Journal articles: 'Nuclear twin family model'

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Slawinski, Brooke L., Kelly L. Klump, and S. Alexandra Burt. "The etiology of social aggression: a nuclear twin family study." Psychological Medicine 49, no. 1 (April 2, 2018): 162–69. http://dx.doi.org/10.1017/s0033291718000697.

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AbstractBackgroundSocial aggression is a form of antisocial behavior in which social relationships and social status are used to damage reputations and inflict emotional harm on others. Despite extensive research examining the prevalence and consequences of social aggression, only a few studies have examined its genetic–environmental etiology, with markedly inconsistent results.MethodWe estimated the etiology of social aggression using the nuclear twin family (NTF) model. Maternal-report, paternal-report, and teacher-report data were collected for twin social aggression (N = 1030 pairs). We also examined the data using the classical twin (CT) model to evaluate whether its strict assumptions may have biased previous heritability estimates.ResultsThe best-fitting NTF model for all informants was the ASFE model, indicating that additive genetic, sibling environmental, familial environmental, and non-shared environmental influences significantly contribute to the etiology of social aggression in middle childhood. However, the best-fitting CT model varied across informants, ranging from AE and ACE to CE. Specific heritability estimates for both NTF and CT models also varied across informants such that teacher reports indicated greater genetic influences and father reports indicated greater shared environmental influences.ConclusionsAlthough the specific NTF parameter estimates varied across informants, social aggression generally emerged as largely additive genetic (A = 0.15–0.77) and sibling environmental (S = 0.42–0.72) in origin. Such findings not only highlight an important role for individual genetic risk in the etiology of social aggression, but also raise important questions regarding the role of the environment.

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Klassen, Lea, Eike F. Eifler, Anke Hufer, and Rainer Riemann. "WHY DO PEOPLE DIFFER IN THEIR ACHIEVEMENT MOTIVATION? A NUCLEAR TWIN FAMILY STUDY." Primenjena psihologija 11, no. 4 (January 14, 2019): 433–50. http://dx.doi.org/10.19090/pp.2018.4.433-450.

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Although many previous studies have emphasized the role of environmental factors, such as parental home and school environment, on achievement motivation, classical twin studies suggest that both additive genetic influences and non-shared environmental influences explain interindividual differences in achievement motivation. By applying a Nuclear Twin Family Design on the data of the German nationally representative of TwinLife study, we analyzed genetic and environmental influences on achievement motivation in adolescents and young adults. As expected, the results provided evidence for the impact of additive genetic variation, non-additive genetic influences, as well as twin specific shared environmental influences. The largest amount of variance was attributed to non-shared environmental influences, showing the importance of individual experiences in forming differences in achievement motivation. Overall, we suggest a revision of models and theories that explain variation in achievement motivation by differences in familial socialization only.

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Burt, S. Alexandra, and Kelly L. Klump. "Etiological Distinctions between Aggressive and Non-aggressive Antisocial Behavior: Results from a Nuclear Twin Family Model." Journal of Abnormal Child Psychology 40, no. 7 (April 1, 2012): 1059–71. http://dx.doi.org/10.1007/s10802-012-9632-9.

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Verberne, Thomas J. P. "A Developmental Model of Vulnerability to Suicide: Consistency with Some Recurrent Findings." Psychological Reports 89, no. 2 (October 2001): 217–26. http://dx.doi.org/10.2466/pr0.2001.89.2.217.

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Converging evidence from family, twin, adoption, brain biochemistry, and nuclear biological studies suggests that vulnerability to suicide may be genetically determined. Secondly, there is evidence that the predisposition to suicide remains latent until it becomes activated during puberty. Thirdly, for a suicide attempt to occur, the activated predisposition must be triggered by a stressor. This three-stage developmental model is shown to be consistent with some major demographic, epidemiological, and other correlates of suicide.

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Gladyck, Stephanie, Siddhesh Aras, Maik Hüttemann, and Lawrence I. Grossman. "Regulation of COX Assembly and Function by Twin CX9C Proteins—Implications for Human Disease." Cells 10, no. 2 (January 20, 2021): 197. http://dx.doi.org/10.3390/cells10020197.

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Oxidative phosphorylation is a tightly regulated process in mammals that takes place in and across the inner mitochondrial membrane and consists of the electron transport chain and ATP synthase. Complex IV, or cytochrome c oxidase (COX), is the terminal enzyme of the electron transport chain, responsible for accepting electrons from cytochrome c, pumping protons to contribute to the gradient utilized by ATP synthase to produce ATP, and reducing oxygen to water. As such, COX is tightly regulated through numerous mechanisms including protein–protein interactions. The twin CX9C family of proteins has recently been shown to be involved in COX regulation by assisting with complex assembly, biogenesis, and activity. The twin CX9C motif allows for the import of these proteins into the intermembrane space of the mitochondria using the redox import machinery of Mia40/CHCHD4. Studies have shown that knockdown of the proteins discussed in this review results in decreased or completely deficient aerobic respiration in experimental models ranging from yeast to human cells, as the proteins are conserved across species. This article highlights and discusses the importance of COX regulation by twin CX9C proteins in the mitochondria via COX assembly and control of its activity through protein–protein interactions, which is further modulated by cell signaling pathways. Interestingly, select members of the CX9C protein family, including MNRR1 and CHCHD10, show a novel feature in that they not only localize to the mitochondria but also to the nucleus, where they mediate oxygen- and stress-induced transcriptional regulation, opening a new view of mitochondrial-nuclear crosstalk and its involvement in human disease.

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Papadakos, Grigorios, Justyna A. Wojdyla, and Colin Kleanthous. "Nuclease colicins and their immunity proteins." Quarterly Reviews of Biophysics 45, no. 1 (November 16, 2011): 57–103. http://dx.doi.org/10.1017/s0033583511000114.

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AbstractIt is more than 80 years since Gratia first described ‘a remarkable antagonism between two strains ofEscherichia coli’. Shown subsequently to be due to the action of proteins (or peptides) produced by one bacterium to kill closely related species with which it might be cohabiting, such bacteriocins have since been shown to be commonplace in the internecine warfare between bacteria. Bacteriocins have been studied primarily from the twin perspectives of how they shape microbial communities and how they penetrate bacteria to kill them. Here, we review the modes of action of a family of bacteriocins that cleave nucleic acid substrates inE. coli, known collectively as nuclease colicins, and the specific immunity (inhibitor) proteins that colicin-producing organisms make in order to avoid committing suicide. In a process akin to targeting in mitochondria, nuclease colicins engage in a variety of cellular associations in order to translocate their cytotoxic domains through the cell envelope to the cytoplasm. As well as informing on the process itself, the study of nuclease colicin import has also illuminated functional aspects of the host proteins they parasitize. We also review recent studies where nuclease colicins and their immunity proteins have been used as model systems for addressing fundamental problems in protein folding and protein–protein interactions, areas of biophysics that are intimately linked to the role of colicins in bacterial competition and to the import process itself.

