Publications of Littvay, L.

Littvay L. Twin Studies and Politics. In: Mintz A, Terris L, editors. Oxford Handbook of Behavioral Political Science. Oxford University Press; in press/forthcoming.
Horvath T, Littvay L. Ikerstatisztikai alapok. In: Tarnoki A, Tarnoki D, Littvay L, J M, Melicher D, Pari A, editors. Ikerkutatás és epigenetika. Budapest: Medicina; in press/forthcoming.

Multilevel Structural Equation Modeling

Multilevel Structural Equation Modeling serves as a minimally technical overview of multilevel structural equation modeling (MSEM) for applied researchers and advanced graduate students in the social sciences. As the first book of its kind, this title is an accessible, hands-on introduction for beginners of the topic. The authors predict a growth in this area, fueled by both data availability and also the availability of new and improved software to run these models. The applied approach, combined with a graphical presentation style and minimal reliance on complex matrix algebra guarantee that this volume will be useful to social science graduate students wanting to utilize such models.

The Ideational Approach to Populism: Theory, Method & Analysis

Populism is on the rise in Europe and the Americas. Scholars increasingly understand populist forces in terms of their ideas or discourse, one that envisions a cosmic struggle between the will of the common people and a conspiring elite. In this volume, we advance populism scholarship by proposing a causal theory and methodological guidelines – a research program – based on this ideational approach. This program argues that populism exists as a set of widespread attitudes among ordinary citizens, and that these attitudes lie dormant until activated by weak democratic governance and policy failure. It offers methodological guidelines for scholars seeking to measure populist ideas and test their effects. And, to ground the program empirically, it tests this theory at multiple levels of analysis using original data on populist discourse across European and US party systems; case studies of populist forces in Europe, Latin America, and the US; survey data from Europe and Latin America; and experiments in Chile, the US, and the UK. The result is a truly systematic, comparative approach that helps answer questions about the causes and effects of populism.

Carlin R, Hawkins K, Littvay L. A Map for Future Research. In: Hawkins K, Carlin R, Littvay L, Kaltwasser CR, editors. The Ideational Approach to Populism: Theory, Method & Analysis. Routledge; 2019.

Heritability of the dimensions, compliance and distensibility of the human internal jugular vein wall

Aims The elasticity of the internal jugular vein (IJV) is a major determinant of cerebral venous drainage and right atrium venous return. However, the level of genetic determination of IJV dimensions, compliance and distensibility has not been studied yet. Methods 170 adult Caucasian twins (43 monozygotic [MZ] and 42 dizygotic [DZ] pairs) were involved from the Italian twin registry. Anteroposterior and mediolateral diameters of the IJV were measured bilaterally by ultrasonography. Measurements were made both in the sitting and supine positions, with or without Valsalva maneuver. Univariate quantitative genetic modeling was performed. Results Genetic factors are responsible for 30–70% of the measured properties of IJV at higher venous pressure even after adjustment for age and gender. The highest level of inheritance was found in the supine position regarding compliance (62%) and venous diameter during Valsalva (69%). Environmental and measurement-related factors instead are more important in the sitting position, when the venous pressure is low and the venous lumen is almost collapsed. The range of capacity changes between the lowest and highest intraluminal venous pressure (full distension range) are mainly determined by genetic factors (58%). Conclusions Our study has shown substantial heritability of IJV biomechanics at higher venous pressures even after adjustment for age and gender. These findings yield an important insight to what degree the geometric and elastic properties of the vascular wall are formed by genetic and by environmental factors in humans.

A Counterfactual Impact Evaluation of a Bilingual Program on Students’ Grade Point Average at a Spanish Universit

This observational study intends to estimate the causal effects of an English as a Medium of Instruction (EMI) program (as predictor) on students Grade Point Average (GPA) (as outcome) at a particular University in Spain by using a Counterfactual Impact Evaluation (CIE). The need to address the crucial question of causal inferences in EMI programs to produce credible evidences of successful interventions contrasts, however, with the absence of experimental or quasi-experimental research and evaluation designs in the field. CIE approach is emerging as a methodologically viable solution to bridge that gap. The program evaluated here consisted in delivering an EMI program in a Primary Education Teacher Training Degree group. After achieving balance on the observed covariates and recreating a situation that would have been expected in a randomized experiment, three matching approaches such as genetic matching, nearest neighbor matching and Coarsened Exact Matching were used to analyze observational data from a total of 1288 undergraduate students, including both treatment and control group. Results show unfavorable effects of the bilingual group treatment condition. Potential interpretations and recommendations are provided in order to strengthen future causal evidences of bilingual education programs’ effectiveness in Higher Education.

Where did all the environmentalism go? ‘Politics can be different’ (LMP) in the 2018 Hungarian parliamentary elections

In April 2018, Lehet Más a Politika (LMP) reinforced its position as the strongest Green party in Central and Eastern Europe, passing the 5% parliamentary threshold for the third time and becoming the sole opposition party to gain votes. In the preceding 4 years, LMP had dealt with the resignation of its most visible co-chair András Schiffer and rebranded itself as an anti-corruption critic of Viktor Orbán’s Fidesz government, which distracted from the environmental issues. LMP resisted electoral coordination with other parties; consequently, Fidesz gained another supermajority, exploiting the distorted election system it established in 2011, which penalized a divided opposition. LMP, post-election, suffered deep intra-party tensions and the departure of prominent LMP politicians including its co-chairs.

Are the Variants of the Circle of Willis Determined by Genetic or Environmental Factors? Results of a Twin Study Running title: Circle of Willis Variants in Twins

Background: Anatomic variants of the circle of Willis (CW) are commonly observed in healthy subjects. Genetic and environmental factors influencing these variants remain unclear. Our aim was to assess the genetic and environmental background affecting variant CW phenotypes. Methods: A total of 122 adult healthy twins from the Hungarian Twin Registry (39 monozygotic (MZ) and 22 dizygotic (DZ) pairs, average age 49.7 ± 13.4 years) underwent Time-of-Flight magnetic resonance angiography and transcranial Doppler sonography. We investigated the anterior and posterior CW according to morphological categories. Prevalence and concordance rates of CW variants were calculated. MZ twins discordant for CW variants were analyzed for cardiovascular risk factors and altered blood flow. Results: Complete CW (45.0%) and bilaterally absent posterior communicating artery (PCoA) (22.5%) were the most prevalent variants in the anterior and posterior CW, respectively. There was no significant difference regarding the prevalence of variants across zygosity except for bilaterally hypoplastic PCoA (p = .02). DZ concordance was higher compared to MZ twins regarding morphological categories of the CW. Cardiovascular risk factors were not significantly associated with variant CW in MZ twins discordant to CW morphology. Flow parameters did not differ significantly among MZ twins discordant to CW variants. Conclusion: CW variants may not be determined by substantial genetic effects and are not influenced by altered blood flow in healthy individuals. Further investigations are needed to identify potential environmental factors affecting these variants.

