Quantitative behavior genetics
- Longitudinal and extended family studies of twins raised together (TwinLife, BiLSAT,JeTSSA)
- Behavioral genetics of personality and related attributes (e. g., attitudes, interests, goals, etc.)
- Behavioral genetics of environmental variables
- Multivariate methods of formal genetics
- The Five Factor Model of Personality
- Personality disorders
- Personality development
- Personality states
Validity of assessment
- Multi-trait multi-method models
- Validity of external assessment
Projects and twin research
TWINLIFE - The DFG longitudinal study
TWINLIFE (“Genetic and social causes of life chances. A genetically informative, longitudinal study of the life course and individual development“) is funded by the German Research Foundation DFG,) and extends the study of individual differences as the basis for social inequality by introducing a form of heterogeneity that has not been included in social science research so far: genetic variation. The project is by no means looking for a “happiness-gene“ or a “success-gene“, which very likely do not exist. Instead, it focuses on social influences that are responsible for the unfolding of genetic predispositions, whether advantageous predispositions develop and disadvantageous predispositions are effectively inhibited. The project therefore accounts for the indubitable fact that we are not born as equal, blank slates. Conversely, our fate is also not determined from the start, since family environments, networks, organizations, and societal institutions exert a manifold influence. The research question is thus neither about genes or environment, nor about genes and environment, but about the complicated interplay of genes and environment across the life span, namely gene environment interaction and covariance.
DFG-Projekt: Study of Personality Architecture and Dynamics
In recent years, many studies on personality have been published that relied on a small set (mostly five) of trait dimensions to address the construct personality. The respective personality traits (e.g., extraversion or neuroticism) are often defined as broad, relatively stable and biologically anchored dispositions to individual differences in thinking, feeling, and behavior. Studies on other psychological characteristics of individual differences specifically related to the self, the individual environment, individual cognitions and motivations (e.g., self-esteem, attitudes, values, motives, major life goals, or interests) have rarely been published with the label personality. However, is the restriction of the construct personality to few trait concepts theoretically and empirically justified?
An integrative model of personality should include all characteristics that are essential to capture the complex psychological functionality (i.e., feeling, thinking, striving, and behaving) in which one person differs from another. Essential characteristics of personality have to describe the entire core of personality. Which characteristics of an adult person are core characteristics and which characteristics result from specific core characteristics or interactions between core characteristics and experiences (i.e., surface characteristics)? This project should address those questions on the basis of longitudinal and genetically informative data.
The combination of longitudinal and behavioral genetic designs should test the labeling of trait dimensions (of the five-factor model) as potential core characteristics and other individual attributes (e.g., self-esteem, locus of control, social attitudes, religiousness, major life goals, and interests) as potential surface characteristics on the basis of four criteria: Core characteristics are (1) more stable and (2) more heritable than surface characteristics, (3) they predispose surface characteristics rather than vice versa, and (4) genetic influences on surface characteristics are completely mediated by core characteristics. Thus, change in core characteristics over time should predispose change in surface characteristics. This research project allows a test of several personality models and unique implications for an integrative personality model for the description and explanation of stability and change in individual differences in personality on different levels of perspectives along a continuum from core to surface characteristics.
Bielefeld Longitudinal Study of Adult Twins (BiLSAT)
The Bielefeld longitudinal study of adult twins (BiLSAT) was initiated in 1993. Data collection was finished in 2008. In addition to establishing a twin address register, comprising more than 1100 monozygotic as well as same and opposite sex dizygotic twin pairs raised together, the study is concerned with the question of change and stability of personality, assessed via self- and peer reports. The inclusion of personality ratings by peers is a methodological improvement compared to the inclusion of self-reports only. The study is theoretically framed by the Five Factor Model of Personality which encompasses the dimensions extraversion, neuroticism, agreeableness, conscientiousness, and openness to experience. Twins (aged 14-80 years, mean 30.9 years) were recruited via newspaper articles and announcements as well as twin clubs. They were first sent two different sets of personality questionnaires, about one year apart. A total of 1118 twin pairs completed the first set, 798 twin pairs completed the second set. After another five years the twins were contacted for a third time. This assessment served as a repeated measurement occasion. The set was complemented by brief scales on interests, goals, and values, as well as a questionnaire on life events. Data allows for longitudinal analyses of genetic and environmental influences on stability and change in personality. 341 twin pairs participated in this wave. A fourth wave followed five years later (202 pairs), and a last wave was collected in 2007 (261 pairs). Those waves were mainly designed to assess personality in order to describe personality change in adulthood over multiple time points, and to estimate genetic and environmental influences on personality development.
Jena Twin Study of Social Attitudes (JeTSSA)
JeTSSA is a cross-sectional twin study established by Prof. Dr. Riemann at the University of Jena. The focus of the study was the assessment of social attitudes, personality, and environmental variables, in order to estimate genetic and environmental effects. In addition, the study allows for the investigation of genetic correlations as well as gene environment correlations between inherited attributes such as personality and attitudes, as well as family and social environments. The sample consists of 226 monozygotic and 168 dizygotic twins raised together as well as their life partners, parents, and peers. The uniqueness of JeTSSA is therefore the availability of multiple rater perspectives.