How chimpanzees bond over a movie together
Chimpanzees watching a video together get the same sense of bonding and closeness that humans can feel from watching a movie or TV show together, say US university researchers.
Pairs of chimps were monitored as they watched videos - and psychologists found an increased sense of closeness between them in a way previously thought to be unique to humans.
Researchers say it shows the "deep evolutionary roots" of the heightened emotional impact of watching something with someone else.
It also raises questions about what is lost when there are fewer shared experiences - such as if families stop watching television together and are separately plugged into social media or using their own mobile phones.
Chimps' favourite movie?
"Experiences are richer watching together," says report co-author Wouter Wolf, from the department of psychology and neuroscience at Duke University in the US.
The study, being published by the Royal Society, put chimpanzees and bonobos in front of a screen showing a video.
Eye-trackers were used to make sure the apes were watching the film and fruit drinks were used to encourage them to stay relatively still and in the same place.
Mr Wolf says the choice of video was decided by previous research revealing what apes most liked to watch - which was film of other apes.
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Using data from 45 apes, mostly chimpanzees and some bonobos, the researchers studied changes in behaviour after they had watched a video of a family of chimps playing with a young chimp.
Watching the film together made them much more likely to bond afterwards - such as staying close together, touching or interacting with each other.
The psychologist says the findings have challenged the idea that there was something "uniquely human" about such shared social experiences from watching an activity.
The research concluded that this sense of feeling closer from watching something with someone is "present in both humans and great apes and thus has deeper evolutionary roots than previously suspected".
The psychologist says it might say something about how people in an audience or watching a sports event can feel a sense of bonding with people they otherwise do not know.
Heard it on the ape vine
Mr Wolf says there is something very distinctive about the enjoyment of shared watching - with a sense of irritation if this is interrupted.
"Experiencing and sharing something between two people creates common ground," he says.
"If you go to the movies together, you're sitting side by side, it's a really social phenomenon."
But he says "you get really annoyed if the other person starts to play with their phone. It's annoying because you're no longer watching together".
The psychologist says part of the attraction of social media is that it taps into the human appetite for sharing moments - creating a sense of seeing something together.
Humans are "addicted to sharing", he says.
"But do you get the deeper experience from social media? The quality of such a social network online is different," he says.