Genetic and environmental determinants of longitudinal stability of arterial stiffness and wave reflection. A twin study

Background: We aimed at evaluating the impact of genetic and environmental factors on longitudinal changes in aortic pulse wave velocity (aPWV) and aortic augmentation index (aAIx). Method: Three hundred and sixty-eight Italian and Hungarian adult twins (214 monozygotic, 154 dizygotic) underwent repeated evaluations of aPWV and aAIx (TensioMed Arteriograph). Within-individual/cross-wave, cross-twin/within-wave and cross-twin/cross-wave correlations were calculated; bivariate Cholesky models were fitted to calculate additive genetic (A), shared environmental (C) and unique environmental (E) components. Results: For both aPWV and aAIx, cross-twin correlations in monozygotic pairs (r between 0.35 and 0.56) were all significant and always higher than in dizygotic pairs, both at wave 1 and at wave 2. Heritability and unshared environmental proportion of variance at each wave were substantially time-invariant for aPWV (heritability 0.51, 95% CI 0.36–0.63 at wave 1; 0.49, 95% CI 0.34–0.62 at wave 2), whereas for aAIx, we observed a diminished genetic effect (heritability 0.57, 95% CI 0.45–0.67 at wave 1; 0.37, 95% CI 0.21–0.51 at wave 2). Overlapping genetic factors explained a high proportion (0.88, 95% CI 0.61–1.00) of longitudinal covariance for aPWV, and had a relatively lower impact on aAIx (0.55, 95% CI 0.35–0.70). Genetic correlations of aPWV (r = 0.64, 95% CI 0.42–0.85) and aAIx (r = 0.70, 95% CI 0.52–0.87) between waves were lower than 1, suggesting a potential contribution of novel genetic variance on arterial stiffening. Conclusion: Changes in aPWV and aAIx over time are largely genetically determined. Our results might stimulate further studies on genetic and epigenetic factors influencing the process of vascular ageing.

Genetically determined pattern of left ventricular function in normal and hypertensive hearts

We sought to assess the inheritance of left ventricular (LV) function using speckle‐tracking echocardiography and the impact of hypertension on modifying the genetically determined pattern of contraction in a population of twins. We recruited 92 Caucasian twin pairs, including 74 hypertensive (HTN) siblings. Beyond standard echocardiographic protocol, a speckle‐tracking analysis was performed, including global longitudinal strain (GLS). Systolic function, as assessed by ejection fraction, showed moderate heritability (61%); however, GLS showed higher and dominant heritability (75%). Heterogeneity models revealed that there were no differences between the HTN and non‐HTN subjects regarding the heritability of GLS. However, the heritability estimates of diastolic function parameters, including early diastolic strain rate, were low. LV systolic biomechanics is highly heritable. GLS shows dominant heritability, despite the presence of early‐stage hypertensive heart disease. Early diastolic parameters are rather determined by environmental factors. These findings suggest the presence of a genetic framework that conserves systolic function despite the expression of diastolic dysfunction and may underlie the phenotypic progression towards heart failure with preserved ejection fraction.

Investigation of circle of Willis variants and hemodynamic parameters in twins using transcranial color-coded Doppler sonography

Morphological and hemodynamic variations of the circle of Willis (CW) may have an important impact on cerebrovascular events. However, the environmental and genetic influence remains unclear. For this reason we studied the variations and hemodynamic parameters of the CW in twins using transcranial color-coded sonography (TCCS). Sixty-four twins, 19 monozygotic (MZ) and 13 dizygotic (DZ) pairs from the Italian Twin Registry (average age 45.0 ± 13.7 years) underwent TCCS and risk factor assessment. We examined CW morphology and recorded peak systolic velocity (PSV), end-diastolic velocity (EDV) and pulsatility index (PI). Raw heritability was determined for hemodynamic parameters, whereas concordance and discordance rates were calculated for CW morphological variants. A normal CW anatomy was observed in the majority of MZ and DZ twins (76.5% and 92.3%, respectively). The most frequent variant was a missing anterior cerebral artery (ACA). There was no significant difference in the prevalence of most CW variants depending on the zigosity. Concordance rates were low regarding the presence of variant CW anatomy both in MZ and DZ groups (0.14 and 0.00, respectively). Women had a significantly higher PI in vertebral arteries (VA) and in the right ACA (p = 0.01, p = 0.02 and p < 0.01, respectively). An inverse correlation was observed between hemodynamic parameters and age. Morphological variants of the CW do not seem to be heritable; they are most likely determined by environmental factors. In contrast, hemodynamic parameters of the CW are moderately heritable and this might have implications in the management and prevention of cerebrovascular diseases.

Tight co-twin similarity of monozygotic twins for hTERT protein level of T cell subsets, for telomere length and mitochondrial DNA copy number, but not for telomerase activity

Our study analyzed lymphocyte subpopulations of 32 monozygotic twins and compared the level of the catalytic reverse transcriptase protein subunit (hTERT) in T lymphocytes (Tly), helper- (Th), cytotoxic- (Tc) and regulatory T cell (Treg) subgroups. Four variables related to telomere and mitochondrial biology were simultaneously assessed, applying multi-parametric flow cytometry, TRAP-ELISA assay and qPCR standard curve method on peripheral blood mononuclear cell (PBMC) samples of genetically matched individuals. Twin data of telomerase activity (TA), hTERT protein level, telomere length (TL) and mitochondrial DNA copy number (mtDNAcn) were analyzed for co-twin similarity. The present study has provided novel information by demonstrating very high intraclass correlation (ICC) of hTERT protein level in T lymphocytes (0.891) and in both Th (0.896), Treg (0.885) and Tc (0.798) cell subgroups. When comparing results measured from PBMCs, intraclass correlation was also high for telomere length (0.815) and considerable for mtDNA copy number (0.524), and again exceptionally high for the rate-limiting telomerase subunit, hTERT protein level (0.946). In contrast, telomerase activity showed no co-twin similarity (ICC 0). By comparing relative amounts of hTERT protein levels in different lymphocyte subgroups of twin subjects, in Treg cells significantly higher level could be detected compared to Tly, Th or Tc cell subgroups. This is the first study that simultaneously analyzed co-twin similarity in MZ twins for the above four variables and alongside assessed their relationship, whereby positive association was found between TL and mtDNAcn.

