Homosexual orientation

Homosexual orientation is a sexual orientation. The term is used to refer to "an enduring pattern of or disposition to experience sexual, affectional, or romantic attractions primarily to" people of the same sex; "it also refers to an individual’s sense of personal and social identity based on those attractions, behaviors expressing them, and membership in a community of others who share them."citation |url=http://www.apahelpcenter.org/articles/article.php?id=31 |title=Sexual Orientation and Homosexuality |periodical=APAHelpCenter.org |accessdate=2007-09-07] [http://www.courtinfo.ca.gov/courts/supreme/highprofile/documents/Amer_Psychological_Assn_Amicus_Curiae_Brief.pdf APA California Amicus Brief Please fix this cite and remove this comment when done.] ] The exact proportion of the population that is homosexual is difficult to estimate reliably,LeVay, Simon (1996). "Queer Science: The Use and Abuse of Research into Homosexuality." Cambridge: The MIT Press ISBN 0-262-12199-9 ] but studies place it at 2–7%.ACSF Investigators (1992). AIDS and sexual behaviour in France. "Nature, 360," 407–409.] Billy, J. O. G., Tanfer, K., Grady, W. R., & Klepinger, D. H. (1993). The sexual behavior of men in the United States. "Family Planning Perspectives, 25," 52–60.] Binson, D., Michaels, S., Stall, R., Coates, T. J., Gagnon, & Catania, J. A. (1995). Prevalence and social distribution of men who have sex with men: United States and its urban centers. "Journal of Sex Research, 32," 245–254.] Bogaert, A. F. (2004). The prevalence of male homosexuality: The effect of fraternal birth order and variation in family size. "Journal of Theoretical Biology, 230," 33–37.] Fay, R. E., Turner, C. F., Klassen, A. D., & Gagnon, J. H. (1989). Prevalence and patterns of same-gender sexual contact among men. "Science, 243," 338–348.] Johnson, A. M., Wadsworth, J., Wellings, K., Bradshaw, S., & Field, J. (1992). Sexual lifestyles and HIV risk. "Nature, 360," 410–412.] Laumann, E. O., Gagnon, J. H., Michael, R. T., & Michaels, S. (1994). "The social organization of sexuality: Sexual practices in the United States." Chicago: University of Chicago Press.] Sell, R. L., Wells, J. A., & Wypij, D. (1995). The prevalence of homosexual behavior in the United States, the United Kingdom and France: Results of national population-based samples. "Archives of Sexual Behavior, 24," 235–248.] Wellings, K., Field, J., Johnson, A., & Wadsworth, J. (1994). "Sexual behavior in Britain: The national survey of sexual attitudes and lifestyles." London, UK: Penguin Books.]

Sexual orientation is also distinguished from other aspects of sexuality, "including biological sex (the anatomical, physiological, and genetic characteristics associated with being male or female), gender identity (the psychological sense of being male, female or other), and social gender role (adherence to cultural norms defining feminine and masculine behavior)." Etymologically, the word "homosexual" is a Greek and Latin hybrid with "homos" (often confused with the later Latin meaning of "man", as in "Homo sapiens") deriving from the Greek word for "same", thus connoting affections between members of the same sex, including lesbianism.citation |title=Etymology of Homosexuality |accessdate=2007-09-07 |url=http://www.drama.uwaterloo.ca/Gross%20Indecency/homosexuality_word.shtml |periodical=University of Waterloo]

Sexuality

A person's sexual orientation is closely related to other aspects of their sexuality, such as their sexual identity and sexual behavior. Homosexuality refers to sexual behavior with or attraction to people of the same sex, in addition to a homosexual orientation.

Sexual identity

A person's sexual identity, as it relates to sexual orientation, is how one identifies their own sexuality. A person with a homosexual identity may identify themselves as lesbian (for women) or gay (for men and women). If a person with a homosexual orientation does not identify as gay or lesbian, they are often referred to as closeted. Since sexual orientation is difficult to measure, and one's sexual identity does not necessarily match their true sexual orientation, professional literature will often use the term same-sex attraction to refer to anyone who is attracted to the same sex, includes both homosexuals and bisexuals, regardless of sexual identity.

Sexual behavior

Many people with a homosexual orientation enter in same-sex relationships. Studies have found same-sex and opposite-sex couples to be equivalent to each other on measures of relationship satisfaction and commitment. Many lesbians and gay men form durable relationships. For example, survey data indicate that between 18% and 28% of gay couples and between 8% and 21% of lesbian couples in the U.S. have lived together 10 or more years. [ [http://www.apa.org/topics/sorientation.html#whatisnature APA - What is Nature] ] The types of relationships vary by region and what is permitted by law. The level of acceptance ranges from making same-sex relationships illegal, to having no official stance, to officially recognizing same-sex marriages.

People may not express their sexual orientation in their sexual behavior. [http://www.apahelpcenter.org/articles/article.php?id=31 APA Help Center] ] People with a homosexual orientation may be celibate, have sexual relationships with the same sex, the opposite sex, or both. A heterosexual marriage where one of the spouses has a homosexual orientation is referred to as a mixed-orientation marriage. Likewise, people of different sexual orientations may have same-sex relationships. In professional literature, people who have sexual relationships with their own gender may be referred to as men who have sex with men or women who have sex with women.

