The Place of Heritability in the Genetic-Social-Developmental Personality-Model

When welcoming a newborn, one of the first questions to come to mind is whether its physical characteristics would resemble the mother or father, which can be easily answered through a little observation. On the other hand, it is not so easy to observe the effects of the genes when it comes to the child’s psychological characteristics, such as intelligence, personal preferences, temperament; however, genetic studies show that a considerable portion of the social and psychological personality traits actually depends on genetic factors.

What is Behavioral Genetic Heritability?

Heritability stands for the share of the genetic diversity that is effective in the prevalence of a trait in a society. Identical twins (100% genetically same) are compared to fraternal twins (50% same) in order to measure the impact of heritability. Thus, it is possible to observe to what extent a trait is hereditary, or to what extent it is under the influence of environment. Accordingly, by observing a physical or a psychological trait;

• The hereditary effect is shown by the fact that the connection between the genetics of identical twins is more than that of fraternal twins;
• The effect of the shared environment (school, family, country, etc.) is shown by the fact that a connection is found between both identical and fraternal twins;
• The effect of the unshared environment (different schools, friends, or original experiences) is shown by the fact that no connection is found between identical and fraternal twins.

In a meta-analysis carried out by Polderman (2015), 2748 twin studies, which cover the past 50 years, are analyzed. It analyzes how many of the 17,804 traits in a total of 14.5 million twin pairs are hereditary. These traits include biological functions, such as height, sight, hearing, cardiovascular function, as well as personality, temperament, and behavioral problems, which can be defined by many of us as psychological traits. As a result of the meta-analysis, the fact that a trait varies in a society, psychological and social personality traits included, can be explained by genetic factors by 50%. The remaining half, however, can be explained by environment (unshared environment, special occasions experienced) and a calculation error.

By personality traits, not only those that are included in the big five-factor personality model, such as introversion-extraversion, openness to experiences, agreeableness, but also personal and social attitudes and behaviors such as;

• Political liberality-conservatism;
• Social dominance;
• Authoritarianism;
• Whether one is prejudiced towards opposite groups (Barlow, Sherlock and Zietsch, 2017),;
• Tendency to take part in surveys used in scientific research (Littvay, Popa, & Fazekas, 2013) can be explained with genetic traits. Besides, there are studies that show;
• 47% of the participation in religious service activities;
• 41% of having a religious position for profession (missionary, priest, etc.) (Waller, Kojetin, Bouchard Jr, Lykken, & Tellegen, 1990) can be explained with heritability.

On the other hand, emphasizing that the effects of genes on personality traits must not lead to a genetic determinism attitude, Barlow (2019) uses twin studies to explain the place of the shared and unshared environments. Shared environment consists of the common effects that twin babies are exposed to during their development, such as the country, home, experiences lived through with family, or the social standards of the school and society. However, in the meta-analysis carried out by Polderman, when genes are taken into account, shared environment has little to no effect in explaining the differences in personality traits. The effects of genes in the perception of environment are shown as an explanation to this. For instance; “commitment to school” was researched in a study carried out with young twin children (Jacobson & Rowe, 1999). The students were asked if their needs were satisfied in respect of being accepted, supported, and valued by their teachers and friends at the school, which helped observe how the children perceived the school environment. Of the diversity of the answers given, 45% could be explained with heritability in female twins, and 17% in male twins. It was put forward that the remainder of the diversity in the answers could stem from unshared environment (from different, dissimilar experiences) or from error.

How Do Genes Interact with Environment?

It is quite clear that not a single gene or environmental factor can determine the occurrence of social, cognitive and psychological traits. Pieces of research analyzing the interaction of environment and genes, find three main connections in the gene-environment interaction by taking into account the extent to which the diversity in a personality trait and the diversity in environmental factors coincide:

