We performed an abstract search of PsycINFO for studies that included any combination of terms from three categories: genetics (twin, genetic, adoption, adopted, adoptee), methodology (longitudinal, aging, stability), and personality (personality, temperament, trait). This search produced 578 potential articles. Articles written in a language other than English or that sampled a clinical population were removed. To be included in the current study, the article had to provide information from which within- and across-time sibling group correlations could be derived (either raw or implied by a behavioral genetic model), compare siblings of similar ages (rather than parent-child correlations), and assess personality traits through self- or informant-report formats. As is common with large, longitudinal studies, multiple articles were published using similar, updated data. When this was the case, we removed redundant articles and kept the publication with the most time points or the most measures. In order to test whether effect sizes differ for broad or narrow measurement of personality, we included studies that used the same data but reported the results at different levels of trait generality (e.g., Blonigen, Carlson, Hicks,
