The major aim of the German TwinLife study is the investigation of gene-environment interplay driving educational and other inequalities across developmental trajectories from childhood to early adulthood. TwinLife encompasses an 8-year longitudinal, cross-sequential extended twin family design with data from same-sex twins of four age cohorts (5, 11, 17, and 23 years) and their parents, as well as their non-twin siblings, partners, and children, if available, altogether containing N = 4,096 families. As such, TwinLife includes unique and openly accessible data that allows, but is not limited to, genetically informative and environmentally sensitive research on sources of inequalities regarding educational attainment, school achievement, and skill development.

Self-efficacy, internal locus of control, self-esteem and emotional stability are characterized by substantial theoretical overlap and empirical associations. In previous research, these four characteristics were frequently suggested to represent a common personality construct referred to as core self-evaluations (CSE). However, neither the structure of the construct CSE has been sufficiently validated nor its genetic and environmental sources examined, so far. The current study bridges this gap. Applying multitrait-multirater analyses of 2377 self- and 1176 informant-reports, we found substantial common variance beyond self-rater specificity, item specificity and random measurement error. Furthermore, using genetically informative data from 1146 twins, we investigated common and specific genetic and environmental sources of variance in the four characteristics. Common variance was substantially attributable to additive genetic and nonshared environmental influences, which were mediated by a higher-order latent variable. The results support the validity of the construct’s hierarchical structure with a common latent core trait accounting for the covariance between the four characteristics. Beyond nonshared environmental components specific to the four characteristics, nonadditive genetic sources accounted for common variance in self-efficacy and internal locus of control, whereas specific additive genetic factors explained variance in emotional stability, implying that these characteristics also include divergently valid aspects of personality.