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Kendler, Kenneth S. "The sporadic v. familial classification given aetiological heterogeneity: II. Power analyses." Psychological Medicine 18, no. 4 (November 1988): 991–99. http://dx.doi.org/10.1017/s0033291700009910.

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SynopsisThis paper examines the power of the sporadic v. familial method as applied to schizophrenia and major depression. The model used assumes aetiological heterogeneity with a subpopulation of cases due to a ‘major’ environmental event and the remainder resulting from a generalized single major locus. The findings suggest that, for sample sizes to which it is commonly applied, the sporadic v. familial classification has low power to detect aetiological heterogeneity. When applied to nuclear families, substantial power requires at a minimum 100–150 proband families. If the proportion of environmental cases in the population is low, or the ‘test’ for environmental aetiology in probands does not have high sensitivity and specificity, the required sample sizes are considerably larger. Adding monozygotic twins increases the power of the method, but including second-degree relatives does not. The optimal approach to the sporadic v. familial method will differ as a function of the frequency of the disorder and the relative effort and expense of examining probands versus family members. Other methods should be considered for discriminating genetic and environmental forms of illness.

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Duffy, David L., Lindon J. Eaves, and G. P. Vogler. "Informativeness of twin-nuclear family and nuclear family designs for segregation analysis." Genetic Epidemiology 8, no. 4 (1991): 231–35. http://dx.doi.org/10.1002/gepi.1370080404.

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Engelen, G. B. "New nuclear twin shell model." Radiation Effects 94, no. 1-4 (March 1986): 85–88. http://dx.doi.org/10.1080/00337578608208360.

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Bleidorn, Wiebke, Anke Hufer, Christian Kandler, Christopher J. Hopwood, and Rainer Riemann. "A Nuclear Twin Family Study of Self–Esteem." European Journal of Personality 32, no. 3 (May 2018): 221–32. http://dx.doi.org/10.1002/per.2136.

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Twin studies suggest that both genes and environments influence the emergence and development of individual differences in self–esteem. However, different lines of research have emphasized either the role of genes or of environmental influences in shaping self–esteem, and the pathways through which genes and environments exert their influence on self–esteem remain largely unclear. In this study, we used nationally representative data from over 2000 German twin families and a nuclear twin family design (NTFD) to further our understanding of the genetic and environmental influences on individual differences in self–esteem. Compared with classical twin designs, NTFDs allow for finer–grained descriptions of the genetic and environmental influences on phenotypic variation, produce less biased estimates of those effects, and provide more information about different environmental influences and gene–environment correlation that contribute to siblings’ similarity. Our NTFD results suggested that additive and non–additive genetic influences contributed to individual differences in self–esteem as well as environmental influences that are both shared and not shared by twins. The shared environmental component mostly reflected non–parental influences. These findings highlight the increased sensitivity afforded by NTFDs but also remaining limitations that need to be addressed by future behavioural genetic work on the sources of self–esteem. Copyright © 2018 European Association of Personality Psychology

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Keller, Matthew C., Sarah E. Medland, Laramie E. Duncan, Peter K. Hatemi, Michael C. Neale, Hermine H. M. Maes, and Lindon J. Eaves. "Modeling Extended Twin Family Data I: Description of the Cascade Model." Twin Research and Human Genetics 12, no. 1 (February 1, 2009): 8–18. http://dx.doi.org/10.1375/twin.12.1.8.

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AbstractThe classical twin design uses data on the variation of and covariation between monozygotic and dizygotic twins to infer underlying genetic and environmental causes of phenotypic variation in the population. By using data from additional relative classes, such as parents, extended twin family designs more comprehensively describe the causes of phenotypic variation. This article introduces an extension of previous extended twin family models, the Cascade model, which uses information on twins as well as their siblings, spouses, parents, and children to differentiate two genetic and six environmental sources of phenotypic variation. The Cascade also relaxes assumptions regarding mating and cultural transmission that existed in previous extended twin family designs. The estimation of additional parameters and relaxation of assumptions is potentially important, not only because it allows more fine-grained descriptions of the causes of phenotypic variation, but more importantly, because it can reduce the biases in parameter estimates that exist in earlier designs.

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Medland, Sarah E., and Matthew C. Keller. "Modeling Extended Twin Family Data II: Power Associated With Different Family Structures." Twin Research and Human Genetics 12, no. 1 (February 1, 2009): 19–25. http://dx.doi.org/10.1375/twin.12.1.19.

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AbstractModeling the data from extended twin pedigrees allows the estimation of increasing complex covariance relationships in which the effects of cultural transmission, nonrandom mating and genotype x environment covariation can be incorporated. However, the power to detect these effects in existing data sets has not yet been examined. The present study examined the effects that different family structures (i.e., the ratio of MZ to DZ families and the importance of cousins vs. avuncular relatives) have on statistical power. In addition, we examined the power to detect genetic and environmental effects within the context of two large data sets (VA30K and the OZVA60K). We found that power to detect additive genetic and cultural transmission effects were maximized by over sampling MZ families. In terms of ascertainment, there was little difference in power between samples that had focused on recruiting a third generation (the children of twins) versus those that had focused on recruiting the siblings of the twins. In addition, we examined the power to detect additive and dominant genetic effects, cultural transmission and assortative mating in the existing VA30K and OZVA60K samples, under two different models of mating: phenotypic assortment and social homogamy. There was nearly 100% power to detect assortative mating and cultural transmission, against a background of small additive and dominant genetic and familial environmental effects. In addition, the power to detect additive or dominant genetic effects quickly asymptoted, so that there was almost 100% power to detect effects explaining 20% or more of the total variance. These results demonstrate that the Cascade model has sufficient power to detect parameters of interest in existing datasets. Mx scripts are available from www.vipbg.vcu.edu/~sarahme/cascade.

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Rabe-Hesketh, S., A. Skrondal, and H. K. Gjessing. "Biometrical Modeling of Twin and Family Data Using Standard Mixed Model Software." Biometrics 64, no. 1 (May 2, 2007): 280–88. http://dx.doi.org/10.1111/j.1541-0420.2007.00803.x.

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Blom, Victoria, Lennart Bodin, Gunnar Bergström, and Pia Svedberg. "Applying the demand-control-support model on burnout in managers and non-managers." International Journal of Workplace Health Management 9, no. 1 (March 7, 2016): 110–22. http://dx.doi.org/10.1108/ijwhm-06-2015-0033.