Gender identity

The earliest writers on a homosexual orientation usually understood it to be intrinsically linked to the subject's own sex. For example, it was thought that a typical female-bodied person who is attracted to female-bodied persons would have masculine attributes, and vice versa. [Minton, H. L. (1986). "Femininity in men and masculinity in women: American psychiatry and psychology portray homosexuality in the 1930s", Journal of Homosexuality, 13(1), 1-21.
*Terry, J. (1999). "An American obsession: Science, medicine, and homosexuality in modern society." Chicago: University of Chicago Press] This understanding was shared by most of the significant theorists of homosexuality from the mid nineteenth to early twentieth century, such as Karl Heinrich Ulrichs, Richard von Krafft-Ebing, Magnus Hirschfeld, Havelock Ellis, Carl Jung and Sigmund Freud, as well as many gender variant homosexual people themselves. However, this understanding of homosexuality as sexual inversion was disputed at the time, and through the second half of the twentieth century, gender identity came to be increasingly seen as a phenomenon distinct from sexual orientation. Transgender and cisgender people may be attracted to men, women, or both, although the prevalence of different sexual orientations is quite different in these two populations (see sexual orientation of transwomen). An individual homosexual, heterosexual or bisexual person may be masculine, feminine, or androgynous, and in addition, many members and supporters of lesbian and gay communities now see the "gender-conforming heterosexual" and the "gender-nonconforming homosexual" as negative stereotypes. However, studies by J Michael Bailey and KJ Zucker have found that a majority of gay men and lesbians report being gender-nonconforming during their childhood years. [Bailey, J.M., Zucker, K.J. (1995), "Childhood sex-typed behavior and sexual orientation: a conceptual analysis and quantitative review." Developmental Psychology 31(1):43]

Demographics

Measuring the prevalence of homosexuality presents a number of difficulties:

* Survey data regarding stigmatized or deeply personal feelings or activities are often inaccurate. Participants often avoid answers which they feel society, the survey-takers, or they themselves dislike.Fact|date=June 2008
* The research must measure some characteristic that may or may not be defining of sexual orientation. The class of people with same-sex desires may be larger than the class of people who act on those desires, which in turn may be larger than the class of people who self-identify as gay/lesbian/bisexual."Demographics of the Gay and Lesbian Population in the United States: Evidence from Available Systematic Data Sources", Dan Black, Gary Gates, Seth Sanders, Lowell Taylor, Demography, Vol. 37, No. 2 (May, 2000), pp. 139-154 (available on JSTOR).]
* In studies measuring sexual activity, respondents may have different ideas about what constitutes a "sexual act."Fact|date=June 2008

Reliable data as to the size of the gay and lesbian population is of value in informing public policy. For example, demographics would help in calculating the costs and benefits of domestic partnership benefits, of the impact of legalizing gay adoption, and of the impact of the U.S. military's Don't Ask Don't Tell policy. Further, knowledge of the size of the "gay and lesbian population holds promise for helping social scientists understand a wide array of important questions—questions about the general nature of labor market choices, accumulation of human capital, specialization within households, discrimination, and decisions about geographic location."

Estimates of the incidence of an exclusive homosexual orientation range from >1% to 10% of the population, usually finding there are slightly more gay men than lesbians. [S. Hite, The Hite Report on Male Sexuality, New York, A. Knopf, 1991.] [S. S. et C. L. Janus, The Janus Report on Sexual Behavior, New York, John Wiley & Sons, 1993.] Alfred C. Kinsey, "Sexual Behavior in the Human Male", 1948, ISBN 0-7216-5445-2(o.p.), ISBN 0-253-33412-8(reprint).]

Sexual orientation and the law

* Employment discrimination refers to discriminatory employment practices such as bias in hiring, promotion, job assignment, termination, and compensation, and various types of harassment. In the United States there is "very little statutory, common law, and case law establishing employment discrimination based upon sexual orientation as a legal wrong."citation |title=Sexual Orientation and the Law |first=James M |last=Donovan |author2=American Association of Law Libraries Standing Committee on Lesbian and Gay Issues |year=2007 |publisher=William S. Hein & Co. |isbn=083770166X § 5:17] Some exceptions and alternative legal strategies are available. President Bill Clinton's Executive Order 13087 (1998) prohibits discrimination based on sexual orientation in the competitive service of the federal civilian workforce,citation |title=Executive Order 13087 of May 28, 1998 |url=http://frwebgate.access.gpo.gov/cgi-bin/getdoc.cgi?dbname=1998_register&docid=fr02jn98-135.pdf |format=PDF |periodical=Federal Register |volume=63 |number=105 |date=1998-06-02 |accessdate=2007-09-07] and federal non-civil service employees may have recourse under the due process clause of the U.S. Constitution.Ashton v. Civiletti, 613 F.2d 923, 20 Fair Empl. Prac. Cas. (BNA) 1601, 21 Empl. Prac. Dec. (CCH) P 30297 (D.C. Cir. 1979)] Private sector workers may have a Title VII action under a quid pro quo sexual harassment theory,Kelly v. City of Oakland, 198 F.3d 779, 81 Fair Empl. Prac. Cas. (BNA) 1455, 77 Empl. Prac. Dec. (CCH) P 46281 (9th Cir. 1999)] a "hostile work environment" theory,Oncale v. Sundowner Offshore Services, Inc., 523 U.S. 75, 118 S. Ct. 998, 1002 (1998)] a sexual stereotyping theory,Price Waterhouse v. Hopkins, ussc|490|228|1989] or others.

* Housing discrimination refers to discrimination against potential or current tenants by landlords. In the United States, there is no federal law against such discrimination on the basis of sexual orientation or gender identity, but at least thirteen states and many major cities have enacted laws prohibiting it.citation |accessdate=2007-09-07 |url=http://realestate.findlaw.com/tenant/tenant-fair-housing/tenant-fair-housing-orientation.html |title=Renter's Rights Against Sexual Orientation Discrimination]

* Hate crimes (also known as bias crimes) are crimes motivated by bias against an identifiable social group, usually groups defined by race, religion, sexual orientation, disability, ethnicity, nationality, age, gender, gender identity, or political affiliation. In the United States, 45 states and the District of Columbia have statutes criminalizing various types of bias-motivated violence or intimidation (the exceptions are AZ, GA, IN, SC, and WY). Each of these statutes covers bias on the basis of race, religion, and ethnicity; 32 of them cover sexual orientation, 28 cover gender, and 11 cover transgender/gender-identity.citation |url=http://www.adl.org/99hatecrime/state_hate_crime_laws.pdf |title=State Hate Crime Laws |periodical=Anti-Defamation League |date=June 2006 |accessdate=2007-05-04]

