Empirical studies suggest that around 40 to 50 percent of the variance of a person’s personality is explained by genetic factors, while the remaining variance is explained by environmental factors (Bleidorn, Kandler, & Caspi, 2014; Bleidorn, Kandler, & Spinath, 2010; Sanchez-Roige, Gray, MacKillop, Chen, & Palmer, 2018; Wright, Pahlen, & Krueger, 2017). However, both may be correlated. That is, one’s genetic predisposition may influence the type of environments that they are prone to choose, especially environments that complement their personality traits. This selection effect is referred to as “niche picking” (Scarr & McCartney, 1983). The tendency to select specific environments will amplify any observed genetic differences, making it difficult for researchers to disentangle genetic versus environmental influences on personality development. Notably, cross-country comparisons show somewhat stronger evidence for genetic influences over environmental factors (Bleidorn et al., 2014).
As for genetic versus environmental influences on particular personality traits, the empirical evidence appears to be less conclusive, due to inconsistent and evolving measures of personality and different methodologies and analytical samples used across studies (Sanchez-Roige et al., 2018). Personality or disposition has been conceptualized in several ways. One of the most common is the Five Factor model (also known as the Big Five trait taxonomy; John & Srivastava, 1999), which consists of five domains: (1) neuroticism, (2) extraversion, (3) openness, (4) agreeableness, and (5) consciousness. Some researchers have found that certain traits, like conscientiousness, openness, and extraversion, appear to increase over time (Kandler, 2012; Lucas & Donnellan, 2011; Roberts & Wood, 2006; Wortmann), suggesting environmental factors may play a stronger role than genetic factors for in shaping some personality traits more than others. However, the observed association between specific personality traits and genetic versus environmental factors may vary based on whether researchers use self-rated or informant-rated personality scores. For example, Mõttus and colleagues (2017) found that estimates of heritability were higher when using self-rated scores, although all associations between personality traits and gene-environment factors tended to be influenced by age for both self-rated and informant-rated measures. Among studies that have attempted to isolate and identify specific gene associations with personality traits, three appear to be specific to Chromosome 8, particularly in relation to extraversion and neuroticism (Lo et al., 2016; Okbay et al. 2016). For example, Lo and colleagues (2016) found that extraversion was associated with the single nucleotide polymorphism (SNP) rs6481128, near the gene PCDH15, which is important for calcium-dependent cell-to-cell adhesion, and the SNP rs2164273, near gene MTMR9, a myotubularin-related protein, which is associated with the neurotransmission and neurodevelopment of schizophrenia (Bowden et al. , 2008).
Collectively, these studies suggest that genetic and environmental factors are dynamic and likely work in concert to shape an individual’s personality traits over time. It’s best to conceptualize genes as fuel with the environment being the match; the two interact to form a person’s personality.