Sexuality is more fluid than people think, and your behaviour doesn't necessarily determine your sexual identity or sexual orientation, according to a senior psychology lecturer.
The idea that every individual has an innate sexual identity is a relatively recent development in Western societies. Most people tend to assume that sexuality is fixed: either you're straight, gay or bisexual.
"I think what's become clearer over the last hundred or so years is that sexuality is much more fluid and much more dependent on the social and cultural and historical context we find ourselves in," Auckland University of Technology's Dr Pani Farvid told Newshub.
"Some of the labels we use like homosexuality, heterosexuality and bisexuality all have a history. Even the term 'heterosexual' really only came into use in the late 1800s when sexologists started analysing sexuality and categorising it."
Is sexuality really that simple?
Some experts have suggested that sexuality is fluid and exists on a spectrum.
One of the most famous was Alfred Kinsey (died 1956), the creator of the Kinsey scale and known as 'the father of the sexual revolution'. The Kinsey scale was created to demonstrate that sexuality does not fit into two strict categories: homosexual and heterosexual. Instead, Prof Kinsey believed that sexuality is fluid and subject to change over time.
Dr Farvid says the scale was "quite forward-thinking and revolutionary in the 1950s".
"But it has been critiqued since then because it's still based on that binary model of homosexuality and heterosexuality where you're somewhere in between. Our current understanding of sexuality has really gone beyond that binary model."
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Another famous expert was Austrian neurologist Sigmund Freud (died in 1939), who introduced the term 'innate bisexuality' that suggests all humans are born bisexual, but through psychological development (which includes both external and internal factors) most people identify as heterosexual because it's considered normal.
"I think we're all born with the capacity to take on any sexuality, but the option that's presented to us as the most normal or natural is heterosexuality, so most people identify as heterosexual," says Dr Farvid.
"I can imagine that psychologically - as a child or teenager - even if someone has an attraction to someone of the same gender, they might force it to one side because it's not considered normal."
She says while there is a lot more acceptance of people taking on different identities nowadays, being non-heterosexual means you are still part of a minority and you "can be stigmatised".
Is it the same for men and women?
Today more men are coming forward and claiming that the common categories of sexuality are too rigid, according to psychologist Ritch Savin-Williams in his book Mostly Straight: Sexual Fluidity Among Men. Younger generations are increasingly open to "looser boundaries" regarding sexuality, he says.
The book features 40 interviews with men who claim to be "mostly straight".
"I think within our society it's more acceptable for a woman to present herself as being more sexually fluid because two women together is eroticised in a particular way for the heterosexual male gaze," says Dr Farvid.
"Male bisexuality is more problematised because there is much more homophobia when it comes to that sort of interaction."
Mr Savin-Willaims has warned that men fear being rejected by society for coming out as sexually fluid because it's more culturally acceptable for women to be.
However, Dr Farvid noted that within the "queer sphere" there is much more visibility of gay men than lesbian women. She said it's an interesting dynamic to look at, and more research is needed to understand why this is the case.
Tara Pond, a doctoral candidate in psychology at AUT, told Newshub it's important to change the narrative around sexuality to "incorporate and validate all sexualities".
"At the moment, bisexuality and other sexualities are being erased which leads to real-world consequences: high rates of mental health and sexual abuse among bisexual people are some examples.
"At a personal level, as a bisexual woman I feel like my sexuality is erased, invalidated or viewed negatively on an everyday basis on the street, in the media, and in society."
Arguments against sexual fluidity
Not everyone agrees that sexuality is fluid from a scientific perspective.
Aside from the obvious religious arguments against the theory, a 2015 study showed that sexuality could be far less flexible than sexologists like Prof Kinsey once claimed.
Washington State University researchers surveyed more than 33,000 American adults and found that a categorical model was better suited for describing sexual orientation than a spectrum model.
"I think we can still celebrate individual differences and some fluidity while acknowledging that these findings suggest there is also a categorical difference," said the study's lead author Alyssa Norris in an interview with The Daily Beast.
Dr Farvid also noted that the phrase “I was born this way” is controversial when it comes to homosexuality. “Historically, this was a useful strategy for claiming legitimacy in terms of sexual orientation, but we now know that such essentialist claims are not very useful for understanding the nuances of sexuality,” says Dr Farvid.
The issue with this claim is that it suggests external factors have no influence on a person's sexual identity. But the notion that sexuality is fluid and "open to our own crafting", as Dr Farvid puts it, can lead people to think that if sexuality is a choice, then gay people could be taught to be straight.
This could, for example, lead to contentious gay conversion 'therapy', often carried out in the name of religion, despite there being no scientific or medical evidence to support the practise, according to the Royal College of Psychiatrists in London.
Dr Farvid says the reason why she supports the idea that sexuality is fluid is because it "destabilises the notion that heterosexuality is the norm".