According to Alfred Kinsey's research into human sexuality in the mid-20th century, many humans do not fall exclusively into heterosexual or homosexual classifications but somewhere between. The Kinsey scale measures sexual attraction and behavior on a seven-point scale ranging from 0 (exclusively heterosexual) to 6 (exclusively homosexual). According to Kinsey's study, a substantial number of people fall within the range of 1 to 5 (between heterosexual and homosexual). Although Kinsey's methodology has been criticized, the scale is still widely used in describing the continuum of human sexuality.
Bisexuality has been observed in various human societies and elsewhere in the animal kingdom throughout recorded history. The term bisexuality, however, like the terms hetero- and homosexuality, was only coined in the 19th century.
Because bisexuality is often an ambiguous position between homosexuality and heterosexuality, bisexuals form a heterogeneous group and the relations between their behaviors, feelings, and identities are not always consistent. Some who might be classified by others as bisexual on the basis of their sexual behavior self-identify primarily as homosexual. Equally, otherwise heterosexual people who engage in occasional homosexual behavior could be considered bisexual, but may not identify as such. For people who believe that sexuality is a distinctly defined aspect of the character, this ambiguity is problematic. On the other hand, some believe that the majority of people contain aspects of homosexuality and heterosexuality, but that the intensities of these can vary from person to person. Some people who engage in bisexual behavior may be supportive of homosexual people, but still self-identify as heterosexual; others may consider any labels irrelevant to their positions and situations. In 1995, Harvard Shakespeare professor Marjorie Garber made the academic case for bisexuality with her 600 page, Vice Versa: Bisexuality and the Eroticism of Everyday Life in which she argued that most people would be bisexual if not for "repression, religion, repugnance, denial" and "premature specialization.
Bisexuality is often misunderstood as a form of adultery or polyamory, and a popular misconception is that bisexuals must always be in relationships with men and women simultaneously. Rather, individuals attracted to both males and females, like people of any other orientation, may live a variety of sexual lifestyles. These include lifelong monogamy, serial monogamy, polyamory, polyfidelity, promiscuity, group sex, and celibacy. For those with more than one sexual partner, these may, or may not, all be of the same gender.
A 2002 survey in the United States by National Center for Health Statistics found that 1.8 percent of men ages 18–44 considered themselves bisexual, 2.3 percent homosexual, and 3.9 percent as "something else". The same study found that 2.8 percent of women ages 18–44 considered themselves bisexual, 1.3 percent homosexual, and 3.8 percent as "something else". The Janus Report on Sexual Behavior, published in 1993, showed that 5 percent of men and 3 percent of women consider themselves bisexual and 4 percent of men and 2 percent of women considered themselves homosexual. The 'Health' section of The New York Times has stated that "1.5 percent of American women identify themselves [as] bisexual."
Dr. Alfred Kinsey's 1948 work Sexual Behavior in the Human Male found that "46% of the male population had engaged in both heterosexual and homosexual activities, or "reacted to" persons of both sexes, in the course of their adult lives". The Kinsey Institute has stated that "Kinsey said in both the Male and Female volumes that it was impossible to determine the number of persons who are "homosexual" or "heterosexual". It was only possible to determine behavior at any given time". Kinsey's book, and its companion Sexual Behavior in the Human Female, have received vocal criticism for their findings and methodology. The New York Times called his research "conscientious and comprehensive and Professor Martin Duberman called it "skillful" and "a monumental endeavor".
Dr. Fritz Klein believed that social and emotional attraction are very important elements in bisexual attraction. For example, a bisexual might be attracted to both feminine women and feminine men, but have little interest in masculine individuals. This individual, while they might be highly attracted to certain members of both sexes, would be unlikely to be attracted to most males in modern western society (who tend to be masculine). As this study employed 2-minute clips of standard heterosexual and homosexual pornography, the study would be blind to the this type of bisexual. One third of the men in each group showed no significant arousal. The study did not claim them to be asexual, and Rieger stated that their lack of response did not change the overall findings.
Human bisexuality has mainly been studied alongside with homosexuality. Van Wyk & Geist (1995) argue that this is a problem for sexuality research because the few studies that have observed bisexuals separately have found that bisexuals are often different from both heterosexuals and homosexuals. Furthermore, bisexuality does not always represent a halfway between the dichotomy. Research indicates that bisexuality is influenced by biological, cognitive and cultural variables in interaction, and this leads to different types of bisexuality.
