Twins and their Psychological characteristics (original) (raw)

The Personalities of Twins: Just Ordinary Folks

Twin Research, 2002

Twin studies have demonstrated that personality traits show moderate genetic influence. The conclusions drawn from twin studies rely on the assumptions that twins are representative of the population at large and that monozygotic and dizygotic twins are comparable in every way that might have bearing on the traits being studied. To evaluate these assumptions, we used Multidimensional Personality Questionnaire (MPQ) data from three samples drawn from the Minnesota Twin Registry (totaling 12,971 respondents) to examine the effect sizes associated with mean differences on the 11 MPQ scales and 3 higher-order MPQ factors for singletons versus twins and MZ twins versus DZ twins. The singletons in the samples were family members of the participating twins. We also used ratios of scale variances to examine the significance of variance differences. The only mean or variance difference replicated across all three samples was greater Social Closeness (about.1 standard deviation) for twins than for singletons. This difference was obtained for both males and females. It would appear that, with respect to personality, twins are not systematically different from other people. Our results also highlight the importance of replication in psychological research because each of our large samples showed differences not replicated in other samples.

International journal of humanities and social sciences, 2016

This study aims at investigating the self-differentiating perceptions and the separation-individuation’s process in emerging adulthood twins. A group of 40 Italian pairs of twins (21 couples dizygotic-DZ and 19 monozygotic-MZ) aged 20-30 years, were evaluated using the test of graphic projection Family Life Space (DSSVF) and through a specific questionnaire ad hoc constructed for this research. The research hypothesis focuses on Zazzo’s test of parallel testimony and gives empirical evidence about the capacity of MZ Twins to use more internal resources of the couple than DZ Twins. This causes the split slowdown on identification. The data show that there are no differences between non-bisexual MZ and DZ couple. Moreover, there is a weaker reciprocal relation in the opposite sex DZ couple than in the others.

STUDY OF PERSONALITY DIFFERENCE AMONG IDENTICAL TWINS AND FRATERNAL TWINS IN PAKISTAN

The present research was conducted to study the difference between personality traits of identical and fraternal twins. At the same time it studies the personality traits of identical twins as well as fraternal twins. Two scales were administered that included self constructed demographic data and California Psychological Inventory.One hundred and twenty participants were interviewed during the present study. The sample was drawn from different areas of NWFP that included Malakand, Charsadda, Swabi, Mardan, and Peshawar. These participants belonged to the upper middle and lower socio-economic classes.. All participants were interviewed individually and their responses were recorded on the spot by the researcher. It was indicated that identical and fraternal twins have few differences in their personalities. It was concluded that despite sharing the same genes, their different environment, parents rearing practices and education do bring changes in their personalities. If family environment is good and they have better education and recreation facilities and their living standard is good, the child's personality will be composed and balanced. Parents and other people should understand such twins and treat them as separate individuals because they have individual personalities.

Personality Factors in Monozygotic and Dizygotic Twins: A Comparative Study

Psychological Reports, 1992

To explore similarities or differences on a number of psychological variables relating to personality for members of 16 pairs of monozygotic and 16 pairs of dizygotic twins and between the two groups, the Rorschach, Luscher, Cattell 16 PF, Bern Sex-role Inventory, and Symptom Distress Check List were given to 64 subjects. Analysis confirms data in the literature concerning significant similarities on some personality traits for monozygotic and dizygotic pairs, but with some differences between the groups tested. The particular similarity between the twins may be more attributable to the type of relationship developed early between the twins and the mother than to a greater genetic than environmental influence.

A longitudinal study of twins from birth to adulthood

Norsk Epidemiologi, 2016

Temperamental variation in infancy was the starting point for this longitudinal study of twins followed frombirth to adulthood. The influence of early individuality on later development was a research question in thefollow-ups, and by choosing twins as a group, it was possible to uncover the effect of environmental andgenetic factors at the different ages. Developmental psychopathology turned out to be a relevant framework,where mental health and well-being are seen as the result of a continuous transaction between geneticallybasedindividuality and a changing and varying environment (Maughan & Rutter, 2008). The twin methodwas an adequate tool to gain a better understanding of these processes. The overall clear message from thestudy is that whereas heritability of temperament can be seen from infancy on, environmental factors are ofcrucial importance for an understanding of mental development and health, but the effect of environmentalfactors probably varies a great deal in dependen...

