There’s a famous moment in When Harry Met Sally, when Billy Crystal’s character explains the age old riddle of male and female friendships.
“Men and women can never be friends,” he tells Meg Ryan, “because the sex part always gets in the way.”
And he’s right, sort of.
Spoiler alert, Harry meets Sally, Harry befriends Sally and the two fall madly in love.
It’s a narrative we’ve seen played out time and time again, spanning the Dukes of Shakespeare to the Hugh Grants of Richard Curtis.
So why is it that the friends-to-lovers paradigm bears such perennial relevance? And does it work IRL?
It’s been scientifically proven that the longer you’ve known somebody, the more attractive you’ll find them, researchers at the University of Texas found.
They asked students to rate each other at the beginning of the semester, and again at the end.
Naturally, these rates increased hugely over time, explaining how – in numerical terms - a "six" can easily become a "nine" in a matter of weeks.
In other words, when it comes to long-term attraction, aesthetics has very little to do with it.
A further study carried out by the same professors asked 167 couples how long they’d known one another before becoming romantically involved and whether they were friends first.
They found that, on average, the couples had known each other four months before dating. Plus, 40 per cent of them were friends beforehand.
You never feel more comfortable than when you’re with your friends, right? They’re the ones you laugh with, the ones you cry with and they often know you better than your own family.
So it makes sense that some of us are inclined to fraternise with friendship when both parties are of the same sexual orientation.
In fact, some of the best relationships often start out as friendships. Think of Sheryl Sandberg, who was friends with her late husband Dave for six years before they became romantically involved. Then there’s Mila Kunis and Ashton Kutcher, who met on the set of That 70s Show and started dating 14 years later.
So, why is it that platonic familiarity so frequently leads to romance?
“The purity of an initial friendship allows you to see someone’s character before it’s blurred by sexual intentions and wanting to ‘get’ something physical out of it,” dating expert Matthew Hussey told The Independent.
Certainly, no relationship can stand the test of time without the foundations of a strong friendship, agrees love and relationships author Daniel Jones.
“The most enduring romantic relationships - long-term marriages and partnerships - end up being much more about compatibility and companionship than sexuality,” he told us.
The question remains, how do you know when it’s time to take things up a notch and, more importantly, how can you tell if your feelings are reciprocated?
“Think about how much time you spend together on your own,” suggests dating expert James Preece. “Do they get jealous when you mention other people or go on dates? You can test them a little to see how they react when you talk about what you are up to when you aren't with them. They might not say much but you'll be able to read a lot into their body language and their willingness to discuss the topic.”
Jones believes that in order for a friendship to turn into something more, there has to be a looming, momentous change in one of your lives i.e. they’re about to move abroad.
“That's when friends often end up in bed together,” he told The Independent, “when the friendship has a built-in deadline and they feel they have less to lose.”
When it comes to the big admission of how you feel, it’s best to test the waters rather than go all in with an undying Notebook-style confession, according to Hussey.
“Instead of telling someone 'I like you, what do you think?', which forces theme into a position of having to give you an answer, start flirting with them a little and see what happens.”
Jones, however, advises being more straightforward.
“I think being honest and direct can save you a lot of grief and agonising,” he explains. “I see a lot of stories where people never admit to their feelings and just keep hoping the other person will figure out how they feel, but that can turn into a kind of prolonged torture. Just say it. Don't build it up with all kinds of weighty baggage that backs the other person into a corner.”
That’s not to say that coming clean is easy, when friends begin dating each other, there’s naturally a lot more at stake.
"I think going from friends to more than that is often scary because if it doesn't go well, it's pretty much impossible to go back to your friendship the way it was before,” says 24-year-old Laura from London.
“I have a friend who is possibly more than a friend after we crossed the line, but he's also definitely not my boyfriend or anything close to that, so we have a really confusing relationship where neither of us actually knows how the other feels."
As for the whole friends with benefits conundrum?
Unless it’s a short-term, contractual agreement (“thou shalt not acquire romantic feelings”), it’s a turn-of-phrase that’s best left to rom coms, advised the dating experts.
“Sooner or later one person will want more, either from that relationship or from some other relationship”, says Jones.
Preece agrees, “Sex without love is still a hugely intimate thing, which requires lots of trust. The only time friends with benefits can succeed is if you aren't really that bothered about each other - so you won't have been that good friends at all,” he said.
So bite the bullet, take the leap, embrace failure and any other romantic clichés you can think of.
Life is short: if you love them, let them know.
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