Personality - Everyone in this world is unique, but what makes someone who they are? PDF

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Everyone in this world is unique, but what makes someone who they are?...

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Everyone in this world is unique, but what makes someone who they are? It is very hard to classify humanity so they focus on personality traits instead. It is believed that genes are important but environment and the interaction between genes and environment would influence personality traits as well. Genes are made up of DNA and every person contains two types of genes which are inherited from their biological father and mother which shows that personality traits might pass on from parents to their children. On the other hand, monozygotic twins (MZ) are a very good example of the interactions between genes and environment because MZ twins are having the same genes but there are some differences between them, for example, their personality or their particular aptitudes.

There are five major personality traits that are widely accepted, which are openness, conscientiousness, extraversion, agreeableness and neuroticism. Openness is a short form for “openness to experience”. People who have this personality trait are mostly enjoyed in adventure. They are more likely to be curious about everything and wanted to have new experiences. Besides that, conscientiousness people are very organized and they have a strong sense of duty. For example, if they are going to travel, they would be well-prepared and planned everything because they are planners. With respect to extraversion, people with this personality trait are chatty and would communicate with people assertively. Agreeable people are probably trustable and helpful to each other whereas disagreeable people are suspicious of others and cold. Lastly, people high in neuroticism are more likely to get anxiety and depression because they worry too much whereas people low in neuroticism are emotionally stable.

Some people would say personality is congenital which means that it is heritable and some people argue that it’s not caused by the genes. Identical twins (MZ) share 100% of the same

genes whereas fraternal twins (DZ) only share around 50% so this could be claimed that the similarity of MZ twins would be higher than DZ twins. For example, if MZ twins had grown up in different environment but they still have the same personality, this could indicate/suggestthat genes are playing a role in our behaviour. Bouchard (1979) discovered a study which named The Minnesota Study of Twins Reared Apart (MISTRA) and this idea was came from identical twins Jim Lewis and Jim Springer, we called it “Jim Twins”. Regarding the MISTRA, Jim Twins are the first pair of separated twins which had been separated at birth and they were reunited in Ohio at age 39. Bouchard (1979) conducted a study which is a medical and psychological assessment, comparing monozygotic twins reared apart and monozygotic twins reared together. They recruited those MZ twins through media appeals and advertisements and those MZ twins were given personality and mental ability tests and some life history interviews. Researchers had studied about 71 pairs of monozygotic twins’ sample which reared apart in 1988 (Bouchard, McGue, Hur & Horn, 1988). They found out that both MZAs and MZTs’ correlation on personality tests was around .50 and they concludedthat the similarity of MZ twins does not depend on whether they live together or stay apart and the personality differences are caused by genetic differences and mostly non-shared environmental factors. (Bouchard & McGue, 1990, p286). There are some problems with this study because MZ twins that reared apart are very rare so the results that Bouchard collected might not to generalise to every twin., Bouchard (1984) gained a lot of data on the life histories of their twins but then he did not publish the information that they collected so it might give some strong evidences to support their studies.

Regarding to the contribution of environment to personality traits, some studies have found that the shared environmen would affect at some personality traits. Historically, most of the studies have supported the statement that personality traits are moderately heritable. In

addition, Bouchard et al. (1990) carried outan adoption study about a pair of twin sisters raised apart. Both of the sisters enjoyed reading although they were not in the same environment. The sister of the twin was raised in a poorer environment but it did not influence the craving of reading books, she went to the library and sought out the books that she wanted to read. The study can be applied to personality and it suggested that environment did not play a big role in human behaviour. On the other hand, Bergeman CS et al. (1993) conducted an adoption and twin study about genetic and environmental effects on the personality traits which are openness to experience, agreeableness and conscientiousness. They recruited 82 pairs of MZ twins and 171 pairs of DZ twins reared apart and 132 pairs of MZ twins and 167 pairs of DZ twins reared together (Bergeman CS et al., 1993). They found that genetics contributed to personality traits substantially and environmental contributed a little as well (Bergeman et al., 1993). The results for agreeableness were different. Bergeman et al (1993) discovered that the genetic only contributed about 12% of the variance whereas shared rearing environment accounted 21%. In the model-fitting analyses, they also found that gender and age had few significant differences for genetic and environmental parameters. It is believed that environmental also plays an important role but not as big as genes.

Gene-environmental interaction has now become a very familiar topic, in the past, researchers who wanted to focus on the heritability in personality traits and tended to ignore the environmental influences. In contrast, researchers who wanted to focus on the environmental influences in personality traits also tended to ignore the genes influences. It is believed that personality traits are not formed by only genes or environmental situation, the interactions of genes and environmental influences might also contribute in human personality traits. With respect to gene-environmental interactions, Bergeman et al (1988) conducted a study which focused about the interactions between genotype and environment

in personality development. They used identical twins reared apart in this study. During this study, GE interaction suggested that different genotype in individuals might respond differently to specific environments (Begerman et al, 1988). They recruited 99 pairs of MZ twins reared apart. They used hierarchical multiple regression to assessthe interactions between personality and environmental measures after they had removed the main outcome of genotype and environment. According to Begerman CS et al (1988), “Analyses yield evidence for 11 significant interactions that provide the first evidence for GE interaction in human development using specific environmental measures”. Therefore, this suggests that the genes-environmental interactions also contributed to the human personality not only because of the heritability and environment alone (ibid).

GE interactions also contribute to individual differences in personality as measured in the second half of the life course not only because of the heritability and environment (ibid).

Pervin (2003) stated a quote, “there is never gene without environment, or environment without gene”. In conclusion, genes, environment and the interactions between genes and environment play a big role in human personality.

References Bergeman C.S. (2017). Genetic and environmental effects on openness to experience, agreeableness, and conscientiousness: an adoption/twin study. - PubMed NCBI. Ncbi.nlm.nih.gov. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/8345444 Bergeman CS, (2017). Genotype-environment interaction in personality development: identical twins reared apart. - PubMed - NCBI. Ncbi.nlm.nih.gov. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/3268285 Dick, D. (2011). Gene-Environment Interaction in Psychological Traits and Disorders. Annual Review Of Clinical Psychology, 7(1), 383-409. http://dx.doi.org/10.1146/annurev-clinpsy-032210-104518 Joseph, J. (2001). Separated Twins and the Genetics of Personality Differences: A Critique. The American Journal Of Psychology, 114(1), 9-11. http://dx.doi.org/10.2307/1423378 Matteson, L., McGue, M., & Iacono, W. (2013). Shared Environmental Influences on Personality: A Combined Twin and Adoption Approach. Behavior Genetics, 43(6), 491504. http://dx.doi.org/10.1007/s10519-013-9616-8 Reference, G. (2017). What is a gene?. Genetics Home Reference. Retrieved from https://ghr.nlm.nih.gov/primer/basics/gene What is personality? To what extent is personality a product of genetic influences?. (2017). KANAYO. Retrieved from https://doctorkanayo.com/2012/05/20/what-ispersonality-to-what-extent-is-personality-a-product-of-genetic-influences/...