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Purpose – The purpose of this paper is to study the demand-control-support (DCS) model on burnout in male and female managers and non-managers, taking into account genetic and shared family environmental factors, contributing to the understanding of mechanisms of how and when work stress is related to burnout. Design/methodology/approach – A total of 5,510 individuals in complete same-sex twin pairs from the Swedish Twin Registry were included in the analyses. Co-twin control analyses were performed using linear mixed modeling, comparing between-pairs and within-pair effects, stratified by zygosity and sex. Findings – Managers scored higher on demands and control in their work than non-managers, and female managers seem to be particularly at risk for burnout facing more demands which are not reduced by a higher control as in their male counterparts. Co-twin analyses showed that associations between control and burnout as well as between demands and burnout seem to be affected by shared family environmental factors in male non-managers but not in male managers in which instead the associations between social support and burnout seem to be influenced by shared family environment. Practical implications – Taken together, the study offers knowledge that shared environment as well as sex and managerial status are important factors to consider in how DCS is associated to exhaustion. Originality/value – Using twin data with possibilities to control for genetics, shared environment, sex and age, this study offers unique insight into the DCS research, which focusses primarily on the workplace environment rather than individual factors.

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KENDLER, KENNETH S., STEVEN H. AGGEN, CAROL A. PRESCOTT, KRISTEN C. JACOBSON, and MICHAEL C. NEALE. "Level of family dysfunction and genetic influences on smoking in women." Psychological Medicine 34, no. 7 (October 2004): 1263–69. http://dx.doi.org/10.1017/s0033291704002417.

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Background. An adoption study of alcoholism suggests that in women, the impact of genetic risk factors become greater in the presence of conflict in the family of origin. Is the same true for cigarette smoking (CS)?Method. We obtained, in a sample of 1676 twins from female–female twin pairs from a population-based register, a measure of maximum lifetime CS (divided into six ordinal categories) and family dysfunction (FD) assessed as the mean report of up to four informants (twin, co-twin, mother, father). Statistical analysis was conducted by traditional regression analysis and a moderator structural equation twin model using the computer program Mx.Results. With increasing levels of FD, maximum CS increased substantially while correlations for CS in monozygotic (MZ) and dizygotic (DZ) twins decreased modestly. Regression analyses demonstrated reduced twin-pair resemblance for CS with increasing levels of FD. The best-fit structural equation model found high levels of heritability for CS and no evidence for a role of shared environment. With increasing levels of FD, the proportion of variance in CS due to genetic factors (i.e. heritability) decreased while that due to unique environmental effects increased.Conclusions. Several different statistical methods suggested that, contrary to prediction, heritability of CS decreased rather than increased with higher levels of dysfunction in the family of origin. The hypothesis that genetic effects for psychiatric and drug-use disorders become stronger in more adverse environments is not universally true.

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Prescott, Carol A., Deanna Lyter Achorn, Ashley Kaiser, Lindsey Mitchell, John J. McArdle, and Susan J. Lapham. "The Project TALENT Twin and Sibling Study." Twin Research and Human Genetics 16, no. 1 (October 29, 2012): 437–48. http://dx.doi.org/10.1017/thg.2012.71.

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Project TALENT is a US national longitudinal study of about 377,000 individuals born in 1942–1946, first assessed in 1960. Students in about 1,200 schools participated in a 2-day battery covering aptitudes, abilities, interests, and individual and family characteristics (Flanagan, 1962; www.projectTALENT.org). Follow-up assessments 1, 5, and 11 years later assessed educational and occupational outcomes. The sample includes approximately 92,000 siblings from 40,000 families, including 2,500 twin pairs and 1,200 other siblings of twins. Until recently, almost no behavior genetic research has been conducted with the sample. In the original data collection information was not collected with the intent to link family members. Recently, we developed algorithms using names, addresses, birthdates, and information about family structure to link siblings and identify twins. We are testing several methods to determine zygosity, including use of yearbook photographs. In this paper, we summarize the design and measures in Project TALENT, describe the Twin and Sibling sample, and present our twin-sib-classmate model. In most twin and family designs, the ‘shared environment’ includes factors specific to the family combined with between-family differences associated with macro-level variables such as socioeconomic status. The school-based sampling design used in Project TALENT provides a unique opportunity to partition the shared environment into variation shared by siblings, specific to twins, and associated with school- and community-level factors. The availability of many measured characteristics on the family, schools, and neighborhoods enhances the ability to study the impact of specific factors on behavioral variation.

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Kaprio, J., R. J. Rose, S. Sarna, H. Langinvainio, M. Koskenvuo, H. Rita, and K. Heikkilä. "Design and Sampling Considerations, Response Rates, and Representativeness in a Finnish Twin Family Study." Acta geneticae medicae et gemellologiae: twin research 36, no. 1 (January 1987): 79–93. http://dx.doi.org/10.1017/s000156600000461x.

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AbstractKinships composed of twin parents, their spouses and children, offer a robust and flexible sampling design for research in genetic epidemiology. Families-of-twins designs circumvent some of the sampling problems that arise when independent data sets are combined, and these designs provide unique evaluations of maternal influences, assortative mating and X-linkage. Unfortunately, empirical studies of families of twin parents have been limited by relatively small samples and by the self-selection biases intrinsic in ascertainment of families from volunteer twin registries.A large and representative cohort of monozygotic and dizygotic twin parents, drawn from a population-based twin registry, provides the optimal sampling frame for twin-family research. This paper reviews the sampling considerations underlying the initial family study based on the Finnish Twin Cohort and evaluates the representativeness of the sampled twins. Spouses and adult children (over 18 years) of 236 pairs of twins, about equally divided by gender and zygosity, were evaluated by a postal questionnaire. Individual response rates exceeded 86% and in 464 of the 472 nuclear families (98.3% ), at last one member of the twin's family completed the questionnaire. The sampled twins, selected for fecundity to maximize statistical power of the obtained data, were broadly representative of non-selected twins drawn from the Cohort, with whom they were matched on age, gender, and zygosity. Such results suggest that the Finnish Cohort has excellent potential for extended twin-family research designs.

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KENDLER, K. S., S. H. AGGEN, K. C. JACOBSON, and M. C. NEALE. "Does the level of family dysfunction moderate the impact of genetic factors on the personality trait of neuroticism?" Psychological Medicine 33, no. 5 (June 26, 2003): 817–25. http://dx.doi.org/10.1017/s0033291703007840.

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Background. While the family environment can directly influence later risk for psychopathology, dysfunction in the family of origin may also moderate the impact of genetic factors on liability for psychiatric disorders. Can a similar pattern be seen for the personality trait of Neuroticism (N) – which is a risk factor for many psychiatric conditions?Method. Our sample of 957 complete female–female twin pairs from a population-based register had measures of self-reported N and multiple reporters (twin, co-twin, mother, father) for family dysfunction (FD). Statistical analysis was conducted by traditional regression analysis and a moderator structural equation twin model operationalized in the computer program Mx.Results. Dividing the sample into quartiles based on increasing levels of FD, the mean of N increased substantially while correlations of N in monozygotic (MZ) and dizygotic (DZ) twins were relatively constant. Regression analyses did not suggest greater twin resemblance for N with increasing levels of FD. The best-fit structural equation model was the standard un-moderated model in which the proportion of variance in N due to genetic (39%) and unique environmental effects (61%) remained constant across values of FD.Conclusions. Although a false-negative result due to limited power cannot be excluded, these analyses do not support the hypothesis that FD moderates the impact of genetic factors on levels of N.

