It’s no secret that humans who watch movies, play video games or root for the home team together are usually more sociable afterwards—we discuss which characters we like, relive the play-by-play or commiserate over a loss with one another. But it turns out bonding over a shared experience isn’t just a human thing. A new study by researchers from Duke University in the journal Proceedings of the Royal Society B shows that chimpanzees and bonobos are more social after watching a movie together as well.
For the study, which was conducted at Ngamba Island Chimpanzee Sanctuary in Uganda, Sean Coughlan at the BBC reports researchers worked with 21 chimps, placing pairs of the apes in separate but adjoining caged rooms in front of a computer monitor and playing 1-minute videos of baby chimps frolicking. The team used eye trackers to make sure the animals were actually watching the video and gave them some movie refreshments, in this case fruit juice, to keep them planted in front of the screens. In some cases, they also had chimps watch videos next to each other on separate screens, but with a plastic barrier in between to isolate them from one another.
After the credits rolled, the team opened the doors between the rooms then observed the behavior of the apes. The researchers assessed how long it took the chimps to approach their cinephile partners, how close they got and how long they then hung out together, all indicators of sociability. It turns out, chimps that watched the videos with a partner hung out with their companion about seven seconds longer than chimps that watched the movies in isolation. Katie Camero at Science reports that only apes that watched the films together groomed one another. The team also conducted a similar study at the Wolfgang Kohler Primate Research Center in the Leipzig Zoo, pairing 19 chimps and 7 bonobos with human companions. In that case, the apes approached their movie buddies 12 seconds faster than pairs that watched the movies solo.
The finding overturns some of what we know about social bonding. “Humans have an enormous variety of social bonding activities that we don’t see in other species because they’re somewhat cultural—for example listening to music or watching movies,” first author Wouter Wolf tells Anna Ploszajski at The Guardian. “We thought that this kind of connecting through shared experiences was uniquely human.”
This study shows that's not the case, and the authors conclude that this sense of bonding is “present in both humans and great apes and thus has deeper evolutionary roots than previously suspected.”
Primatologist Frans de Waal, not associated with the study, says it makes sense that the shared experience has an effect on the apes. “The effect of synchronization on behavior … is a very old, innate empathy mechanism,” he tells Ploszajski. “Whether [the great apes] understand the shared experience, well, that’s a different thing … I don’t think it’s easily demonstrated.”
So what’s the evolutionary advantage of feeling more bonded after watching Toy Story 4 with your friends? “Experiencing and sharing something between two people creates common ground. If you go to the movies together, you're sitting side by side, it’s a really social phenomenon,” Wolf tells Coughlan at the BBC. “You get really annoyed if the other person starts to play with their phone. It’s annoying because you’re no longer watching together.”
He also says one of the reasons social media is so popular is that it plays on this innate human desire for shared experience. But it’s not clear, and probably unlikely, that watching the same video clip on Facebook as 75 of your digital friends creates the same type of social bond as spilling popcorn on your friend's lap when a demon onscreen leaps out of a closet.
Editor's Note, July 22, 2019: A previous version of this article included a photo of chimpanzees dressed as humans. Thank you to the many scientists on Twitter who alerted us to the problematic nature of such photographs.