Genetic and Environmental Effects on Eudaimonic and Hedonic Well-Being: Evidence from a Post-Communist Culture

Prior behavioral genetic studies in positive psychology were entirely based on data from Western democracies, leaving the question open whether the magnitude of genetic effects on well-being indicators is similar in substantially different societal contexts. The aim of this study, therefore, was to investigate the structure of the genetic and environmental influences on happiness, life satisfaction, meaning in life, optimism, sense of coherence, and general well-being in a non-Western sample. Altogether, 100 monozygotic and 36 same-sex dizygotic twin pairs from Hungary (73 % female; Mage = 43 years, SD = 16 years) participated in the survey. Univariate classical twin modeling (ACE analysis) was performed using structural equation models. Heritability estimates of the positive psychological variables were largely variable, ranging from 0 % (happiness and meaning in life) to 67 % (life satisfaction). Also, estimates for the influence of common environment fell between 0 % (life satisfaction, sense of coherence, and well-being) and 60 % (meaning in life). Unshared environmental influences however, explained a moderate variance of all investigated variables (33–62 %). Most results were in line with previous findings from Western countries; however, some notable differences—e.g., lower hereditary influence for happiness or more robust role of shared environmental effects for optimism—were also established. These findings suggest that the communist and post-communist legacy did not produce drastic differences in the structure of heritability and environmental influences as compared to countries with longer traditions of democracy and economic prosperity.

Van-e összefüggés az epikardiális zsírszövet és a koszorúér-betegség között?

A zsírszöveti kompartmenteknek szerepe lehet az ateroszklerózis kialakulásában. Korábbi adatok az abdominalis zsírszövet és a fokozott kardiovaszkuláris kockázat közötti összefüggést már igazolták, napjainkban vizsgálat tárgyát képezi az epikardiális zsírszövet (EAT) szerepe is. Egyre több adat utal arra, hogy az EAT megnövekedett mennyisége a koronáriabetegség (CAD) kockázatát növeli. Jelenlegi vizsgálatunk során arra kerestünk választ, hogy igazolható-e összefüggés az EAT térfogata és a CAD jelenléte között felnőtt, korábban kardiális eseményt nem szenvedett egyének körében. A vizsgálatot a BUDAPEST-GLOBAL-tanulmány keretei között végeztük. Összesen 195 beteg (életkor: 56,1±9,4 év; nők 64,1%) adatait elemeztük. Minden résztvevőről kontrasztanyag nélküli CT-felvétel készült a mellkasi és felhasi régióban az EAT és az abdominalis zsírszövet mennyiségének méréséhez. A CAD jelenlétét vagy hiányát koronária-CT-angiográfi a lelete alapján állapítottuk meg és a betegeket koronáriabetegségben nem szenvedők (CAD-negatív; n=89) és koronáriabetegségben szenvedők (CAD-pozitív; n=106) csoportba soroltuk. A CAD-pozitív csoport életkora, haskörfogata, EAT- és abdominalis zsírszövetértéke számottevően nagyobb volt, mint a CAD-negatív csoporté. A CAD-pozitív csoportban értékelhetően kisebb arányban voltak a nők, az előzményi adatok között gyakrabban szerepelt hipertónia, dyslipidaemia és diabétesz. A CAD-pozitív csoport szérum trigliceridértéke értékelhetően nagyobb volt, mint a CAD-negatív csoporté, a többi lipid- és vércukorértéket tekintve a két csoport között számottevő különbség nem mutatkozott. Az életkor (esélyhányados: 1,1; p<0,001), a hipertónia (esélyhányados 3,3; p<0,05), a női nem (esélyhányados 0,1; p<0,001) és az EAT 10 cm3-nyi értéke (esélyhányados 1,3; p=0,001) a CAD független prediktorainak bizonyult. Az EAT mennyiségének 10 cm3-rel való növekedése a CAD kockázatát 30%-kal megnövelte. A női nem protektív tényezőnek adódott, következésképpen a férfi nem pozitív prediktív tényezőnek minősült. Az EAT mennyisége összefüggésben áll a CAD jelenlétével, ezért érdemes megfontolni értékének szerepeltetését a kardiovaszkuláris kockázatbecslő rendszerekben, a pontosság növelése érdekében. Is there any association between epicardial adipose tissue compartment and coronary artery disease? Various fat compartments might have an important role in the pathophysiology of atherosclerosis. Previous studies demonstrated an association between abdominal adipose tissue compartments and increased cardiovascular risk however the role of epicardial adipose tissue (EAT) is still unclear. It has been suggested that increased EAT quantity increases the risk of coronary artery disease (CAD). Our aim was to assess the relationship between the volume of EAT and the presence of CAD in subjects with negative cardiovascular medical history. We included 195 subjects (age: 56.1±9.4 years, female 64.1%) from the BUDAPEST-GLOBAL study. All subjects underwent coronary CT angiography (CTA) and were classifi ed into groups with and without CAD (CAD-positive: n=106 and CAD-negative: n=89, respectively), based on the presence or absence of any plaque in coronary CTA. We measured the EAT volume on a native cardiac scan and the abdominal adipose tissue areas on a single CT-slice acquired at the L3/L4 level. Subjects from the CAD-positive group were older, had a larger waist circumference, EAT volume and abdominal adipose tissue areas than subjects from the CAD-negative group. There were fewer females in the CAD-positive group, and in this group the presence of hypertension, dyslipidemia and diabetes were more frequent. Considering the lipid and glucose levels, we observed a signifi cant difference only in the serum triglyceride levels. Age (OR: 1.1 p<0.001), hypertension (OR: 3.3 p<0.05), female sex (OR: 0.1 p<0.001) and the volume of EAT in 10 cm3 clusters (OR: 1.3 p=0.001) were independent predictors for CAD. A 10 cm3 increment in the volume of EAT increases the risk of CAD with 30%. Female sex was a protective factor therefore male sex is a positive predictive factor. Since EAT shows a signifi cant association with the presence of CAD, it is reasonable to consider the quantity of EAT in risk assessments to improve the accuracy of CAD risk prediction.

Heritability of the femoral intima media thickness

Background The measurement of femoral intima-media thickness (IMT) is underutilized in the clinical practice, although it is a surrogate marker of cardiovascular disease. Materials and methods 388 Hungarian and Italian twins (121 monozygotic, 73 dizygotic pairs) underwent bilateral B-mode sonography of femoral arteries. IMT was measured by semiautomated software, where available, or by calipers. Results Within-pair correlation in monozygotic twins was higher than in dizygotics for each parameter. Age-, sex- and country-adjusted genetic effect accounted for 43.9% (95% confidence interval, CI 21.3%–65.2%) and 47.2% (95% CI, 31.4%–62.6%) of the variance of common and superficial femoral artery IMT, respectively, and unshared environmental effect for 56.1% (95% CI 34.6%–78.5%) and 52.8% (95% CI, 37.2%–68.5%). These results did not change significantly after correcting for body mass index or central systolic blood pressure. Conclusions Genetic factors have a moderate role in the determination of common and superficial femoral IMT; however, the influence of environmental (lifestyle) factors remains still relevant. Environmental factors may have a role in influencing the genetic predisposition for femoral vascular hypertrophy.

