A Study Led By David T. Lykken

Identical twins are many times seen as genetic reproductions representing variations from twin to the other twin and are created because of environmental factors (Cervone & Pervin, 2010). Since identical twins share identical genetics, his or her personality seems to also share similarities. Moreover, the environment can impact fraternal twins, resulting in fraternal twins personalities and his or her characteristics similar to each other. For example, identical twins. Some research shows twins that are raised in the same residence have little differences from those who are raised in a different home.

The idea that they came up with was finding identical or fraternal twins in order to draw a comparison between the behaviors that they share. The most common similarities between the twins (after multiple meetings with pairs of twins) can be concluded as genetic, and other factors could be considered due to the environment, like learning a language. In 1983, Bouchard and Lykken brought together these twins who participated in the study. First, they needed to gather identical twins who were separated at birth. The researcher 's’ goal was to gain as much information as possible on these twins within one week. They had fifty hours of studies on many levels. These studies included personality trait scales, aptitude, IQ tests and occupational interest tests.

The nature vs nurture issue has been a controversial argument among psychologist for decades. This argument exposes two different views. One of them emphasizes that our personality depends solely on genetics (nature). On the other hand, the second view suggests that humans “develop through experience” (Myers 2013, SG 6) (nurture).

Twin studies are a mainstay of the nature verse nurture debate because they allow researchers to conduct “natural experiments” on human beings. When researchers try to determine the relative importance of genetics and environment with regard to a certain condition, they have a hard time because they cannot generally get people with the same genes. This is where twin studies come in. Twins studies are part of the method used in behaviour genetics, which includes all data that are genetically informative. E.g. siblings, adoptees, pedigree data etc. Researchers use this method to estimate the heritability of traits and to quantify the effect of a person 's shared environment (family) and unique environment (the individual events that shape a life) on a trait.

The Minnesota Twin Registry started in 1983 and its goal was to establish a registry of all twins born in Minnesota from 1936 to 1955 to be used for psychological research.., T.J. Bouchard, working in conjunction with the University of Minnesota, started exploring the similarities and differences in characteristics like personality, career interests, and a variety of personal interests between identical twins who were reared apart. Research was conducted on twins from all over the world. The Minnesota Twin study gave scientists a new insight of the role of nature vs. nurture on human development and personality; it was the hope that twin studies would be able to tie genes to specific behaviors. From the study, we understand that twins who were separated at birth and raised in different families

The main focus of this study is whether nature or nurture is stronger. The researches wanted to see if twins who were separated at birth would still grow up to be similar. I believe the results will be that the twins will share some interests and similarities, like all siblings do, but because of the separation they will not be as similar as that might have been if they had been kept together. From my experience, people are born with a personality. There are certain traits that we are born with that the environment we grown up in can influence, but cannot completely change. With that said, the environment we grow up in does play a large role in the people we become and what are opinions are. As we talked about with the sociological imagination, outside influences make a huge impact on our

Methods: The researchers needed a way to study a person who developed in a certain environment and how similar or different that person would be having been raised in a different environment. They came up with an experiment using monozygotic (identical) twins. Half of the pairs of twins were reared together (MZT); the other half were reared apart (MZA) and separated early in life. Each twin was individually given numerous surveys and

These researchers have concluded that there is a strong correlation between the environment and the social behaviors and mental behaviors of a human being in the future. The most critical of these time periods are the childhood of the child and the social groups that the person has been emerged around in the adolescent ages. One of the most widely used studies is the Twin Study where two twins with a very similar genetic makeup are raised in different environments to see how much change there is in their behavior. These twins almost share 100% of their genes however, it has been shown that the only behavior that has been affected is their personality. Yet the personality has been observed to be different by 54% compared between twins who are raised in different environments (DANIEL GOLEMAN 1986). Showing that nurture is a lot more in control of how one acts and how they are more influenced by their environment. It becomes dangerous when one’s environment can begin to affect their behavior, as they can stray for the worst and make situations like past serial killers come true. Personality being affected by the environment can not be prevented, however, the type of environment that will influence future personalities can be changed and made for the better. They can be improved upon to prevent any future serial killers from being

In this study, they are used several type of method, one of the technique is used two or more test instrument to ensure the adequate coverage, for example the participants were given a battery of personality and mental ability tests, interest and value inventories and psychomotor tests. In addition, separate of examiners administer the IQ test, life history interview, psychiatric interview and sexual life history interview. The twin also complete questionnaire independently under the constant supervision of the staff members. Twin studies are valuable to researchers because identical twins share 100% of their genes and fraternal twins share, on average, 50% of their genes. Both identical and fraternal twins share certain aspects of their environment (e.g. religious practices in the home). This allows researchers to estimate the heritability of certain traits. Participants are asked about academic ability, personality, and interests; family and social relationships; mental and physical health; physiological measurements. Of interest to researchers are prevalence of psychopathology, substance

Developments in genetic research and cognitive psychology in recent years support the notion that personality is ingrained in individuals, and therefore unchanging. While it had been hypothesised since the 1960s that individuals could be genetically predisposed to psychiatric disorders (Heston, 1966), this field of study has expanded to explore the predisposition of personality traits, where it is now

It has been argued that if genes influence behaviour and character, and we cannot choose our genes, then our behaviour is outside our control and we are not responsible. However, we take the view that genes are not deterministic, and that there is scope for an

Human character and behaviour are not only shaped by the genes that encompass the individual’s genotype. Human character comprising mainly of personality, sexuality, morality and intelligence are the products of genetic determinism as well as external environmental factors. “Single genes can have surprisingly strong influences on particular aspects of behaviour.” (Frank., 2009)

From these studies, researchers have found that twins who have grown up in the same household share similarities in the way they think, act, dress, speak, etcetera. However, with the first type of twin studies, researchers could not differentiate whether the similarities were due to them having identical/similar genetic makeups or growing up in the same environments. Therefore, in order for psychologists to know whether similarities in twins are genetic or socially influenced, they studied twins who grew up in completely different households and environments. The study showed that despite growing up with a different family and in a different environment, they still had noticeable similarities in fashion, interests, and thought processes (K.W. Brown, personal communication, August 29, 2017). Twin studies, as well as other studies, have greatly contributed to our understanding of overall role that genes play in the development of psychological traits and behavior.

The conclusion that 50% of the variations were generic was not generally acknowledged because of the ascription that much of the greater similarity of monozygotic (MZ) twins compared to dizygotic (DZ) twins was the consequence of environmental effect. This ascription was widely accepted by the psychologists at that time (Thomas & Bouchard 1994). In 2000, McCrae and his colleague concluded a notion that personality was more influenced by human biology (nature). Kandler’s research (2012) indicates that heritability appears more and more stable with the increase of age, leading to personality formation from childhood up to young adulthood. The most possible explanation of this phenomenon is that people form self-concept gradually when getting older (McShane, Olekalns & Travaglione 2013). The researcher also claims that the development of personality will be shaped by external environment (nurture) to larger extent (Kandler 2012). After years of debates, most experts are now reaching an agreement that personality is affected by both nature and nurture, although the weight of each has been being studied and argued (McShane, Olekalns & Travaglione 2013).

Some psychological models assert that a proportion of our personality is inborn and permanent (Hollander, 1971), that a psychological core at the center of our personality gives us enduring, inner characteristics. Hans Eysenck (1965) suggests that our motivation and emotion are related to biological differences in brain function and proposed that 75% of our personality is based on genetic influence and 25% on environmental influence. Research by Peter Whybrow (1999) on identical twins separated at birth examined how their different environments shaped their personalities. He found that around 40% of personality should be credited to genetics, with 60% determined by outside factors.