Nature Vs Nature Essay Research Paper Nature

Nature Vs Nature Essay, Research Paper

Nature vs. Nurture

Psychologists have often questioned whether personality traits are inherited,

and therefore a result of genetics, or if they are caused by the environment,

and are therefore made. This has come to be known as the nature versus nurture

controversy. Many psychologists throughout history have asked this question, and

most agree the answer is both.

Nature versus nurture has been an on going argument for over a century and

will carry on further. Scientists have been unable to conclude this question of

which carries most responsibility for behavior. The argument of nature versus

nurture is examined through the role of genetics in one?s personality. Then

the role of environment in a one?s personality. Finally showing how both

nature and nurture coincide to influence behavior in children, that the genetic

makeup shapes one?s personality, thus determining how their environment is


Though one?s personality is not determined strictly by genetics, there is

more evidence to support the idea that personality is inherited than there is to

support the idea personality is made based on the environment and based on one?s

experience. Many experiments and studies have been done to determine where one?s

personality stems from, yet, few studies have been as effective as those studies

based on twins, and adopted children. Both types of studies are extremely

successful in determining where one?s personality comes from. In a twins

study, the genes are regulated while in an adoption study the environment is

regulated. Thus, question comes of introverted and extroverted personalities.


One who is introverted is often thought to be someone that keeps to himself

and rarely chooses to socialize in large groups. He is thought to be a longer

and in many cases to lack the social skills necessary to enjoy himself in

situations that are new to him. In reality, someone who is an introvert is

simply more affected by stimuli than someone who is an extrovert. While an

extrovert may be able to study in a noisy environment with many interruptions

and distractions, an introvert is more likely to opt for a quiet corner of the

library, free of extemporaneous noise.

A study was conducted that tested identical adult twins pairs that had been

raised living apart from one another (Plomin, 1993). The twins were given self

report tests to rate the extent to which they felt that they had grown up in an

environment that was based around acceptance or rejection. In addition to

testing these two traits, the extent to which their parents disciplined the

twins was also tested. The reason for the self report tests to be centered

around these topics because Plomin thought that it was important to determine a

correlation between the environment one is raised in, and one?s personality.

Plomin tested 59 pairs of identical twins reared apart and 142 pairs of

fraternal twins reared apart. What Plomin discovered was that traits once

thought to be created based on the environment that one lives in, are really ?influenced

by genetic factors? (Plomin and Bergman, 1991). Many of the twins studied were

said to have similar personalities, yet because they were raised apart, the only

basis for the similarity is a genetic one. Though the twin studies were

successful in proving that personality is in fact genetically based, many

scientists were not convinced that one?s genes are the only factor that create

one?s personality. Because ?twins share the same womb, birth date and

family, many possible environmental confounds were controlled? ( Plomin 1993)

thus making adoptive studies a more accurate assessment of the inheritance of


It has been hypothesized that adopted twins raised independent of their

parents will develop a personality more similar to their adoptive parents than

to their birth parents. The reason for this hypothesis is that many people

assume that one learns who is and how one should act from the people living

around them. Through extensive studies, Plomin (1993) was able to discern that

adopted children are actually more similar to their birth parents than to their

adoptive parents. Additionally, adopted twins reared apart are more similar to

one another than similar to their adopted siblings. Though scientists have been

able to conclude that genes do effect behaviors and personality, the question

still remains what genes effect what behaviors.

Studies that look at the influence of genetics and environment on personality

use of the concept of genetic similarity of siblings. By examining genetic

similarity one can look at the differences in siblings as they grow up, with the

knowledge that the subjects came from similar genetic backgrounds. Lynn, Hampson,

and Agahi (1989) found support for the idea that traits are inherited in a study

that examined Irish siblings. The siblings were not twins. The authors

hypothesized that shared family environment has an effect on intelligence but

not on personality. The study examined correlations between young Irish siblings

in the areas of intelligence, neuroticism, extroversion, and psychoticism. 386

sibling pairs were used in the study. Using the Junior Mill Hill Vocabulary Test

and a version of the Junior Eysenck Personality Inventory to measure these

traits, the authors correlated the scores of siblings against one anothers. It

showed that shared family environment does have and effect on personality, and

it therefore supports that personality traits are a result of environment.

By comparing the level of extroversion in one child against his or her

sibling, a correlation of .31 was obtained. This correlation is higher than the

correlation predicted from the additive genetic model , which predicts the

correlation predicted from the additive genetic model, which predicts the

correlation between the siblings based only on their genetic makeup. This

suggests that the difference is a result of some shared environmental factors,

and these factors cause the siblings to more alike than the genetic model alone

says that they should be. These environmental factors include the copying of

each other by the siblings and the parents acting as socialization models.

Although the siblings were found to have a high extroversion correlation when

their levels of extroversion were compared as adolescents, this correlation

decreased to .19 when they become adults and left home. These findings suggest

that the drop from .31 to.19 is a result of the fact that after growing up, the

socialization/observational learning effects diminish. In other words, siblings

naturally influence one another while they live together, however this influence

diminishes once they are separated. This study clearly shows environmental

factors contribute to the personality characteristic of extroversion and it

supports the argument that personality traits are a result of environment (

Agahi, Hampson, and Lynn, 1989).

