Twin Studies Unit 2

During the procedure researchers desired to acquire as much information as accessible during the one-week visit. The testing consisted of 50 hours of four personality trait scales, three aptitude and occupational interests and two intelligence tests in which each twin had to fulfill. The researcher’s results show that genetic influences resemble to justify for most of the disparities in human characteristics. Bouchard and Lykken have come to the realization that genetic has a major impact on the characteristics of human and that it is no longer a deliberation. Instead ideas must be looked upon to advance. Our clarifications on fundamental views about skills, interest, parenting, education, abilities, and social behavior come from the viewpoint that individual’s knowledge and judgement shape their character and not the genes. Bouchard and Lykken will be the first to contradict with clarifications and propose their own suggestions. Genetic influence mainly drives intellect. These influences contain education, family setting and social class. Also, in Bouchard and Lykken’s findings are some genetic and environmental influence combinations that determine individual

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.

Parallel to this, the focus on genetics is Particularly convicted in twin studies, which establish a comparison between monozygotic twins that are identical and dizygotic twins, which are opposingly non-identical. This distinction can be identified in Torgersens study, which compared MZ and same sex DZ twins where one proband had an anxiety disorder, and it was discovered that such disorders were 5x more frequent in MZ twin pairs, who mutually shared identical genetics.

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.

This shows that homosexuality is a genetic trait since 100% identical twins were gay. The twins have the same DNA and are exhibiting the same trait. Another study to conduct research on environmentally caused conditions was conducted to see the correlation between peptic ulcer disease and identical/non-identical twins who had been reared apart. The results showed that peptic ulcer disease isn’t entirely caused by genetic as the twins had been brought up apart, the disease may also have been caused by their environment. Their diets may also be a factor. There is an ethical issue with conducting this experiment, as it is highly unethical to separate twins. Some diseases caused by genetics are cystic fibrosis and sickle cell anaemia. Some diseases caused by the environment are a cold and scarlet

Claire has many amazing friends and Abby Lee is one of them. She would like to be referred to as twin #1. There are many proper reasons for this. Abby is older than Melanie (current twin #1 and future twin #2) and has known Claire for longer. Abby also angers Claire less of the time. Lastly Abby is smarter than Melanie.

The dizygotic twins show a higher correlation than their other siblings even when reared apart supporting the theory that nature does have a major influence on human intelligence.

Twin A number of studies have attempted to compare the relative importance of genetics and environment in determining sexual orientation . In a study of 1991 , Bailey and Pillard conducted a study of twins recruited by " editions homophile " , and found that 52 % of monozygotic ( MZ ) brothers ( of whom 59 are in question ) and 22 % of dizygotic ( DZ ) twins were agrees to homosexuality

During the second half of the 20th century, psychology was dominated by the behaviorism theory which states that all human behavior is controlled by environmental factors. Adopted monozygotic twins who were separated at birth were to be reunited later on as adults. The purpose of this study was to see if monozygotic twins that were raised together (MZT) were more similar than monozygotic twins that were raised apart (MZA). The twins each had one week visit, testing about 50 hours every week. These tests included four personality trait scales, three aptitude and occupational interest inventories and two intelligence tests. Along with these tests, there were interviews that were held. These included a life history interview, a psychiatric interview and a sexual history interview. All the assessments that were done were held individually so that the twins did not influence each other’s answers.

As a child grows from birth to adulthood, certain traits appear (Heredity, 2011). Geneticists argue that personality traits and intelligence are a part of these sets of chromosomes. In fact, at the University of Texas, scientists found 20 gene candidates that could have an impact on alcoholism (Bryner, 2006). Research has also been conducted with sets of identical twins in order to better understand the role that genetics play in human characteristics (Onkal, 2005). Twin studies were pioneered by English scientist, Francis Galton, over a century ago (Powell, 2010). These studies were carried out by separating sets of identical twins at birth and raising them in contrasting environments. These twins were scrutinized using IQ tests and other examinations. In most cases, IQ scores showed that a child brought up in a wealthier area with better schooling and more involved parents would be more intelligent than a child raised with a family with a low income, low education background (Onkal, 2005).

Through the use of twins, researchers can determine the affect of environment and genetics on personality. This can be done as some twins, known as monozygotic twins (identical twins) have identical genetics and as such any similarity can be presumed to be based on genetics while any difference can be based on environment. Through adoption studies researches can determine if identical twins that were separated at birth are similar and if they are more similar to their

In a twin study, identical twins are compared to fraternal twins. If something happens more often in identical twins, then that behavior is influenced by genetics. A 1991 study showed that if a gay man had an identical twin, the twin would also be gay 52% of the time while a 1993 study showed that if a lesbian woman had an identical twin, the twin would also be lesbian 48% of the time. If the twins were fraternal instead of identical, the percentage drops to 22%. The significant differences in these percentages show a genetic component to sexual orientation.

Bouchard, T., et al (1990). Sources of human psychological differences: the Minnesota study of twins reared apart. Science, 250, 223- 139

Studies of identical and fraternal twins suggest that there is a genetic influence on sexual orientation. If being gay were strictly genetic, then in identical twins, there would be a 100% concordance rate for sexual orientation. But one study in 1995 found a 52% correlation for male identical twins and 22% for male fraternal twins. A study on females came up with similar results. If one identical twin was a lesbian, in 48% of cases, the other twin was also a lesbian. For fraternal twins, the concordance was 16%. (source Simon LeVay)

Biological approach employs laboratory experiments including comparative, twin studies which compare monozygote and dizygote twins for traits, and adoption studies to examine the influence of genetics on behavioural conditions