Investigating cognitive transfer within the framework of music practice: genetic pleiotropy rather than causality

The idea of far transfer effects in the cognitive sciences has received much attention in recent years. One domain where far transfer effects have frequently been reported is music education, with the prevailing idea that music practice entails an increase in cognitive ability (IQ). While cross‐sectional studies consistently find significant associations between music practice and IQ, randomized controlled trials, however, report mixed results. An alternative to the hypothesis of cognitive transfer effects is that some underlying factors, such as shared genes, influence practice behaviour and IQ causing associations on the phenotypic level. Here we explored the hypothesis of far transfer within the framework of music practice. A co‐twin control design combined with classical twin‐modelling based on a sample of more than 10,500 twins was used to explore causal associations between music practice and IQ as well as underlying genetic and environmental influences. As expected, phenotypic associations were moderate (r = 0.11 and r = 0.10 for males and females, respectively). However, the relationship disappeared when controlling for genetic and shared environmental influences using the co‐twin control method, indicating that a highly practiced twin did not have higher IQ than the untrained co‐twin. In line with that finding, the relationship between practice and IQ was mostly due to shared genetic influences. Findings strongly suggest that associations between music practice and IQ in the general population are non‐causal in nature. The implications of the present findings for research on plasticity, modularity, and transfer are discussed.     

Genetic and environmental transactions underlying educational attainment

This report used a population-representative longitudinal twin study with two birth cohorts to explore the association between intelligence and education by understanding how genetic and environmental influences on intelligence moderate genetic and environmental influences on school grades and educational attainment. Nonshared environmental influences on grades were strong when IQ was low, but decreased across the range of IQ. Shared environmental influences common to age 24 educational attainment and age 17 IQ were strong when IQ was low, but genetic influences common to IQ and education were strong when IQ was high. These results suggest that the causal mechanisms linking educational variables with intelligence differ for people with different levels of intelligence.     

Herrnstein''s syllogism: genetic and shared environmental influences on IQ, education, and income

Genotypes may influence the phenotypic associations among IQ, education, and income. To investigate this hypothesis, we believe that the appropriate methodology requires estimation of genetic and environmental influences using data able to separate these influences. The National Longitudinal Survey of Youth (NLSY) is a nationally representative sample that contains genetically-informative full- and half-siblings (28–35 years old in 1992; Ns=1943 full-siblings, 129 half-siblings). A biometric genetic model was fit that estimated the shared environmental and genetic variance components of IQ, years of education, and hourly income. The total heritabilities were 0.64 for IQ, 0.68 for education, and 0.42 for income. Heritabilities due to a common genetic factor were 0.35 for IQ, 0.52 for education, and 0.12 for income. Environmental influences due to a common shared environmental factor were 0.23 for IQ, 0.18 for education, and 0.08 for income. The model predicted a correlation of 0.63 between IQ and education and 0.34 between IQ and income. Sixty-eight percent of the former and 59% of the latter was genetically mediated; the remainder was mediated by common shared environment. These findings suggest that social inequality in the United States has its origin in both genetically-based traits and in different environmental backgrounds.     

Genetic effects on male sexual coercion

The genetic and environmental influences on sexual coercion, and to what extent its associations with alcohol use and psychopathy depend on shared genetic and environmental effects, were explored in a Finnish population-based sample of 938 men, aged 33-43 years, using the classical twin study design. All three phenotypes were associated positively and affected by genes (sexual coercion 28%, alcohol use 60%, psychopathy 54%), with 46% of the correlation between sexual coercion and psychopathy, 89% of the correlation between alcohol use and psychopathy and 100% of the correlation between sexual coercion and alcohol use being explained by shared genetic effects. Further, the results showed that a proportion of the variance in sexual coercion was derived from a highly genetic source that was common with alcohol use and psychopathy. This latent factor was hypothesized to reflect a general tendency for antisocial behavior that is pervasive across different situations. Relevant theories on sexual coercion were discussed in light of the results.     

Most people with mental disorders are happy: A 3-year follow-up in the Dutch general population

The nature of the associations between life satisfaction, anxiety, and depression remains elusive. Using questionnaire data from a large population-based sample (N = 6326) of young adult Norwegian twins (aged 18–31 years) we explored the extent to which latent genetic and environmental factors are (1) common or distinct, and (2) sex-specific. Phenotypic correlations ranged between 0.44 and 0.70 in females, and between 0.41 and 0.69 in males. Environmental influences accounted for 75% of these correlations in females, and less than 50% in males. Genetic and environmental sources of life satisfaction, symptoms of anxiety, and symptoms of depression were shared mostly, but the magnitude of the effects was different in males and females. In both sexes, however, aetiological factors enhancing life satisfaction were simultaneously protecting against feelings of sadness and displeasure, but contributed less to countervailing anxiety and tension.     

