When you go to a movie or a concert with your friend, oftentimes it seems that you shared a similar experience. Your brains, you say, are on the same wavelength. Now, neurological science gives that phrase some new backing. Using new portable headsets that monitor brain activity, researchers have found that the brainwaves of people who are engaged in the same class really do “sync up.”

Thanks to studies performed in laboratory settings, we had an inkling that this might be the case. A growing body of brain-scanning research is beginning to reveal how human brains display synchronicity—likely a key factor that makes many of our cooperative behaviors possible, from performance art to team sport.

“If you pay more attention, you're more in sync,” explains Suzanne Dikker, a cognitive neuroscientist at both New York University and Utrecht University in the Netherlands and a co-author on the new study. “Now we've gone out there and confirmed that this is true in a real world setting,” she says.

That remarkable feat was made possible thanks to portable electroencephalogram (EEG) headsets, which researchers used to monitor students' brain activity during an entire semester of biology classes at a New York high school. Each week, 12 high school seniors and their teacher attended class wearing the headsets, for a total of 11 classes overall. The more engaged those students were with their teacher and classmates, it turned out, the more their brainwave patterns were in sync with one another.

“The central hub seems to be attention,” says Dikker. “But whatever determines how attentive you are can stem from various sources from personality to state of mind. So the picture that seems to emerge is that it's not just that we pay attention to the world around us; it's also what our social personalities are, and who we're with.” The results were published this week in the journal Current Biology.

To bolster the brainwave data, Dikker and her colleagues had the students complete pre and post-class questionnaires on a number of factors she suspected might be linked to different brain activities. For instance: how focused they were on any given day, how much they enjoyed their teacher, how much they liked each individual student around them, and their satisfaction levels with different group activities they performed in class.

After analyzing a semester's worth of brain activity data and comparing it to the self-reported student data, a pattern emerged. During the times when students' brain waves were more in sync with one another, they were also more engaged with the class. Moreover, the more in sync they were, the more likely they were to have given the course and its teacher high marks.

Classroom experiences weren't the only factor that predicted how much students' brains were likely to sync up, however. Whether individuals considered themselves to be group people also seems to have played a role. Students categorized themselves on the group affinity scale by indicating whether they agreed with statements like “social groups really shape who we are as individuals.”

“I'm personally intrigued by the finding that personality effects synchrony with the people around you as well,” says Dikker. “If you're a person who likes to be in groups in general, then you're going to be more in sync with the people around you.” This was true even when such people weren't interacting with the group at all but were simply watching the teacher lecture or watching a video, she adds.

The researchers also found that a one-on-one interaction prior to class could alter the way people reacted during the group's shared experience. In the study, student pairs who reported feeling closer to one another also tended to experience more brain synchronicity during class—but only when they had spent time face-to-face just before the class began.

“How much they liked each other only seemed to matter if they had actually interacted with one another,” she says. “So your likelihood of keeping that person in your periphery, and kind of paying attention them, is higher if you've already interacted with each other before class.”

The new findings are part of a field of research that dates back about a decade and began with functional magnetic resonance imaging (fMRI) studies showing that people's brains respond similarly when watching a film. Princeton University neuroscientist Uri Hasson was involved in many of those studies, and has used fMRI studies to show that when someone tells a story, the brain responses of both the storyteller and listener become coupled. The more similar those brain responses become, he found, the better listeners understood the story.

The use of portable EEG systems to monitor natural teacher-student interactions in a real-world classroom, Hasson says, represents exciting potential for such work. This kind of data, he says, suggests that measuring how the brain activity of students and teachers sync up can be a useful gauge for how much students are comprehending overall in the classroom. Someday, it could help us develop more efficient teaching practices.

“Using knowledge gathered at the lab to develop real-life applications that can enhance the communication among people in the classroom is a great achievement,” Hasson said via email. He added that this work “is likely to lead to a true development of new tool kits to assess and improvement the ways we interact with students in class.”

It’s been known for some time that our brains tend to track the temporal structure of the world around us—say, the patterns and cadence of a speaker's voice—and change their patterns to match it, says Dikker. The point: to help us better analyze information. Even watching an engaging video together can help synchronize viewers' brains, says Lucas Parra, a brain researcher at the City College of New York.

Parra has used EEG technology in his lab to find that the level of engagement correlates with many different factors, from how much a person enjoys the video, to how much the person remembers its content, to how much the person perceives the passage of time. Similar studies have shown that shared video experiences create eye movement and pupil dilation synchronization as well, and these movements even seem to predict how much people enjoy what they watch.

“The main finding with EEG is that measuring inter-subject correlation, in people's brains, is a really good metric for how engaged people are with a stimulus, typically video,” Parra says. “So it's very natural to expect that you'd also see that in pairwise interaction in real life, which is something that they emphasize in this paper, that when two individuals are interacting somehow their brains are also in sync.”

He adds: "This might be the first study to look at that in real life."

The study's real world methods are, in fact, as intriguing as its results. As EEG technology becomes more portable and affordable, scientists will likely gain more insight into what our brains are up to while we're out living our lives. Headsets like the ones Dikker's high school students learned to use might help us understand the progression of neurological diseases. They could also help identify the environments in which each of our brains functions at its best—and that kind of performance-boosting road map would be welcomed by students and the rest of us alike.