There is currently a debate on the importance of biological influences on sexual orientation. Biological explanations have been put to question by social scientists, particularly by feminists who encourage women to make conscious decisions about their life and sexuality. A difference in attitude between homosexual men and women has also been reported as men are more likely to regard their sexuality as biological, "reflecting the universal male experience in this culture, not the complexities of the lesbian world." There is also evidence that women's sexuality may be more strongly affected by cultural and contextual factors.
Most of the few available scientific studies on bisexuality date from before the 1990s. Interest in bisexuality has generally grown, but research focus has lately been on sociology and gender studies as well as on bisexuals with HIV and AIDS.
Krafft-Ebing was the first to suggest that bisexuality is the original state of human sexuality. Freud has famously summarized on the basis of clinical observations: "[W]e have come to know that all human beings are bisexual - - and that their libido is distributed between objects of both sexes, either in a manifest or a latent form." According to Freud, people remain bisexual all their lives in a repression to monosexuality of fantasy and behaviour. This idea was taken up in the 1940s by the zoologist Alfred Kinsey who was the first to create a scale to measure the continuum of sexual orientation from hetero to homosexuality. Kinsey studied human sexuality and argued that people have the capability of being hetero or homosexual even if this trait does not present itself in the current circumstances.
From an anthropolocial perspective, there is large variation in the prevalence of bisexuality between different cultures. Among some tribes it appears to be non-existent while in others a universal, including the Sambia of New Guinea and other similar Melanesian cultures.
Even though only a small percentage of people have bisexual traits, this does not outrule the possibility of bisexual behaviour of the majority in different circumstances. Similarly, although evolutionary psychologists consider most males as promiscuous by nature, the majority of American men are faithful to their wives, appearing essentially monogamous. These traits can be explained as the result of culture constraints on evolutionary predispositions.
Recent research suggests that, for most women, high sex drive is associated with increased sexual attraction to both women and men. For men, however, high sex drive is associated with increased attraction to one sex or the other, but not to both, depending on sexual orientation
More recent research, however, associates high sex drive and increased attraction to both sexes only in women. Bisexual men's pattern has been more similar to heterosexuals with a stronger correlation with high sex drive and other-sex attraction.
Women usually have a better hearing sensitivity than males, but homosexual and bisexual women have been found to have weaker sensitivity than heterosexual women while homosexual and bisexual men have hypermasculinized hearing.
There is research evidence that the ratio of the length of the 2nd and 4th digits (index finger and ring finger) is somewhat negatively related to prenatal testosterone and positively to oestrogen. Studies measuring the fingers found a statistically significant skew in the 2D:4D ratio (long ring finger) towards homosexuality with an even lower ratio in bisexuals. It is suggested that exposure to high prenatal testosterone and low prenatal oestrogen concentrations is one cause of homosexuality whereas exposure to very high testosterone levels may be associated with bisexuality. Because testosterone in genereal is important for sexual differentiation, this view offers an alternative to the suggestion that male homosexuality is genetic.
The prenatal homonal theory suggests that a homosexual orientation results from exposure to excessive testosterone causing an over-masculinized brain. This is contradictory to another hypothesis that homosexual preferences may be due to a feminized brain in males. However, it has also been suggested that homosexuality may be due to high prenatal levels of unbinded testosterone that results from a lack of receptors at particular brain sites. Therefore the brain could be feminized while other features, such as the 2D:4D ratio bould be over-masculinized.
In some cultures, historical and literary records from most literate societies indicate that male bisexuality was common and indeed expected. These relationships were generally age-structured as in pederasty or shudo. or gender-structured as in the Two-Spirit or bacchá practices. Most of the commonly cited examples of male "homosexuality" in previous cultures would more properly be categorized as bisexuality. Determining the history of female bisexuality is more problematic, in that women in most of the studied societies were under the domination of the males, and on one hand had less self-determination and freedom of movement and expression, and on the other were not the ones writing or keeping the literary record. Sappho, however, is a notable exception.
