You know when your partner thought you “never swore”, based on how you spoke to acquaintances, only to find out a year down the track that you’re actually as foul-mouthed as a sailor? Yeah. Turns out there are many different things that start to happen down the line of a long-term relationship, and many more things that you discover about one another.

Not all great, but all bond you as one united front ready to conquer life. Or something. The Independent has summarised a few of these brilliant changes, but our team have added a few of their own.

You and your partner develop your own private language. 

In jokes can be tragic, but they develop very quickly between couples. According to a study from Robert Hooper, a University of Texas professor of communication, secret communication accomplishes two things: It helps deepen your bond — romantic or platonic — and establishes a unique, shared identity. Private language can include everything from inside jokes to nicknames, writes Ohio State University psychologist Carol Bruess in a study of romantic couples. Bruess' research suggests a link between how often partners use these private words and how satisfied they are with their relationship. Bruess found that the more often couples used secret words and phrases, the happier they tended to say they were.

You stop self censoring.

Ah, back to the swearing. You might swear only around your partner because you've become some comfortable around them you're capable of letting out your true self. University of California at Berkeley psychologist Daniel Kahneman, for example, tells Shenk: "Like most people, I am somewhat cautious about exposing tentative thoughts to others." But after he'd spent a few years working with his research partner, cognitive psychologist Amos Tversky, "this caution was completely absent."

You start to look alike.

In his influential 1987 study, psychologist Robert Zajonc found that there's a very obvious reason that married couples start to look alike. They use the same muscles so often that, over time, they start to mirror each other.

You start to sound alike.

Part of that is a result of a phenomenon that psychologists call "emotional contagion." Basically, when two people spend enough time together, they begin to match each other's speech patterns. We mimic everything from the other person's accent to the amount and length of pauses he or she puts between words and sentences. There's some evidence to suggest that these changing speech patterns can even serve as one indicator of how long a couple might stay together.

You act like you're one person to other people.

You no longer have individual opinions on things you do together. " ?

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We

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? loved that movie. ?

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We

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? go to this brunch place." You're driving people mad, but because you do certain things together, you're happy to say they were with you.

You don't care about bodily functions anymore.

The doors are left open every time. You're happy to let one rip right at the kitchen table. Basically, judgement goes right out the door. A long with your dignity, probably.