Twin Studies of General Mental Ability

Handbook of Behavior Genetics, 2009

Twin studies are a crucial source of information about genetic and environmental influences on general intelligence. A brief summary of key events and controversies in the history of twin studies of intelligence is followed by a review of the contributions of twin studies to the field thus far. We then discuss new twin research designs, analytic methods, findings and their implications. Topics include evidence of genetic and environmental influences on general intelligence from studies of twins and non-twins, twins reared apart and together, virtual twins, the significance of shared environmental factors, the effects of prenatal environments, the impact of parenting practices, epigenetic processes (e.g., DNA methylation), the heritability of relevant endophenotypes, and the search for specific genes underlying intelligence. Links between twin studies and other research areas, both within and outside behavioral genetics, are explored.

Sources of human psychological differences: The Minnesota Study of Twins Reared Apart": Response

1991

Since 1979, a continuing study of monozygotic and dizygotic twins, separated in infancy and reared apart, has subjected more than 100 sets of reared-apart twins or triplets to a week of intensive psychological and physiological assessment. Like the prior, smaller studies of monozygotic twins reared apart, about 70% of the variance in IQ was found to be associated with genetic variation. On multiple measures of personality and temperament, occupational and leisure-time interests, and social attitudes, monozygotic twins reared apart are about as similar as are monozygotic twins reared together. These findings extend and support those from numerous other twin, family, and adoption studies. It is a plausible hypothesis that genetic differences affect psychological differences largely indirectly, by influencing the effective environment of the developing child. This evidence for the strong heritability of most psychological traits, sensibly construed, does not detract from the value or importance of parenting, education, and other propaedeutic interventions. M jr ONOZYGOTIC AND DIZYGOTIC TWINS WHO WERE SEPArated early in life and reared apart (MZA and DZA twin pairs) are a fascinating experiment of nature. They also provide the simplest and most powerful method for disentangling the influence of environmental and genetic factors on human characteristics. The rarity of twins reared apart explains why only three previous studies of modest scope are available in the literature (1-4). More than 100 sets of reared-apart twins or triplets from across the United States and the United Kingdom have participated in the Minnesota Study of Twins Reared Apart since it began in 1979. Participants have also come from Australia, Canada, China, New Zealand, Sweden, and West Germany. The study of these rearedapart twins has led to two general and seemingly remarkable conclusions concerning the sources of the psychological differences-behavioral variation-between people: (i) genetic factors exert a pronounced and pervasive influence on behavioral variability,

Critical social Psychology: Limitations of mainstream psychological twin studies

Critical social Psychology: Limitations of mainstream psychological twin studies., 2018

This paper offers a critique of traditional psychological studies of twins. The paper highlights the limitations of mainstream psychological research, and the way that assumptions about the nature of twins which are then confirmed in the way the studies are carried out, reinforce a conventional stereotyped image of them as individuals locked in a relationship with another individual. The paper argues that twin research in psychology has invariably treated the subjects of studies as objects and as vehicles to promote social inequalities. Mainstream twin studies reinforce conventional stereotypes of a supposed 'twin similarity', thereby undermining personal uniqueness and authentic individual differences. Findings from these studies imply that this similarity is 'natural' for identical twins and so differences are 'artificial'. The studies make unsubstantiated theorising and poorly evidenced assumptions about heredity, and over-generalise claims based on ostensibly 'separated' twins, though very few of these have actually been studied. In these studies intelligence, personality and happiness are treated as innate givens, predetermined by inheritance, and social factors are routinely neglected or side-lined. The studies of 'intelligence' in these studies have perpetuated a discourse of 'twin inferiority', and thereby reinforced notions of pathology, prejudice and stigma. Twins are represented in the psychological literature on personality and social relationships as having problems with independent activity, as being socially incompetent, and as struggling in their relationships with fellow twins positioned as victims or bullies. The paper will concludes with the suggestion that social constructionist approaches, by virtue of their 'denaturalising' stance may enable us to reflect critically on constructions of twins in mainstream research and open up alternative forms of research.

