What happens to couples who live together for a long time.

Living with a partner for a long time changes a person's psychology, their perception of reality and the way they look at the world around them. Moreover, it affects not only their views and character, but also the little things.
The author of the book "The Power of Two" Joshua Wolfe Schenk believes that these little things have a significant impact on the thought process of a person and make it seem joint, united. This unity of thoughts and feelings allows couples to find unexpected and quite creative solutions to problems that partners would hardly find alone.
Psychologists have identified five things that people living together come to sooner or later.
1. 🌈 Secret language
When you and your partner develop your own secret language, you can say that you start thinking together. What a secret language is is easiest to explain using the example of notes or letters from partners, the text of which does not mean anything in itself and at the same time has a certain meaning that you cannot explain.
This secret language is one of the first signs that you're starting to act in sync, writes Schenk.
According to research by University of Texas professor Robert Hopper, secret communication achieves two goals: first, it strengthens your connection, whether romantic or platonic, and second, it creates a unique, shared identity.
Secret languages come in many forms, ranging from inside jokes to nicknames, says Ohio State University psychologist Carol Bruiss. In her research on romantic couples, she suggests a clear correlation between how often partners use these secret words or phrases and their relationship satisfaction. Bruiss says the more often couples use secret words and phrases, the happier they feel.
2. 🌈 Stop self-censorship
Most of us talk to strangers, acquaintances, and even close friends in a completely different way than we talk to our partners in private.
When we are around other people, most of us control ourselves. This means that we try to please our interlocutors or people around us by adjusting our behavior to their assessment.
When we are alone with our partner, we forget about this behavior algorithm and say what we think. In other words, we stop constantly controlling ourselves and checking before we say something. At such moments, we are more open and frank.
Many of the couples Shank interviewed for his book had relationships like this. University of California, Berkeley psychologist Daniel Kahneman, for example, explained to the author: “Like most people, I’m cautious about sharing my thoughts with other people.”
However, after several years of living or working together, such caution disappears completely.
3. 🌈 Using one language
Partners who have been together for many years not only use a secret language, but also begin to speak very similarly to each other. They use the same words, phrases, and syntactic forms.
Part of this imitation is due to what psychologists call “emotional contagion.” In simple terms, when people spend enough time together, they start to talk alike. We imitate everything: the way he or she speaks, the frequency and length of pauses between words and phrases he or she makes, and much more.
There is some evidence to suggest that such imitations can be used to fairly accurately predict how long a couple will remain together.
In 2010, scientists studied the language used by couples and also analyzed the text messages that partners exchanged. It turned out that partners whose borrowings and imitations extended to text messages were, in most cases, still dating or living together three months later.
4. 🌈 Similarity in appearance
In a very important and influential study conducted in 1987, its author, psychologist Robert Zajonc, discovered that there is a very simple explanation for the well-known fact that over time, spouses begin to resemble each other in appearance. It is that they use the same muscles so often that over time they gradually become similar to each other.
This coordination of movements, according to Schenk, is not random. It is a reflection of what psychologists call a “joint coordination structure.” It includes how we synchronize our gaze, our body movements, and everything else.
5. 🌈 Secret jokes that no one except your partners find funny
According to research, couples who have been together for a long time begin to copy each other's body language. This makes them look even more similar to each other because they are drawing on information and knowledge that only the two of them know. This secret information then becomes part of your gestures, what you say to each other, and how you say it.