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Sims, J., D. Carroll, J. K. Hewitt, and J. R. Turner. "A Family Study of Developmental Effects upon Blood Pressure Variation." Acta geneticae medicae et gemellologiae: twin research 36, no. 4 (October 1987): 467–73. http://dx.doi.org/10.1017/s0001566000006838.

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AbstractIn an earlier study of blood pressure variation in middle aged parents and their young adult twin offspring, the greater blood pressure variation observed in the parent sample was accounted for in terms of an increasing influence of individual environmental experiences with increasing age and a commensurate reduction in the impact of heredity. In the present study, the sample size was enlarged to provide a more powerful test of these effects. Maximum likelihood model-fitting techniques were applied to blood pressure covariation in balanced pedigrees, consisting of 85 families (40 MZ and 45 DZ twin pairs). As before, our analysis indicated that a developmental effect was a salient factor in the older age group.

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Kochunas, Brendan, and Xun Huan. "Digital Twin Concepts with Uncertainty for Nuclear Power Applications." Energies 14, no. 14 (July 14, 2021): 4235. http://dx.doi.org/10.3390/en14144235.

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Digital Twins (DTs) are receiving considerable attention from multiple disciplines. Much of the literature at this time is dedicated to the conceptualization of digital twins, and associated enabling technologies and challenges. In this paper, we consider these propositions for the specific application of nuclear power. Our review finds that the current DT concepts are amenable to nuclear power systems, but benefit from some modifications and enhancements. Further, some areas of the existing modeling and simulation infrastructure around nuclear power systems are adaptable to DT development, while more recent efforts in advanced modeling and simulation are less suitable at this time. For nuclear power applications, DT development should rely first on mechanistic model-based methods to leverage the extensive experience and understanding of these systems. Model-free techniques can then be adopted to selectively, and correctively, augment limitations in the model-based approaches. Challenges to the realization of a DT are also discussed, with some being unique to nuclear engineering, however most are broader. A challenging aspect we discuss in detail for DTs is the incorporation of uncertainty quantification (UQ). Forward UQ enables the propagation of uncertainty from the digital representations to predict behavior of the physical asset. Similarly, inverse UQ allows for the incorporation of data from new measurements obtained from the physical asset back into the DT. Optimization under uncertainty facilitates decision support through the formal methods of optimal experimental design and design optimization that maximize information gain, or performance, of the physical asset in an uncertain environment.

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Kendler, Kenneth S., Charles O. Gardner, and Carol A. Prescott. "Toward a Comprehensive Developmental Model for Alcohol Use Disorders in Men." Twin Research and Human Genetics 14, no. 1 (February 1, 2011): 1–15. http://dx.doi.org/10.1375/twin.14.1.1.

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The multiple risk factors for alcohol use (AU) and alcohol use disorders (AUDs) are interrelated through poorly understood pathways, many of which begin in childhood. In this report, the authors seek to develop an empirical, broad-based developmental model for the etiology of AU and AUDs in men. We assessed 15 risk factors in four developmental tiers in 1,794 adult male twins from the Virginia population based twin registry. The best fitting model explained 39% of the variance in late adolescent AU, and 30% of the liability to lifetime symptoms of AUD. AU and AUDs can be best understood as arising from the action and interaction of two pathways reflecting externalizing genetic/temperamental and familial/social factors. Peer group deviance was important in each pathway. Internalizing symptoms played a more minor role. Familial/social factors were especially important influences on AU, while genetic/temperamental factors were more critical for AUDs. We conclude that AU and AUDs in men are complex traits influenced by genetic, family, temperamental, and social factors, acting and interacting over developmental time.

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Wang, Lei, and Xiao-Fang Han. "Standard-model-like Higgs-pair production and decay in left–right twin Higgs model." Physics Letters B 696, no. 1-2 (January 2011): 79–86. http://dx.doi.org/10.1016/j.physletb.2010.12.009.

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Vink, Jacqueline M., and Dorret I. Boomsma. "A Comparison of Early and Late Respondents in a Twin–Family Survey Study." Twin Research and Human Genetics 11, no. 2 (April 1, 2008): 165–73. http://dx.doi.org/10.1375/twin.11.2.165.

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AbstractDifferences between early (within 30 days) and late (after 30 days) respondents in a survey study were analyzed in twins and siblings registered with the Netherlands Twin Register. We compared early and late respondents on personality traits, health, lifestyle, and demographic variables. The odds of being a late respondent were significantly higher for men (OR 1.14), alcohol use on a daily/weekly basis (OR 1.20), having a relationship (OR 1.40), higher score on experience seeking scale (OR 1.02), and criticizing the questionnaire as too long (OR 1.27). The odds of being a late respondent were significantly lower for nontwin subjects (OR 0.71), regular cycling (OR 0.83), and judging the questionnaire to be fun (OR 0.80). There were no significant interactions with sex. To examine to what extent early and late response is influenced by genetic factors, twin and sibling data of 5040 subjects were analyzed. The best model includes genetic factors (31%), shared environmental influences (36%), and unique environmental influences (43%) on variation in response time.

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Maes, Hermine H., Michael C. Neale, Nicholas G. Martin, Andrew C. Heath, and Lindon J. Eaves. "Religious attendance and frequency of alcohol use: same genes or same environments: a bivariate extended twin kinship model." Twin Research 2, no. 2 (April 1, 1999): 169–79. http://dx.doi.org/10.1375/twin.2.2.169.

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AbstractReligious attendance has been shown to correlate negatively with alcohol use. We investigated whether this relationship is driven by genetic or environmental factors. Data on frequency of church attendance and frequency of alcohol use were obtained from twins and their families in the Virginia 30 000 study. A comprehensive bivariate model of family resemblance was fitted to the data using Mx. This model is described in detail. Results indicate that genetic factors primarily account for the relationship between alcohol and church attendance in males, whilst shared environmental factors, including cultural transmission and genotype-environment covariance, are stronger determinants of this association in females.

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Bouchard, Thomas J., Matt McGue, David Lykken, and Auke Tellegen. "Intrinsic and extrinsic religiousness: genetic and environmental influences and personality correlates." Twin Research 2, no. 2 (April 1, 1999): 88–98. http://dx.doi.org/10.1375/twin.2.2.88.

