You don’t need scientific research to confirm you and your best friend practically share a brain—the evidence is in your relationship. From the way you banter back and forth Gilmore Girls-style without missing a beat (or catching a breath) to your shared obsession over Ariana Grande and Pete Davidson’s whirlwind relationship, there’s no one else you’d rather have by your side on your wedding day. (Besides your future spouse, of course!)
But science actually does offer some evidence that the similarities you share with your BFF go way beyond your taste in celebrity crushes. In a study published in Nature Communications earlier this year by researchers at Dartmouth College, close friends were found to have similar patterns of brain activity while viewing video clips.
First, the study’s authors mapped the relationships between 279 graduate students at an unnamed college by having them complete an online survey. A “friend” was considered anyone they spent a lot of time with when they didn’t have to, such as going out for drinks or watching movies together. People who mutually named one another were considered to have the strongest ties.
From there, 42 of the students agreed to have their brains scanned in a functional MRI while they watched 14 different video clips featuring an array of subject matter, including a gay wedding celebration, a documentary about caring for baby sloths and footage from “America’s Funniest Home Videos.” As the study’s authors write, measuring brain activity this way—they described it as akin to watching TV while someone else surfed channels—was “an unobtrusive window into individuals’ unconstrained thought processes as they unfold.”
What they found when they compared the participants’ brain scans wasn’t surprising—at least, not if you and your bestie are the kind of dynamic duo who complete each other’s sentences and binge-watch the same shows on Netflix. Researchers were able to pair the 42 students up in 861 different ways, which included friend pairs and non-friend pairs; the scans of friend pairs showed their brain responses to be more alike than the scans of non-friend pairs. Those results were consistent even when the researchers factored in variables such as age, gender, nationality, and ethnicity.
As the study’s authors write, their results suggest that friends are exceptionally similar to one another in terms of how they perceive, interpret, and react to the world around them. They also show that “it is possible to predict whether or not two individuals are friends…based only on the similarity of temporal patterns in their neural responses during free viewing of complex, real-world scenes.”
They also note, however, that they don’t know if “we become friends with people who respond to the environment similarly, or [if] we come to respond to the world similarly to our friends.”
While that question remains to be answered, the study appears to offer more credence to the whole idea of having “chemistry” with someone. As Thalia Wheatley, an associate professor of psychological and brain sciences at Dartmouth and one of the study’s authors, told Science Daily: “We are a social species and live our lives connected to everybody else.”
See more: 7 Ways to Keep Your Friends Close, From Your Engagement to Your Wedding—and Beyond
Of course, the best connections are with people who understand why we have a Google alert set up for Ariana and Pete news. Natch.