Vertebral artery diameter and flow: nature or nurture

BACKGROUND AND PURPOSE In contrast with the carotid arteries, the vertebral arteries (VAs) show considerable variation in length, caliber, and vessel course. This study investigated whether the variation in diameter and flow characteristics of the VAs might be inherited. METHODS A total of 172 Italian twins from Padua, Perugia, and Terni (54 monozygotic, 32 dizygotic) recruited from the Italian Twin Registry underwent B‐mode and pulsed‐wave Doppler ultrasound assessment of their VAs. VA diameters, peak systolic velocity (PSV) and end diastolic velocity (EDV) were assessed at the level of a horizontal V2 segment. Univariate quantitative genetic modeling was performed. RESULTS Fourteen percent of the sample had VA hypoplasia. Within pair correlation in monozygotic twins was higher than in dizygotics (.552 vs. .229) for VA diameter. Age‐ and sex‐adjusted genetic effect, under the most parsimonious model, accounted for 54.7% (95% CI: 42.2‐69.1%) of the variance of VA diameter, and unshared environmental effect for 45.3% (95% CI: 30.9‐57.8%). No heritability was found for the PSV of VA, but shared (34.1%; 95% CI: 16.7‐53.7%) and unshared (65.9%; 95% CI: 45.9‐83.1%) environmental factors determined the variance. EDV of VA is moderately genetically influenced (42.4%; 95% CI: 16.1‐64.9%) and also determined by the unshared environment (57.6%; 95% CI: 34.7‐83.7%). CONCLUSIONS The diameter of the VAs is moderately genetically determined. Different factors influence the PSV and EDV of VAs, which may highlight the complex hemodynamic background of VA flow and help to understand the vertebral flow anomalies found by ultrasound.

The inheritance of corneal endothelial cell density

Background: Although it is known that some corneal diseases and degenerations have a significant heritable background, heritability on corneal endothelial cell density (ECD) has never been clearly determined. Our aim was to determine the heritability of corneal ECD. Material and methods: Corneal ECD of 114 eyes (66 eyes of 33 monozygotic and 48 eyes of 24 dizygotic pairs; mean age 49.0 ± 15.5 years) was investigated by Konan Noncon Robo NSP-9900 specular microscopy. Structural equation modeling (ACE model) was applied. Results: Endothelial corneal cell density was highly heritable (82.0%, 95%CI, 70.0–92.0%), whereas the unique environmental contribution was 18.0% (95%CI, 8.0–29.0%). Shared environmental factors had no influence on the endothelial corneal cell density. Discussion: In this twin study, we established first that the density of the corneal endothelial cells is strongly heritable, which should stimulate future genetic studies to identify genes and pathways that are involved in determining ECD which might in turn lead to future treatments to prevent EC loss.

Az alvás alatti légzészavarok hátterében álló örökletes tényezők: egy ikervizsgálat tapasztalatai

Bár az obstruktív alvási apnoe (OSA) gyakran előforduló betegség, a kialakulásukban szerepet játszó örökletes tényezők szerepe mindmáig ismeretlen. A Magyar Ikerregiszter 110 ikertagja (39 egypetéjű, monozigóta, MZ, és 16 kétpetéjű, dizigóta, DZ ikerpár; átlag életkor 50+-16 év) éjjeli poliszomnográfiás vizsgálaton esett át. Regisztráltuk az apnoe hypopnoe indexet (AHI), a légzészavar indexet (respiratory disturbance index, RDI) és az oxigén deszaturációs indexet (ODI). Az ikerpárok közötti korrelációkat összehasonlítva kiszámítottuk a nyers öröklődési mutatókat (Falconer-formula). OSA 23 vizsgált személynél fordult elő (21%). Mindhárom mért paraméter esetén a korrelációs együtthatók magasabbak voltak az egypetéjű iker-pároknál (0,80 vs. 0,15, 0,70 vs. 0,12 és 0,80 vs. 0,42, MZ vs. DZ, AHI, RDI és ODI esetén), amik magas (1,30, 1,17 és 0,76) nyers örökletességi mutatót jelentenek. Gyenge összefüggés igazolódott az alvászavarral összefüggő változók és a testsúly-testmagasság index (BMI, p<0,005, R2=0,078-0,224), illetve a reggeli systolés és diastolés vérnyomásértékek (SBP, DBP) között (p<0,05, R2=0,043-0,093, kivéve az RDI-t, ahol p=ns). Ezek nyers örökletességi indexe magasnak (BMI: h2=1,730, reggeli SBP és DBP: h2=0,568, h2=0,422) bizonyult. Vizsgálatunkban elsőként mutattuk ki az alvásfüggő légzészavar paramétereinek örökletességét, mely felveti az OSA kialakulásáért felelős genetikai faktorok szerepét. Ezt részben a BMI magas örökletessége magyarázhatja. A vizsgálat folytatása szükséges nagyobb ikermintán, hogy megállapíthassuk a közös és egyéni környezeti tényezők pontos szerepének mértékét. További kutatások feladata feltárni, hogy érdemes-e szűrni az OSA-s betegek közeli rokonait. A kutatást a Magyar Pulmonológiai Alapítvány támogatta (MPA, 2013).

Genetic and Environmental Effects on the Abdominal Aortic Diameter Development

Background Configuration of the abdominal aorta is related to healthy aging and a variety of disorders. Objectives We aimed to assess heritable and environmental effects on the abdominal aortic diameter. Methods 114 adult (69 monozygotic, 45 same-sex dizygotic) twin pairs (mean age 43.6 ± 16.3 years) underwent abdominal ultrasound with Esaote MyLab 70X ultrasound machine to visualize the abdominal aorta below the level of the origin of the renal arteries and 1-3 cm above the bifurcation. Results Age- and sex-adjusted heritability of the abdominal aortic diameter below the level of the origin of the renal arteries was 40% [95% confidence interval (CI), 14 to 67%] and 55% above the aortic bifurcation (95% CI, 45 to 70%). None of the aortic diameters showed common environmental effects, but unshared environmental effects were responsible for 60% and 45% of the traits, respectively. Conclusions Our analysis documents the moderate heritability and its segment-specific difference of the abdominal aortic diameter. The moderate part of variance was explained by unshared environmental components, emphasizing the importance of lifestyle factors in primary prevention. Further studies in this field may guide future gene-mapping efforts and investigate specific lifestyle factors to prevent abdominal aortic dilatation and its complications.

