Nature Vs. Nurture
Twin Study Overview - Dealing With Schizophrenia
What Is Schizophrenia
Understanding the Debate of Nature Vs. Nurture
I am a Pennsylvania State University student who has been
asked to do a web site on a topic that relates to Biological
Anthropology. I have examined the factors of genetics and
the environmental influences that will shape a person's make-up.
I have used the relationship of twins, raised together and those
raised separately. I have also examined the disorder of schizophrenia
and its relationship to this subject.
For decades scientists have quarreled over the
stereotypical question of "nature vs. nurture".
Scientists have used twin studies to understand
heredity and environmental influences on behavioral development.
Twin and adoption studies can tell the extent to which family
resemblance is due to shared genes and the extent of shared
environment. Because of the identical genes carried by monozygotic
twins (identical) they have an appeal to scientist. With the
it discusses that there is a strong genetic link to the
development of psychological disturbances and drug dependencies.
These findings have added the studies of the relative importance
between heredity and environment in an individual's development.
In the case of the human brain development, some researchers are
convinced that genetic predispositions are what lead people to
what they are. On the other hand, there are many others that
promote the factor of the environment, stating that outside
forces are what impact the lives of humans and shape them as
they grow. Both genetics and the environment alter the synaptic
organization of the brain. By using the nature vs. nurture debate,
many studies have been done on twins, including ones that were
raised together and raised separately, to try to come to an outcome.
This topic has been studied intensely, and many scientists try
to use schizophrenia disorder as a means to try to understand why
one twin might have the disease and the other might not.
WHAT IS SCHIZOPHRENIA
Before we can discuss schizophrenia relating to the "nature vs. nurture"
debate, we must understand exactly what schizophrenia entails.
Symptoms of any type of schizophrenia must be present for at
least six months before it can be diagnosed. There are many
types of schizophrenia. The most prevalent form is called
paranoid schizophrenia which is found in 40% of .5 - 1% of
the people diagnosed with the disorder. Paranoid schizophrenia
is characterized by delusions and hallucinations surrounding
persecution, and by feelings of jealousy and grandiosity.
The second form of schizophrenia is called catatonic. This type
of schizophrenia is characterized by a person retaining a fixed
and bizarre position for an extended period of time. At times
catatonics also suffer from periods of restless movement.
The third form is disorganized or hebephrenic schizophrenia.
With this type of schizophrenia, the patient is incoherent
and experiences flat or inappropriate emotions, with disorganized
behavior and bizarre stereotyped movements and grimaces.
In explaining the disorder of schizophrenia as it pertains,
is a good tool in explaining nature's contribution to this disorder.
They give the different types of schizophrenia, the causes,
and treatments. Each category is nature related, meaning that
they feel that it is a genetic disorder. Each treatment that
is given is a type of medicine that is taken orally.
Another treatment is elecoconclusive therapy that relieves
some symptoms of catatonia and depression in schizophrenics.
They do mention psychotherapy, but only if it is combined with
some type of medication. Another useful
website is http://news.bbc.co.uk/hi/english/health/medical_notes/newsid_1079000/1079451.stm
which explains major breakthroughs for the treatment of mental
illnesses. Scientists are hoping to identify the genes which
might cause mental health disorders. They believe that after
they identify these genes, new drugs can be used to help sustain
UNDERSTANDING THE DEBATE OF NATURE VS. NURTURE
At the beginning of the twentieth century, most people viewed
"nature" as the most important determinant of behavior.
Simple genetic traits are those that are not affected by
the environment's influences in one's life and are seen to
support "nature". During the period of the 1930's to 1960's,
the belief shifted. During that time many people believed that
"nurture", or environmental factors, was the main determinant of
behavior. Complex traits, or those traits that are affected by growth
and the environment stands out here. It is clear that identical twins
are neither physically nor behaviorally identical to one another.
If they do not have identical diets and nutrition, then they will not
be the same height or weight. Or they may surer dissimilar injuries,
or wear their hair different lengths. Isn't it true that identical
twins will wear different clothes, have different types of friends,
choose different kinds of mates and like different social activities?
They usually choose different occupations and have different life-long ambitions. Identical twins will often not share the exact same values or beliefs.
If genetically identical twins, were raised in different environments
then their physical and behavioral characteristics would differ
accordingly. Let us think about identical twins that are separated
from their parents at birth. An upper middle class family living in
Korea raises one twin, while a tribe in Saudi Arabia has raised the
other twin. Being raised in such different environments, how
identical could these twins end up looking and acting? With such
different value systems will they have the same beliefs?
Will they have the same needs, desires, and ambitions? Living in
such different areas could they possibly like the same kinds of
people, enjoy the same foods, have the same sense of style in their
clothes? By living such different lives, obviously the answer is no!
Danielle Cappelletti, of Marshall, University, feels that there is
minimal evidence that exists to prove that schizophrenia is genetic.
In her website, www.behavior.org/behaviordigest/v9n1/digest_v9n1_shcizophrenia.cfm
she refers to psychiatrist Peter R. Breggin, who believes that
the twin studies that have been done to prove that schizophrenia
is genetic is wrong. Breggin says that there are so few cases of
identical twins that are reared apart, that it is almost impossible
to make a conclusive argument about the genetic influences of a
mental disorder, such as schizophrenia.
Breggin discusses a study that was done on people with schizophrenia.
He says that while the percentages of twins that both are
schizophrenic are high, they are not the usual 100% or 50% that are
normally seen among people with genetically transmitted disorders.
Breggin refers to a study that was done that proved many percentages
for people with schizophrenia. The study shows that the average
population has a 10% chance of being schizophrenic. In the case of
identical twins, with one who has the disorder, the other has a 48%
chance of also acquiring the disorder. In the case of fraternal twins
there is a 17% chance of a schizophrenic disorder.
If a person's genes solely cause schizophrenia, than if one identical
twin has the disease, than the other should also.
In the website titled "Nature, Nurture: Not Mutually Exclusive,"
www.snc.edu/psych/korshaun/natnur02.htm Beth Azar discusses that
human behaviors are not influenced by nature or nature, but nature
Robert Plomin, PHD. Explains that the genetic influence on traits
such as personality, intelligence, and behavioral disorders, such
as schizophrenia account for half of the variance. This proves that
the environment influences the rest of the variance.
When there is talk about the environment, there are two influences:
Davis Reiss, M.D., as well as his collegues, including Plomin, began
the Non-shared Environment and Adolescent Development project.
This project included twins. Within this website, this project is
discussed to a great extent and talks about many of their findings.
Throughout their study, they found that parental behavior (genetics)
is influenced by genetics and now called "The Nature of Nurture".
Their research provided three examples.
1. Shared environmental factors which are common to children
reared together and cause similarities in their behavior; and
2. Non-shared environmental factors which are factors such as
school, different social activities, and the different interactions
that the children have with their parents. The different encounters
that the children have can influence them differently.
The following website, http://naminyc.nami.org/Torrey/revwtwin.html
explains the facts in the book, "Schizophrenia and Manic-Depressive
Disorders". E. Fuller Torrey and his colleagues describe their
research by studying 66 pairs of identical twins, one of whom has
schizophrenia, and one whom does not. Throughout their research
they examined brain wave patterns, blood flow patterns, medical
records, the twins position in the womb, and even the whorls of the
fingerprints. In the end, Torrey and his colleagues admit to the
uncertainty of what exactly causes schizophrenia. They also mention
that genes do play a role, but like stated by so many others, the
role of genes determining schizophrenia is not as much believed as
In reality, most studies done on identical twins, show that it is
very unusual to find that both twins are affected by the disease.
Relatives, and especially relatives who are more genetically linked,
of somebody with schizophrenia, are more likely to also develop the
disease as seen in the below chart. Below is a chart taken from
1. Parents who transmit a gene to a child like being musically
gifted will most likely have parents who not only are also musically
talented, but also provide an environment that helps to promote the
2. Children who have musical ability will most likely be selected
by a teacher for a special event. This gives that child a better
chance then somebody who might not possess the genetic talent, but
might be able to provide the same work. But because of the known
ability from the one child, they are given special opportunities.
3. Musically gifted children might seek out friend who also
have a musical talent, once again giving them different environmental
Source: Reprinted by permission of the author. From Gottesman, I.I., Schizophrenia Genesis: The Origins of Madness, New York: W.H. Freeman, 1991, p.96 (c) 1991 Irving I.
Our lives - are thy pre-chosen? Do we live with the script that is written in our genes.
If we could decipher every gene and the functions of each gene, could we understand who would acquire schizophrenia, heart disease, or become a violent person? Within the website, http://news.bbc.co.uk/hi/english/in_depth/sci_tech/2000/human_genome/default.stm
, there is a discussion on not only does a gene need to exist, but the type of environment one grows up in, has just as high a percentage on influencing a person to acquire a type of disorder. Dr. Sue Meyer said, "Gathering knowledge and understanding is a good thing, but we need a bit of humility. We are not just a collection of genes." For many decades, the question of "nature vs. nurture" has existed, and there is still not one right answer. Still unable to decide if one is more important, twin studies have been a constant experiment to find the truth. This website,
explains how the very complex interaction of the environment and genetic makeup between the two is what the real answer is. This website also explains how siblings who grow up in the same family, still grow up in very "different" families. They might have a close genetic make-up, but the difference in the household between the first-born and the second born is very different. As explained in this website, "The child's development is a complex dance in which nature and nurture both lead and are led."
So which is it, "Nature vs. Nurture"? In website, earthsky.com/1999/esmi990311.html, Adam Methany and his colleagues push towards the genetically linked side. If somebody were to ask, lets say a Penn State college student, what they might think, their answer might be siding towards the environment (nurture). Doesn't each experience that somebody goes through, change that person and make them somebody that they weren't 10 minutes before.
Throughout this website, as well as all the others that were refereed to, nobody is exactly sure which influence is stronger. Although it is known that both factors have a very strong influence. So in the end, I am going to have to jump on the bandwagon and say the title should no longer be "nature vs. nurture", but "nature and nurture". Biology and environment are both very important. Each plays a role in shaping who we all are in the past, present, and future.