Socioeconomic status and school grades: Placing their association in broader context in a sample of biological and adoptive families

SES has long interested researchers investigating school achievement. Its effects are often addressed by studying predictors of achievement in economically disadvantaged samples living primarily in biological families, confounding genetic and environmental influences. Little is known about SES's purely environmental effects. We measured them in 617 adoptive and biological families, adjusting for sample restriction of SES range. Controlling for gender, parenting, parental expectations for educational attainment (PEEA), IQ, engagement in school, and genetic and shared environmental influences on sibling pairs, SES still made a small but significant nonshared environmental contribution to school grades. IQ, PEEA, and SES had collinear associations with school grades, as did engagement and parenting. The associations of IQ and engagement with school grades were largely independent of each other. The link between PEEA and IQ was stronger in adoptive than biological offspring. We discuss the implications of these findings.     

Genetic and environmental influences on antisocial behavior: a meta-analysis of twin and adoption studies

A meta-analysis of 51 twin and adoption studies was conducted to estimate the magnitude of genetic and environmental influences on antisocial behavior. The best fitting model included moderate proportions of variance due to additive genetic influences (.32), nonadditive genetic influences (.09), shared environmental influences (.16), and nonshared environmental influences (.43). The magnitude of familial influences (i.e., both genetic and shared environmental influences) was lower in parent-offspring adoption studies than in both twin studies and sibling adoption studies. Operationalization, assessment method, zygosity determination method, and age were significant moderators of the magnitude of genetic and environmental influences on antisocial behavior, but there were no significant differences in the magnitude of genetic and environmental influences for males and females.     

Happiness and health: environmental and genetic contributions to the relationship between subjective well-being, perceived health, and somatic illness

The aim was to identify genetic and environmental influences on the covariances between subjective well-being (SWB), perceived health, and somatic illness. Analyses were based on 6576 Norwegian twins aged 18-31. Heritabilities ranged from .24 to.66. SWB correlated .50 with perceived health, -.25 with musculoskeletal pain, and -.07 with allergy. Common genetic factors accounted for 45%-60% of associations. SWB and perceived health was to a high extent influenced by the same genes (r(g)=.72 and.82 for males and females, respectively). For SWB and musculoskeletal pain, r-sub(g) =-.29 and -.42 for males and females, respectively. Effects were partly sex specific. Environmental factors shared by twins did not affect the covariances. Results support a differentiated view of SWB-health relations, and imply that both genes and environment play important roles in the associations between well-being and health.     

Personality related traits as predictors of music practice: Underlying environmental and genetic influences

Little is known about reasons for individual differences in practice behavior – why do some individuals practice more than others? Here we explore personality related traits such as openness, motivation and flow proneness as well as IQ as potential predictors of music practice. Using a large Swedish twin cohort of more than 10,500 individuals we also estimated genetic and environmental influences underlying such associations. Significant associations with music practice were found for IQ, intrinsic motivation, music flow, and openness. With all predictors in the same model (including sex and age) we could explain about 25% of variance in music practice. However, IQ and intrinsic motivation became non-significant in the full model, with music specific flow being the strongest predictor of music practice. Multivariate genetic modeling with the two remaining significant predictors (openness and music flow) and music practice suggested that the associations between the variables were largely due to shared genetic influences with some additional non-shared environmental influences. Our findings suggest that common genes may influence both music practicing behavior and traits related to artistic interests and musical enjoyment (flow).     

Alcohol Use in Adolescent Twins and Affiliation with Substance Using Peers

Affiliation with substance using peers is one of the strongest predictors of adolescent alcohol use. This association is typically interpreted causally: peers who drink incite their friends to drink. This association may be complicated by uncontrolled genetic and environmental confounds because teens with familial predispositions for adolescent substance use may be more likely to select into social networks where drinking is common. We test this alternative hypothesis using a sample of 1,820 twin and sibling pairs, and their same-sex best friends, from three waves of the National Longitudinal Study of Adolescent Health. Across all three waves, peer report of substance use did not influence adolescent alcohol use when genetic and shared environmental predispositions for drinking were considered. The association between alcohol use and peer behavior may be a spurious association attributable to a shared genetic liability to drink alcohol and associate with peers who drink alcohol.     