In 124 CE the bisexual Roman emperor Hadrian met Antinous, a 13- or 14-year-old boy from Bithynia, and they began their pederastic relationship. Antinous was deified by Hadrian when he died six years later. Many statues, busts, coins and reliefs display Hadrian's deep affections for him. Ancient Rome, Arab countries up to and including the present, China, and Japan, all exhibit patterns of analogous bisexual behavior. In Japan in particular, due to its practice of shudo and the extensive art and literature associated with it, the record of a primarily bisexual lifestyle is both detailed and quite recent, dating back as recently as the 19th century. Bisexual behavior was also common among Roman and Chinese emperors, the shoguns of Japan, and others.
Ancient Greek religious texts, reflecting cultural practices, incorporated bisexual themes. The subtexts varied, from the mystical to the didactic.
Ancestral law in ancient Sparta mandated same-sex relationships with youths who were coming of age for all adult men, so long as the men eventually took wives and produced children. The Spartans thought that love and erotic relationships between experienced and novice soldiers would solidify combat loyalty and encourage heroic tactics as men vied to impress their lovers. Once the younger soldiers reached maturity, the relationship was supposed to become non-sexual, but it is not clear how strictly this was followed. There was some stigma attached to young men who continued their relationships with their mentors into adulthood. For example, Aristophanes calls them euryprôktoi, meaning "wide arses", and depicts them like women.
In Ancient Greece it is believed that males generally went through a homosexual stage in adolescence, followed by a bisexual stage characterized by pederastic relationships in young adulthood, followed by a (mostly) heterosexual stage later in life, when they married and had children. Alexander the Great, the Macedonian king, is thought to have been bisexual, and to have had a male lover named Hephaestion.
Since the 1970s, there have been waves of bisexual chic, in which celebrities and other persons of some notoriety have embraced and advocated bisexuality. This has led to more acceptance of bisexuals in some regards; however, some have latched onto bisexual chic for publicity's sake, with varying degrees of sincerity and permanency. Such celebrities as David Bowie, Dave Navarro, Anne Heche and others have claimed bisexuality only to later renounce the idea (although Bowie has since retreated some on renunciation).
The term "flex sex" developed in the late 2000s, regarding women that generally regard themselves as heterosexual, but who occasionally have sex with other women.
Some in the homosexual community accuse those who self-identify as bisexual of duplicity, believing they are really homosexuals who engage in heterosexual activity merely to remain socially acceptable. They may be accused of "not doing their part" in gaining acceptance of "true" homosexuality. Some homosexual people may also suspect that a self-described bisexual is merely a homosexual in the initial stage of questioning their presumed heterosexuality, and will eventually accept that they are homosexual; this is expressed by a glib saying in gay culture: "Bi now, gay later." These situations can and do take place, but do not appear to be true of the majority of self-described bisexuals. Nonetheless, bisexuals do sometimes experience lesser acceptance from homosexual people, because of their declared orientation. Biphobia can sometimes be the results of repressed bisexual desire in homosexual people.
Bisexuals are often associated with men who engage in same-sex activity while closeted or heterosexually married. The majority of such men—said to be living on the down-low—do not self-identify as bisexual.
Because some bisexual people do not feel that they fit into either the homosexual or the heterosexual world, and because they have a tendency to be "invisible" in public, some bisexual persons are committed to forming their own communities, culture, and political movements. However, since "Bisexual orientation can fall anywhere between the two extremes of homosexuality and heterosexuality", some who identify as bisexual may merge themselves into either homosexual or heterosexual society. Still other bisexual people see this merging as enforced rather than voluntary; bisexual people can face exclusion from both homosexual and heterosexual society on coming out. Psychologist Beth Firestein states that bisexuals also tend to internalize social tensions related to their choice of partners. Firestein suggests bisexuals may feel pressured to label themselves as homosexuals instead of occupying a difficult middle ground in a culture that has it that if bisexuals are attracted to people of both sexes, they must have more than one partner, thus defying society's value on monogamy. These social tensions and pressure may and do affect bisexuals' mental health. Specific therapy methods have been developed for bisexuals to address this concern.
Relatively few supportive bisexual communities exist, therefore there is not as much support from people who have gone through similar experiences. This effectively can make it more difficult for bisexuals to "come out" as such.
