science of us

When Your Sense of Self Includes Your Best Friend

Photo: Terence Le Goubin/Getty Images

In so many ways, your friends shape how you see the world. You meet and befriend new people through them. You hold vicarious grudges against people you’d otherwise have no reason to hate. You share ideas that expand your taste or work their way into your daily routine. You filter new things through the lens of your shared history, referencing past experiences together to make sense of whatever’s in front of you. You take their perspective and their advice and use it to figure out how you feel about your job, your family, your life, yourself.

And a study recently published in the Journal of Social and Personal Relationships took things a step further: Your friends, the researchers found, literally make you see the world differently, or at least your own reflection. When asked to indicate whether a face on a screen belonged to them or to someone else, participants took longer to distinguish between their own image and a friend’s than they did between their face and that of a familiar celebrity. In other words, the act of recognizing a friend as an entirely separate person seems to take a little extra mental energy — it’s a process, rather than an intuitive reaction, to look at them and think, Oh yeah, this is someone else.

The study was small, but it’s also a pretty lovely reminder that a friendship — a true, close, fulfilling one — is less a connection between two individuals than it is the blurring of the boundaries between two selves. One 2013 study found that our brains react the same way to a threat against a friend as they do to perceived personal danger; another, from 2010, found that the same is true when it comes to making mistakes. Past research has also found that good friends often act as a sort of Google for each other’s life histories, a phenomenon called “transactive memory”: You outsource pieces of knowledge to another person rather than storing it in your own mind, knowing you can always call on them to get it back. You’ve mapped out their head well enough to know what it holds.

People like to talk about close relationships completing them, or making them feel whole. It might be more accurate, though, to say that they make you more. Psychologists call this “self-expansion” — the idea that as a relationship deepens, your sense of self grows, ultimately coming to encompass part of the other person within it. You’re no longer neatly contained in your individual vessel; instead, you’re spilling over the edges of yourself, reaching to wrap up your friends into the core of who you are, right down to your most basic of senses.

When Your Sense of Self Includes Your Best Friend