Environmental Factors Account for Variability of Hepatic Vein Flow: a Doppler assessment in healthy twins

Doppler interrogation studies of the liver blood flow indicate altered hepatic vein waveforms in association with impaired hepatocellular function. However, little is known about the mechanisms responsible for variations of these parameters in the absence of disease. We aimed to investigate the contribution of heritable and environmental factors to the physiological variability of hepatic vein flow in a twin cohort. Two hundred twenty-eight healthy adult Hungarian twins (69 monozygotic, 45 same-sex dizygotic pairs) underwent Doppler sonography of the hepatic vein. Age- and sex-adjusted heritability of the highest velocity (amplitude of S wave) of hepatic vein flow was negligible. Shared environment contributed to 33% (95% CI, 16%-51%), and unshared environment was responsible for the largest portion (67%; 95% CI, 49%-84%) of the variance. Duration of sports activities was significantly (P < 0.05) related to the magnitude of hepatic vein flow, while other risk factors and lifestyle characteristics had no significant influence. The data suggest that genetic factors have little impact on the parameters of hepatic venous blood flow. The variability observed in healthy twins by the Doppler interrogation can be explained by the effect of unshared environmental components primarily related to regular physical activity. These findings underscore the importance of unique environments in physiological variations of hepatic venous blood flow.

The importance of context in the genetic transmission of US party identification

In this study, we discuss one example where behavior genetic findings vary greatly across political contexts. We present original findings on how party identification is heritable around the 2008 election on a sample of twins from Minnesota. As this is in contrast with findings from the late 1980s and with how a mid‐2000 study interpreted their results, we explain how the increasing partisan ideological polarization could be responsible for these seemingly contradictory findings. In the Minnesota sample, we show a genetic correlation between party identification and ideology, a finding consistent in the political science literature. We highlight how heritability of political characteristics, like all others, is population specific and highly context dependent stressing its nondeterministic nature.

Rationale, design and methodological aspects of the BUDAPEST-GLOBAL study (Burden of Atherosclerotic Plaques Study in Twins - Genetic Loci and the Burden of Atherosclerotic Lesions)

The heritability of coronary atherosclerotic plaque burden, coronary geometry, and phenotypes associated with increased cardiometabolic risk are largely unknown. The primary aim of the Burden of Atherosclerotic Plaques Study in Twins—Genetic Loci and the Burden of Atherosclerotic Lesions (BUDAPEST‐GLOBAL) study is to evaluate the influence of genetic and environmental factors on the burden of coronary artery disease. By design this is a prospective, single‐center, classical twin study. In total, 202 twins (61 monozygotic pairs, 40 dizygotic same‐sex pairs) were enrolled from the Hungarian Twin Registry database. All twins underwent non–contrast‐enhanced computed tomography (CT) for the detection and quantification of coronary artery calcium and for the measurement of epicardial fat volumes. In addition, a single non–contrast‐enhanced image slice was acquired at the level of L3‐L4 to assess abdominal fat distribution. Coronary CT angiography was used for the detection and quantification of plaque, stenosis, and overall coronary artery disease burden. For the primary analysis, we will assess the presence and volume of atherosclerotic plaques. Furthermore, the 3‐dimensional coronary geometry will be assessed based on the coronary CT angiography datasets. Additional phenotypic analyses will include per‐patient epicardial and abdominal fat quantity measurements. Measurements obtained from monozygotic and dizygotic twin pairs will be compared to evaluate the genetic or environmental effects of the given phenotype. The BUDAPEST‐GLOBAL study provides a unique framework to shed some light on the genetic and environmental influences of cardiometabolic disorders.

Genetic and environmental influence on thyroid gland volume and thickness of thyroid isthmus: a twin study

OBJECTIVES: Decreased thyroid volume has been related to increased prevalence of thyroid cancer. SUBJECTS AND METHODS: One hundred and fourteen Hungarian adult twin pairs (69 monozygotic, 45 dizygotic) with or without known thyroid disorders underwent thyroid ultrasound. Thickness of the thyroid isthmus was measured at the thickest portion of the gland in the midline using electronic calipers at the time of scanning. Volume of the thyroid lobe was computed according to the following formula: thyroid height*width*depth*correction factor (0.63). RESULTS: Age-, sex-, body mass index- and smoking-adjusted heritability of the thickness of thyroid isthmus was 50% (95% confidence interval [CI], 35 to 66%). Neither left nor right thyroid volume showed additive genetic effects, but shared environments were 68% (95% CI, 48 to 80%) and 79% (95% CI, 72 to 87%), respectively. Magnitudes of monozygotic and dizygotic co-twin correlations were not substantially impacted by the correction of covariates of body mass index and smoking. Unshared environmental effects showed a moderate influence on dependent parameters (24-50%). CONCLUSIONS: Our analysis support that familial factors are important for thyroid measures in a general twin population. A larger sample size is needed to show whether this is because of common environmental (e.g. intrauterine effects, regional nutrition habits, iodine supply) or genetic effects.

Has the Tea Party Era Radicalized the Republican Party? Evidence from Text Analysis of the 2008 and 2012 Republican Primary Debates

Much ink has been spilled to describe the emergence and likely influence of the Tea Party on the American political landscape. Pundits and journalists declared that the emergence of the Tea Party movement pushed the Republican Party to a more extreme ideological position, which is generally anti-Washington. To test this hypothesis, we analyzed the ideological positions taken by candidates in the 2008 and 2012 pre-Iowa caucus Republican presidential-primary debates. To establish the positions, we used the debate transcripts and a text-analytic technique that placed the candidates on a single dimension. Findings show that, overall, the 2012 candidates moved closer to an anti-Washington ideology—associated with the Tea Party movement—and away from the more traditional social conservative Republican ideology, which was more salient in the 2008 debates. Both Mitt Romney and Ron Paul, the two candidates who ran in both elections, shifted significantly in the ideological direction associated with the Tea Party.

Central and Eastern European Special Issue

From November 16–19, 2014, twin researchers of the world will descend on the lovely city of Budapest, Hungary for the 3rd World Congress on Twin Pregnancy, held in conjunction with the 15th Congress of the International Society of Twin Studies (ISTS). It is the first time a Central and Eastern European country will host the congress. On this occasion, we were honored by the request from the editor of Twin Research and Human Genetics, Nick Martin, to put together a special issue highlighting twin research conducted in Central and Eastern Europe (CEE).