A common symbol of the Bisexual community is the bisexual pride flag, which has a deep pink stripe at the top for homosexuality, a blue one on the bottom for heterosexuality, and a purple one, blended from the pink and blue, in the middle to represent bisexuality.
Another symbol that uses the color scheme of the bisexual pride flag is a pair of overlapping pink and blue triangles, the pink triangle being a well-known symbol for the homosexual community, forming purple where they intersect.
Many homosexual and bisexual individuals have a problem with the use of the pink triangle symbol as it was the symbol that Hitler's regime used to tag homosexuals (similar to the yellow Star of David that is constituted of two opposed, overlapping triangles). Because pink triangles were used in the persecution of homosexuals in the Nazi regime, a double moon symbol was devised specifically to avoid the use of triangles. This bisexual symbol is a double moon that is formed when the sex-specific attributes of the astrological symbol of Mars & Venus (representing heterosexual union) are reduced to the two circles open on both ends, thus symbolizing that bisexuals are open to either-sex unions. The color of the bisexual double moon symbol varies. The symbol is most often displayed with rainbow colors, signifying that bisexuals belong to the gay community. It also may appear with the pink-purple-blue colors of the bisexual pride flag. The double moon symbol is common in Germany and surrounding countries. Another symbol used for bisexuality is a purple diamond. From an upside down triangle and a right way up one, pink and blue, placed overlapping.
Many species of animals are involved in the act of forming sexual and relationship bonds between the same sex; even when offered the opportunity to breed with members of the opposite sex, they picked the same sex. Some of these species are gazelles, antelope, bison, and sage grouse.
In some cases animals will choose intercourse with different sexes at different times in their life, and sometimes will perform intercourse with different sexes at random. Homosexual intercourse can also be seasonal in some animals like male walruses, who often engage in homosexual intercourse with each other outside of the breeding season and will revert to heterosexual intercourse during breeding season.
In some cases bisexuality is actually a form of fitness favored by evolution. For example, in the absence of male whiptail lizards (Cnemidophorus), females reproduce by pairing up with each other. During the breeding season females will take turns switching between "male" and "female" roles as their hormones fluctuate. Estrogen levels are high during ovulation ("female" role) and much lower after laying eggs ("male" role). While in the "male" role, a female lizard will mount another in the "female" role and go through the motions of sex to stimulate egg-laying. The hatchlings produced are all female. This all-female species has evolved from lizards with two sexes, but their eggs develop without fertilization (parthenogenesis). Female whiptail lizards can lay eggs without sex, but they lay far fewer eggs than if they engage in sexual stimulation by another female.
Comparatively positive and notable portrayals of bisexuality can be found throughout mainstream media.
Especially noteworthy are the bisexual themes in the films of Federico Fellini. While individual films are rarely "bisexual" themselves, he has made films that both employ prominent heterosexual characters and themes La Strada, La Dolce Vita, 8 1/2, and Amarcord and also made blatantly homosexual themed films such as Satyricon and involving homosexual themes and characters in many of his less famous films. Fellini was suspected of being bisexual in real life, though the extent to which he had many sexual relationships at all, much less of both sexes, is unclear.
In popular music, many of the songs of The Smiths are commonly cited as classic examples. In the songs and stage presentation of Suzie Quatro and Joan Jett, there have been additional examples. In 1995, Jill Sobule sung about bi-curiosity in her song "I Kissed a Girl". The video for the song was slightly less subtle alternating images of Jill Sobule and her boyrfriend (played by Fabio) with images of her with her girlfriend. the song appeared on Beavis and Butt-head. The recently popular song "I Kissed a Girl" by Katy Perry also hints at bisexuality, or at least bi-curiosity, with lyrics such as "I kissed a girl just to try it/I hope my boyfriend don't mind it" and "You're my experimental game/Just human nature".
In notable graphic novels, Love and Rockets (1981 to 1996) subtly portrays bisexuality; Krazy Kat (1913 to 1944) is a comic-strip character whose love is not limited by sex; Alan Moore's Lost Girls (1991 to 2006) portrays bisexual versions of three famous literary characters; Terry Moore's Strangers in Paradise (1993 to 2007) includes several bisexual characters.