Sex differences in the genetic and environmental influences on childhood conduct disorder and adult antisocial behavior

Sex differences in the genetic and environmental influences on childhood conduct disorder and adult antisocial behavior were examined in a large community sample of 6,383 adult male, female, and opposite-sex twins. Retrospective reports of childhood conduct disorder (prior to 18 years of age) were obtained when participants were approximately 30 years old, and lifetime reports of adult antisocial behavior (antisocial behavior after 17 years of age) were obtained 8 years later. Results revealed that either the genetic or the shared environmental factors influencing childhood conduct disorder differed for males and females (i.e., a qualitative sex difference), but by adulthood, these sex-specific influences on antisocial behavior were no longer apparent. Further, genetic and environmental influences accounted for proportionally the same amount of variance in antisocial behavior for males and females in childhood and adulthood (i.e., there were no quantitative sex differences). Additionally, the stability of antisocial behavior from childhood to adulthood was slightly greater for males than females. Though familial factors accounted for more of the stability of antisocial behavior for males than females, genetic factors accounted for the majority of the covariation between childhood conduct disorder and adult antisocial behavior for both sexes. The genetic influences on adult antisocial behavior overlapped completely with the genetic influences on childhood conduct disorder for both males and females. Implications for future twin and molecular genetic studies are discussed.     

Weak etiologic links between control and the externalizing behaviors delinquency and substance abuse in adolescence

Impulsive/disinhibitory personality traits have consistently been associated with externalizing symptomatology such as delinquency and substance use problems, often starting in adolescence. Yet the etiological nature of this co-occurrence is not well understood. Using a classic twin study design with self-report data from 717 male and female twin pairs, aged 15–18 years, a hierarchical psychometric model was examined. In this model the shared variance and etiological structure between control, delinquency and substance abuse symptoms, was modeled through a common externalizing factor. Model fitting indicated that the genetic and environmental influences differed in strength between male and female adolescents. The heritability of the externalizing factor was 45% in males and 10% in females, though neither was statistically different from zero. A statistically significant influence of shared environmental factors was seen for both sexes, 21% in males and 54% in females. In both sexes, the externalizing factor accounted for little variance in control, indicating a weak association and little shared etiology with externalizing liability. These results illuminate further that facets of impulsivity are differentially associated with vulnerability for externalizing symptomatology.     

Sexual behavior in young adulthood: a population-based twin study.

OBJECTIVE: With behavior genetic analyses of data from young adult twins, we evaluated theoretical perspectives that differentially emphasize biological dispositions, social/cultural factors, or universal pathways to explain individual differences in sexual behaviors. DESIGN: We fit biometric sex limitation models to three aspects of sexual behavior reported by 4,925 Finnish twins ages 23-27. MAIN OUTCOME MEASURE: From a postal questionnaire, we obtained self-report information on initiation/abstinence of sexual intercourse, onset age, and number of sexual partners. RESULTS: Genetic and non-shared environmental influences were significant for all three measures. There were trends for common environmental influences on initiation and, in females, age at first intercourse. Some differential effects in males and females were found. Results comparing onset age and number of partners among experienced twins from pairs concordant and discordant for initiation found genetic and environmental influences on initiation/abstinence overlapped those found for the other aspects of sexual behavior. CONCLUSIONS: These results document genetic variation in individual differences in sexual behavior of young adults. Incorporating genetic dispositions into integrated models of sexual behavior will facilitate more effective health promotion and risk taking intervention.     

The reproduction of intelligence

Although a negative relationship between fertility and education has been described consistently in most countries of the world, less is known about the relationship between intelligence and reproductive outcomes. Also the paths through which intelligence influences reproductive outcomes are uncertain. The present study uses the NLSY79 to analyze the relationship of intelligence measured in 1980 with the number of children reported in 2004, when the respondents were between 39 and 47 years old. Intelligence is negatively related to the number of children, with partial correlations (age controlled) of ?.156, ?.069, ?.235 and ?.028 for White females, White males, Black females and Black males, respectively. This effect is related mainly to the g-factor. It is mediated in part by education and income, and to a lesser extent by the more “liberal” gender attitudes of more intelligent people. In the absence of migration and with constant environment, genetic selection would reduce the average IQ of the US population by about .8 points per generation.     

Sober adolescence–Predictor of psychosocial maladjustment in young adulthood?