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AbstractThis report presents findings for the Intrinsic (IR) and Extrinsic (ER) religiousness scales from the Minnesota Study of Twins Reared Apart. The scales were shown to be internally consistent, sufficiently distinct from the scales of the California Psychological Inventory and the Multidimensional Personality Questionnaire and unrelated to a number of measures of response style to justify treating them as distinct traits. The I scales also showed considerable evidence of construct validity in its correlations with religious fundamentalism and authoritarianism as assessed by the MMPI and Altemeyer's Right-Wing Authoritarianism scale. Data on IR and ER from 35 pairs of monozygotic twins reared apart (MZA) and 37 pairs of dizygotic twins reared apart (DZA) were fitted to a biometric model and demonstrated significant heritability (0.43 and 0.39), with a model containing genetic plus environmental factors fitting significantly better than a model containing only an environmental component. Twin similarity could not be explained by placement on a self-reported measure of family Moral Religious Emphasis as measured by the Family Environment Scale.

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McGuffin, Peter, Randy Katz, and Joan Rutherford. "Nature, nurture and depression: a twin study." Psychological Medicine 21, no. 2 (May 1991): 329–35. http://dx.doi.org/10.1017/s0033291700020432.

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SYNOPSISWe studied a series of twins systematically ascertained through 214 probands (84 monozygotic, 130 dizygotic) who had had one or more episodes of hospital-treated major depression. A variety of definitions of depression were applied to the co-twins all of which resulted in (a) markedly higher rates of disorder than are found in the general population, (b) significantly higher monozygotic than dizygotic concordance. The results of applying a simple additive model in which depression is considered as a threshold trait suggested that both genetic factors and shared family environment make substantial and significant contributions to the familiality of depression.

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GABEL, LAWRENCE L., and JAMES A. PEARSOL. "The Twin Epidemics of Substance Use and HIV: A State-level Response Using a Train-the-trainer Model." Family Practice 10, no. 4 (1993): 400–405. http://dx.doi.org/10.1093/fampra/10.4.400.

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Rebollo, Irene, Marleen H. M. de Moor, Conor V. Dolan, and Dorret I. Boomsma. "Phenotypic Factor Analysis of Family Data: Correction of the Bias Due to Dependency." Twin Research and Human Genetics 9, no. 3 (June 1, 2006): 367–76. http://dx.doi.org/10.1375/twin.9.3.367.

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AbstractTwin registries form an exceptionally rich source of information that is largely unexploited for phenotypic analyses. One obstacle to straightforward phenotypic statistical analysis is the inherent dependency, which is due to the clustering of cases within families. The present simulation study gauges the degree of the bias produced by the dependency of family data on the estimates of standard errors and chi-squared, when they are treated as independent observations in a phenotypic model, and assesses the efficiency of an estimator, which corrects for dependency. When family-clustered data are used for phenotypic analysis, in treating individuals as independent, and using standard maximum likelihood estimation, there is a tendency for the chi-square statistic to be overestimated, and the standard errors of the parameters to be underestimated. The bias increases with family resemblance, due to heritability or shared environment. The source of family resemblance — either heritability (h2) and/or shared environment (c2) — interacts with the composition of the sample. In the absence of c2, samples with twins, parents and spouses show the lowest bias, whereas in the presence of c2 samples with only twins show the lowest bias. In all conditions the bias remained below 15%. The use of the ‘complex option’ available in Mplus (clustering corrected robust maximum likelihood estimation) reduces the bias to the levels observed when only independent cases are considered. Thus with the use of robust estimates the bias due to family dependency becomes practically negligible in all conditions of dependency. In conclusion, the present study shows that the bias due to dependency in family data does not form a serious obstacle to phenotypic data analysis.

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Hopper, J. L., P. L. Derrick, and C. A. Clifford. "Innovations in the Statistical Analysis of Twin Studies." Acta geneticae medicae et gemellologiae: twin research 36, no. 1 (January 1987): 21–27. http://dx.doi.org/10.1017/s0001566000004554.

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AbstractAdvances in computer technology have made possible a greater sophistication in the statistical analysis of pedigree data, however this is not necessarily manifest by fitting more comprehensive causative models. Planned twin and family studies measure numerous explanatory variables, including perhaps genetic and DNA marker information status on all pedigree members, and the cohabitation of all pairs of individuals. A statistical analysis should examine the contribution of these measured factors on individual means, and in explaining the variation and covariation between individuals, concurrently with the postulated effect of unmeasured factors such as polygenes. We present two models that meet this requirement: the Multivariate Normal Model for Pedigree Analysis for quantitative traits, and a Log-Linear Model for Binary Pedigree Data. For both models, important issues are examination of fit, detection of outlier pedigrees and outlier individuals, and critical examination of the model assumptions. Procedures for fulfilling these needs and examples of modelling are discussed.

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Hur, Yoon-Mi. "Genetic and Environmental Influences on Self-Concept in Female Preadolescent Twins: Comparison of Minnesota and Seoul Data." Twin Research and Human Genetics 8, no. 4 (August 1, 2005): 291–99. http://dx.doi.org/10.1375/twin.8.4.291.

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AbstractIt has been argued that culture significantly influences the developmental basis of self-concept. The goal of the present study is to compare the relative importance of genetic and environmental factors to explain individual differences in various dimensions of self-concept in female preadoles- cents of Minnesota in the United States and Seoul in South Korea. Two hundred and eighteen monozygotic (MZ) and 137 dizygotic (DZ) twin pairs from the Minnesota Twin Family Study (MTFS) and 74 MZ and 42 DZ twin pairs from the Seoul Twin Family Study (STFS) completed the 6 cluster scales of the Piers–Harris Children's Self-Concept Scale (P–H). The 6 cluster scales of the P-H include Popularity, Physical Appearance and Attributes, Behavior, Intellectual Competence and School Status, Anxiety, and Happiness and Satisfaction. Univariate model- fitting analyses were performed. In both samples, a model incorporating shared and nonshared environmental influences fitted the data best for Popularity, Anxiety, and Intellectual Competence and School Status, whereas a model including additive genetic and nonshared environmental factors provided the best fit for Physical Appearance and Attributes, and Behavior. The univariate model did not yield an adequate fit for Happiness and Satisfaction. For Physical Appearance and Attributes, and Intellectual Competence and School Status, estimates of additive genetic and environmental factors were significantly different between the MTFS and the STFS samples. For Popularity, Anxiety, and Behavior, however, the genetic and environmental estimates were comparable between the two samples.

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Segal, Nancy L. "Terminating Twins: Survival of One/Twin Research Reviews: Twin Discordance for Primordial Dwarfism; Twin Study of Public Service Motivation; Four-Parameter Model for Twin Research; Global Twinning at a Peak; Germline Differences of Monozygotic Twins/In the News: Twins and Dyngus Day; Triplets Born in Austrian Displaced Persons’ Camp; Superior, Film About Estranged Identical Twin Sisters; Adopting Own Twins After Surrogacy; Twins and Primordial Dwarfism Revisited." Twin Research and Human Genetics 24, no. 3 (June 2021): 187–90. http://dx.doi.org/10.1017/thg.2021.19.

