperactivity/impulsivity. Familial risk factors (genetic and shared environment), but not individual-specific environmental factors contributed to the positive correlations between each of the two ADHD subdomains and anxiety. The genetic contributions to ADHD-depression comorbidity only partly overlapped with genetic contributions to ADHD-anxiety comorbidity. Our findings indicate that shared risk factors for ADHD and comorbid depression were familial as well as individual-specific, while shared risk factors for ADHD and comorbid anxiety were primarily familial.

Autism spectrum disorder is associated with sensory processing alterations, such as sensory hyper- and hypo-responsiveness. Twin studies are scarce in this field, but they are necessary in order to disentangle the genetic and environmental contributions to this association. Furthermore, it is unclear how different neurodevelopmental/psychiatric conditions contribute to altering sensory processing. We investigated the association between autistic traits/autism spectrum disorder diagnosis and sensory processing alterations in twins (N = 269), using the adult/adolescent sensory profile, which differentiates four sub-domains: Low Registration, Sensation Seeking, Sensory Sensitivity, and Sensation Avoiding. While the associations between autistic traits and "Low Registration" and "Sensation Avoiding" persisted within monozygotic (genetically identical) twins, "Sensory Sensitivity" was only associated with autistic traits within dizygotic twins. In multivariate analyses with different neurodevelopmental/psychiatric diagnoses as predictor variables, autism spectrum disorder and attention deficit hyperactivity disorder were the strongest predictors for two adult/adolescent sensory profile sub-domains each. The results suggest that the association between autistic traits and "Sensory Sensitivity" is influenced by genetics while non-shared environmental factors influence the associations between autistic traits and "Low Registration" and "Sensation Avoiding." They further indicate that altered sensory processing is not specific to autism spectrum disorder, while autism spectrum disorder is a strong predictor of certain sensory processing alterations, even when controlling for other (comorbid) neurodevelopmental/psychiatric conditions.

This paper uses administrative North Carolina data linked from high school to college and national surveys to characterize the largest contributor to the STEM gender gap: engineering. Disparities are the result of differential entry during high school or earlier rather than postsecondary exit. Differences in pre-college academic preparation account for 5 to 7% of the gap. Females' relative lack of academic self-confidence explains 8%, while other-regarding preferences and professional goals capture a further 14%. Empirical evidence using identifying variation in the gender composition of twins in North Carolina shows that opposite-sex pairs are more likely to pursue gender-stereotypical majors.

Parent-child similarity is a function of genetic and environmental transmission. In addition, genetic effects not transmitted to offspring may drive parental behavior, thereby affecting the rearing environment of the child. Measuring genetic proclivity directly, through polygenic risk scores (PRSs), provides a way to test for the effect of nontransmitted parental genotype, on offspring outcome, termed a "genetic nurture" effect--in other words, if and how parental genomes might affect their children through the environment. The current study used polygenic risk scores for smoking initiation, cigarettes per day, and drinks per week to predict substance use in a sample of 3,008 twins, assessed prospectively from age 17-29, and their parents, from the Minnesota Center for Twin and Family Research. Mixed-effects models were used to test for a genetic nurture effect whereby parental PRSs predict offspring tobacco and alcohol use after statistically adjusting for offspring's own PRS. Parental smoking initiation PRS predicted offspring cigarettes per day at age 24 ([beta] = 0.103, 95% CI [0.03, 0.17]) and alcohol use at age 17 ([beta] = 0.091, 95% CI [0.04, 0.14]) independent of shared genetics. There was also a suggestive independent association between the parent PRS and offspring smoking at age 17 ([beta] = 0.096; 95% CI [0.02, 0.17]). Mediation analyses provided some evidence for environmental effects of parental smoking, alcohol use, and family socioeconomic status. These findings, and more broadly the molecular genetic method used, have implications on the identification of environmental effects on developmental outcomes such as substance use. [The article was co-written with the GWAS & Sequencing Consortium of Alcohol and Nicotine Use (GSCAN).]

The present study examined, within a longitudinal family-informed design and across middle childhood, the predictive associations between preference for solitude and social wariness, two forms of social withdrawal, and peer difficulties. Specifically, preference for solitude, rather than social wariness, was expected to predict peer victimization and rejection, two aspects of peer difficulties. A total of 1,014 children from the Quebec Newborn Twin Study were assessed by teachers and peers at ages 6, 7, and 10 years. Multilevel analyses conducted across three levels, between family, within family, and within person, revealed that preference for solitude, rather than social wariness, increased the risk for peer difficulties in terms of both peer victimization and peer rejection. Specifically, preference for solitude was systematically associated with peer rejection starting at age 6 years and became progressively associated with peer victimization over time. This pattern was found both between and within families. In addition, the predictive association with peer rejection was found within genetically identical, monozygotic twin pairs, suggesting that this predictive association existed after taking into account genetic vulnerabilities. Social wariness was systematically unrelated to peer difficulties. These findings suggest that preference for solitude, rather than social wariness, is a risk factor for peer difficulties. They underscore the relevance of distinguishing these dimensions of social withdrawal and illustrate the usefulness of a family-informed design to document the processes underlying childhood social adjustment.

Valid and reliable teacher ratings serve as the foundation for screening and assessment of youth with behavioral disorders and twin studies offer an opportunity to study those ratings. We conducted a meta-analysis of 15 empirical investigations of aggressive and rule-breaking behavior using teacher ratings in the context of a twin research design. We retrieved n = 53 correlations from n = 7,885 pairs of monozygotic (MZ) twins and n = 67 correlations from n = 11,696 pairs of dizygotic (DZ) twins with two goals: (a) to test the best-fitting models for predicting similarity (correlations) in teacher ratings of MZ and DZ twin pairs and (b) to identify significant predictors in the respective models. We found that, for both MZ and DZ twins, the best-fitting model included all predictors and interactions. In the MZ model, we found a significant positive interaction between the percentage of same teachers who completed the ratings and male twins; in the DZ model, we found a significant negative interaction between the percentage of same teachers who completed the ratings and opposite sex twins. Teacher ratings converged and diverged in expected ways, advancing research in the context of the attributions-bias-context (ABC) model of informant ratings.

This study examines whether, and how, multiple risks in early childhood are associated with an increased likelihood of a poor language or literacy outcome in early adolescence. Using data from 210 participants in the longitudinal Twins Early Developmental Study, we focus on the following risk factors at age 4: family risk, and poor language, speech, emergent literacy and nonverbal skills. The outcomes of interest at age 12 are language, reading fluency and reading comprehension. We contrast a 'cumulative risk' model, counting the presence or absence of each risk factor (breadth), with a model that also considers the severity of the early deficits (depth). A 'cumulative risk index' correlated modestly but significantly with outcome (r = 0.32-0.40). Odds ratios confirmed that having many risk factors (3-6) confers a higher probability of a poor outcome (OR 7.86-17.71) than having one or two (OR 3.65-7.28). Logistic regression models showed that predictive validity is not improved by including information about the severity of each deficit. Even with rich information on children's risk status at age 4, we can make only a moderately accurate prediction of the likelihood of a language or literacy disorder 8 years later (Area Under the Curve = 0.74-0.84; Positive Predictive Value = 0.33-0.55, Negative Predictive Value = 0.86-0.91). Taken together, and consistent with the idea of 'cumulative risk', these results suggest that the breadth of risk is a core predictor of outcome, and furthermore, that the severity of early deficits does not add significantly to this prediction.