Theorizing Sex Differences in Political Knowledge: Insights from a Twin Study

It is well established that women and men differ in their psychological orientation to politics (Burns, Schlozman, and Verba 2001; Dolan 2011; Fox and Lawless 2004; Thomas 2012). In addition to willingness to run for office, expressing interest in politics, and political efficacy, men and women tend to differ in reporting their factual knowledge of politics, but how do we explain the gap? This question is not merely important from a measurement standpoint (e.g., Mondak and Anderson 2004) but also has implications for our understanding of gendered political attitudes and behaviors. The gap can be reduced when controlling for a number of factors, but there remains a residual when measuring knowledge with the scale most widely used. This paper aims at providing insight on how we think not only about measuring something like “political knowledge” but also how we theorize gendered political behavior. We present a behavioral genetic analysis of sex differences in political knowledge using a genetically informative twin design to parse out the source of variation in knowledge. We do so predicated on a framework for thinking about gendered patterns in political behavior as well as findings from the existing literature on gender differences in the psychological orientation to politics. We believe our findings give us insight on what is wrong with current and seemingly gender-neutral measures of political knowledge.

Genetic Influences on Political Ideologies: Twin Analyses of 19 Measures of Political Ideologies from Five Democracies and Genome-Wide Findings from Three Populations

Almost 40 years ago, evidence from large studies of adult twins and their relatives suggested that between 30 and 60 % of the variance in social and political attitudes could be explained by genetic influences. However, these findings have not been widely accepted or incorporated into the dominant paradigms that explain the etiology of political ideology. This has been attributed in part to measurement and sample limitations, as well the relative absence of molecular genetic studies. Here we present results from original analyses of a combined sample of over 12,000 twins pairs, ascertained from nine different studies conducted in five democracies, sampled over the course of four decades. We provide evidence that genetic factors play a role in the formation of political ideology, regardless of how ideology is measured, the era, or the population sampled. The only exception is a question that explicitly uses the phrase “Left–Right”. We then present results from one of the first genome-wide association studies on political ideology using data from three samples: a 1990 Australian sample involving 6,894 individuals from 3,516 families; a 2008 Australian sample of 1,160 related individuals from 635 families and a 2010 Swedish sample involving 3,334 individuals from 2,607 families. No polymorphisms reached genome-wide significance in the meta-analysis. The combined evidence suggests that political ideology constitutes a fundamental aspect of one’s genetically informed psychological disposition, but as Fisher proposed long ago, genetic influences on complex traits will be composed of thousands of markers of very small effects and it will require extremely large samples to have enough power in order to identify specific polymorphisms related to complex social traits.

Within family transmission of secondhand smoke sensitivity and smoking attitude

Introduction and objective: The role of genetic factors in nicotine dependence is well understood, but no information is available on the inheritability of second-hand smoke (SHS) exposure sensitivity and their co-variance. Material and Methods: 186 adult same-gender pairs of twin (146 monozygotic, 40 dizygotic; 44±17 years±SD) completed a questionnaire. Results: The model showed a significant role of unshared environmental factors influencing the co-variance between smoking habit and SHS sensitivity (re=-0.191, 95% CI, -0.316 to -0.056, or the total phenotypic correlation of rph=-0.406, p<0.001) without evidence for genetic covariation. Age, gender and country-adjusted analysis indicated 51.5% heritability for smoking habit (95% confidence interval/CI/, 6.2 to 89.8%), 49.7% for SHS sensitivity (95%CI, 19.1–72.0%), 35.5% for general opinions on SHS exposure in restaurants/cafés (95%CI, 10.7–58.6%), and 16.9% in pubs/bars (95%CI, 0.0–49.0%). Conclusions: The co-variance between SHS sensitivity and smoking habits is driven mainly by the unshared environment. SHS sensitivity is moderately inheritable. The considerable influence of environmental factors on general opinions on SHS exposure in designated indoor public venues emphasizes the importance of smoking bans and health behaviour interventions at the individual level in developing an anti-smoking attitude.

Heritability of cerebral arterial velocity and resistance

Aims Cerebrovascular resistance is a pressure-dependent mechanism resulting from cerebral autoregulation, which is the normal buffering of changes in arterial blood pressure. Lifestyle habits are known to have an influence; however, its magnitude is still unclear. The aim of this study was to assess the contribution of additive genetic, shared and unshared environmental factors to changes in middle cerebral artery (MCA) mean flow velocities (MFVs) and pulsatility index. Methods One hundred and forty-three Italian twin pairs from Padua, Perugia and Rome (68 monozygotic, 75 dizygotic, 55 ± 12 years) underwent transcranial Doppler sonography of the MCA bilaterally. Univariate quantitative genetic modeling was performed to decompose the phenotypic variance of averaged MFV and pulsatility index into additive genetic, shared and unique environmental effects adjusted by age and sex. Results MFV was heritable in 30.6% [95% confidence interval (CI) 0.8–67.3%], and shared and unshared environmental factors explained 47.7 and 21.6% of the variance (95% CI 14.4–71.9% and 12.6–32.0%). Pulsatility index was not genetically determined, but unique and common environmental factors were responsible for 54.2 and 38.1% of the variance (95% CI 36.3–71.8% and 0.0–57.8%). Conclusion These findings underline the importance of identification of the specific genes and common environmental factors related to MFV. Individuals with positive family history of stroke related to the atherosclerosis of MCA might take advantage from preventive ultrasound screening. More emphasis should be placed on the prevention of the known related common environmental factors on MFV and the individual lifestyle risk factors on pulsatility index.

Validity of Survey Response Propensity Indicators: A Behavior Genetics Approach

Objectives This study explains how behavior genetic analysis using a twin design can help us assess the validity of our measures. Methods We test multiple indicators of response propensity, a measure used by survey researchers to better understand the similarities and differences between survey respondents and nonrespondents. The response propensity indicators evaluated include response to follow‐up surveys and subsequent waves of a panel and the completion of a sensitive recontact information sheet to aid subsequent recontact efforts. Results A classical and the newly proposed method of validation all point to insufficient validity of our response propensity measures. Construct validation using data from the National Survey of Midlife Development in the United States exhibited little correlation between indicators. Genetic analysis suggests that the success of subsequent data‐collection efforts is predominantly driven by additive genetic effects, while nonresponse to inquiries for recontact information is influenced predominantly by familial environmental predictors. Conclusion Our results indicate that different underlying constructs drive the response propensity indicators, suggesting that nonresponse is, at minimum, multidimensional.

The Hungarian Twin Registry

The first Hungarian Twin Registry was established in Budapest in 1970 through the mandatory reporting of multiple-births. In the 1980s a second, volunteer adult registry was also founded. Unfortunately, both registries ceased to exist in the 1990s. Efforts started in 2006 to revive a Hungarian twin registry. The team spearheading this effort reports here on this progress. Currently, the voluntary Hungarian Twin Registry consists of 310 adult twin pairs and multiplets. Current research focuses on cardiovascular and respiratory health and yielded multiple awards and publications. Efforts are on the way to expand into social, psychological, and obesity studies.

