Personality: Inherited or Determined?

Personality is commonly referred to as an individual’s stable, recognizable characters and traits. According to Arciero and Bondolfi (2009), personality evolves over time to construct a complex domain of temperament and character; and it is believed that “personality is what lies behind a specific individual’s ‘acts’” (p. 15). Is personality inherited or determined? To answer this question, this paper reviews genetic and environmental factors and influences on personality development and mental disorders. The effects of interactions and correlations between genes and the environment are also discussed, and an argument is made that the xyz view is the best supported.

Genetic Influence

If personality is inheritable, then people’s characteristic patterns of behavior would be encoded in genes and passed across generations. In studies of behavioral genetics, researchers attempt to explain how individual differences in personality traits and behaviors are passed from parents to children and shared by biological relatives (Funder, 2013). The study of quantitative genetics is a major approach of behavioral genetics research (Ryckman, 2013). Recent studies of quantitative genetics confirm that all behavior is genetically influenced to a substantial degree (Rutter as cited in Keating, 2011). Genetic effects were found not only on mental disorders such as autism and schizophrenia but also on basic psychological traits such as intelligence and emotions; furthermore, genetic influences were also identified for individual differences in religious commitment, the likelihood of being divorced, or engagement in antisocial behavior (Keating, 2011).

In behavioral genetics research, empirical data from large samples of identical (monozygotic) and non-identical (dizygotic) twins are often used for comparison analysis regarding personality trails (Briley & Tucker-Drob, 2014). As discussed in Brooks (1998), many studies concluded that personality traits could be determined by genetics. In a longitudinal twin study about stability and change of personality traits from late adolescence to early adulthood, Blonigen, Carlson, Hicks, Krueger, and Iacono (2008) discovered that the rank-order stability in personality is largely genetic.

Because many twin studies have pointed to substantial heritability of personality disorders in general, researchers have attempted to discover the influence of specific genes on personality and mental disorders. A study of genetic polymorphisms found that borderline personality disorders are specifically influenced by the effect of the serotonin transporter gene (Bukh, Bock, & Kessing, 2014). Hirvonen and Hietala (2011) revealed that the risk of schizophrenia is related to genetic abnormalities in neurotransmitter with changes in the dopamine system. However, behavioral genetics studies also found that not all mental disorders are inherited. For example, moderate mental retardation seems to be heritable but severe mental retardation apparently is not heritable (Funder, 2013). This finding implies that severe mental retardation does not come from the low IQ parents but is probably related to the environment, i.e., perhaps an infection with the mother during pregnancy or head injury during birth (Plomin et al. as cited in Funder, 2013).

Environmental Influence

The acclaimed psychologist Gordon Allport defines personality as the “dynamic organization within the individual of those psychophysical systems that determine his or her unique adjustment to the environment” (Allport as cited in Arciero & Bondolfi, 2009, p. 15). This definition implies that the environment has critical impacts on the formation of personality. For years, many influential psychologists presumed that personality was mostly determined by the environment (Funder, 2013). Neo-Freudian psychologists John Bowlby and Karen Horney reported that personality was molded by early experiences and parental practices during infant and early childhood; trait theorist Raymond Cattell asserted that the environment had a tremendous impact on personality, especially at later stages of development (Ryckman, 2013).

Environmental factors were found to have dominating effects on many personality disorders and mental illness. In a longitudinal study examining adolescent antisocial behavior, Burt, McGue, and Iacono (2010) elucidated that the environment (shared or non-shared) made predominate impacts on the stability of antisocial behavior over time. In research on narcissism, Luo, Cai, and Song (2014) illustrated that both dimensions of narcissism (intrapersonal grandiosity and interpersonal entitlement) were considerably influenced by non-shared environment.

Many studies assert that personality is not fixed to the genetic build-up but can be changed by external and environmental factors. According to Martin, Oades, and Caputi (2014), intentional personality change is feasible by coaching and intervention through step-wise procedures developed on the basis of theories in cognitive, behavioral, and positive psychology. Zimmermann and Neyer (2013) state that non-normative life experiences affect an individual’s personality traits. Their study demonstrates that international mobility can change a person’s personality in the respect of agreeableness, neuroticism, and openness with a significant increase of agreeableness and a substantial decline of neuroticism.

Gene-Environment Interactions and Correlations

The above discussions indicate that neither gene nor environment has absolute effects on personality development. According to Ryckman (2013), personality may be classified as the biology-determined constitutional traits and the experience-based environmental-mold traits; in other words, nature creates some personality traits, whereas nurture makes other constructs of personality. Therefore, personality is the result of a complex interaction between an individual’s genes and the environment.

According to Keating (2011), gene-environment interactions refer to the role of genetics in influencing people’s vulnerability to particular environmental risk factors. In the interactions, genetic factors operate through effects on individual differences in susceptibility to environmental risks. Thus, a unique personality or specific mental disorder may be formed within an individual and be driven by the combination of genetic and environmental influences. As discussed in Briley and Tucker-Drob (2014), traditional behavioral genetic perspectives emphasized too much on genetic determinism, but new behavioral genetic studies have addressed the dynamic influence of gene-environment interactions. For instance, in a comprehensive quantitative study on genetic and environmental mechanisms of differential stability of personality across the life span, researchers found that genetic stability increased from moderate in infancy to near perfect by age 30 and remained near perfect across adulthood; and environmental stability showed instability in childhood but increased to about half as stable as genetic influences by adolescence (Briley & Tucker-Drob, 2014).

Genes and the environment correlate in many ways to mold an individual’s personality. According to Klahr and Burt (2014), gene-environment correlations refer to genetically influenced exposures to particular environmental experiences; people select the environment and experiences which are often consistent with their genotype, and then the environment and experiences further activate genotype. In passive gene-environment correlations, parents not only pass genes on to their children but also act in ways that influence their parenting experiences; in active gene-environment correlations, people not only present their genetically influenced behavior, but more importantly, also demonstrate learned behavior by selecting and shaping their environments. The personality development involves a shift from passive gene-environment correlation effects in childhood and early adolescence to active gene-environment correlation processes in late adolescence and adulthood (Scarr & McCartney as cited in Bornovalova, Hicks, Iacono, and McGue, 2013).

Summary

Personality is a complex system of characters and dispositions; it is developed over time to become stable and specific to an individual. Studies of behavioral genetics using twin subjects had found that both normal personality and traits related psychopathology are heritable. On the other hand, many studies showed significant influence by environmental factors on personality development and mental disorders. Studies also found that personality could be changed intentionally or unintentionally by coaching interventions or life events. Historically, genetic determinism was the main focus in behavioral genetics, but more recent behavioral genetics researches have attempted to study the gene-environment interactions and correlations. New studies indicate that personality is both inherited and determined, which means that some parts of personality are from genes and some traits are built from experience. Genes interact with the environment in complex ways to influence personality uniquely for each individual.

References

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