McCartney, Harris, and Bernieri (1990), examine the developmental changes in

twins by doing a meta-analysis of various twin studies from 1967 to 1985.

Initially, the genetic makeup of the sets of twins was identified by determining

if the twins were monozygotic, sharing all of their genes, or dizygotic, sharing

about fifty percent of their genes. Then the differences within the genes of the

twins were measured. With each set of twins, the study looked the correlations

between the two with respect to intelligence, sociability, and activity. The

results on sociability are the ones that are useful to us, as this

characteristic is closely related to the trait of introversion/extroversion. To

see what role, if any, environment plays in determining personality traits, the

study then correlated sociability with the variables shared environment and

non-shared environment to see if differences existed between the two. When all

the pairs of MZ twins were used, those that had a shared environment, meaning

that they grew up together instead of being separated after birth, had a

correlation of .40. Those twins who did not share the same environment had a

correlation of .33. When only the two twins with a mean age greater than five

years of age were used, a difference of .22 was found. These differences suggest

that the environment does influence sociability. The difference in the

correlations does not suggest that environment is the ultimate factor in

determining personality, but it does provide clear evidence that environment

plays a role in affecting personality (Bernieri, Harris, and McCartney, 1990).

Stanley Greenspan, a clinical professor of psychiatry, behavioral science,

and pediatrics at George Washington University Medical School, has been

concerned with how parents can shape the personalities of their children. He

proposes that some combination of genes and early and ongoing environment shape

a childs personality. Greenspan?s work is not limited to one personality

trait, but rather all personality types. He acknowledges that genes predispose

children to a basic personality type. He also says that parents who are aware of

their childs personality can create and environment for them that will help

develop positive personality characteristics. For example, and aggressive,

active child can become more aggressive, and possibly antisocial if his or her

parents do not impose rather strict limits. This child can learn to deal with

the aggressiveness in positive ways, such as expending his energy in physical

activities, if the parents provide opportunity for the child to do so. This is

just one example of how with an understanding of their children parents can

shape the childs personality. Greenspan?s book the Challenging Child, which

describes his work , provides additional support for the premise that

environment plays a role in the development of one?s social development of one?s


Personality traits are not set at birth. On the other hand, they are not

caused completely by environment. The nature versus nurture argument will never

have a clear winner, but the research this paper has found shows that genetics

is not the only cause of personality traits. McCartney, etal. (1990) and Lynn,

etal. (1989), showed that environmental factors played a part in raising the

similarity between the two individuals in a pair of siblings. The work of

Greenspan also shows that this is the case. This research show that

environmental factors indeed play a part in developing one?s personality

The ?Nature vs. Nurture? debate is summed up best when one says that is

neither strictly the environment or one?s genes that determines one?s

personality. It seems that one is given the basis for his personality through

the genes that his parents pass on to him, yet this blue print for personality

can be altered based on influence from the environment. ?You are born with a

certain temperament. But your experience in your early years, in you childhood,

then ..modifies that temperament. It can change that temperament ?[A] child is

born with a temperament that makes the child very bold, assertive, reckless,

perhaps even violent, ..that.. dispositions can be changed through socialization?

(Gergen and Gallagher 1996)

Thus it seems that while this ?Nature vs. Nurture? argument is still

somewhat unresolved there is more evidence based on twin and adoption studies

that lead researchers and scientists to conclude that one?s personality is in

fact inherited than there is to say that personality is made. While the

environment plays a role in determining one?s genetic disposition, the world

around a person never exclusively determines ones? personality, but rather

shapes his or her already existing disposition. The genetic makeup shapes one?s

personality, thus determining how their environment is perceived.


Agahi, Hampson and Lynn (1989). Genetic and environmental mechanisms

determining intelligence, neuroticism, extroversion, and psychoticism: An

analysis of Irish siblings. British Journal of Psychology, 72-85

Bernieri, Harris, and McCartney (1990). Growing up and Growing Apart: A

Developmental Meta-Analysis of Twin Studies. Psychological Bulletin, 107,


Braungart, M., Plomin R., Defries,J., etal. (1992) Genetic Influence on

Tester-Rated Infant Temperament as Assessed by Bayley?s Infant Behavior

Record: Nonadoptive and Adoptive Siblings and twins. Developmental Psychology

28, 40-47.

Chipuer, H. Plomin, R. ,Penderson, G. etal. (1993) Genetic Influence on

family Environment: The Role of Personality. Developmental Psychology, 29,


Gergen, D. (1996, May) How Heredity and Experience Make you Who You Are.

[36]. [on line]. Available http://web-

Greenspan, Stanley. The Challenging Child. Reading, Mass: Addison- Wesley,


?The Nature/Nurture Question ? 1995 [30]. \parInternet, available




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