Magyarországi ikerkutatások: négy évtized eredményei

Az ikervizsgálatok szerepet játszanak a fenotípusos változók kialakulásáért felelős genetikai és környezeti tényezők arányának, továbbá a genotípusok közötti genetikai kapcsoltság vizsgálatában. Magyarországon az ikerkutatások döntően az 1970-es években kezdődtek és alapjukat három ikernyilvántartás (köztük két iker-regiszter) biztosította. A vizsgálatok elsősorban a különböző veleszületett rendellenességekre, a fogamzásgátló tabletták és a folsav ikergyakoriságra való hatására, az ikrek pszichoszexuális viselkedésének megismerésére, az alkoholfogyasztási szokások örökletességének becslésére irányultak. Először mutatták ki a laktóz(mal)abszorpció monogénes mendeli öröklődését. 2007-ben alakult meg a Magyar Ikerregiszter, amelynek segítségével több ikervizsgálatra nyílt ismét lehetőség, például a metabolikus szindróma és az érelmeszesedés hátterének megértésére. Nemzetközi ikervizsgálat során többek között az artériás stiffness, a centrális vérnyomás, a carotis intima/media falvastagság, a vénás biomechanika, a testösszetétel, a légzésfunkció és a dohányzási szokások vizsgálatára is sor került. Először sikerült kimutatni a nem alkoholos zsírmáj örökletességének hiányát és a carotisplakkok kialakulásában az öröklődés szerepét. A dolgozat a Magyar Ikerregiszter jövőbeni terveiről is áttekintést nyújt. Orv. Hetil., 2013, 154, 1579–1586. | Twin studies play a role in examining the contribution of genetic variations and environmental factors responsible for the determination of phenotypic variables and of genetic linkage between genotypes. Hungarian twin studies, supported by three twin registries (among them two twin-database), date back to 1970s. Studies mainly focused on various congenital abnormalities, the effect of contraceptive pills and folic acid on the frequency of twin pregnancies, as well as psychosexual and alcohol consumptional behaviors. Monogenic Mendelian inheritance of lactose (mal)absorption was demonstrated for the first time. Hungarian Twin Registry was founded in 2007, which contributed to the current understanding on the background of several disorders, e.g. metabolic syndrome and atherosclerosis. As part of an international twin study, among others, arterial stiffness, central blood pressure, carotid intima/media thickness, venous biomechanics, body composition, lung function and smoking characteristics were also assessed. Absence of genetic background in non-alcoholic fatty liver disease and high inheritance of carotid plaque characteristics were demonstrated for the first time. The review also aims to summarize future plans of the Hungarian Twin Registry. Orv. Hetil., 2013, 154, 1579–1586.

Choosing sides. The genetics of why we go with the loudest

Recent developments in spatial voting have moved beyond finding the most appropriate utility function and started to assess individual differences in decision strategy. The question is not if a proximity or directional worldview performs better in general, rather under what conditions do people pick one strategy over the other? We draw on psychological theories to develop a survey-based measure of individual decision strategy and take a behavior genetic route to explaining the individual differences. We argue that dispositional traits shape whether an individual develops a directional or proximity worldview of the political arena. Utilizing a classical twin design, we capitalize on the documented relationship between partisanship and a directionalist worldview. We find that, in the Minnesota Twin Political Survey, both the strength of party identification and directional voting are moderately (~20 percent) but significantly (p < 0.05) heritable with no socialized component contributing to the variance. The covariation between the two traits is predominantly driven by common underlying genetic effects (p < 0.01). Implications for the rational voter models are discussed in light of the findings.

Do Heritability Estimates of Political Phenotypes Suffer From an Equal Environment Assumption Violation? Evidence From an Empirical Study

Using data from the Minnesota Twins Political Survey, this paper tests for the presence of unequal environments (EEA) by zygosity in political attitudes. Equal environment measures used include shared bedroom, friends, classes, and dressing alike. Results show an EEA violation at p < .05 in 5% of the models tested. The violations' impact on heritability estimates and their confidence levels appear random in magnitude and direction. No reasonable post hoc explanation emerged for understanding the presence of the violation in some items but not others. This article establishes reasonable priors for the absence of EEA violations in political phenotypes based on the tested environmental components. The findings place the burden on critics to present theoretical work on the specific mechanisms of EEA violations based on which additional empirical assessments could (and should) be conducted.

Should researchers use single indicators, best indicators, or multiple indicators in structural equation models?

Background Structural equation modeling developed as a statistical melding of path analysis and factor analysis that obscured a fundamental tension between a factor preference for multiple indicators and path modeling’s openness to fewer indicators. Discussion Multiple indicators hamper theory by unnecessarily restricting the number of modeled latents. Using the few best indicators – possibly even the single best indicator of each latent – encourages development of theoretically sophisticated models. Additional latent variables permit stronger statistical control of potential confounders, and encourage detailed investigation of mediating causal mechanisms. Summary We recommend the use of the few best indicators. One or two indicators are often sufficient, but three indicators may occasionally be helpful. More than three indicators are rarely warranted because additional redundant indicators provide less research benefit than single indicators of additional latent variables. Scales created from multiple indicators can introduce additional problems, and are prone to being less desirable than either single or multiple indicators.

Littvay L. Measuring Social and Political Phenotypes. In: Somit A, Peterson SA, editors. Biology and Politics: The Cutting Edge. Bingley: Emerald Group Publishing; 2011. p. 97-114. (Research in Biopolitics).

Psychosexual Study of Communist Era Hungarian Twins

Our aim in this study is to describe the characteristics of sexual development in twins and estimate the role of heritability and environmental factors as causes of certain sexual disorders. Two hundred and ten adult same-sex twin pairs (92 monozygotic [MZ] female, 41 MZ male, 55 dizygotic [DZ] female and 22 DZ male pairs) were involved in the study. Data were collected in 1982 by self-administered questionnaires that included items on sexual maturation, sexual life, contraception, mutual sexual activity within twin pairs and alcohol use. The ratio of married to unmarried twins was nearly the same in MZs and DZs, with the exception that the divorce rate was higher in MZ female twins (14%), and DZ and male twins were slightly more likely to be single. Menarche was later in twins compared to non-twin Hungarian women. 57% of MZs experienced menarche within 3 months of each other, 77% within 6 months while it occurred for 30% and 43% respectively in DZs. The first seminal emission indicated some delay in male twins compared with the Hungarian general population sample. MZ first kisses occurred later than DZ's first kisses. The same was true for the first petting, masturbation and first sexual intercourse. Anorgasmy is 27% heritable but the estimate is not statistically significant. Concordance rate for premature ejaculation in MZs was greater than in DZs but the structural equation model showed significant misfit. Age at menarche appeared to be strongly heritable.

