At one point in a person’s life, there is an individual who someone immediately clicks with. Whether the activity is an extracurricular club or English class, you just seem to… click.

Even if the two people have different personalities, different ages, or different cultures, conversations just keep flowing like water with no awkward pauses. The topic could be something the people like or totally hate. Many people have described that “clicking” with someone as an unforgettable moment. It’s like a mirror. 

“Clicking” may seem like a miraculous magic trick, but in reality it comes down to one thing: science. If clicking with a person may seem like “being on the same instructions”, there’s a reason for that. According to Greater Good, “In what’s called ‘interpersonal synchronization,’ people click in an unspoken meeting of the minds,” such as meeting at a coffee house or laughing at the same comedian. This synchronization happens when a certain word or phrase causes both individuals to create a face towards each other, then it’s the body positions and speaking patterns that make two people realize that they just “clicked”.

A 2018 study conducted by neuroscientist Pavel Goldstein of the University of Colorado Boulder along with other researchers studied 22 straight couples, ages 23 to 32. Goldstein put a mild burn on the female partners and studied the reactions of the males. While the male participants comforted their partner, the researchers measured each partner’s brain waves.

Goldstein found that being in each other’s presence simply aligned their brain waves to be alike, mostly alpha–mu band wavelengths, according to Greater Good. Alpha–mu band wavelengths are primarily focused on attention. The couples became synchronised, mirroring each other based on what they’re focusing on. Complete zen was achieved the moment that the couples held hands, achieving synchronization, or as scientists like to call it, “brain-to-brain coupling.” 

The idea of being friends with someone a person likes is called neural homophily, Greater Good states. Responding the same way with a roommate or work partner describes that someone responds to the world in the same way. That’s why when friends watch the same video or experience the same thing, their brains react almost the same. They laugh at the same parts, get bored at the same time, and focus on the same details. 

Homophily also depicts that phrase “birds of a feather flock together” because people who share the same ethnicity, beliefs, or culture will be more likely to befriend each other. Even after accounting age, gender, education, and culture, people who become friends still show more similar brain responses than others.

When two people connect, their attention, timing, and emotional responses line up. That’s why conversation feels easy and someone would react the same way at the same time.