Psychology

Most lesbian, gay, and bisexual people who seek psychotherapy do so for the same reasons as heterosexuals (stress, relationship difficulties, difficulty adjusting to social or work situations, etc.); their sexual orientation may be of primary, incidental, or no importance to their issues and treatment. Whatever the issue, there is a high risk for anti-gay bias in psychotherapy with lesbian, gay, and bisexual clients.Cabaj, R; Stein, T. eds. "Textbook of Homosexuality and Mental Health", p. 421 ] Psychological research in this areas has been relevant to counteracting prejudicial ("homophobic") attitudes and actions, and to the LGBT rights movement generally.ed. Sandfort, T; et al. Lesbian and Gay Studies: An Introductory, Interdisciplinary Approach. Chapter 2.]

History

Psychology was one of the first disciplines to study a homosexual orientation as a discrete phenomenon. The first attempts to classify homosexuality as a disease were made by the fledgling European sexologist movement in the late nineteenth century. In 1886 noted sexologist Richard von Krafft-Ebing listed homosexuality along with 200 other case studies of deviant sexual practices in his definitive work, "Psychopathia Sexualis". Krafft-Ebing proposed that homosexuality was caused by either "congenital [during birth] inversion" or an "acquired inversion". In the last two decades of the nineteenth century, a different view began to predominate in medical and psychiatric circles, judging such behavior as indicative of a type of person with a defined and relatively stable sexual orientation. In the late 19th and early 20th centuries, pathological models of homosexuality were standard.

Today, the consensus of medical and scientific professional organizations is that homosexuality is not a mental illness. In 1973 the American Psychiatric Association (APA) removed homosexuality as a disorder from the "Sexual Deviancy" section of the Diagnostic and Statistical Manual of Mental Disorders, the DSM-II.citation |title=Recalling APA's Historic Step |url=http://www.psych.org/pnews/00-09-01/recalling.html |first=Alfred M |last=Freedman |periodical=APA News |date=2000-09-01 |accessdate=2007-05-04] The World Health Organization's ICD-9 (1977) listed homosexuality as a mental illness, and in 1990, a resolution was adopted to remove it in the ICD-10 (1993).citation |title=Homophobic stigma - A community cause |url=http://www.pinknews.co.uk/news/articles/2005-1496.html |date=2006-05-17 |periodical=PinkNews.co.uk |first=Marc |last=Shoffman |accessdate=2007-05-04] The ICD-10 added ego-dystonic sexual orientation to the list, which refers to people who want to change their gender identities or sexual orientation because of a psychological or behavioral disorder (ICD10|F|66|1|f|60). Groups that advocate reparative therapy, including both secular organizations such as NARTH and religious organizations such as Exodus International, do not accept this position.

Malleability of sexual orientation

The American Psychiatric Association has stated "some people believe that sexual orientation is innate and fixed; however, sexual orientation develops across a person’s lifetime."cite web
url=http://www.aglp.org/pages/cfactsheets.html#Anchor-Gay-14210
title=Gay, Lesbian and Bisexual Issues
author=American Psychiatric Association
publisher=Association of Gay and Lesbian Psychiatrics
date=May 2000] In combination with other major American medical organizations, they have put out a statement which said: "Sexual orientation develops across a person's lifetime—different people realize at different points in their lives that they are heterosexual, gay, lesbian, or bisexual."cite web
url=http://www.apa.org/pi/lgbc/publications/justthefacts.html
title=Just the Facts About Sexual Orientation & Youth: A Primer for Principals, Educators and School Personnel
accessdate=2007-08-28
year=1999
publisher=American Academy of Pediatrics, American Counseling Association, American Association of School Administrators, American Federation of Teachers, American Psychological Association, American School Health Association, The Interfaith Alliance, National Association of School Psychologists, National Association of Social Workers, National Education Association] A report from the Centre for Addiction and Mental Health states: "For some people, sexual orientation is continuous and fixed throughout their lives. For others, sexual orientation may be fluid and change over time." [cite web
url=http://www.camh.net/Publications/Resources_for_Professionals/ARQ2/arq2_question_a2.html
title=ARQ2: Question A2 - Sexual Orientation
accessdate=2007-08-28
publisher=Centre for Addiction and Mental Health] One study has suggested "considerable fluidity in bisexual, unlabeled, and lesbian women's attractions, behaviors, and identities." [cite journal
title=Female bisexuality from adolescence to adulthood: Results from a 10-year longitudinal study.
last=Diamond
first=Lisa M.
publisher=Developmental Psychology
date=January 2008|volume=44
number=1
url=http://www.apa.org/journals/releases/dev4415.pdf
pages=5–14|format=PDF] [cite news
title=Bisexual women - new research findings
publisher=Women's Health News
date=17 January 2008
url=http://www.news-medical.net/?id=34415]

