Interaction between Parental Education and Twin Correlations for Cognitive Ability in a Norwegian Conscript Sample

Gene-environment interaction analysis of school quality and educational inequality

We study to what extent schools increase or decrease environmental and genetic influences on educational performance. Building on behavioral genetics literature on gene-environment interactions and sociological literature on the compensating and amplifying effects of schools on inequality, we investigate whether the role of genes and the shared environment is larger or smaller in higher-quality school environments. We apply twin models to Dutch administrative data on the educational performance of 18,384 same-sex and 11,050 opposite-sex twin pairs, enriched with data on the quality of primary schools. Our results show that school quality does not moderate genetic and shared-environmental influences on educational performance once the moderation by SES is considered. We find a gene-environment interplay for school SES: genetic variance decreases with increasing school SES. This school SES effect partly reflects parental SES influences. Yet, parental SES does not account for all the school SES moderation, suggesting that school-based processes play a role too.

A Longitudinal Analysis of Gene x Environment Interaction on Verbal Intelligence Across Adolescence and Early Adulthood

The Scarr-Rowe hypothesis proposes that the heritability of intelligence is higher in more advantaged socioeconomic contexts. An early demonstration of this hypothesis was Rowe and colleagues (Rowe et al., Child Dev 70:1151-1162, 1999), where an interaction between the heritability of verbal intelligence and parental education was identified in adolescent siblings in Wave I of the National Longitudinal Study of Adolescent to Adult Health. The present study repeated their original analysis at Wave I using contemporary methods, replicated the finding during young adulthood at Wave III, and analyzed the interaction longitudinally utilizing multiple measurements. We examined parental education, family income, and peer academic environment as potential moderators. Results indicated increased heritability and decreased shared environmental variance of verbal intelligence at higher levels of parental education and peer academic environment in adolescence. Moreover, moderation by peer academic environment persisted into adulthood with its effect partially attributable to novel gene-environment interactions that arose in the process of cognitive development.

Remember This: Age Moderation of Genetic and Environmental Contributions to Verbal Episodic Memory from Midlife through Late Adulthood

It is well documented that memory is heritable and that older adults tend to have poorer memory performance than younger adults. However, whether the magnitudes of genetic and environmental contributions to late-life verbal episodic memory ability differ from those at earlier ages remains unresolved. Twins from 12 studies participating in the Interplay of Genes and Environment in Multiple Studies (IGEMS) consortium constituted the analytic sample. Verbal episodic memory was assessed with immediate word list recall (N = 35,204 individuals; 21,792 twin pairs) and prose recall (N = 3,805 individuals; 2,028 twin pairs), with scores harmonized across studies. Average test performance was lower in successively older age groups for both measures. Twin models found significant age moderation for both measures, with total inter-individual variance increasing significantly with age, although it was not possible definitively to attribute the increase specifically to either genetic or environmental sources. Pooled results across all 12 studies were compared to results where we successively dropped each study (leave-one-out) to assure results were not due to an outlier. We conclude the models indicated an overall increase in variance for verbal episodic memory that was driven by a combination of increases in the genetic and nonshared environmental parameters that were not independently statistically significant. In contrast to reported results for other cognitive domains, differences in environmental exposures are comparatively important for verbal episodic memory, especially word list learning.

Joint Consideration of Means and Variances Might Change the Understanding of Etiology

Twin and adoption studies compare the similarities of people with differing degrees of relatedness to estimate genetic and environmental contributions to trait population variance. The analytic workhorse of these kinds of variance-focused designs is the intraclass correlation, which estimates similarity between pairs of individuals. Group means, by contrast, play no overt role in estimating genetic and environmental influences. Although this focus on variance has made very important contributions to understanding psychological characteristics, we contend that the exclusion of mean effects from behavioral genetic designs may have obscured key environmental influences and impeded full appreciation of the ubiquity and nature of gene-environment interplay in human outcomes. We provide empirical examples already in the literature and a theoretical framework for thinking through the incorporation of mean effects using largely forgotten, non-Mendelian theory regarding how genes influence human outcomes. We conclude that the field needs to develop models capable of fully incorporating mean effects into twin and adoption studies.

Understanding the Effects of the COVID-19 Pandemic on Youth Psychopathology: Genotype-Environment Interplay

BACKGROUND

Adversity has consistently been found to predict poor mental health outcomes in youth. Perhaps the most omnipresent form of adversity in the past several decades has been the coronavirus pandemic of 2020, a global health crisis linked to elevated rates of numerous forms of youth psychopathology. The ongoing nature of the pandemic renders it critical to identify the mechanisms underlying its effects on mental health.

METHODS

The current study examines pandemic-related disruption across multiple domains (e.g., home life, finances) as an etiologic moderator of several common forms of youth psychopathology. Participants were 637 adolescent twin pairs from the Twin Study of Behavioral and Emotional Development in Children (TBED-C). Mothers reported on disruption experienced by the family, using the Epidemic-Pandemic Impacts Inventory.

RESULTS

A series of biometric genotype-by-environment interaction models revealed that disruption augmented the nonshared environmental contributions to emotional distress and conduct problems but had little effect on the etiology of attention-deficit hyperactivity problems.