1. Active Gene – Environment Correlations: Human beings not only act as a receiver in their relationship with environment, they also can also create their environment or transform their current environment based on their personality, preferences, interests, or needs. For instance, while a sociable person seeks and creates an environment in which he can have many social interactions or deepen his current relationships, people who tend to act impulsively may prefer stimulating and unpredictable situations, and they even can enter places where there is violence. The effects of genes can manifest themselves through personality traits in the process of a person creating his environment.
2. Stimulating Gene – Environment Correlations: It stands for individual differences receiving different reactions from the environment. A personality trait, which is transmitted genetically, causes one to receive different reactions from the environment. For instance, the behaviors the parents thought their children (environmental reaction) directly coincide with the diversity in the child’s genotype (Avinun & Knafo, 2014).
3. Passive Gene – Environment Correlations: It represents the effects of the genes the parents carry in the creation of the environment provided to the child. For instance, intelligent parents make efforts to provide their children with an environment that would stimulate their minds. It would be possible to mention the passive gene-environment correlation if the change in the child’s genotype coincides with the change in the environment provided by the parent or sibling, and if this environment provided is correlated with a hereditary trait in the child (e.g. Intelligence).

Barlow’s compilation of studies (2019), which is mentioned above, emphasizes that genetics should not be overlooked in comprehending human beings psychologically, and it also mentions that studies on genetics create changes in humans’ comprehension, just like how it could happen as we read this article. For instance,

• While racism and sexism are at low levels in people who deny the genetic foundation of human psychology, racism and sexism tend to rise in those who agree to the importance of the genetic effect in psychology (Bastian & Haslam, 2006; Keller, 2005).
• When psychiatric disorders are taken into consideration, the tendency to blame those with such disorders declines in people who come to learn the biological tendencies in the foundation of these disorders. On the other hand,
• Individuals, who have a biological attitude against mental disorders, are observed to assume a more pessimistic attitude against healing, while assuming a much more fearful attitude towards getting sick (Haslam & Kvaale, 2015; Kvaale, Haslam, & Gottdiener, 2013).

As can be understood from these studies, the part played by genetic factors in explaining personality traits should not be underestimated. Nevertheless, this genetic attitude should not lead people to sexism, or pessimism towards mental disorders. Thus, as can be seen from the aforementioned gene-environment interactions, genes do not destroy the power of environment; on the contrary, they help us see the effects of social environment down to the finest detail. As such, one must better comprehend the place of heritability in the genetic, social, developmental and personality model that is created to understand human beings.

REFERENCES:
– Polderman, T. J., Benyamin, B., De Leeuw, C. A., Sullivan, P. F., Van Bochoven, A., Visscher, P. M., & Posthuma, D. (2015). Meta-analysis of the heritability of human traits based on fifty years of twin studies. Nature genetics, 47(7), 702-709.
– Barlow, F. K. (2019). Nature vs. nurture is nonsense: On the necessity of an integrated genetic, social, developmental, and personality psychology. Australian journal of psychology, 71(1), 68-79.
– Jacobson, K. C., & Rowe, D. C. (1999). Genetic and environmental influences on the relationships between family connectedness, school connectedness, and adolescent depressed mood: sex differences. Developmental Psychology, 35(4), 926.
– Barlow, F. K., Sherlock, J. M., & Zietsch, B. P. (2017). Is prejudice heritable? Evidence from twin studies.
– Littvay, L., Popa, S. A., & Fazekas, Z. (2013). Validity of survey response propensity indicators: A behavior genetics approach. Social Science Quarterly, 94(2), 569-589.
– Waller, N. G., Kojetin, B. A., Bouchard Jr, T. J., Lykken, D. T., & Tellegen, A. (1990). Genetic and environmental influences on religious interests, attitudes, and values: A study of twins reared apart and together. Psychological science, 1(2), 138-142.
– Avinun, R., & Knafo, A. (2014). Parenting as a reaction evoked by children’s genotype: A meta-analysis of children-as-twins studies. Personality and Social Psychology Review, 18(1), 87-102.
– Bastian, B., & Haslam, N. (2006). Psychological essentialism and stereotype endorsement. Journal of Experimental Social Psychology, 42(2), 228-235.
– Keller, J. (2005). In genes we trust: the biological component of psychological essentialism and its relationship to mechanisms of motivated social cognition. Journal of personality and social psychology, 88(4), 686.
– Haslam, N., & Kvaale, E. P. (2015). Biogenetic explanations of mental disorder: The mixed-blessings model. Current Directions in Psychological Science, 24(5), 399-404.
– Kvaale, E. P., Haslam, N., & Gottdiener, W. H. (2013). The ‘side effects’ of medicalization: A meta-analytic review of how biogenetic explanations affect stigma. Clinical psychology review, 33(6), 782-794.