However, they have said "most people experience little or no sense of choice about their sexual orientation."cite web
url=http://www.apa.org/topics/orientation.html
title=Answers to Your Questions About Sexual Orientation and Homosexuality
accessdate=2008-05-26
publisher=American Psychological Association] American medical organization have further stated therapy cannot change sexual orientation, and have expressed concerns over potential harms. The director of the APA's LGBT Concerns Office explained: "I don't think that anyone disagrees with the idea that people can change because we know that straight people become gays and lesbians.... the issue is whether therapy changes sexual orientation, which is what many of these people claim." [cite web
url=http://www.cnsnews.com/Culture/Archive/200608/CUL20060815a.html
title=Psychologists Disagree Over Therapy for Homosexuals
last=Bansal
first=Monisha
publisher=Cybercast News Service
accessdate=2007-08-28] The American Psychiatric Association has stated "To date, there are no scientifically rigorous outcome studies to determine either the actual efficacy or harm of "reparative" treatments," and supports research to further determines risks versus its benefits. [cite web
url=http://www.psych.org/psych_pract/copptherapyaddendum83100.cfm
title=Position Statement on Therapies Focused on Attempts to Change Sexual Orientation (Reparative or Conversion Therapies)
accessdate=2007-08-28
year=2000
month=May
publisher=American Psychiatric Association] Similarly, United States Surgeon General David Satcher issued a report stating that "there is no valid scientific evidence that sexual orientation can be changed". [ [http://www.surgeongeneral.gov/library/sexualhealth/call.htm#III The Surgeon General's call to Action to Promote Sexual Health and Responsible Sexual Behavior] ", A Letter from the Surgeon General U.S. Department of Health and Human Services, 2001-07-09. Retrieved 2007-03-29.]

Partially because of religious reasons, some gay men and lesbians seek to change their sexual orientations through religious faith and practice. In a survey of 882 people who were undergoing conversion therapy, attending ex-gay groups or ex-gay conferences, 22. 9% reported they had not undergone any changes, 42.7% reported some changes, and 34.3% reported much change in sexual orientation.cite journal
last=Nicolosi
first=Joseph
title=Retrospective self-reports of changes in homosexual orientation: A consumer survey of conversion therapy clients
coauthors=Byrd, A. Dean; Potts, Richard W.
url=http://doi.apa.org/index.cfm?fuseaction=showUIDAbstract&uid=2000-00515-002
publisher=Psychological Reports
date=June 2000|volume=86
pages=1071–1088] Exodus International is the largest ostensibly ex-gay group. A major ally of Exodus International is Focus on the Family, who works with Exodus International in their Love Won Out ministry.

Sociology

Coming out

Many people with a homosexual orientation have a so-called "coming out" at some point in their lives. Generally, coming out is described in three phases. The first phase is the phase of "knowing oneself," and the realization and acceptance that one has a homosexual orientation. This is often described as an internal coming out. The second phase involves one's decision to come out to others, e.g. family, friends, and/or colleagues. This occurs with many people as early as age 11, but others do not clarify their sexual orientation until age 40 or older. The third phase more generally involves living openly embracing a homosexual orientation.citation |accessdate=2007-05-04 |url=http://dev.hrc.org/issues/3333.htm |periodical=Human Rights Campaign |title=The Coming Out Continuum] In the United States today, people often come out during high school or college age. At this age, they may not trust or ask for help from others, especially when their orientation is not accepted in society. Sometimes their own parents are not even informed.

Outing is the practice of publicly revealing the sexual orientation of a closeted person.citation |last=Neumann |first=Caryn E |url=http://www.glbtq.com/social-sciences/outing.html |title=Outing |year=2004 |periodical=glbtq.com] Notable politicians, celebrities, military service people, and clergy members have been outed, with motives ranging from malice to political or moral beliefs. Many commentators oppose the practice altogether,citation |title=The Dictionary of Bias-Free Usage: A Guide to Nondiscriminatory Language |last=Maggio |first=Rosalie |year=1991 |publisher=Oryx Press |isbn=0897746538 |page=208] while some encourage outing public figures who use their positions of influence to harm other gay people.citation |url=http://www.newstatesman.com/200704230064 |title=Outing hypocrites is justified |first=Peter |last=Tatchell |date=2007-04-23 |accessdate=2007-05-04 |periodical=The New Statesman]

Homophobia

Homophobia is a fear of, aversion to, or discrimination against homosexuals. [ [http://www.bartleby.com/61/90/H0259000.html The American Heritage Dictionary of the English Language: Fourth Edition.] ] cite web|url=http://www.webster.com/dictionary/homophobia|title=webster.com|accessdate=2008-01-29|date=2008] cite web|url=http://dictionary.reference.com/browse/homophobia homophobial|title=Dictonary.com|accessdate=2008-01-29|date=2008|publisher=Dictonary.com] cite web|url=http://reference.aol.com/dictionary?dword=homophobia&lookupbtn=Look+Up|title=aol.com|accessdate=2008-01-29|date=2008|publisher=aol.com] It manifests in different forms, and a number of different types have been postulated, among which are internalized homophobia, social homophobia, emotional homophobia, rationalized homophobia, and others. [ [http://allies.tamu.edu/Did%20You%20Know/riddle.htm The Riddle Homophobia Scale] from Allies Committee website, Department of Student Life, Texas A&M University]

In the United States, the FBI reported that 15.6% of hate crimes reported to police in 2004 were based on perceived sexual orientation. Sixty-one percent of these attacks were against gay men.citation |title=Crime in the United States 2004: Hate Crime |url=http://www.fbi.gov/ucr/cius_04/offenses_reported/hate_crime/index.html |periodical=FBI |accessdate=2007-05-04] The 1998 murder of Matthew Shepard, a gay student, is one of the most notorious incidents in the U.S.

Social construct

Because a homosexual orientation is complex and multi-dimensional, some academics and researchers, especially in Queer studies, have argued that it is a historical and social construction. In 1976 the historian Michel Foucault argued that homosexuality as an identity did not exist in the eighteenth century; that people instead spoke of "sodomy", which referred to sexual acts. Sodomy was a crime that was often ignored but sometimes punished severely (see sodomy law).

Foucault further argued that it was in the nineteenth century that homosexuality came into existence as practitioners of emerging sciences and arts sought to classify and analyze different forms of sexuality. Finally, Foucault argues that it was this emerging discourse that allowed some to claim homosexuality as a human identity.Fact|date=April 2007

The term homosexual is often used in European and American cultures to encompass a person’s entire social identity, which includes self and personality. In Western cultures some people speak meaningfully of gay, lesbian, and bisexual identities and communities. In other cultures, homosexuality and heterosexual labels don’t emphasize an entire social identity or indicate community affiliation based on sexual orientation. [Zachary Green and Michael J. Stiers. "Multiculturalism and Group Therapy in the United States: A Social Constructionist Perspective". Springer Netherlands 2002. Pages 233-246.]