CONCLUSIONS

Our results indicate that identical and fraternal twin similarity in both emotional symptoms and conduct problems decreased with greater disruption, such that children in the same family became less alike, and did so regardless of their degree of genetic resemblance. Put differently, each twin sibling appeared to have their own idiosyncratic experience of pandemic-related disruptions, with downstream consequences for their mental health.

Race, Ethnicity, and the Scarr-Rowe Hypothesis: A Cautionary Example of Fringe Science Entering the Mainstream

In 2020, Pesta et al. published an article entitled "Racial and Ethnic Group Differences in the Heritability of Intelligence: A Systematic Review and Meta-Analysis" in the journal Intelligence. The authors framed their analysis as an examination of the Scarr-Rowe hypothesis, which holds that the heritability of intelligence varies as a function of socioeconomic status. Pesta et al. concluded that the heritability of intelligence does not differ across racial and ethnic groups in the United States. They claimed their results challenge the Scarr-Rowe hypothesis and support the hereditarian position that mean differences in IQ among racial and ethnic groups are attributable to genetic differences rather than environmental disparities. In this commentary, we outline severe theoretical, methodological, and rhetorical flaws in every step of Pesta et al.'s meta-analysis. The most reliable finding from Pesta et al. is consistent with the Scarr-Rowe hypothesis and directly contradicts a hereditarian understanding of group differences in intelligence. Finally, we suggest that Pesta et al. serves as an example of how racially motivated and poorly executed work can find its way into a mainstream scientific journal, underscoring the importance of robust peer review and rigorous editorial judgment in the open-science era.

The influence of adverse childhood experiences on internalizing and externalizing problems in early adulthood: Evidence of a gene × environment × sex interaction

BACKGROUND

Although adverse childhood experiences (ACEs) have negative effects on subsequent wellbeing, questions remain regarding how and why they do so. Sex, environmental effects, and genetic influences may play a role in both one's exposure to ACEs as well as one's reactions to ACEs.

OBJECTIVE

To understand the combined genetic and environmental influences on males' and females' exposure and reactions to ACEs, and to determine whether sex differences in offending and depressive symptoms were partially impacted by genetic influences.

METHODS

We employed a sample of monozygotic twins (n = 217 pairs), same-sex dizygotic twins (n = 185 pairs), and same-sex full siblings (n = 446 pairs) from the National Longitudinal Study of Adolescent to Adult Health (N = 848 pairs) and estimated a series of multivariable biometric models. Participants were aged between 12 and 21 during Wave I, between 13 and 22 at Wave II, between 18 and 26 at Wave III, and 24 and 32 at Wave IV.

RESULTS

First, there appears to be a stronger genetic influence on ACEs exposure among males than females. Second, genetic influences were stronger on offending among males and depression among females. Third, ACEs moderate the genetic influences on offending and depressive symptomology among males and females: among males, genetic influences on offending decreased as exposure to ACEs increased, while among females, genetic influences on depressive symptoms decreased as exposure to ACEs increased.

CONCLUSIONS

Systematic sex differences in the exposure and reactions to ACEs are at least partially due to genetic differences. Exposure to ACEs is partially influenced by genetics among males, but not females, and the more male and females' experience ACEs, the less influence genes have on their offending and depressive symptomology, respectively.

How should we understand the absence of sex differences in the genetic and environmental origins of antisocial behavior?

Available twin-family data on sex differences in antisocial behavior (ASB) simultaneously suggest that ASB is far more prevalent in males than in females, and that its etiology (i.e. the effects of genes, environments, hormones, culture) does not differ across sex. This duality presents a conundrum: How do we make sense of mean sex differences in ASB if not via differences in genes, environments, hormones, and/or cultures? The current selective review and critique explores possible contributions to these seemingly incompatible sets of findings. We asked whether the presence of sex differences in behavior could be smaller than is typically assumed, or confined to a specific set of behaviors. We also asked whether there might be undetected differences in etiology across sex in twin-family studies. We found little evidence that bias or measurement invariance across sex account for phenotypic sex differences in ASB, but we did identify some key limitations to current twin-family approaches. These included the questionable ability of qualitative sex difference analyses to detect gender norms and prenatal exposure to testosterone, and concerns regarding specific analytic components of quantitative sex difference analyses. We conclude that the male preponderance in ASB is likely to reflect a true sex difference in observed behavior. It was less clear, however, that the genetic and environmental contributions to ASB are indeed identical across sex, as argued by prior twin-family studies. It is our hope that this review will inspire the development of new, genetically-informed methods for studying sex differences in etiology.