Notable novels containing significant bisexual characters are:
Non-fiction scholarship, such as Marjorie Garber's Vice Versa: Bisexuality and the Eroticism of Everyday Life (1995), and Camille Paglia's Sexual Personae (1990), has uncovered previously hidden histories of bisexuality.
On the TV sitcom Will & Grace, the character of Karen Walker appears to be bisexual and—although married to a man—often kisses Grace and seems to have had many female lovers throughout her life. The character Jack Harkness of Doctor Who and Torchwood is from 51st century, in which mankind has become more open minded sexually since it's integration with alien cultures. He is often described as "omnisexual" by his fans, remarking on the question of sexual orientation "You people and your quaint little categories." Harkness is the first openly non-heterosexual character depicted in the long-running Doctor Who. Torchwood also features bisexual characters Toshiko Sato, and Ianto Jones. Rebecca Romijn portrayed a bisexual con artist in the film Femme Fatale.
In the sci-fi television series Babylon 5, characters including Susan Ivanova and Talia Winters are portrayed as bisexual or pansexual. There seems to be a general feeling in the show that it is accepted and common for people to follow their hearts wherever they may take them, ignoring sex. Other examples include the characters Marcus Cole and Stephen Franklin posing as a married couple, and series creator J. Michael Straczynski indicating that the station commander John Sheridan would have been propositioned by the male Lumati ambassador if Susan Ivanova had not been handling those negotiations.
In the 1996 Broadway musical turned movie Rent, Idina Menzel plays Maureen Johnson, a character who has a relationship with both Mark Cohen (Anthony Rapp [who is openly bisexual in real life]), and Joanne Jefferson (Tracie Thoms/Fredi Walker). In the musical, Menzel's character sings the following lines in the song "Take Me or Leave Me":
In the television program "Bottom", Richie is shown consistently throughout the series to be trying to get a girlfriend but to be either secretly attracted to men or accidentally finding more luck with men. He maintains a facade of heterosexuality throughout this, although in the stage adaptations he is shown to be far more attracted to men but still also to women.
In the video game series Metal Gear Solid, the villain Vamp is known to be bisexual, as reported by Hideo Kojima. In the Fox television series, The O.C., Marissa Cooper (played by Mischa Barton ) has a same-sex fling with the character Alex Kelly, played by Olivia Wilde.
The high rated MTV series, A Shot At Love With Tila Tequila, is a bisexual reality show. Tila Tequila or Tila Nguyen, is the bisexual bachelorette, trying to find love from 16 straight males and 16 lesbians.
The tv series Buffy the Vampire Slayer the character Willow Rosenberg, while identifying as a lesbian, is hinted to have a bisexual side to her. She forms strong heterosexual relationships across the first 3 seasons and her vampire alter ego displays overt bisexuality.
In the medical comedy Scrubs the surgeon Todd is a misogynist who makes sex jokes at any opportunity. In the earlier seasons he is hinted at having gay tendencies and in the season five episode My Lunch he is seen looking at pictures of topless men. Elliott and Carla convince him to come out but at the end of the episode he is revealed to be bisexual and walks down the hallway, hitting on a male and female nurse. The janitor asks him "What the hell are you?" to which he replies "I'm the Todd".
In an article about Brokeback Mountain, sex educator Amy Andre argued that in films, bisexuals are always depicted negatively:
Using a content analysis of more than 170 articles written between 2001 and 2006, sociologist Richard N. Pitt, Jr. concluded that the media pathologized black bisexual men’s behavior while either ignoring or sympathizing with white bisexual men’s similar actions. He argued that the "Down Low" black bisexual is often described negatively as a duplicitous heterosexual man whose behaviors threaten the black community. Alternately, the "Brokeback" white bisexual (when seen as bisexual at all) is often described in pitying language as a victimized homosexual man who is forced into the closet by the heterosexist society around him.
On the HBO drama Oz, Christopher Meloni played Chris Keller, a bisexual sociopath who tortured, raped, and had numerous sexual encounters with various men and women whom he met. Desperate Housewives features Andrew Van De Kamp.
A Saturday Night Live joke ran thus:
In one of his comedy routines, George Carlin admits to thinking about what a curse bisexuality must be: "Could you imagine wanting to fuck everybody you meet? Think of all the phone numbers you'd accumulate! You might as well just walk around with the White Pages under your arms."