Which, heredity or environment, plays a bigger role in the development of personality?
From many readings and exposure to the topic on personality, it is fair to say that personality is the varying behaviours of an individual that is unique from other individuals in the population. A personality trait is a supposedly stable characteristic that causes an individual to behave similarly in various situations. Trait theories are aimed at identifying and measuring these individual personality traits. One of them is Eysenck's theory of personality emphasizes slightly more on biological nature. He explains that the introversion-extraversion dimension is biologically based in different levels of arousal of the brain (Eysenck and Eysenck, 1985). Besides gene factors, environment also plays a part in developing an individual's personality. Social interaction is important for adolescents as it influences their growing up process which shapes their personality development. Although environment does play a small part in influencing traits, it is strongly arguable that it is mainly the genetic build up that ultimately contributes to our personality.
There have been studies made to see how far heredity accounts for individual's difference on personality dimensions. People's personality characteristics are influenced by their genetic history. One common way to study heritability of personality traits would be, by comparing identical twins with fraternal twins. Identical twins have a perfect genetic match while fraternal twins share half of their genes. They can be used to represent the population. It gives the closest possible relationship between two individuals and studying them helps in getting a clearer view between heredity and environment. Similar traits in identical twins would be hereditary, and what is different would be regarded as environmental. If identical twins were more similar in tests for personality traits, it implies that genetic factors take a considerable amount in accounting for personality traits.
In the study of Loehlin, McCrae, Costa and John (1998), they came up with three different measures from questions used in the National Merit Twin Study, and behaviour-genetic models were applied to what the three measures has in common, and also to the differences. The results went along with recent studies in the same area, and proved that all five dimensions are equally heritable while shared family environments are minimal to the Big Five personality traits. Therefore, it is evident that genes contributed a higher percentage than family environments to personality traits, (Loehlin et al., 1992). The behaviour-genetic model also implies by estimation that almost half of the Big Five personality traits are of genetic factors, about four-fifth of the remaining is due to unique experiences to the individual, the way one reacts to certain situations, interaction of the gene and environment, and none due to the actual environment (Loehlin et al., 1998).
Another way to study heritability is by adoption studies. All adoption studies have similar results stating that adopted children bear little or no resemblance to their adoptive parents or siblings (McCrae, Costa, Ostendorf, Angleitner, HÅ™ebíÄková, Avia, Sanz, Sánchez-Bernardos, Kusdil, Woodfield, Saunders, Smith, 2000). An adoption study by Stewart, Conger, Neiderhiser, Ge, Troughton, Cadoret, Yates (1996) was made to explore which heritable traits of adopted children bring out responses by their adoptive parents and the subsequent influence it will cause between the two groups. It was found that there was a link between biological parents' characteristics and the child's exhibited personality. Genetic effects were determined by various observers. The children of parents with more disorders have a higher possibility to being anti-social as compared to parents with single disorders. Hence, an adopted child's personality is influenced by genetic factors, which is what recent studies have also concluded.
The world is subjected to changes over periods of time. If individual differences in personality traits are consistently stable throughout a long period of time, it gives evidence that personality traits will not be affected by aging, and all events associated with it like: death of family members, menopause or retirement (Costa, McCrae, Zonderman, Barbano, Lebowitz & Larson, 1986). Undeniably, there is something present within every individual innately that maintains our character, or helps us reverse back to our original self after some readjustments.
Nevertheless, in spite of such examples, there are still reasons why environment helps develop an individual's personality. The environment plays an important role, by defining
the conditions under which human personality evolved; they shape a vast array of skills, values, attitudes, and identities; they provide the concrete forms in which personality traits are expressed; and they supply the trait indicators from which personality traits are inferred and trait levels are assessed (McCrae et al., 2000, p.173).
There are three ways to divide the views on environment. They are the shared environment, non-shared environment, or interaction between heredity and environment. Shared environment is that of having the same parents, the same classmates or the same teachers. It has zero or extremely little contribution to personality traits, as has been explained. Non-shared environment is interpreted to be attending an extra club activity or different teachers. It is the one and only experience for different children in the family (McCrae et al., 2000). It also has limited effects to the environment. Gene-environment correlation is when an individual's heredity leads to his or her environmental settings with different social interactions happening to different kinds of people. Indeed, a child born to be more sociable would no doubt receive more social interaction as compared to another that is less out-going. Appearance also affects a child's environment. A physically attractive person or a child exhibiting positive character would receive more attention than a normal looking or an anti-social child. So in the case of twin studies, they have almost the same physical appearances thus receiving an equal amount of attention from their family environment, which evidently tells us that environmental measures shows genetic influence (Bryden, Lamb, Plomin, Grimshaw, Bergeman, 1991).
There are other aspects of the environment. Some examples would be religion, homosexuality, food preferences, media and so on (McCrae et al., 2000). Individuals unconsciously adapt and integrate to these environments which indirectly shape their personality characteristics. This normally happens to culture groups that value your status in their population rather than looking at individual inborn features. Some personality characteristics tend to be deeply influenced by the environment instead of genes.
In addition, the environment can be said to be directly related to personality traits, as the way an individual respond to particular situations is by observing what the surroundings require. The traits that one possess must fit into the society he or she inhabits. An example given is such that "an agreeable person must learn how to be polite in terms of cultures rules of etiquette" (McCrae et al., 2000, p.173).
In conclusion, the environment is no doubt crucial in the process of the development of our personality, but the essential determinant of an individual personality is still the genetic configuration. Different people with certain genotypes will tend to blend into environments suitable for them. Hence there is this idea that our genes make the environment we will be venture in. However, this can also be seen from a different point of view. People, who are already born into a certain type of culture, unknowingly bring out or develop certain personality traits to blend in and fit themselves into their society. Thus it is very difficult to determine the actual contributions of gene and environment to personality traits.