Theories of causality

The American Academy of Pediatrics has stated that "sexual orientation probably is not determined by any one factor but by a combination of genetic, hormonal, and environmental influences."citation |title=Sexual Orientation and Adolescents |url=http://aappolicy.aappublications.org/cgi/reprint/pediatrics;113/6/1827.pdf |periodical=American Academy of Pediatrics Clinical Report |accessdate=2007-02-23] The amount that each influence plays is highly debated. One study on Swedish twins suggested that there was a moderate, primarily genetic, familial effects, and moderate to large effects of the nonshared environment (social and biological) on same-sex sexual behavior. [cite journal
first=Niklas
last=Långström
coauthor=Qazi Rahman, Eva Carlström, Paul Lichtenstein.
title=Genetic and Environmental Effects on Same-sex Sexual Behaviour: A Population Study of Twins in Sweden
publisher=Archives of Sexual Behaviour
date=7 June 2008
doi=10.1007/s10508-008-9386-1
url=http://www.ncbi.nlm.nih.gov/pubmed/18536986]

The American Psychological Association has stated that "there are probably many reasons for a person's sexual orientation and the reasons may be different for different people". It also stated that for most people, sexual orientation is determined at an early age.citation |url=http://www.apa.org/topics/orientation.html |title=Answers to Your Questions About Sexual Orientation and Homosexuality |periodical=American Psychological Association |accessdate=2007-05-04]

The American Psychiatric Association has stated that, "to date there are no replicated scientific studies supporting any specific biological etiology for homosexuality. Similarly, no specific psychosocial or family dynamic cause for homosexuality has been identified, including histories of childhood sexual abuse."

Research into how sexual orientation may be determined by genetic or other prenatal factors plays a role in political and social debates about homosexuality, and also raises fears about genetic profiling and prenatal testing.citation |url=http://www.chicagotribune.com/features/lifestyle/health/chi-gaygene_bd12aug12,1,5608849.story?ctrack=1&cset=true |title=Study of gay brothers may find clues about sexuality |first=Robert |last=Mitchum |periodical=Chicago Tribune |date=2007-08-12 |accessdate=2007-05-04]

Genetic explanations

In 1993, Dean Hamer found the genetic marker Xq28 on the X chromosome. Hamer's study found a link between the Xq28 marker and male homosexuality, [cite journal |author=Hamer DH, Hu S, Magnuson VL, Hu N, Pattatucci AM |title=A linkage between DNA markers on the X chromosome and male sexual orientation |journal=Science |volume=261 |issue=5119 |pages=321–7 |year=1993 |pmid=8332896 |doi=10.1126/science.8332896] but the original study's results have been disputed. [ [http://news.bbc.co.uk/1/hi/sci/tech/325979.stm Doubt cast on 'gay gene'] , April 23, 1999, BBC News] Several mutations have been identified in flies, such as changes in the fruitless gene, cause male flies to court and attempt to mate with other males; however, when a modified male fruit fly is isolated with only female fruit flies, then he will attempt to mate with them.

Twin studies give indications that genes may predispose some men to seek partners of the same sex. Hamer commented "From twin studies, we already know that half or more of the variability in sexual orientation is not inherited. Our studies try to pinpoint the genetic factors, not to negate the psychosocial factors." [cite journal
url=http://www.time.com/time/magazine/article/0,9171,1101951113-133393,00.html
title=New Evidence of a "Gay Gene"
last=Toufexis
first=Anastasia
date=June, 24, 2001
publisher=Time] One common type of twin study compares the monozygotic (or "identical") twins of people possessing a particular trait to the dizygotic (non-identical, or "fraternal") twins of people possessing the trait. Bailey and Pillard (1991) in a study of gay twins found that 52% of monozygotic brothers and 22% of the dizygotic twins were concordant for homosexuality. [cited in Wilson and Rahman 2005, p47] Bailey, Dunne and Martin (2000) used the Australian twin registry to obtain a sample of 4,901 twins. [cite journal |author=Bailey JM, Dunne MP, Martin NG |title=Genetic and environmental influences on sexual orientation and its correlates in an Australian twin sample |journal=J Pers Soc Psychol |volume=78 |issue=3 |pages=524–36 |year=2000 |pmid=10743878 |doi=] Recently, Långström and colleagues reported on a study of 3,826 twin pairs, comprising all twins between the ages of 20 and 47 in Sweden. [cite journal |author=Långström N, Rahman Q, Carlström E, Lichtenstein P |title=Genetic and environmental effects on same-sex sexual behavior: A population study of twins in Sweden |journal=Arch Sex Behav |volume= |issue= |pages= |year=2008 |pmid=18536986 |doi=10.1007/s10508-008-9386-1] Their results showed that genetic factors explained about 34-39% of the variation, whereas specific environmental effects explained the remaining 61-66% in men. In women, the genetic part of the variation was 18-19%, with 16-17% for shared environmental and 64-66% for unique environmental factors.

Prenatal hormonal theory

The hormonal theory of sexuality holds that, just as exposure to certain hormones plays a role in fetal sex differentiation, such exposure also influences the sexual orientation that emerges later in the adult. [Dörner, G., Rohde, W., Stahl, F., Krell, L., & Masius, W.-G. (1975). A neuroendocrine predisposition for homosexuality in men. "Archives of Sexual Behavior, 4," 1–8.] [Ellis & Ames (1987). Neurohormonal functioning and sexual orientation: A theory of homosexuality-heterosexuality. "Psychological Bulletin, 101," 233–258.]

