Feb. 23, 2011 -- Ever since Madonna planted that wet kiss on Britney Spears in front of millions of television viewers at the 2003 MTV Video Music Awards, women have been loosening up sexually with other women.
These so-called flexisexuals say that although they are not gay or even bisexual, they enjoy flirting and kissing girls -- but they still enjoy having sex with men.
One female senior at Hofstra University in New York said she is apt to turn to women when she's had too much to drink.
"I just kiss girls because it's funny and entertaining to do when under the influence," she said. "When you just kiss a guy, you deal with the pressures of feeling like you have to go further, and with girls that is never an issue."
The student, who declined to give her name for fear a future employer might Google her sexual escapades, is one of many young women who are more flexible in their attitudes about sex.
Experts say they may be influenced by the growing visibility of same-sex couples and more open attitudes about sex in general.
Pop culture, itself, seems to celebrate that flexibility in songs like Katie Perry's, "I Kissed a Girl [and I Liked It]," a song that 19-year-old Alisha Garrison said "made girls be more free to do whatever they want."
"It's not really experimenting, but maybe trying to get some attention," said Garrison, an urban planning student from Simi Valley, Calif.
Perry admits in her lyrics, "I got so brave, drink in hand, I lost my discretion."
Flexisexual is also known as heteroflexible, pansexual or queer, all subtle variations that mean they are not closing any doors.
Women say it has has more to do with their view of the world than their practice in the bedroom.
"When I was younger, girls bounced around in high school about sexuality," said Jamilla Wright, a public relations major at the University of Texas. "I think the older we get the more comfortable we are with it being based more on the individual than either-or as far as sexuality is concerned."
"Labels matter less," said the 21-year-old.
Hollywood has its own examples: Lindsay Lohan, 24, who dated Samantha Ronson, denied she was a lesbian and "maybe" bisexual. She has since returned to men.
Angelina Jolie, 35 and now happily ensconced with Brad Pitt, had a sexual relationship with Jenny Shimizu. And Drew Barrymore, 35, has reportedly said, "Being with a woman is like exploring your own body, but through someone else."
There is even a dating site ? Flexisexual -- where women can find "sexy, open-minded women looking to explore their sexuality, chat, hook up with and more."
"This is where straight women who feel curious about bisexual passion or romance, start out," it says. "The common interest makes it easy for like-minded individuals to connect with each other and find someone compatible, compared to leaving it up to chance."
For many of today's women in their late teens and 20s, openness to intimate physical relationships with either gender has become a way of life, rather than an "experiment."
This relatively new phenomenon is likely a product of a generation unconcerned with labels. Often, it begins in the enlightened college cocoon, where women can explore their sexuality, though a recent ABC report from San Antonio, Texas, said flexisexuality is also part of the high school culture.
Experts say more sexual experimentation occurs when people have not yet found a partner, before they settle into monogamous relationships. College is also a safe cocoon for self-discovery.
Studies Say Women are More Fluid in Their Sexuality
Many scientific studies have also confirmed that both heterosexual and lesbian women tend to become sexually aroused by both male and female erotica or have a bisexual arousal pattern.
A 2003 study from Northwestern University found that compared with men, women's sexual arousal patterns may be less tightly connected to their sexual orientation and more "flexible."
Some girls say this has nothing to do with their sexual identity. They just like to live up to the ménage-a-trois fantasy of the men they seek to please.
"I think girls kiss girls to draw attention from guys, who think it's sexy and seductive," said Lauren DeGiorgi, a senior majoring in psychology at East Carolina University. "But we're usually drunk when it happens."
"Current generations are more open-minded and may promote that lax attitude by making this behavior more acceptable - probably among younger, easily influenced girls," said Heather, a college junior from San Diego, Calif., who did not want to use her last name.
And some think it even "indirectly mocks" the gay community, according to Caleb Fox, a 20-year-old from the University of Texas.
"Straight men really like the idea of two 'hot' girls making out," he said. "And because I don't think these 'flexisexuals' are really lesbians, it doesn't seem that they're actually seeking a romantic relationship with another woman -- it's more about a show. And from a feminist standpoint it continues the objectification of women."
Lisa Diamond, associate professor of gender studies at University of Utah, has been studying the topic for years, and confirms women are, indeed, more flexible in their sexuality and for a variety of cultural, and perhaps biological, reasons.
"I think there is a growing awareness of the fact that you don't have to be 100 percent gay to have the capacity to enjoy same-sex contact," said Diamond, who is author of the 2008 book, "Sexual Fluidity: Understanding Women's Love and Desire."
"In the old days, any instance of same-sex attraction was automatically put in the category of bisexual or lesbian and now we realize women are more complicated than that," she said. "There are more examples floating around in popular culture, and the term reflects that."
Claire, the sister in the HBO series, "Six Feet Under," had a sexual dalliance with a female friend, but decided it wasn't her thing and returned to boys.
Diamond said women's capacity for fluidity has always existed, but only now has society had a cultural understanding after collecting data from around the world.
"We had a pretty rigid view of the way sexuality and orientation works," she said. "But sex researchers have been aware of it for many years. It has taken folks awhile to realize you can have a periodic attraction, but that does not make that sexual identity legitimate."
Men appear to be more "rigid" in their sexuality but that may be because society is more judgmental, according to Diamond.
"Although we find it titillating when girls kiss girls and see images of same-sex sexuality being marketed to a heterosexual male audience, it's not viewed as threatening and alarming," she said. "We don't see the same cultural permission for men."
If HBO had a narrative with a heterosexual man having an encounter with another man, "no one would believe it," she said. "You never see that kind of a plot for a male character."
ABC News reporters Brianna Gays, Ashley Jennings and Tia Castenada contributed to this report.