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AbstractSelective termination is the term used for the elimination of an abnormal fetus. In contrast, multifetal pregnancy reduction refers to the termination of one or more members of a twin or higher-order multiple birth set, respectively, to reduce the high risks associated with these pregnancies. The procedure can also be used when a serious physical condition is detected prenatally in a member of a multiple birth set. In a minority of cases, selective termination has reduced two healthy fetuses to one when parents wanted just one additional child in the family. In the present article, the perspectives of a surviving twin whose family wished to terminate both healthy fetuses are examined. Next, past and present twin studies of primordial dwarfism, public service motivation, an analytical model, the global twinning rate and germline differences are summarized. The article concludes with a synopsis of twin-related news that covers twins and Dyngus Day, triplets born in an Austrian displaced persons’ camp, the film Superior — about estranged identical twin sisters, a couple adopting their own twins after surrogacy and a new case of twins and primordial dwarfism, a condition introduced in the research reviews.

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Lin, Chaucer C. H., Po-Hsiu Kuo, Chiu-Hsia Su, and Wei J. Chen. "The Taipei Adolescent Twin/Sibling Family Study I: Behavioral Problems, Personality Features, and Neuropsychological Performance." Twin Research and Human Genetics 9, no. 6 (December 1, 2006): 890–94. http://dx.doi.org/10.1375/twin.9.6.890.

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AbstractThe present study aimed to investigate genetic and environmental influences on behavioral problems, personality features, and neuropsycho-logical performance among adolescents in Taipei, Taiwan. Between 1996 and 1998, with the assistance of the Twin Association and junior high schools in Taipei City, we solicited a list of twins from 51 junior high schools in Taipei. Names, addresses, and telephone numbers of the twins enrolled in these schools were obtained. The vast majority of the recruited twins were between 12 and 16 years old. The recruited twins received assessments for behavioral problems, general and schizotypal personality, and cognitive functions. Their parents rated their children on behavioral/ emotional problems and were assessed on their own general and specific personality. Same-sex sibling pairs (ages vary within 2 years) and their parents from three schools were also recruited to increase sample size for the group with a kinship coefficient of .50. Twins' zygosity was determined by a combination of DNA typing and physical similarity. The Mx program was used to estimate parameters for the full model and its reduced models. The recruitment, measurements, data managements, and published results are described in this article.

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Waller, Niels G., and Phillip R. Shaver. "The Importance of Nongenetic Influences on Romantic Love Styles: A Twin-Family Study." Psychological Science 5, no. 5 (September 1994): 268–74. http://dx.doi.org/10.1111/j.1467-9280.1994.tb00624.x.

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Research in several disciplines reveals large individual differences in orientations to romantic love, yet the origins of the differences have been unclear In this first behavior genetic study of romantic love, biometric model fitting reveals that in contrast to other personality and attitude domains, where genetic factors account for approximately 50% of the reliable variance and shared environment has little effect, individual differences in romantic love are due almost exclusively to environment Moreover, the common family environment plays a sizable role in determining love styles, a finding compatible with theories stressing the importance of family inter-actions in personality development

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Heath, Andrew C., Nicholas G. Martin, Michael T. Lynskey, Alexandre A. Todorov, and Pamela A. F. Madden. "Estimating Two-Stage Models for Genetic Influences on Alcohol, Tobacco or Drug Use Initiation and Dependence Vulnerability in Twin and Family Data." Twin Research 5, no. 2 (April 1, 2002): 113–24. http://dx.doi.org/10.1375/twin.5.2.113.

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AbstractGenetic research on risk of alcohol, tobacco or drug dependence must make allowance for the partial overlap of risk-factors for initiation of use, and risk-factors for dependence or other outcomes in users. Except in the extreme cases where genetic and environmental risk-factors for initiation and dependence overlap completely or are uncorrelated, there is no consensus about how best to estimate the magnitude of genetic or environmental correlations between Initiation and Dependence in twin and family data. We explore by computer simulation the biases to estimates of genetic and environmental parameters caused by model misspecification when Initiation can only be defined as a binary variable. For plausible simulated parameter values, the two-stage genetic models that we consider yield estimates of genetic and environmental variances for Dependence that, although biased, are not very discrepant from the true values. However, estimates of genetic (or environmental) correlations between Initiation and Dependence may be seriously biased, and may differ markedly under different two-stage models. Such estimates may have little credibility unless external data favor selection of one particular model. These problems can be avoided if Initiation can be assessed as a multiple-category variable (e.g. never versus early-onset versus later onset user), with at least two categories measurable in users at risk for dependence. Under these conditions, under certain distributional assumptions, recovery of simulated genetic and environmental correlations becomes possible. Illustrative application of the model to Australian twin data on smoking confirmed substantial heritability of smoking persistence (42%) with minimal overlap with genetic influences on initiation.

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Eaves, Lindon, Andrew Heath, Nicholas Martin, Hermine Maes, Michael Neale, Kenneth Kendler, Katherine Kirk, and Linda Corey. "Comparing the biological and cultural inheritance of personality and social attitudes in the Virginia 30 000 study of twins and their relatives." Twin Research 2, no. 2 (April 1, 1999): 62–80. http://dx.doi.org/10.1375/twin.2.2.62.

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AbstractMeasures of four dimensions of personality (Psychoticism, Extraversion, Neuroticism, and Lie scores) and six aspects of social attitudes (to sex, taxation, militarism, politics, religion and a general conservatism scale) were obtained by mailed questionnaire from 29 691 US subjects including adult twins (n = 14 761) their parents (n = 2360), their spouses (n = 4391), siblings (n = 3184) and adult children (n = 4800). After correction for the average effects of age, sex and source of sample, familial correlations were computed for 80 distinct biological and social relationships. The data allow for the estimation of the additive and non-additive effects of genes, assortative mating, vertical cultural inheritance and other non-parental effects of the shared environment on differences in personality and social attitudes. The interaction of genetic and environmental effects with sex may also be analyzed. Model-fitting analyses show that personality and social attitude measures differ markedly in major features of family resemblance. Additive and dominant genetic effects contribute to differences in both personality and attitudes, but the effects of the family environment, including vertical cultural transmission from parent to child, are much more marked for social attitudes than for personality. There is substantial assortative mating for social attitudes and almost none for personality. The causes of family resemblance depend significantly on sex for almost every variable studied. These findings clarify and extend the more tentative findings derived from previous twin, family and adoption studies.

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Hopper, J. L., J. B. Carlin, G. T. Macaskill, P. L. Derrick, L. B. Flander, and G. G. Giles. "Incorporation of Twins in the Regressive Logistic Model for Pedigree Disease Data." Acta geneticae medicae et gemellologiae: twin research 39, no. 2 (April 1990): 173–80. http://dx.doi.org/10.1017/s0001566000005407.

