If there's one thing that is universally agreed about human sexuality, it's this: the things that are the most taboo, turn us on the most.

This goes some way to explain why some sex kinks, previously thought of as 'abnormal', are making their way into mainstream sex culture.

A study done last year in Quebec, found eight types of sexual behaviour previously considered 'anomalous' (a departure from the norm) are now neither rare or unusual.

These include voyeurism, fetishism (the compulsive use of an object or part of body as a stimulus for sexual satisfaction), frotteurism (rubbing the pelvic area against a non-consenting person for pleasure in a crowded area) and masochism.

Think wearing high heels in bed or role-playing a Red Room Fifty-Shades style fantasy is risqué?

Think again.

Here's four increasingly popular sex kinks that are on the rise…

Tracey Cox has revealed the very surprising sex kinks that are on the rise with the foot fetish an old but growing trend

Women watching gay porn

According to Pornhub, one of the biggest porn websites in the world, gay male porn is the second most popular category viewed by women visiting the site.

It was findings like this that prompted researchers to study 275 women who watch gay porn (age 18-74 and a mix of straight and bisexual) to investigate why it appeals.

The obvious answer: the men in gay porn are usually a lot more attractive than men in heterosexual porn where the focus is on the woman being sexy.

The second most common reason was that the men didn't seem to be acting: they really did look like they were having sex and enjoying it. Because the sex was more authentic, it was more of a turn-on.

Finally, if you're watching two (or more) men at it with no women around, there's no reason to compare yourself to the females on screen or watch women be exploited or objectified.

I know lots of straight women who watch lesbian or gay male porn and absolutely no bog-standard heterosexual porn – often for those reasons.

'I don't want to watch what I do in bed, that's boring,' one female friend said.

'Watching two men is hot because I get to look at two great bodies at once. Plus, unlike women, it's much more taboo for men to experiment with other men which makes it seem even naughtier.'

Men wanting their wife to have sex with someone else

'Cuckolding' is an increasingly common fantasy for straight men and the fastest growing fetish in the western world.

Tracey says that more and more men are getting excited by the idea of their wives sleeping with someone else - known as cuckolding

But why would watching your partner have sex with someone else turn you on?

There's a voyeuristic element and infidelity is, again, 'forbidden' so appealing on a primal level.

Other theories include enjoying thinking your partner is irresistible because it boosts your ego; alternatively, if you're seriously worried your wife is going to cheat, flipping it on its head to become something you want to happen is one way of dealing with the jealousy.

The most common form of cuckolding is men watching their wives or long-term partners have sex with other men.

This might mean sending them out for an evening and coming back with video footage they then watch together or him, literally, looking over their shoulder as it happens.

For one couple I interviewed - who are in their mid 30s and have been together eight years - cuckolding was a natural progression from voyeurism.

'It started out as a silly trip to a 'dogging' site, just for a nose, followed by lots of pillow talk about what we should try,' said John*.

'Then we joined a site for swingers and located a guy to meet. Originally, it was going to be the three of us but sitting and watching proved to be an incredible thrill. I didn't want to join in, just watch it unfold.'

John says the appeal is that it's still taboo and he quite likes the humiliation of watching his wife have a better orgasm with another man than she does with him.

(Clearly, this is not for the sexually insecure!)

His wife says, for her, the kick is being watched and having an audience.

Both said they felt a bit 'weird' to start and John hasn't told any of his friends, though, interestingly, his wife has told a few close friends.

Her best friend is intrigued, others either laugh or struggle to understand.

They've been happily at it for around five years now – with no plans to stop.

The idea of cuckolding is less abhorrent to the general public than you think.

One YouGov survey in the US asked 1000 people how they would react if their partner wanted to have sex with someone else.

Tracey says that more women are choosing to watch gay porn with Pornhub revealing that it is the second most popular category for women

Predictably, the majority of both men and women said 'no way' but 42 per cent of men and 24 per cent of women didn't completely rule out the idea.

Other research suggests men and the under 30s are much more open to sexually sharing their partners than previous generations.

Having a romantic or sexual relationship with an object instead of a person

It may well be a reflection on a society where human-to-human contact is on a sharp decrease because of technology that object sexuality also appears to be on the rise.

This is when people develop deep emotional, sexual or romantic attachments to inanimate objects – sometimes, even marrying them.

One woman, Erika La Tour Eiffel, believes she is 'married' to the Eiffel Tower; another, Amanda Liberty, 'married' the Statue of Liberty. Others are sexually attracted to and in love with dolls, cars, trees, fences, amusement park rides - and the list goes on.

The rise in the use of 'real dolls' and sex robots has edged this rare category of sexuality a little closer to mainstream with some arguing there is no difference between falling in love with a doll made for sexual pleasure and one that isn't.

It's still an inanimate object.

Objectum Sexuality is also on the rise according to Tracey, referring to those who fall in love with objects. Pictured: Amanda Liberty who is 'married' to the Statue of Liberty

Given the former fetishes, this seems positively tame and devotees argue it isn't, in fact, a fetish.

The website objectum-sexuality.org specifically states: 'While a fetishist must have their desired object present as a catalyst to achieve sexual gratification, the love for our object is not based on a habitual psychosexual response. The object captivates us on many more levels than just sexual arousal.'

In other words, because there's love as well as sex, it's not officially a fetish.

Object sexuality tends to attract shy, lonely people who have difficulty establishing normal relationships or who prefer one-sided relationships because they can't tolerate criticism.

A rough childhood is also a common characteristic: an object can't hurt your feelings, while a real-life person can.

Foot fetish parties

It was popular in your grandmother's day and foot fetishism is still one of the most common forms of sexual fetishism with feet the most sought after non-sexual body part.

Shoes, socks, foot accessories, the smell of feet or the shape of them – foot worship can take many forms.

Now all can be indulged at a foot fetish party: events where men can suck on the toes of foot models, be trodden on or be 'used as a rug'.

Competition to be a foot model is strong: it's easy money and there's no actual sex involved. There's also a spike in the amount of men hiring dominatrix for private sessions.

Nearly every female celebrity has a community devoted to either her feet or her shoes and Elvis Presley, Andy Warhol, Casanova and serial killer Ted Bundy were all alleged foot fetishists.

What's the attraction?

Good old Sigmund Freud thought that people sexualised feet because they looked like penises. (Of course he did.)

Other psychologists maintain it has to do with early childhood imprinting and conditioning experiences: a sexy neighbour who didn't wear shoes, for instance, flirting with a young boy as he becomes sexualised.

That's all it takes for feet and arousal to become linked.

Another theory is that foot worship is appealing to men in particular because it doesn't demand perfect sexual performance or prior experience: far less scary than actually sleeping with a woman.

Liking feet and high heels and needing foot action to become aroused are too different things, obviously.

You'd be hard-pressed to find a guy in Britain who didn't get aroused by his wife or girlfriend leaving her high-heels on during sex and models, celebrities and just about every female on social media constantly post sexy images wearing high shoes or boots.

Tracey has an all-new website and brand new products added to her range. Check it out at traceycox.com

*Names have been changed