The Beach Boys wrote a whole song about the experience, and we have plenty of informal phrases that try to capture the feeling. "We just clicked," you might tell your friend of a great date. Or, "It felt like we were totally on the same wavelength," you could say after a particularly productive meeting.

Everyday language is full of expressions describing how two people can feel "tuned into" each other. But that's just a manner of speaking, a metaphor for music, poetry, and gushy romantics, right? As a level-headed and scientifically minded adult, you'd assume there isn't any way human brains could literally "tune into" each other.

Well, if so, science has a big surprise in store for you. You might call it "good vibrations," "being on the same wavelength," or even "a mind meld," but neuroscience calls it "brain coupling," and apparently it is a real, measurable, research-validated phenomenon.

How'd your date go? You could consult a brain scan.

Some scientists take surveys or run through checklists. Others examine samples or conduct tests. Princeton University neuroscientist Uri Hasson does something a little different -- he brings real-life into the lab, peering into people's brains with fMRI machines while they engage in complex, everyday activities like watching movies or listening to other people tell stories about their disastrous prom nights.

As Princeton News explained (hat tip to Soul Cafe of the pointer), this work has yielded fascinating insights into how the brain integrates information over time, but it has also uncovered something incredible about what happens when two people profoundly connect. Apparently, when we really relate to another person on a deep level the activity in our brains literally mirrors theirs.

That means that when Hasson and his team looked at brain scans of a person telling the story of a bad prom date and a person listening to it, the images were surprisingly similar despite the fact that one person was speaking and the other listening, two obviously distinct brain functions. And even more intriguing, the stronger the connection between the two people as gauged by a post-scan interview -- the more they "clicked," in other words -- the more their their brain scans mirrored each other.

"The stronger the coupling between the speaker and the listener's brain responses, the better the understanding," Hasson told Princeton News of his findings. "Sometimes when you speak with someone, you get the feeling that you cannot get through to them, and other times you know that you click. When you really understand each other, your brains become more similar in responses over time."

As Wired pointed out in its writeup of Hasson's research a few years back, there's still a lot we don't know about the phenomenon, including exactly how it works and how face-to-face interactions compare to phone calls or video conferences, for example, but the research so far is a cool confirmation of centuries of gut instinct -- you really get can "be on the same wavelength" as someone, science now knows.

Want to learn more about Hasson's work? Check out his TED talk below: