Megan Rolerkite

Professor Ameri

Constructed Self UNST

10 March 2004

Nature versus Nurture in Twins

Nature versus nurture has been a continuing debate and is far from being settled. Whether or not our characteristics are determined by the environmental factors that surround us or they were imbedded in our genes is a question many scientists will argue. The challenge concerning the debate is that it is difficult to know if someone is born with traits or whether their environment affected them. It is unethical to take a child out of its natural surroundings to test nature versus nurture, so identical twins have become the most reliable test cases for finding the answers of what is learned and what is inherited.

I believe that nurture has a lot to do with the development of a human, but nature has a larger impact in determining personality traits and the make up of a person. A human is born with certain characteristics and even though their nurture may influence these characteristics to change or be enhanced, their genes have a large influence on how they will live their life.

There are two types of twins, monozygotic (MZ) and dizygotic (DZ). Monozygotic twins are more commonly known as identical and dizygotic are better known as fraternal twins. Fraternal twins come from two separate eggs, so genetically they are about the same as nontwin siblings. On the other hand, identical twins share an egg, so they share the genes within the egg. Tests can be done to determine if a set of twins are identical or fraternal. To identify whether or not the twins are identical, appearance is the most obvious shared trait. Identical twins have almost identical or mirrored looks. Twins that have mirrored appearance will have similarities on the opposite side of their body. For example, one might have a birth mark on his/her right shoulder and the other twin might have a similar looking birth mark on his/her left shoulder. Another similarity in identical twins is that they share the same blood type and when a skin graph is taken, it will always take root in the other twin.

Identical twins growing up together not only will have the same genes but also the same, or close to the same environment as one another. Studies show that many of these twins growing up together will have similar personality characteristics, but how do we know if their similar personalities are the result of their shared genes or if it is primarily due to their shared environment? In any case, the environment a child or a set of twins is surrounded in affects the person they are and will become. Another thing to consider about twins that are raised together and how their environment shapes their lives was argued by Farber, “The interaction between twins leads to differences between the pair. Individuality is crucial to the healthy intrapsychic functioning of twins. Thus twins must create “artificial differences” between themselves to attain a sense of individuality” (Shave 88). An example of this might be if both of the children played baseball and one was better at the game, the other child may feel inferior and lose interest or move on to another sport or dislike sports in general. If Farber hypothesized correctly, then studying identical twins that live together would not be the best way to try and define the difference between nature and nurture.

One amazing case story of identical twins that were raised together is from the movie Sex Unknown. This movie demonstrates how important nature is to humans. It all began in 1965; Janet Ramier gave birth to identical twin boys. She named the healthy boys Bruce and Brian. At about 8 months of age the boys were having problems urinating and the doctors recommended that they be circumcised. The doctor used an unconventional form of circumcision and accidentally destroyed Bruce’s penis. There was no way of reconstructing the penis, so psychologist, John Money, advised the family to raise the child as a girl. John Money believed that at birth your gender identity was neither male nor female, that your nurture is what caused you to feel male or female. So, at age two Bruce had a sex change operation and was turned into Brenda. John Money assured the family that when Brenda hit puberty she would receive hormone treatments and she would live a happily normal life, as a girl.

Unfortunately, growing up Brenda didn’t exactly live a happy life. Even though she received hormone treatments to make her more feminine, she was laughed at and called “cave woman.” She never really fit in or had any friends. She felt forced to play with dolls and wear pink, when she really wanted to play with her brother’s toys and dress like him.

When Brenda was 14 her mother revealed to her that she was born as a male, and within a few months she rejected the female gender imposed on her and started living her life as a male, named David. He has undergone surgery to have his penis reconstructed and is living with his wife and her three children. David said that he never felt like a female and always knew that he wasn’t like other girls.

Psychologist, John Money, believed that if Janet nurtured Brenda as a female she would naturally play with dolls, wear dresses, and wear makeup. Brenda never felt comfortable living life as a female. When the news got out that Brenda’s case was not a success story, Money argued that it was because she was growing up with a twin brother that had an influence on her femininity.

Even though Money won’t admit it, Brenda’s case was a horrible mistake to begin with, and if they would have left her as a male then she may have had a somewhat normal life and not have wasted fourteen years of her life trying to fit. In this case nurture was not the only impact on Brenda feeling alone in the world. She was born genetically a male and no amount of nurturing would ever be enough to turn her into a female. Even though her mom gave her dolls to play with, she wanted to play with her brother’s trucks and do things that are considered typical male behavior. David exclaimed that, “It didn't work because that's life, because you're human and you're not stupid and eventually you wind up being who you are.”

Although the Bruce and Brian case helped to explain some of the nature versus nurture controversy, the best way to tell the effects of nature versus nurture without destroying a child’s life, is in twins that have been reared apart and raised in two separate environments. Twins separated at an early age may help scientists determine if the difference in nurture has caused change in the characteristics the twins are born with or if their genetics shape the person regardless of their nurture. One thing that needs to be determined is what traits is a person born with, and which characteristics do people picks up because of their environment.

The problem with studying separated sets of twins is the small sample that is available for researchers. Many twins that have been put up for adoption will both be adopted by a family, but even though the separation is rare it may be very useful when trying to determine if hereditary traits effect a person more then environmental factors.

IQ scores have been at the center of the nature versus nurture debate. Studying twin’s IQ scores may help us figure out if intelligence is something that can be taught through nurturing or if your intelligence is determined at birth? In 1962, Shields did a study on twins, that included 37 pairs of twins that were separated at an early age. Shields compared IQ scores among the sets of twins. He concluded that, “Intrapair IQ correlations for MZ twins reared together and those reared apart were similar. However, DZ twins reared together had considerably lower IQ correlations than either of the monozygotic groups” (Ainslie 4). Shield’s studies proved that even identical twins that were separated had closer IQ scores than normal siblings or fraternal twins raised together.

The Identical Twins: the original clones site stated that, “If the same person took an IQ test twice, on average it would show a 87% correlation. Identical twins reared apart have a 76% correlation in IQ scores while fraternal twins reared together only had a 55% correlation” (Redden). This study suggests that intelligence is hereditable and even though your nurture may influence your ability to achieve a certain degree of intelligence, genes have a larger effect on how smart you are. This may partly be because people are born with certain abilities, and your nurture may try and force other interest or beliefs on you, but your true capabilities will override your nurturing. For example, if a set of identical twins are born with the ability to excel in science, but they may lack the ability to fully understand math and no matter how much practice they undergo they will never grasp the concept or have enough interest to become excellent at it. They may receive special tutoring or constantly study, but your hereditary ability largely impacts a person.

In a research project conducted by the National Merit Twin study, they tested 850 sets of twins, 60% of which were identical. They concluded that, “Both Identical and fraternal twins are considerably less similar in personality and interest than they are in ability. General ability in identical twins was an 86% correlation, special abilities were a 74% correlation, Activities was a 64% correlation, Interest had a 53% correlation, and personality was a 50% correlation. The results for the fraternal twins are a 62% correlation for general ability, 52% correlation for special ability, 49% for activities, 27% correlation for interest, and 28% correlation for personality”( Osborne 20).

Many studies of twins reared apart have uncanny results. Take for instance, the twins named Jim from Twins Reared Apart by Susan Farber. The boy’s birth mother was only fourteen and immediately gave her identical twin boys up for adoption. The boys were separated when they were only four weeks old, and didn’t meet until 40 years after their birth. Even though the twins were raised by two different families, when they met they were the same height and weight, but even more surprising, they were both named Jim. Also, they both had dogs named Toy, they both took law enforcement training, they enjoyed the same hobbies, both of their first wives were named Linda, both of their second wives were named Betty, and they both named their first son, James Allan. Both men chain smoked Salem cigarettes, bit their fingernails, drove the same color and model Chevy, vacationed in the same spot, and excelled at math but struggled in spelling (33). This amazing story shows that nature played a huge part in the twin’s lives. Even though they weren’t raised by the same family they had similar interest and attracted to the same things.

The similarities in these men’s lives were more than coincidental. This isn’t the only study of twins separated that have shocking characteristics, Twins Reared Apart by Susan Farber, describes another set of twins, Edwin and Fred who were separated at infancy and met at age 26. Upon meeting they realized they both were electricians, and they were married at the same time to similar types of women. They both had four year old sons and fox terriers named Trixie. When growing up, both boys often told playmates that they had a brother who died. (33-34).

The boys telling people they had a dead brother symbolized that they felt something missing in their lives; they must have sensed that they use to have something that is no longer there. Maybe this goes back to the baby’s connection in the womb. Identical twins share an egg so they may have more of a connection than fraternal twins who have two separate eggs. ““Environment” begins as soon as the egg is fertilized, It is possible that the environment within the womb may have a decisive, and, in some instances, a more decisive influence than the world into which the neonate emerges at birth” (Farber 13). So, maybe when the twins were separated they knew that they once had something that is now missing. In the womb, which was an established environment, they had a partner, and now they’re alone.

Burlingham suggest that, “Identical twins, when they grow up, often fail to develop into two separate human beings. It remains a matter of conjecture whether this is due to the twinship itself, or due to the attitude of the mother who in their infancy could not tell them apart…thus treating them as one being instead of two”(Shave 16). In the case of separated twins you have to eliminate the possibility of the mother not being able to tell the two apart or that she treats the children as one. This makes me believe that separated twins still have the feeling of twinship even though growing up their twin sibling may not be present.

There are many interesting cases of twins that have been raised in two separate environments but still have the same interest and live very parallel lives. Many scientists have devoted a lot of time to try and find out exactly where the line is drawn between nature and nurture and which one plays a bigger part in a person’s life. Both nature and nurture contribute to the interest, personality, ability, and goals of a person. But, twins that have been separated and live very different lives still have the influence of their hereditary genes that guide the person they are and will become. Nature and Nurture help to make up a person, and help to determine what it means to be human. Finding the balance between nature and nurture will essentially help to determine the difference between what characteristics a person is born with and what they learn through nurturing. It’s not easy to establish the difference between nature and nurture because the only laboratory control groups are monozygotic twins.

The studies of the twins that were reared apart and had similar interest, abilities, and personalities show that nature has a huge impact on a person and what it means to be human. The Bruce and Brian case is a good example that proves that gender identity isn’t an effect of nurturing, that a child is born with ties to a specific gender. The correlations in the IQ scores of the twins demonstrate that nature has a larger effect than nurture on intelligence. The twins that were separated early in childhood had surprisingly high IQ correlations.

The debate between nature and nurture will probably never be solved. Identical twins reared apart have helped to clarify how important nature is in the make up of a person, but it takes both nature and nurture for the full development of a unique human being. Nature and nurture are both important to a person and both affect what it means to be human, but through these studies it shows that nature has a tendency to over rule nurture.

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