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To disentangle genetic and environmental contributions to individual differences, classical twin models (CTMs) are predominantly used. Prior research revealed several conditions under which CTMs spawn biased heritability and environmentality estimates, including the simultaneous relevance of nonadditive genetic and shared environmental influences, the presence of assortative mating, and passive gene-environment covariance. Nuclear twin family models (NTFMs), adding information from parents of twins, can handle these conditions. Little is known, however, on the actual impact of such conditions considering the empirical properties displayed by various personality-related phenotypes. The present study therefore investigated differences between NTFMs and CTMs in terms of error-adjusted heritability and environmentality across 93 personality-relevant constructs based on data from 636 twin pairs and 320 parents. Overall, NTFMs resulted in significantly lower heritability and higher environmentality estimates, suggesting an overall overestimation of heritability in CTMs. These trends pertained to about two-thirds of the investigated constructs, but reversely directed changes were detectable under specific conditions. We discuss the extent to which the assumptions underlying CTMs might bias conclusions regarding genetic and environmental contributions to personality differences and demonstrate benefits of NTFMs. Furthermore, we provide user tutorials for implementing CTMs and NTFMs based on the open-source and user-friendly statistical program JASP. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]