Prenatal stress

It has been hypothesized that prenatal stress (stress to the mother during pregnancy) can increase the probability of the child being homosexual. [Dörner, G., Geier, T., Ahrens, L., Krell, L., Münx, G., Sieler, H., Kittner, E., & Müller, H. (1980). Prenatal stress as possible aetiogenetic factor of homosexuality in human males. "Endokrinologie, 75," 365–368.] [Dörner, G., Schenk, B., Schmiedel, B., & Ahrens, L. (1983). Stressful events in prenatal life and bi- and homosexual men. "Experimental and Clinical Endocrinology, 31," 83–87.] [Ellis, L., & Cole-Harding, S. (2001). The effects of prenatal stress, and of prenatal alcohol and nicotine exposure, on human sexual orientation. "Physiology and Behavior, 74," 213–226.]

Physiological differences in gay men and lesbians

Recent studies have found notable differences between the physiology of gay people and non-gay people. There is evidence that:
* The average size of the INAH-3 in the brains of gay men is approximately the same size as INAH 3 in women, which is significantly smaller, and the cells more densely packed, than in heterosexual men's brains.cite journal |author=LeVay S |title=A difference in hypothalamic structure between heterosexual and homosexual men |journal=Science |volume=253 |issue=5023 |pages=1034–7 |year=1991 |pmid=1887219 |doi=10.1126/science.1887219]
* The suprachiasmatic nucleus was found by Swaab and Hopffman to be larger in gay men than in non-gay men, [http://www.dafml.unito.it/anatomy/panzica/pubblicazioni/pdf/1995PanzicaJEI.pdf] the suprachiasmatic nucleus is also known to be larger in men than in women. [cite journal |author=Swaab DF, Zhou JN, Ehlhart T, Hofman MA |title=Development of vasoactive intestinal polypeptide neurons in the human suprachiasmatic nucleus in relation to birth and sex |journal=Brain Res. Dev. Brain Res. |volume=79 |issue=2 |pages=249–59 |year=1994 |pmid=7955323 |doi=]
* The anterior commissure is larger in women than men and was reported to be larger in gay men than in non-gay men, [cite journal |author=Allen LS, Gorski RA |title=Sexual orientation and the size of the anterior commissure in the human brain |journal=Proc. Natl. Acad. Sci. U.S.A. |volume=89 |issue=15 |pages=7199–202 |year=1992 |pmid=1496013 |doi=] but a subsequent study found no such difference. [Lasco, M. S., Jordan, T. J., Edgar, M. A., Petito, C. K., & Byne, W. (2002). A lack of dimorphism of sex or sexual orientation in the human anterior commissure. "Brain Research, 936," 95–98.]
* Gay men report, on an average, slightly longer and thicker penises than non-gay men. [cite journal |author=Bogaert AF, Hershberger S |title=The relation between sexual orientation and penile size |journal=Arch Sex Behav |volume=28 |issue=3 |pages=213–21 |year=1999 |pmid=10410197 |doi=10.1023/A:1018780108597]
* Gay men's brains respond differently to fluoxetine, a selective serotonin reuptake inhibitor. [cite journal |author=Kinnunen LH, Moltz H, Metz J, Cooper M |title=Differential brain activation in exclusively homosexual and heterosexual men produced by the selective serotonin reuptake inhibitor, fluoxetine |journal=Brain Res. |volume=1024 |issue=1-2 |pages=251–4 |year=2004 |pmid=15451388 |doi=10.1016/j.brainres.2004.07.070]
* The functioning of the inner ear and the central auditory system in lesbians and bisexual women are more like the functional properties found in men than in non-gay women (the researchers argued this finding was consistent with the prenatal hormonal theory of sexual orientation).cite journal |author=McFadden D |title=Masculinization effects in the auditory system |journal=Arch Sex Behav |volume=31 |issue=1 |pages=99–111 |year=2002 |pmid=11910797 |doi=10.1023/A:1014087319682]
* The startle response (eyeblink following a loud sound) is similarly masculinized in lesbians and bisexual women. [cite journal |author=Rahman Q, Kumari V, Wilson GD |title=Sexual orientation-related differences in prepulse inhibition of the human startle response |journal=Behav. Neurosci. |volume=117 |issue=5 |pages=1096–102 |year=2003 |pmid=14570558 |doi=10.1037/0735-7044.117.5.1096]
* Three regions of the brain (medial prefrontal cortex, left hippocampus, and right amygdala) are more active in gay men than non-gay men when exposed to sexually arousing material. [cite journal |author=Safron A, Barch B, Bailey JM, Gitelman DR, Parrish TB, Reber PJ |title=Neural correlates of sexual arousal in homosexual and heterosexual men |journal=Behav. Neurosci. |volume=121 |issue=2 |pages=237–48 |year=2007 |pmid=17469913 |doi=10.1037/0735-7044.121.2.237]
* Gay and non-gay people emit different armpit odors. [cite journal |author=Martins Y, Preti G, Crabtree CR, Runyan T, Vainius AA, Wysocki CJ |title=Preference for human body odors is influenced by gender and sexual orientation |journal=Psychol Sci |volume=16 |issue=9 |pages=694–701 |year=2005 |pmid=16137255 |doi=10.1111/j.1467-9280.2005.01598.x]
* Gay men are more likely to have a counter-clockwise hair whorl pattern. [http://www.iisc.ernet.in/academy/jgenet/Vol83No3/251.pdf]
* Gay and non-gay people's brains respond differently to two human sex pheromones (AND, found in male armpit secretions, and EST, found in female urine). [cite journal |author=Savic I, Berglund H, Gulyas B, Roland P |title=Smelling of odorous sex hormone-like compounds causes sex-differentiated hypothalamic activations in humans |journal=Neuron |volume=31 |issue=4 |pages=661–8 |year=2001 |pmid=11545724 |doi=10.1016/S0896-6273(01)00390-7] [cite journal |author=Savic I, Berglund H, Lindström P |title=Brain response to putative pheromones in homosexual men |journal=Proc. Natl. Acad. Sci. U.S.A. |volume=102 |issue=20 |pages=7356–61 |year=2005 |pmid=15883379 |doi=10.1073/pnas.0407998102] [cite journal |author=Berglund H, Lindström P, Savic I |title=Brain response to putative pheromones in lesbian women |journal=Proc. Natl. Acad. Sci. U.S.A. |volume=103 |issue=21 |pages=8269–74 |year=2006 |pmid=16705035 |doi=10.1073/pnas.0600331103]
* Finger length ratios between the index and ring fingers may be different between non-gay and lesbian women. [cite journal |author=Brown WM, Hines M, Fane BA, Breedlove SM |title=Masculinized finger length patterns in human males and females with congenital adrenal hyperplasia |journal=Horm Behav |volume=42 |issue=4 |pages=380–6 |year=2002 |pmid=12488105 |doi=10.1006/hbeh.2002.1830] [cite journal |author=Hines M, Johnston KJ, Golombok S, Rust J, Stevens M, Golding J |title=Prenatal stress and gender role behavior in girls and boys: a longitudinal, population study |journal=Horm Behav |volume=42 |issue=2 |pages=126–34 |year=2002 |pmid=12367566 |doi=10.1006/hbeh.2002.1814] [cite journal |author=Rahman Q, Wilson GD |title=Sexual orientation and the 2nd to 4th finger length ratio: evidence for organising effects of sex hormones or developmental instability? |journal=Psychoneuroendocrinology |volume=28 |issue=3 |pages=288–303 |year=2003 |pmid=12573297 |doi=10.1016/S0306-4530(02)00022-7] [cite journal |author=Brown WM, Finn CJ, Cooke BM, Breedlove SM |title=Differences in finger length ratios between self-identified "butch" and "femme" lesbians |journal=Arch Sex Behav |volume=31 |issue=1 |pages=123–7 |year=2002 |pmid=11910785 |doi=10.1023/A:1014091420590] [cite journal |author=Hall LS, Love CT |title=Finger-length ratios in female monozygotic twins discordant for sexual orientation |journal=Arch Sex Behav |volume=32 |issue=1 |pages=23–8 |year=2003 |pmid=12597269 |doi=10.1023/A:1021837211630]