Sources of Human Psychological Differences: The Minnesota Study of Twins Reared Apart

Science, 1990

Twin studies : Nature-Nurture and beyond

Chapter 2: Twin studies of this thesis: outline and aims 2.1. A twin study on cognitive ability 2.2. A twin study on stress sensitivity in the flow of daily life Chapter 3: Heritability Estimates of Intelligence in Twins: Effect of Chorion Type Chapter 4: Child Psychopathology and Lower Cognitive Ability: a general population twin study of the causes of association. Chapter 5: Deconstructing the familiality of the emotive component of psychotic experiences in the general population Chapter 6: Electronic monitoring of salivary cortisol sampling compliance in daily life Chapter 7: A momentary assessment study of the relationship between affective and neuroendocrine stress responses in daily life Chapter 8: Genes making one feel blue in the flow of daily life: A momentary assessment study of gene-stress interaction. Chapter 9: Epilogue 9.1. Summary and research findings 9.2. Nature-Nurture 9.3. Nature-Nurture in general cognitive ability 9.4. Nature-Nurture in daily life research 9.5. Implications and directions for future research Summary-Samenvatting Dankwoord Curriculum Vitae List of publications Appendix A Experience Sampling Booklet Appendix B Structural Equation Modeling scripts Chapter 1: Introduction: Nature-Nurture and beyond Back to outline Primary interest Belgium East Flanders Prospective Twin Survey 6500 Epidemiology, placentation, congenital anomalies, perinatal factors Scandinavia Danish Twin Register 65000 Aging and age-related health, metabolic and cardiovascular disease Finnish Twin Cohort ?? 48000 Health, personality and substance abuse Norwegian Twin Register 40000 Mental health, obesity, asthma, allergies, health behaviours and perceptions, perinatal influences on health National Institute of Public Health Twin Panel 7668 Physical and mental health, asthma, allergies, obesity and health-related behaviours Swedish Twin Register 57405 Cancer, cardiovascular diseases, dementia, depression, substance use/abuse, cognition, personality, aging and common complex diseases Swedish Young Male Twins Study 1783 Risk factors for metabolic and cardiovascular diseases, obesity and behavioural risk factor Germany Berlin Twin Register 65000 Complex diseases, health-related QTLs, pharmacogenetics German Obsvervational Study of Adult Twins and the Bielefield Longitudinal Study of Adult Twins 2509 Temperament and personality Italy Italian Twin Register 120000 Aging, dementia, cardiovascular diseases, multiple sclerosis, celiac disease, diabetes, asthma, allergies, thyroid diseases and behavioural disorders Register of Italian Athletes 4719 Human biology and development, sport and high-level performance Twin Epidemiological Register of Rome 15500 Lifestyle, development and ageing The Netherlands Nederlands Twin Register 30335 Development, behaviour, emotional problems, cognition, depression, addiction and cardiovascular risk factors UK St Thomas' UK Adult Twin Register 10000 Cardiovascular, metabolic, musculoskeletal, dermatological and ophthalmological diseases Twins' Early development Study 16810 Longitudinal assessment of verbal and non-verbal cognitive development and delay, language development and delay, childhood behaviour problems Northern Region Multiple 1216 Effects of multiple pregnancy, obstetric and paediatric Back to outline Pregnancy Register management and outcomes of pregnancy Australia Australian Twin Register 27582 General resource for medical and scientific research Western Australian Twin Register 4729 Asthma, allergy, ADHD, early speech and behaviour China Chinese National Twin Programme 4576 Aetiologies of common diseases and health-related behaviour Japan Osaka University Aged Twin Register 12000 Aging, dementia, physical diseases, lipids, cognition, lifestyle, life satisfaction and quality of life South-Korea Korean Twin Register 154783 Complex human diseases and traits Sri Lanka National Twin Register of Sri Lanka 20294 Multidisciplinary research and international collaborations USA Mid-Atlantic Twin Register 23000 Behavioural and psychiatric disorders NAS-NRC Twin Register of WWII Military Veteran Twins 15924 Somatic and psychiatric diseases, aging Vietnam Era twin Register 7500 Veterans health, effects of combat, psychiatric disorders and substance abuse California Twin Program 13096 Aetiology of disease and genetic markers Southern California Twin Register 2600 Social and moral development, childhood behaviour problems, cognitive abilities Minnesota Twin Register 5599 Individual differences 1.1.2 Summary Genetic epidemiology is the overlap between genetics and epidemiology and focuses on interactions between environmental and genetic factors in the causation of the disease. Its goal is to detect, prevent and treat diseases and disorders. Genetically sensitive study designs such as family studies, adoption and twin studies are optimal tools investigating genetic and environmental risk factors. Twin studies have the unique opportunity to disentangle genetic influences from environmental influences. Large worldwide twin registers are available, such as the East Flanders Prospective Twin Survey, from which twins can be selected for research projects.

Twins and their Psychological characteristics (original) (raw)

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