The debate regarding Nature and nurture and its effects on human behavior and characteristics has a long history. Some theories state that it is nature, our genetics that determine who we are and who we become. While genetics do play a role in our eye color, our natural hair color and texture and whether we are a boy or a girl and whether or not we are susceptible to some diseases based on our genetic makeup, (McLeod, 2007). The theories that are based on nurture argue that we are creature of our environment. Our experiences, socialization and how we are raised make us who we are. The experts will agree that both theories do influence and play a part in human characteristics however each theory will offer explanations that will attempt to strengthen their theory of belief. Persons that believe in heredity (nature) are recognized as nativists. The belief that characteristics are from evolution. Differences are inherent to their genetic code. This belief states that any characteristic that is not observed at birth presents itself later in life at a determined time, (McLeod, 2007). Empiricists are theorists who believe that at birth each one of us is considered a blank slate and that persons are filled with experiences and socialization from the cultures that are lived in and experiences that are endured as well as reactions to them based on how others react, (McLeod, 2007). Compare and Contrast
Langstrom, Rahman, Carlstrom, Lichtenstein, in 2010 completed a study of twins using the Swedish Twin Registry. Twins born in Sweden between the years of 1959 to 1985 were selected for this web based research, known as the Swedish Twin Study of Adults: Genes and Environments (STAGE), (Langstrom, Rahman, Carlstrom, Lichtenstein, 2010). The STAGE completed screens on selected twins that included prominent psychiatric and physical morbidity, health related experiences and behaviors and any trauma, substance abuse as well as sexuality. The STAGE survey assessed twins for
sexual orientation or experience with same sex partners, (Langstrom, Rahman, Carlstrom, Lichtenstein, 2010). The variable for the study were any lifetime same sex partner and total number of lifetime same sex partners. These were divided into 7 groups. That included 0, 1, 2, 3-5. 6-10, 11-20, over 21 partners, (Langstrom, Rahman, Carlstrom, Lichtenstein, 2010). Zygosity was determined using standard physical similarity questions and previously validated genotyping. The study sample was 7652 persons. Monozygotic twins (MZ) included 2,320 people. 807 males and 1,513 females. Dizygotic (DZ) twins accounted for 517 males and 989 females, (Langstrom, Rahman, Carlstrom, Lichtenstein, 2010). The Regional Ethics Committee Stockholm Sweden provided ethical approval for this study. Analysis was separated by gender. Statistical analysis was completed and the results show that heritability estimates are for any life time same sex partner 39% for men, and 34% heritability for total number of partners, (Langstrom, Rahman, Carlstrom, Lichtenstein, 2010). Unique environmental factors were 61% in men and there were no shared environmental factors noted for men. In women 18-19 % were felt to be genetic factors and 64-66% were related to unique environmental factors. Shared environmental factors were 16-17% for women, (Langstrom, Rahman, Carlstrom, Lichtenstein, 2010). This study shows that same sex behavior arises from both heredity and individual specific environment sources. It further shows that genetic influences on any lifetime same sex partner and total number of same sex partners are weaker in women than in men, (Langstrom, Rahman, Carlstrom, Lichtenstein, 2010). The second research study was done by Kendler, Thornton, Gilman, Kessler, 2000. This study was completed in America. This was a telephone and mail survey that was conducted in 1995-1996, (Kendler, Thornton, Gilman, Kessler, 2000). A sample of 3, 032 persons from ages 25-74 years of age, recruited from a random sampling. One respondent per eligible household. This was a two phase survey the first phase being a telephone interview and then a mail questionnaire. Informed consent was through oral agreement. The study was approved by the Human Subjects Committee of Harvard University Medical School, (Kendler, Thornton, Gilman, Kessler, 2000). Twin pairs were recruited using a two part sampling design. The first part to find a twin the second part involved students from the University of Michigan contacting twin households and obtaining consent to participate in the research. Final
number of twin involvement was 794 twins, (Kendler, Thornton, Gilman, Kessler, 2000). Fourteen families included two sets of twins and one family included 3 sets of twins. 756 sets of twins had known zygosity with known sexual orientation from each twin. Non twin siblings were sent a postcard and asked to participate. Non twin individuals numbered 1380, (Kendler, Thornton, Gilman, Kessler, 2000). The age of subjects ranged from 25-74. Sexual orientation was determined by questions on the questionnaire. Responses consisted of heterosexual, homosexual and bisexual. Homosexual and bisexual responses were combined. Zygosity was determined using a test sample of 230 pairs of same sex twins that had not been selected and were genotyped from the Virginia Twin Registry, (Kendler, Thornton, Gilman, Kessler, 2000). Twins and siblings were assessed for resemblance in 3 ways using Proband-wise concordance defines as the proportion of co twin of non-heterosexual twins who were themselves non- heterosexual using statistical analysis and environmental contributions to sexual orientation, 4 variables were reviewed, (Kendler, Thornton, Gilman, Kessler, 2000).
Additive genes, common or familial environment that affects the similarity of all twins and sibling pairs. A special environment that influences the similarity of twin’s only and individual specific environment. Although individuals specific environment was zero. Of the original 2968 individuals 61 were missing data, (Kendler, Thornton, Gilman, Kessler, 2000). Of the remaining number 81 reported a non-heterosexual orientation. There was no significant difference between men or women. With controls for age and gender the rate of non-heterosexual orientation did not differ significantly between the twins and non-twin siblings. Between MZ and DZ twins for same sex or opposite sex twins there was no significance to similarity of their childhoods or adult environments. The pair resemblance for sexual orientations was much great in MZ twins and in any of the other groups, (Kendler, Thornton, Gilman, Kessler, 2000). The resemblance for sexual orientation was also greater in the same sex pairs as opposed to the opposite sex pairs. Biometric twin modeling with the MZ twins and each of the comparison groups estimated a greater resemblance. The analysis of the data indicated that pair resemblance for sexual orientation was greater in monozygotic twin that in any of the groups of dizygotic twins and non-twin siblings. The results suggest that genetic, familial factors contribute partly to sexual orientation, (Kendler, Thornton, Gilman, Kessler, 2000). The contrasts of these studies is that the Swedish one included only twins, while the American research included twins and siblings. Both studies were attempting to determine if sexual orientation was genetic or environmental. The Swedish study included data in regards to sexual encounters as well as total number of encounters while the American study looked at persons that had listed attractions to either same sex, opposite sex or bisexual and then took the bisexual and same sex and grouped that data together. The weaknesses of either study is that with a questionnaire is it possible to have error, and with a study as sensitive as same sex encounters there is a risk of inappropriate responses. Both studies indicate that there is a genetic/familial attribute to sexual orientation. Although the Swedish twin study did indicate that men were more familial then women. In both studies it can be said that sexual orientation is both familial and environmental.
Kendler, K., Thornton, L., Gilman, S., Kessler, R. (2000). Sexual Orientation in a U.S. National Sample of Twin and Non twin Sibling Pairs [Electronic version]. American Journal of Psychiatry, 157, 1843-1846. (Kendler, Thornton, Gilman, Kessler, 2000).
Langstrom, N., Rahman, Q., Carlstrom E., Lichtenstein, P. (2010). Genetic and Environmental Effects on Same Sex Sexual Behavior: A Population Study of Twins in Sweden. [Electronic version]. Arch Sexual Behavior, 39, 75-80. (Langstrom, Rahman, Carlstrom, Lichtenstein, 2010).
McLeod, S., (2007). Nature Nurture in Psychology-Simple Psychology. Retrieved from, Http://www.simplypsychology.org/naturevsnurture.htm