The current project sought to provide an exhaustive, quantitative review of longitudinal, behavioral genetic studies of personality development. This study is the first comprehensive empirical meta-analysis of this literature. The only previous synthesis of the literature is by Kandler (2012). In a short review of the longitudinal, behavioral genetic literature on extraversion and neuroticism, he found evidence that both genetic and environmental mechanisms will be necessary to explain personality development. However, the article mentioned some important limitations such as being a selective review of the literature, a brief and largely descriptive and informal analysis of the data, and being limited to only two personality traits. The current project encompasses formal rigorous meta-analytic modeling of data obtained from an exhaustive aggregation of published studies on all personality traits. We examine effect sizes that fall into three classes: (1) the levels of heritability and environmentality of traits at one point in time; (2) the test-retest stability of phenotypic traits and of genetic and environmental effects; and (3) the contribution of genetic and environmental effects to test-retest stability. Based on our review above,