Sense of Control and Voting: A Genetically Driven Relationship

Objectives The impact of political efficacy on political participation has been established in numerous classical studies of political behavior. However, the effects of more general measures of efficacy on political efficacy and voter turnout have received almost no attention. Additionally, seemingly independent contemporary developments in the field of political science proposed that political participation is heritable. In this study, we propose to link the two literatures, highlighting one possible mechanism through which genetic inheritance of political behavior is possible in the absence of the evolutionary time horizons of voting behavior. We theorize that heritability of psychological dispositions, such as one's sense of control, is more plausible and indirectly, through political efficacy, could have an influence on one's decision to vote. Methods We test our hypotheses using a classical twin study design (ACE models) and Cholesky decomposition models on data from the MIDUS (first wave) and MNTPS twin surveys. Results Empirically we find a relationship between general efficacy and turnout. We show that numerous operationalizations of efficacy are highly heritable and their covariance with turnout is predominantly driven by underlying additive genetic sources. On the other hand, environmental covariation between general and political efficacy and turnout is not significantly different from zero. Conclusions Our analysis contributes to a better understanding of how one's sense of control influences voting behavior. Our results provide sufficient evidence to claim that the covariation between these two traits can primarily be attributed to genetic factors. However, this is certainly not the only pathway that explains the heritability of voter turnout.

Does an EMILY’s List endorsement predict electoral success, or does EMILY pick the winners?

Women's political action committees (PACs)—those committees founded by women to raise money for women candidates—have been and will likely continue to be an important part of American electoral politics. In this article, we investigate the impact of EMILY's List, because it is the standard bearer of women's PACs and is commonly cited as crucial to women's electoral success. Empirical studies of EMILY's List impact to date have largely assumed causal inference by using traditional linear models. We use a propensity score–matching model to leverage on causality and find that an EMILY endorsement helps some candidates and hurts others. Our findings set the stage for further and more nuanced investigations of when, where, and how EMILY's List can enhance the likelihood of electoral success for women.

Ethics and Personality: Empathy and Narcissism as Moderators of Ethical Decision Making in Business Students

Many studies have reported that business students have been more apt to act in self-interested ways when compared to their counterparts in other academic fields. Beginning with the premise that ethical behavior derives in part from personality characteristics, the authors tested whether (a)measures of an empathetic or narcissistic personality predicted self-reported ethical decision making in business students and (b) individual business majors have a tendency to exhibit these personality traits. First, findings demonstrate that empathetic and narcissistic personality traits are significant predictors of ethical decision making. Second, they found that finance majors showed a marked and statistically significant tendency to be less empathetic and more narcissistic as compared to other business students.

Chronic hepatitis C virus infection associated with autonomic dysfunction

Background: Impaired autonomic function has been described in patients with chronic liver diseases from different aetiologies, and has proven to be a poor prognostic indicator. To date, it is not known how chronic hepatitis C virus (HCV) infection affects the autonomic nervous system. Aims: In the present study, we compared cardiovagal autonomic function in patients with chronic HCV infection and healthy controls and examined the relation between autonomic function and serum levels of aminotransferases, HCV RNA, cryoglobulins, albumin and glucose. Methods: Autonomic function was assessed in 45 treatment-naïve patients with chronic HCV infection and in 40 healthy controls by determining spontaneous baroreflex sensitivity (BRS) and heart rate variability (HRV) indices. The R–R interval was determined by electrocardiogram recording; continuous radial artery pressure was monitored simultaneously by applanation tonometry. Laboratory analyses and quantitative polymerase chain reaction for serum HCV RNA level were performed by standard procedures. Results: BRS and HRV time and frequency domain indices were lower in patients with HCV infection compared with healthy controls [7.1±3.4 vs. 11.5±6.5 ms/mmHg for BRS, 168.5±160.9 vs. 370.7±349.4 ms<sup>2</sup> for low-frequency HRV (mean±SD); P<0.01]. Multivariate analysis showed that autonomic dysfunction in HCV-infected patients correlated with elevated alanine aminotransferase levels, but was not associated with serum HCV RNA levels and cryoglobulins. Conclusion: Our results suggest that impaired autonomic function is caused by chronic HCV infection. Further studies are needed, however, to identify the underlying mechanisms.

Questionnaire Design Considerations with Planned Missing Data

This article explores considerations that emerge when using a planned missing data design (PMDD). It describes scenarios where a PMDD can be useful and reveals implications of a PMDD for questionnaire design in terms of the optimal number of questionnaire versions. It takes a confirmatory factor model to explore the PMDD performance. Findings suggest that increasing the number of versions to maximize uniformity of missing data yields no advantage over minimizing data collection cost and complexity. The paper makes recommendations concerning different missing data patterns that can be used. And finally, this article points out how certain fit statistics could be misleading with PMDD. The one fit statistics that consistently performed well with the PMDD is the SRMR.

An Analytical Strategy for Modeling Count (Poisson) Distributed Phenotypes with Genetically Informative Twin and Family Data

Meeting abstract of Behavior Genetics Association, 38th Annual Meeting.

A new way of modeling ascertainment or MAR missing data in the ACE model

Meeting abstract of Behavior Genetics Association, 37th Annual Meeting.

Comparison of Likelihood Based and Bootstrapped Confidence Intervals in the ACE Model

Meeting abstract of Behavior Genetics Association, 37th Annual Meeting.

The Historimetric Database : A platform for quantifying historical information for twin research

Abstract from the 12th International Congress on Twin Studies

Evolutionary Theory and Political Leadership : Why Certain People Do Not Trust Decision Makers

Central to social systems are the attitudes of the rank and file toward those who make political decisions (leaders), and attitudes toward leaders are known to be characterized by two fundamental features. First, the modal attitude is acceptance of the necessity of leaders coupled with acute aversion to leaders who are believed to be motivated by ambition and avarice; second, people are highly variable with some being markedly more sensitive than others to the traits of leaders. But the theoretical basis for these empirical facts has yet to be fully elucidated. In this article, we offer such a theory by drawing on biological evolution and then, using a series of laboratory experiments, provide an empirical test of it. Results are fully consistent with evolutionary theory in showing that people are indeed generally sensitive to leadership traits threatening to the larger group even as certain, expected individuals are a good deal more sensitive than others.

Littvay L. A választási kampány pszichológiája a 2002-es magyarországi parlamenti választások fényében. In: Lányi G, editor. Politika pszichológiai tükörben : Magyarország, 1990-2005. Vol 2. Budapest: Jószöveg Műhely; 2006. p. 241-57. (ELTE Társadalomtudományi Kar Politikai Magatartásvizsgáló Kutatóközpont kiadványai; vol 2).

A választási kampány pszichológiája a 2002-es magyarországi parlamenti választások fényében

Election Campaign Psychology in light of the 2002 Hungarian Parliamentary Elections.