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The aim of this meta-analysis was to systematize available findings in the field of personality heritability and test for possible moderator effects of study design, type of personality model, and gender on heritability estimates. Study eligibility criteria were: personality model, behavior genetic study design, self-reported data, essential statistical indicators, and independent samples. A total of 134 primary studies with 190 potentially independent effect sizes were identified. After exclusion of studies that did not meet inclusion criteria and/or met 1 of the exclusion criteria, the final sample included 62 independent effect sizes, representing more than 100,000 participants of both genders and all ages. Data analyses were performed using the random-effects model, software program R package metafor. The average effect size was .40, indicating that 40% of individual differences in personality were due to genetic, while 60% are due to environmental influences. After correction for possible publication bias the conclusion was unaltered. Additional analyses showed that personality model and gender were not significant moderators of personality heritability estimate, while study design was a significant moderator with twin studies showing higher estimates, .47, compared to family and adoption studies, .22. Personality model also was not a significant moderator of heritability estimates for neuroticism or extraversion, 2 personality traits contained in most personality trait theories and/or models. This study is the first to empirically test and confirm moderator effect of study design on heritability estimates in the field of personality. Limitations of the study, as well as suggestion for future studies, are discussed.
