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Relationships are complex. Confusing. Logic-defying, in some cases.

Of course, this isn’t helped by the constant barrage of cliches and myths thrown around when talking about dating and love.

So which of these beliefs are pure Hollywood fiction, and which of them have actual scientific backing? From the majestic to the more mundane, here are the four relationship myths you need to stop believing in. (Sorry in advance).

1. Opposites attract.

It’s a cliche we’ve probably all told ourselves during bad dates and conversations about unusual couples, but it turns out the old adage “opposites attract” might actually not be the case. In fact, new research suggests it’s the direct, erm, opposite.

A recent study published in the journal of Personality and Social Psychology found most people are attracted to people similar to themselves.

The researchers looked at friends, romantic couples and casual acquaintances interacting in public, and questioned them about their personality traits, attitudes, values and prejudices.

Watch: Anonymous confessions of when people knew their relationship was over. (Post continues after video.)

The similarity in these areas of new connections were then compared to the data gathered from couples and friends who had known each other a long time and were found to be about equal.

While this is no surprise when it comes to friends, who are usually brought together by a common passion, results showed that couples who were in intimate relationships has just as similar values and opinions as newbie connections. Interesting.

Given these ingrained values are unlikely to change over time and with important decision to be made together, this is probably a good thing.

2. “Men and women can just be friends.”

When Harry Met Sally is more accurate than you think. A divisive subject, some believe being best friends with the opposite gender is absolutely possible while others argue “the sex part” always gets in the way. So which is right?

According to a 2015 study published in the journal of Evolutionary Psychology, the problem with platonic friendships between sexes comes down to a biological misunderstanding.

Researchers at the Norwegian University of Science and Technology quizzed more than 300 students between the ages of 18 and 30 about their friendships, sexual attractions and personal experiences with confusing relationships with friends of the opposite sex.

Results showed women generally interpreted sexual interest from men as gestures of friendliness, while men read signs of friendliness as sexual interest. Awks.

So while a platonic friendship isn't impossible, it's highly likely that at some point misread unspoken or spoken feelings will occur from at least one party. (Post continues after gallery.)

3. Staying away from your sick partner means you'll be OK.

Not the stuff of Hollywood movie plots but significant all the same, this is a common myth most couples have probably encountered.

Imagine: your significant other has woken up with a horrible cough/cold/runny nose. Not wanting to also get ill yourself, you decide to keep your distance.

Sure, you'll bring them a bowl of soup and give a chaste kiss on the forehead but avoiding unneccesary close contact will mean you're totally safe, right?

Wrong. A recent study published in the Journal of Nature Immunology found it's not just your late-night Netfix-and-Ice cream habits that match your partner's. If you're married, your immune system is identical too.

Scientists from Belgium's University of Leuven took blood samples from 670 participants including 70 married couples and followed them over six months to see changes in their immune systems. They found that the couples had very similar immune systems, likely due to the fact that they have similar lifestyle habits, doing and visiting the same places.

The takeaway? You're more likely to get sick from each other through breathing in the same pollutants, mould and dust. Ah, love.

4. There's no such thing as "love at first sight".

Apologies, cynics - according to science you actually can fall in love at first sight.

A 2010 paper published by Syracuse University professor Dr. Stephanie Ortigue claimed that you can experience feelings of someone as quickly as 0.2 seconds after first laying eyes on them.

This feeling is apparently created by 12 areas of your brain working in tandem to release chemicals like dopamine, oxytocin and vasopressine that give a euphoric feeling that happens so quickly it feels like love at first sight.

An older study also claimed this feeling is a basic response we get as mammals to speed up the mating process. Sneaky - but also handy to justify that the man you saw on the bus one time is definitely your soulmate.

What relationship myths would you like to get to the bottom of?