We have explored how age at first intoxication with alcohol relates to mental health, social integration and adjustment to the adult role. The data stem from a longitudinal representative study of 2000 Norwegians. The sample was assessed at ages 19–22, 21–24 and 25–28. Among females, only early intoxication was related to young adult symptoms of poor mental health. A U-shaped association between intoxication debut and psychological problems was revealed among males, implying that both early and late beginners had more such problems than those who had followed the mainstream. These associations persisted without change over time. However, males who remained abstainers in adulthood were psychologically healthy, but they showed indications of a delayed entry into the adult role. Male late beginners were also somewhat reluctant to adopt adult role-behaviors. Thus, getting drunk for the first time in mid-adolescence seems to be an ingredient in the normal developmental process in young males.     

What Virtual Twins Reveal About General Intelligence and Other Behaviors

The Fullerton Virtual Twin Study has been assessing the behaviors of an unusual sibship since 1982. Virtual twins (VTs) are same-age, unrelated siblings reared together since infancy. They replicate the rearing situation of twins but without the genetic link, enabling direct assessment of shared environmental effects on behavior. An updated analysis of IQ data, based on an increased sample of 142 VT pairs (7.87 years, SD=8.22), is presented. Intraclass correlations of .28 (IQ) and .11 (subtest profile) indicated modest shared environmental influences on intelligence. Findings from the Twins, Adoptees, Peers and Siblings (TAPS) project that studies virtual twins and other kinships are described.     

Preliminary Evidence for Associations of CHRM2 with Substance Use and Disinhibition in Adolescence

Evidence for shared heritable influences across domains of substance use suggests that some genetic variants influence broad risk for externalizing behaviors. Theories of externalizing psychopathology also suggest that genetic liability for substance use manifests as temperamental risk factors, particularly those related to behavioral disinhibition, during adolescence. The cholinergic muscarinic receptor 2 gene (CHRM2) is a promising candidate for studying genetic influences on broad-based risk for externalizing traits. This study examined a candidate CHRM2 polymorphism (rs1455858) in relation to substance use and personality measures of disinhibition in a sample of high-risk adolescents (n?=?124). Bivariate analyses and structural equation modeling (SEM) evaluated associations of rs1455858 with measures of drug involvement (alcohol, tobacco and marijuana) and disinhibition (indexed by impulsivity and sensation seeking scores). Bivariate analyses showed significant associations of CHRM2 with several behavioral phenotypes. In SEM analyses CHRM2 related significantly to latent measures of substance use and disinhibition; additionally, disinhibition mediated the association of CHRM2 with substance use. These results suggest that CHRM2 variants are potentially relevant for adolescent substance use and that temperamental risk factors could contribute to these associations.     

The genetic and environmental architecture to the stability of IQ: Results from two independent samples of kinship pairs

Existing research has revealed that IQ remains relatively stable over the life course, though questions remain about how stable IQ is and whether the stability of IQ varies across different developmental periods of the life course. Despite this stability, there are also questions surrounding the factors that might explain the stability of IQ. Against this backdrop, we conduct bivariate genetic models to estimate genetic, shared environmental, and nonshared environmental influences on the stability of IQ. To do so, we analyze kinship pairs drawn from two separate longitudinal samples: The National Collaborative Perinatal Project (CPP) and the National Longitudinal Study of Adolescent Health (Add Health). Across both samples, IQ was found to be relatively stable. Moreover, the genetic analyses revealed that between 66% and 83% of the stability in IQ was due to genetic factors and between 43% and 69% of the change in IQ was due to genetic factors. The remainder of the stability and change in IQ was the result of a combination of shared and nonshared environmental influences. Importantly, some substantive race differences emerged in respect to genetic and environmental influences on the stability of IQ. We conclude with a discussion of the limitations of the study and avenues for future research.     

Trait urgency and substance use decision making in adolescents and young adults: The role of socio-affective factors

The personality trait of urgency has been linked to substance use outcomes. This study examined possible mechanisms underlying this relationship. A total of 187 participants divided into two age groups (adolescents aged 15–17 and young adults aged 18–21) completed measures of urgency and affective associations about substance use. They were then asked to read a hypothetical situation in which a protagonist considers using a ‘legal high’, and to report their perceived peer approval and perceived positive and negative consequences of such substance use, as well as the likelihood that they would personally use the substance. Multiple-group path analysis was employed to test a model by which urgency influenced the substance use decision via affective associations and perceived peer approval. In adolescents, urgency was significantly related to positive affective associations, and a significant indirect path from urgency to decision via affective associations was found. In young adults, there was a significant path from urgency to decision via peer approval. Results indicate that high urgency individuals may rely on socio-affective information when considering whether to engage in substance use.