Eysenck's Theory Of Personality Development

Personality is the way one behaves, thinks and feels. Theorists are interested to learn what shapes personality, what causes one to behave, think and feel the way one does. Different theorists have different beliefs in what causes these individual differences. These individual differences can be split into two categories, nature and nurture. Nature would be environment while nature would be the brain and the genes, also known as genotype. Genotypes would form phenotypes such as the physical appearance of one. Hans Eysenck believes that personalities are determined by genes. On the other hand, Jeffrey A. Gray believes that personality is because of the brain. A case study regarding an unfortunate accident involving a metal rod that pierced through the skull resulting in a change of personality. Could personality really be affected by the brain? This research essay would focus in the different causes of individual differences in personality. According to Hans Eysenck, a psychologist, he believed that personality develops from the inherited genes that are from our parents. He developed Big 5 theory which consisted of 5 basis traits that he believed to make up personality. They are Neuroticism, Extraversion, Openness, Agreeableness and Conscientiousness (Maltby, Day & Macaskill, 2013). In order to highlight genes being prevalent in personality development, twin studies are compared. Monozygotic (MZ) twins are identical twins which share 100% of their genetic makeup while dizygotic

After comparing shared and non-shared environment, it was also seen in both studies that a non-shared environment has higher variance compared to a shared environment variance. In addition to having a similar conclusion, there was a trend within the numbers caused by the mean age of the samples. Samples from the Bergeman et al. study had an average age of 59 years while the samples from the Jang et al. study had an average of 31 years. This concludes that age can also be a factor that would influence the environment and the genetic influence (Table 3) (Jang et al., 1996) Besides the 3 traits, environment also affects neuroticism. In another study, it was found that when the individuals experience Stressful Life Events (SLE), their level of neuroticism increases despite their baseline. It was also found that recent SLE would cause a larger effect as compared to distant SLE which suggests that SLE effects would decay over time. In terms of agreeableness, openness and conscientiousness, the traits would increase based on environmental influence but decrease based on genetic influence when age increases. Neuroticism increases based on environments as well however, it would be a temporary effect