social sciences

Personality: genetic factors?

Using methods such as twin studies, we can infer that personality is, at least partially, genetically determined. There is, however, also an environmental component, which is also imperative to personality formation. In these studies, the Big Five personality test is often used to look at how it develops over time.

Big Five personality traits
Using twin studies, researchers have found that there seems to be a genetic component to personality traits (Jang, Livesley, & Vemon, 1996). Twin studies are often used to study the effects of genes, identical twins and fraternal are then compared on these traits. One of the most used personality factor models is the Big Five, the five traits are openness, conscientiousness, extraversion, agreeableness, and neuroticism.

Instability and extraversion
Another group of researchers also looked at twin studies to find out what the genetic component is of psychosocial instability and psychosocial extraversion. They found that half of the variation in these traits could be explained by genetics (Floderus-Myrhed,  Pedersen,  & Rasmuson, 1980). Simply put,  the other half might be explained by environmental factors. So personality is partially shaped by the situations we go through in life.

Personality disorders
However, apart from regular personality traits, one can also study personality disorders. These are detrimental as they affect behavior or thinking processes in a negative manner. Which means it can influence daily functioning for an individual. These types of disorders have also found to be heritable, though most of the variance can be attributed to environmental factors (Jang,  Livesley, Vernon,  & Jackson, 1996).

Anxiety/social phobia
It has been found that fear of negative evaluation, which is one of the characteristics of anxiety or social phobia have genetic influences as well (Stein, Jang, & Livesley, 2002).

Job satisfaction
Another team of researchers looked at the genetic components that influence job satisfaction. They used the aforementioned five factor model of personality and the positive affectivity–negative affectivity personality test. The positive affectivity–negative affectivity assess what type of emotions (negative or positive) respondents tend to experience. Using these two tests, they found that both of these constructs determined job satisfaction.  The positive affectivity–negative affectivity construct explained most of the variance in job satisfaction (Ilies, & Judge, 2003).

Floderus-Myrhed, B., Pedersen, N., & Rasmuson, I. (1980). Assessment of heritability for personality, based on a short-form of the Eysenck Personality Inventory: A study of 12,898 twin pairs. Behavior genetics10(2), 153-162.

Jang, K. L., Livesley, W. J., & Vemon, P. A. (1996). Heritability of the big five personality dimensions and their facets: a twin study. Journal of personality, 64(3), 577-592.

Jang, K. L., Livesley, W. J., Vernon, P. A., & Jackson, D. N. (1996). Heritability of personality disorder traits: a twin study. Acta Psychiatrica Scandinavica94(6), 438-444.

Ilies, R., & Judge, T. A. (2003). On the heritability of job satisfaction: The mediating role of personality. Journal of Applied psychology88(4), 750.

Stein, M. B., Jang, K. L., & Livesley, W. J. (2002). Heritability of social anxiety-related concerns and personality characteristics: a twin study. The Journal of nervous and mental disease190(4), 219-224.

social sciences

Are you genetically similar to your friends?

People pick their friends based on several factors including proximity and similarity. Proximity is of importance because we prefer stimuli we see often as opposed to stimuli we’re not familiar with (mere-exposure effect). This principle also holds for friendships. Apart from starting friendships with people, we’re regularly exposed to, it is also easier to maintain relationships with those nearby us. Similarity is imperative for creating bonds, as it gives us topics to talk about and ideas to agree on. We also understand those who are similar to us a lot better. But could these similarities among you and your friends indicate that you might also be genetically similar?

Research has found that this seems to be the case by looking at a sample of adolescents in the United States. Guo (2006) found that there might be a genetic basis for trait-specific similarities between friends. To analyze genetic differences and similarities, identical (monozygotic) and non-identical (dizygotic) twins are always added to the sample. Interestingly, Guo also found that identical twins were more likely to list their twin as their best friend, compared to non-identical twins. Maybe we can speculate here that because identical twins share more genetic similarities, they might have more trait-specific similarities, which is an important factor in friendship.

Looking at more twin studies, we can see the same result for partner choice as well. Rushton and Bons (2005) compared identical twins to non-identical twins. They found that identical twins had friends and spouses similar to that of their co-twin. Again, we can speculate that there must be an underlying genetic effect for friend and partner choice.

Guo, G. (2006). Genetic similarity shared by best friends among adolescents. Twin Research and Human Genetics, 9(01), 113-121.

Philippe Rushton, J., & Ann Bons, T. (2005). Mate Choice and Friendship in Twins: Evidence for Genetic Similarity. Psychological Science, 16(7), 555-559.