Socioeconomic status amplifies genetic effects in middle childhood in a large German twin sample

The Scarr-Rowe hypothesis predicts that the heritability of cognitive abilities is higher in more privileged socioeconomic conditions, meaning that genetic potential can be more fully expressed in environments characterized by high socioeconomic status (SES) compared to low SES. This gene × SES interaction, however, has been replicated mostly in the United States, but not in other Western nations like the United Kingdom. In the current study, we tested the interaction between childhood SES and the heritability of cognitive ability in 3,074 German twin pairs comprising three age cohorts at different developmental stages (mean ages of 11, 17, and 23 years). Higher SES was associated with significantly higher mean cognitive ability scores in the two younger cohorts, with reduced variances at higher SES levels. Results further support the Scarr-Rowe hypothesis in middle childhood, and to some degree in adolescence, but not in adulthood. This indicates that the role of family SES as a moderator of the heritability of cognitive ability changes as children grow older. Moreover, children's shared experiences appear to be explain more variance in cognitive ability at the lower end of the SES distribution in middle childhood and adolescence.

Attained SES as a moderator of adult cognitive performance: Testing gene-environment interaction in various cognitive domains

We examined whether attained socioeconomic status (SES) moderated genetic and environmental sources of individual differences in cognitive performance using pooled data from 9 adult twin studies. Prior work concerning SES moderation of cognitive performance has focused on rearing SES. The current adult sample of 12,196 individuals (aged 27-98 years) allowed for the examination of common sources of individual differences between attained SES and cognitive performance (signaling potential gene-environment correlation mechanisms, rGE), as well as sources of individual differences unique to cognitive performance (signaling potential gene-environment interaction mechanisms, G × E). Attained SES moderated sources of individual differences in 4 cognitive domains, assessed via performance on 5 cognitive tests ranging 2,149 to 8,722 participants. Attained SES moderated common sources of influences for 3 domains and influences unique to cognition in all 4 domains. The net effect was that genetic influences on the common pathway tended to be relatively more important at the upper end of attained SES indicating possible active rGE, whereas, genetic influences for the unique pathway were proportionally stable or less important at the upper end of attained SES. As a noted exception, at the upper end of attained SES, genetic influences unique to perceptual speed were amplified and genetic influences on the common pathway were dampened. Accounting for rearing SES did not alter attained SES moderation effects on cognitive performance, suggesting mechanisms germane to adulthood. Our findings suggest the importance of gene-environment mechanisms through which attained SES moderates sources of individual differences in cognitive performance. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Genetik der allgemeinen kognitiven Fähigkeit

Intelligenz ist eines der bestuntersuchten Konstrukte der empirischen Verhaltenswissenschaften und stellt eine allgemeine geistige Kapazität dar, die unter anderem die Fähigkeit zum schlussfolgernden Denken, zum Lösen neuartiger Probleme, zum abstrakten Denken sowie zum schnellen Lernen umfasst. Diese kognitiven Fähigkeiten spielen eine große Rolle in der Erklärung und Vorhersage individueller Unterschiede in zentralen Bereichen des gesellschaftlichen Lebens, wie Schul- und Bildungserfolg, Berufserfolg, sozioökonomischer Status und Gesundheitsverhalten. Verhaltensgenetische Studien zeigen konsistent, dass genetische Einflüsse einen substanziellen Beitrag zur Erklärung individueller Unterschiede leisten, die über 60 % der Intelligenzunterschiede im Erwachsenenalter erklären. In den letzten Jahren konnten in großen genomweiten Assoziationsstudien mit häufigen genetischen Varianten Hunderte mit Intelligenz assoziierte Loci identifiziert werden sowie über 1300 assoziierte Gene mit differentieller Expression überwiegend im Gehirn. Mehrere Signalwege waren angereichert, vor allen für Neurogenese, Regulation der Entwicklung des Nervensystems sowie der synaptischen Struktur und Aktivität. Die Mehrzahl der assoziierten Loci betraf regulatorische Regionen und interessanterweise lag die Hälfte intronisch. Von den über 1300 Genen überlappen nur 9,2 % mit solchen, die mit monogenen neurokognitiven Störungen assoziiert sind. Insgesamt bestätigen die Befunde ein polygenes Modell Tausender additiver Faktoren, wobei die einzelnen Loci eine sehr geringe Effektstärke aufweisen. Insgesamt erklären die jetzigen Befunde ca. 10 % der Gesamtvarianz des Merkmals. Diese Ergebnisse sind ein wichtiger Ausgangspunkt für zukünftige Forschung sowohl in der Genetik als auch den Verhaltenswissenschaften.

Does the heritability of cognitive abilities vary as a function of parental education? Evidence from a German twin sample

A well-known hypothesis in the behavioral genetic literature predicts that the heritability of cognitive abilities is higher in the presence of higher socioeconomic contexts. However, studies suggest that the effect of socioeconomic status (SES) on the heritability of cognitive ability may not be universal, as it has mostly been demonstrated in the United States, but not in other Western nations. In the present study we tested whether the importance of genetic and environmental effects on cognitive abilities varies as a function of parental education in a German twin sample. Cognitive ability scores (general, verbal, and nonverbal) were obtained on 531 German twin pairs (192 monozygotic, 339 dizygotic, ranging from 7 to 14 years of age; M_age = 10.25, SD = 1.83). Data on parental education were available from mothers and fathers. Results for general cognitive ability and nonverbal ability indicated no significant gene x parental education interaction effect. For verbal ability, a significant nonshared environment (E) x parental education interaction was found in the direction of greater nonshared environmental influences on verbal abilities among children raised by more educated parents.