Cognitive differences in gay men and lesbians

Recent studies suggest the presence of subtle differences in the way gay people and non-gay people process certain kinds of information. Researchers have found that:
* Gay men and lesbians are significantly more likely to be left-handed or ambidextrous than are non-gay men and women; [cite journal |author=Lalumière ML, Blanchard R, Zucker KJ |title=Sexual orientation and handedness in men and women: a meta-analysis |journal=Psychol Bull |volume=126 |issue=4 |pages=575–92 |year=2000 |pmid=10900997 |doi=] [cite journal |author=Mustanski BS, Bailey JM, Kaspar S |title=Dermatoglyphics, handedness, sex, and sexual orientation |journal=Arch Sex Behav |volume=31 |issue=1 |pages=113–22 |year=2002 |pmid=11910784 |doi=10.1023/A:1014039403752] [cite journal |author=Lippa RA |title=Handedness, sexual orientation, and gender-related personality traits in men and women |journal=Arch Sex Behav |volume=32 |issue=2 |pages=103–14 |year=2003 |pmid=12710825 |doi=10.1023/A:1022444223812] Simon LeVay argues that because " [h] and preference is observable before birth [cite journal |author=Hepper PG, Shahidullah S, White R |title=Handedness in the human fetus |journal=Neuropsychologia |volume=29 |issue=11 |pages=1107–11 |year=1991 |pmid=1775228 |doi=10.1016/0028-3932(91)90080-R] ... [t] he observation of increased non-right-handness in gay people is therefore consistent with the idea that sexual orientation is influenced by prenatal processes," perhaps heredity.
* Gay men [Geoff Sanders, Ph.D. and Marian Wright, B.Sc.(1997), Sexual Orientation Differences in Cerebral Asymmetry and in the Performance of Sexually Dimorphic Cognitive and Motor Tasks] and lesbians are more verbally fluent than heterosexuals of the same sex [ [http://inductivist.blogspot.com/2007/09/homosexuality-and-iq-looking-at.html GSS data on verbal performance of homosexual, heterosexual, and bisexual males and females] ] [cite journal |author=McCormick CM, Witelson SF |title=A cognitive profile of homosexual men compared to heterosexual men and women |journal=Psychoneuroendocrinology |volume=16 |issue=6 |pages=459–73 |year=1991 |pmid=1811244 |doi=] [cite journal |author=Rahman Q, Abrahams S, Wilson GD |title=Sexual-orientation-related differences in verbal fluency |journal=Neuropsychology |volume=17 |issue=2 |pages=240–6 |year=2003 |pmid=12803429 |doi=] (but two studies did not find this result). [Gladue, B. A., W. W. Beatty, et al. (1990). "Sexual orientation and spatial ability in men and women." Psychobiology 18: 101-108.] [cite journal |author=Neave N, Menaged M, Weightman DR |title=Sex differences in cognition: the role of testosterone and sexual orientation |journal=Brain Cogn |volume=41 |issue=3 |pages=245–62 |year=1999 |pmid=10585237 |doi=10.1006/brcg.1999.1125]
* Gay men may receive higher scores than non-gay men on tests of object location memory (no difference was found between lesbians and non-gay women). [cite journal |author=Rahman Q, Wilson GD, Abrahams S |title=Sexual orientation related differences in spatial memory |journal=J Int Neuropsychol Soc |volume=9 |issue=3 |pages=376–83 |year=2003 |pmid=12666762 |doi=10.1017/S1355617703930037]