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AbstractSegregation and twin disease concordance analyses have assumed a theoretical underlying liability following a multivariate normal distribution. For reasons of computation, of incorporation of measured explanatory variables, and of testing of fit and assumptions, newer analytical methods are being developed. The regressive logistic model (RLM) relies on expressing the pedigree likelihood as a product of conditional probabilities, one for each individual. In addition to logistic regression modelling of measured epidemiological variables on disease prevalence, there is modelling of vertical transmission, of transmission of unmeasured genotypes and of sibship environment. This paper discusses methods for the analysis of binary traits in twins and in pedigrees. Some extensions to the RLM for pedigrees which include twins are proposed. These enable exploration of twin concordance in the context of the twins' common parenthood, the sibship similarities within the family, and the twins' similarity in age, sex, genes and environment.

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Hufer, Anke, Anna Elena Kornadt, Christian Kandler, and Rainer Riemann. "Genetic and environmental variation in political orientation in adolescence and early adulthood: A Nuclear Twin Family analysis." Journal of Personality and Social Psychology 118, no. 4 (April 2020): 762–76. http://dx.doi.org/10.1037/pspp0000258.

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Cartier, Michel. "Nuclear Versus Quasi-Stem Families: the New Chinese Family Model." Journal of Family History 20, no. 3 (September 1995): 307–27. http://dx.doi.org/10.1177/036319909502000305.

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Liu, Yao-Bei, and Xue-Lei Wang. "Higgs boson decays and production in the left–right twin Higgs model." Physics Letters B 694, no. 4-5 (January 2011): 417–23. http://dx.doi.org/10.1016/j.physletb.2010.10.037.

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Knudsen, Susanne V. "Deconstructing the nuclear family in Norwegian textbooks." Educar em Revista, spe-1 (2014): 17–34. http://dx.doi.org/10.1590/0104-4060.36466.

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In this article the author presents how Norwegian textbooks in the 1990s and later make the nuclear family the norm of living together. The textbooks are for the secondary school in the curricula subjects of natural Science and environmental studies, social studies and home economics. The nuclear family in the chosen textbooks consists of the biological two-sex model and the cultural and social two-gender model. Some texts show the eagerness to present more than the heterosexual family life, and opens up to homosexuality both as sexual and social behavior. Single living is given little space in the textbook

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Yonetani, Naoto, Keisuke Ishii, Hiroshi Kawamura, Aki Mabuchi, Shusaku Hayashi, and Nobuaki Mitsuda. "Significance of Velamentous Cord Insertion for Twin-Twin Transfusion Syndrome." Fetal Diagnosis and Therapy 38, no. 4 (2015): 276–81. http://dx.doi.org/10.1159/000381639.

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Introduction: The objective of this study was to evaluate the actual association between velamentous cord insertion (VCI) and twin-twin transfusion syndrome (TTTS) in the native cohort concerning the natural history of monochorionic twin pregnancies. Material and Methods: All monochorionic diamniotic twin pregnancies who received prenatal care from <16 weeks of gestation until delivery at our center between 2004 and 2013 were included in this retrospective cohort study. Macroscopically defined cord insertion site was recorded as velamentous, marginal, or central. The effects of VCI on TTTS and a composite of adverse outcomes, including abortion, death, and neurological morbidities ≤28 days of age, were evaluated with a multiple logistic regression model. Results: A total of 357 monochorionic diamniotic twin pregnancies were analyzed. VCI in both twins was noted in 2.5% of cases and VCI in at least one twin was noted in 22.1% of cases. The incidence of TTTS was 8.4%; the incidence of a composite of adverse outcomes in at least one twin was 9.8%. There was no correlation between VCI and TTTS as well as a composite of adverse outcomes. Discussion: VCI in monochorionic twin pregnancies was not a risk factor for TTTS and severe perinatal morbidities.

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42

Nespolo, Massimo, Giovanni Ferraris, and Bernd Souvignier. "Effects of merohedric twinning on the diffraction pattern." Acta Crystallographica Section A Foundations and Advances 70, no. 2 (February 12, 2014): 106–25. http://dx.doi.org/10.1107/s2053273313029082.

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In merohedric twinning, the lattices of the individuals are perfectly overlapped and the presence of twinning is not easily detected from the diffraction pattern, especially in the case of inversion twinning (class I). In general, the investigator has to consider three possible structural models: a crystal with space-group typeHand point groupP, either untwinned (H model) or twinned through an operationtin vector space (t-H model), and an untwinned crystal with space groupGwhose point groupP′ is obtained as an extension ofPthrough the twin operationt(G model). In 71 cases, consideration of the reflection conditions may directly rule out theGmodel; in seven other cases the reflection conditions suggest a space group which does not correspond to the extension ofHby the twin operation and the structure solution or at least the refinement will fail. When the twin operation belongs to a different crystal family (class IIBtwinning: the crystal has a specialized metric), thepresenceof twinning can often be recognized by the peculiar effect it has on the reflection conditions.

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Umur, Asli, Martin J. C. van Gemert, Jeroen P. H. M. van den Wijngaard, Michael G. Ross, and Peter G. J. Nikkels. "Haemodynamic resistance model of monochorionic twin pregnancies complicated by acardiac twinning." Physics in Medicine and Biology 49, no. 14 (June 29, 2004): N205—N213. http://dx.doi.org/10.1088/0031-9155/49/14/n01.

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Tamimy, Z., S. T. Kevenaar, J. J. Hottenga, M. D. Hunter, E. L. de Zeeuw, M. C. Neale, C. E. M. van Beijsterveldt, C. V. Dolan, Elsje van Bergen, and D. I. Boomsma. "Multilevel Twin Models: Geographical Region as a Third Level Variable." Behavior Genetics 51, no. 3 (February 27, 2021): 319–30. http://dx.doi.org/10.1007/s10519-021-10047-x.

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AbstractThe classical twin model can be reparametrized as an equivalent multilevel model. The multilevel parameterization has underexplored advantages, such as the possibility to include higher-level clustering variables in which lower levels are nested. When this higher-level clustering is not modeled, its variance is captured by the common environmental variance component. In this paper we illustrate the application of a 3-level multilevel model to twin data by analyzing the regional clustering of 7-year-old children’s height in the Netherlands. Our findings show that 1.8%, of the phenotypic variance in children’s height is attributable to regional clustering, which is 7% of the variance explained by between-family or common environmental components. Since regional clustering may represent ancestry, we also investigate the effect of region after correcting for genetic principal components, in a subsample of participants with genome-wide SNP data. After correction, region no longer explained variation in height. Our results suggest that the phenotypic variance explained by region might represent ancestry effects on height.

