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
perceived.
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.
(Plomin,1993)
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
personality.
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.
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.
81b
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,
226-233.
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,
110-118.
Gergen, D. (1996, May) How Heredity and Experience Make you Who You Are.
[36]. Web-cr01.pbs.org [on line]. Available http://web- cr01.pbs.org/newshour/gergen/gallagher_5-14.html
Greenspan, Stanley. The Challenging Child. Reading, Mass: Addison- Wesley,
1995
?The Nature/Nurture Question ? 1995 [30]. \parInternet, available
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