Fraternal birth order

There is evidence from numerous studies that homosexual men tend to have more older brothers than do heterosexual men, known as the "fraternal birth order effect." [Blanchard, R. (1997). Birth order and sibling sex ratio in homosexual versus heterosexual males and females. "Annual Review of Sex Research, 8," 27–67.] cite journal |author=Blanchard R, Klassen P |title=H-Y antigen and homosexuality in men |journal=J. Theor. Biol. |volume=185 |issue=3 |pages=373–8 |year=1997 |pmid=9156085 |doi=10.1006/jtbi.1996.0315] One reported that each older brother increases the odds of being gay by 33%. [Blanchard and Klassen (1997); "Birth order and sibling sex ratio in homosexual versus heterosexual males and females". Review of Sex Research, Vol. 8] The fraternal birth order effect is the strongest known predictor of sexual orientation.Bogaert, A. F. (2006). Biological versus nonbiological older brothers and men's sexual orientation. "Proceedings of the National Academy of Sciences, 103," 10777-10774.] Interestingly, this relation seems to hold only for right-handed males.cite journal |author=Blanchard R, Cantor JM, Bogaert AF, Breedlove SM, Ellis L |title=Interaction of fraternal birth order and handedness in the development of male homosexuality |journal=Horm Behav |volume=49 |issue=3 |pages=405–14 |year=2006 |pmid=16246335 |doi=10.1016/j.yhbeh.2005.09.002] [Blanchard, R. (2008). Review and theory of handedness, birth order, and homosexuality in men. "Laterality, 13," 51–70.] There has been no observed equivalent for women. [Blanchard, R., Zucker, K. J., Siegelman, M., Dickey, R., & Klassen, P. (1998). The relation of birth order to sexual orientation in men and women. "Journal of Biosocial Science, 30," 511–519.] Peter Bearman repeated the experiments, but found no correlation between older brothers and male homosexuality and questions the sampling methods used.

The effect has been found even in males not raised with their biological brothers, suggesting an in-utero environmental causation. To explain this finding, a maternal immune response has been hypothesized. Male fetuses produce H-Y antigens which may be involved in the sexual differentiation of vertebrates. Other studies have suggested the influence of birth order was not due to a biological, but a social process. [ [http://www.ncbi.nlm.nih.gov/pubmed/17135133?ordinalpos=30&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum Fraternal birth order and ratio of heterosexual/homosexual feelings in women and men] ]

Environment

Researchers have found childhood gender nonconformity to be the largest predictor of homosexuality in adulthood. [cite journal
last=Bailey
first=J.M.
coauthor = Zucker, K.J
year=1995
url=http://content.apa.org/journals/dev/31/1/43
title=Childhood sex-typed behavior and sexual orientation: A conceptual analysis and quantitative review
publisher=Developmental Psychology
volume=31
pages=43–55] Daryl Bem's Exotic Becomes Erotic theory suggests that some children will prefer activities that are typical of the other sex and that this will make a gender-conforming child feel different from opposite-sex children, while gender-nonconforming children will feel different from children of their own sex, which may evoke physiological arousal when the child is near members of the sex which it considers as being "different", which will later be transformed into sexual arousal. Researchers have suggested that this nonconformity may be a result of genetics, prenatal hormones, personality, parental care or other environmental factorsFact|date=April 2008. Peter Bearman showed that males with a female twin are twice as likely to report same-sex attractions, unless there was an older brother. He says that his findings support the hypothesis that less gendered socialization in early childhood and preadolescence shapes subsequent same-sex romantic preferences. He suggests that parents of opposite-sex twins are more likely to give them unisex treatment, but that an older brother establishes gendersocializing mechanisms for the younger brother to follow.cite journal
last=Bearman
first=Peter
coauthor=Brückner, Hannah
year=2002
title=Opposite-sex twins and adolescent same-sex attraction
publisher=American Journal of Sociology
volume=107
url=http://www.soc.duke.edu/~jmoody77/205a/ecp/bearman_bruckner_ajs.pdf
format=PDF
pages=1179–1205]

From their research on 275 men in the Taiwanese military, Shu and Lung concluded that "paternal protection and maternal care were determined to be the main vulnerability factors in the development of homosexual males." Key factors in the development of homosexuals were "paternal attachment, introversion, and neurotic characteristics."cite journal
last=Lung
first=F.W.
year=2007
title=Father-son attachment and sexual partner orientation in Taiwan
journal=Comprehensive Psychiatry
volume=48
pages=20–26
accessdate=2007-10-30
doi=10.1016/j.comppsych.2006.08.001] Other researchers have also provided evidence that gay men report having had less loving and more rejecting fathers, and closer relationships with their mothers, than non-gay men. [Bell, Weinberg, & Parks, 1981; Bieber et al., 1962; Braatan & Darling, 1965; Brown, 1963; Evans, 1969; Jonas, 1944; Millic & Crowne, 1986; Nicolosi, 1991; Phelan, 1993; Biggio, 1973; Seutter & Rovers, 2004; Siegelman, 1974; Snortum, 1969; Socarides, 1978; West, 1959).] Whether this phenomenon is a cause of homosexuality, or whether parents behave this way in response to gender-variant traits in a child, is unclear. [Isay, Richard A. (1990). Being homosexual: Gay men and their development. HarperCollins. ISBN 0380710226.] [Isay, Richard A. (1996). Becoming gay: The journey to self-acceptance. New York, Pantheon. ISBN 0679421599.]

Innate bisexuality

"Innate bisexuality" (or predisposition to bisexuality) is a term introduced by Sigmund Freud (based on work by his associate Wilhelm Fliess) that expounds that all humans are born bisexual but through psychological development (which includes both external and internal factors) become monosexual, while the bisexuality remains in a latent state.

References

External links

* [http://www.apa.org/topics/sbehaviorsub1.html Answers to Your Questions About Sexual Orientation and Homosexuality] The American Psychological Association
* [http://plato.stanford.edu/entries/homosexuality/ Stanford Encyclopedia of Philosophy - Same-sex Orientation]