Here are six of the benefits.
1. You forge better friendships
Revealing private details about yourself signals you're willing to take the risk of trusting the other person with personal, and perhaps even shameful, information about yourself.
Finding that you have common beliefs, feelings, or even quirks goes a long way toward starting to like someone in the early stages of friendship. It's not the topic that builds connection, it's vulnerability, adds Leslie John, a Harvard professor and behavioural scientist. But confiding in our closest friends shouldn't feel like a chore. "If it does, maybe this person should not be in your inner sanctum. Maybe they're a 'medium' friend, and medium friends are wonderful, but they don't require the same nurturing."
2. It can save marriages
While most long-term couples invest in getting to know each other early on, many eventually abandon that active discovery – despite the fact that we're always changing. Daily routines take over and space for meaningful conversation quietly disappears.
Also, worryingly, we come to believe we know everything about our partner – and stop working to get to know them better. And if they do the same, asking fewer questions, we stop sharing about ourselves as well.
When your partner inevitably fails to meet your (unspoken) needs, it can lead to passive-aggressive behaviour and misinterpretation. "Sometimes, a secure relationship will end, not because someone did something horrible, but because of something quieter. You wake up in 20 years with your spouse and feel like you don't know them or they don't know you."
3. It helps us find a mate
In a study called "What Hiding Reveals", John's team gave people an awkward but revealing choice: imagine you're going to date one of two people, but you can ask each a set of questions. One candidate answers frankly (admitting painful facts); the other refuses to answer.
Which would you choose? Time and again, people picked the revealer. Not because we like bad news, but because we prefer openness to conspicuous withholding.
4. It screens out the right people
John compares the role of self-disclosure in friendships to building a fire. The spark that starts the fire can be some point of common interest you've noticed. But you still need one more thing for a fire to catch: oxygen. And in the world of friendship, that oxygen is attention and reciprocity.
A lack of reciprocation helps you avoid wasting your time and frees you up to look for a better match. "These things often hurt in the moment, but the big picture is it helps you filter faster."
5. It calms us
Brain scans have shown that articulating our feelings changes the brain. It reduces activity in the amygdala, the mind's emotional alarm system, and boosts activity in the brain's regulation centre linked to reasoning and control, according to a study in Psychological Science. In other words, putting feelings into words literally calms the mind. Expanding your emotional vocabulary adds shades and detail, letting you identify what you're feeling.
6. It's easy to start small
Don't go "full throttle overshare", says John. "The answer isn't always to reveal, but to be more thoughtful. And timing is everything – don't bombard your partner when they've just come through the door after work. But try to share a little bit more than you ordinarily would.
"If your counterpart doesn't take the bait, ask a question. We don't ask enough questions because we worry we're prying – but studies have shown that's in our heads. In research from Harvard Business School people who asked lots of follow-up questions were better liked. Why? Because follow-up questions signal we're listening, we care, and we want to hear more.