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Gedda, L., G. Brenci, and C. Rossi. "A Stochastic Model of the Genetic Predisposition to Ageing: An Application to Twin Data." Acta geneticae medicae et gemellologiae: twin research 39, no. 4 (January 1990): 419–25. http://dx.doi.org/10.1017/s0001566000003640.

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AbstractIn previous papers a stochastic model of the ageing process has been proposed. Some genetic parameters (redundance, repair) have been used to explain the observed differential predisposition to the process and family heredity. Because the process is basically due to effective random mutations, any individual of the population would be predisposed differently to ageing according to the structure of his/her genome. In the present paper, the previous model is generalized to take into account an additional genetic parameter, namely, the stability against random mutations, defined as the probability that a random mutation in a codon would produce no mutation in the corresponding protein. Estimation problems connected with the model are approached on the basis of twin data in maximum likelihood estimation as well as in bayesian framework. Some comparisons between the two methods are reported.

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Prescott, Carol A., Ellen E. Walters, Thalida Em Arpawong, Catalina Zavala, Tara L. Gruenewald, and Margaret Gatz. "The Project Talent Twin and Sibling Study: Zygosity and New Data Collection." Twin Research and Human Genetics 22, no. 6 (December 2019): 769–78. http://dx.doi.org/10.1017/thg.2019.117.

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AbstractThe Project Talent Twin and Sibling (PTTS) study includes 4481 multiples and their 522 nontwin siblings from 2233 families. The sample was drawn from Project Talent, a U.S. national longitudinal study of 377,000 individuals born 1942–1946, first assessed in 1960 and representative of U.S. students in secondary school (Grades 9–12). In addition to the twins and triplets, the 1960 dataset includes 84,000 siblings from 40,000 other families. This design is both genetically informative and unique in facilitating separation of the ‘common’ environment into three sources of variation: shared by all siblings within a family, specific to twin-pairs, and associated with school/community-level factors. We term this the GIFTS model for genetics, individual, family, twin, and school sources of variance. In our article published in a previous Twin Research and Human Genetics special issue, we described data collections conducted with the full Project Talent sample during 1960–1974, methods for the recent linking of siblings within families, identification of twins, and the design of a 54-year follow-up of the PTTS sample, when participants were 68–72 years old. In the current article, we summarize participation and data available from this 2014 collection, describe our method for assigning zygosity using survey responses and yearbook photographs, illustrate the GIFTS model applied to 1960 vocabulary scores from more than 80,000 adolescent twins, siblings and schoolmates and summarize the next wave of PTTS data collection being conducted as part of the larger Project Talent Aging Study.

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MATUTE, ERNESTO A. "TWIN AND MIRROR SYMMETRIES FROM PRESYMMETRY." International Journal of Modern Physics A 26, no. 18 (July 20, 2011): 3051–63. http://dx.doi.org/10.1142/s0217751x11053766.

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We argue that presymmetry, a hidden predynamical electroweak quark–lepton symmetry that explains the fractional charges and triplication of families, must be extended beyond the Standard Model as to have a residual presymmetry that embraces partner particles and includes the strong sector, so accounting for the twin or mirror partners proposed to alleviate the naturalness problem of the weak scale. It leads to the full duplication of fermions and gauge bosons of the Standard Model independently of the ultraviolet completion of the theory, even if the Higgs particle is discarded by experiment, which adds robustness to twin and mirror symmetries. The established connection is so strongly motivated that the search for twin or mirror matter becomes the possible test of presymmetry. If the physics beyond the Standard Model repairs its left–right asymmetry, mirror symmetry should be the one realized in nature.

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Weinschenk, Aaron C., and Christopher T. Dawes. "The Effect of Education on Political Knowledge: Evidence From Monozygotic Twins." American Politics Research 47, no. 3 (July 20, 2018): 530–48. http://dx.doi.org/10.1177/1532673x18788048.

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Political scientists have long been interested in the determinants of political knowledge. In many studies, education is the strongest predictor of political knowledge. However, some studies have found that education has no effect on knowledge once confounding variables are taken into account. In addition, some recent work suggests that education remains the strongest predictor of knowledge even after accounting for confounders like personality traits and intelligence. We provide new evidence on the effect of education on political knowledge by utilizing the co-twin control design. By looking at the relationship between education and knowledge within monozygotic twin pairs, we are able to circumvent sources of confounding of the relationship due to genetic factors and early-life family environment because monozygotic twins share both. We find that the relationship between education and political knowledge is highly confounded by genes and/or familial environment. The results from a naive model that does not take into account unobserved family factors indicate that education has a positive and statistically significant effect on political knowledge. However, in a twin fixed-effects model that accounts for confounding due to genetic factors and familial socialization, we find that the effect of education on political knowledge drops substantially and is not statistically significant at conventional levels.

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Roberts, David, and Gordon Claridge. "A Genetic Model Compatible with a Dimensional View of Schizophrenia." British Journal of Psychiatry 158, no. 4 (April 1991): 451–56. http://dx.doi.org/10.1192/bjp.158.4.451.

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Throughout the history of schizophrenia as a psychiatric concept, opinions have differed sharply over its essential nature and its causes, giving rise to a wide range of explanations that have drawn upon ideas from almost all of the social and biological sciences. Only one fact has truly survived the vicissitudes of argument about the condition: that genetic factors contribute to its aetiology. Even that conclusion, first reached in the very early days of schizophrenia research, sank temporarily out of sight during the radical psychiatry challenges of the 1960s. However, the continuing collection of family, twin, adoption and other data over that period put the genetic hypothesis beyond reasonable doubt (McGuffin, 1988).

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IACONO, WILLIAM G., SCOTT R. CARLSON, JEANETTE TAYLOR, IRENE J. ELKINS, and MATT MCGUE. "Behavioral disinhibition and the development of substance-use disorders: Findings from the Minnesota Twin Family Study." Development and Psychopathology 11, no. 4 (December 1999): 869–900. http://dx.doi.org/10.1017/s0954579499002369.

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One variant of substance-use disorder is characterized by behavioral disinhibition. In this report, we martial evidence for a model for the development of this variant. We hypothesize that genetic liability for this variant is reflected in a spectrum of risk indicators linked to the inability or unwillingness to inhibit behavioral impulses. Included in this spectrum are personality traits suggesting low constraint, and externalizing psychopathology, including conduct, oppositional defiant, and attention-deficit disorder in children and antisocial personality disorder and behavior in adults. We further hypothesize that these individual differences in behavioral disinhibition are manifestations of underlying central nervous system processes associated with various psychophysiological anomalies, some of which may index genetic risk for substance abuse. Support for the model is derived from the analysis of findings from the Minnesota Twin Family Study, an epidemiological investigation of approximately 2,700 adolescent twins and their parents.

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Journal articles on the topic 'Nuclear twin family model'

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