This video of an animal having its head stroked may have you scratching your own.
Is it a bird or a bunny?
It's a burning question that has taken its place in the pantheon of internet-dividing debates, like the color of #TheDress in 2015 or whether a voice was saying Yanny or Laurel in a viral audio clip last year.
Daniel Quintana, a biological psychiatry researcher at the University of Oslo in Norway, started the debate with a tweet that showed an animal being rubbed on the head.
"Rabbits love getting stroked on their nose,'' he wrote.
But is it a rabbit? Or is that a bird having the back of its head stroked?
And the correct answer is ... a bird!
The video was originally to Instagram by Paige Davis, a curator of bird training at World Bird Sanctuary in Valley Park, Missouri.
Davis told NBC News the bird was a white-necked raven named Mischief.
"He is an educational ambassador for his species at World Bird Sanctuary, and he teaches people all about ravens, conservation, and ways we can help wildlife every day," Davis said.
Quintana told CNET, "I thought it was fairly clear that the video was of a bird."
"As you can see the translucent nictitating membrane sweep across the eye horizontally (rabbits don't have membranes like this) and the positioning of the 'ears' are a little strange," he said.
Of course! Who didn't see the *checks notes* nictitating membrane across the eye? It's clear as day!
Oh wait, somebody actually did.
Corvids are a bird family that includes ravens and crows, which some other eagle-eyed folks guessed in the comments.
Some pointed out the video was a real-life version of a popular drawing of a duck-rabbit illusion from the 1800s that went viral in 2016.
The odd position of the bunny "ears" — actually the bird's beak — appeared to be the real giveaway.
"When you only see the beak in your peripheral vision, it really seems like they're ears. Without this misleading cue, I thought most people would have seen a bird,'' Quintana said.
Now that the mystery is solved, the bird-bunny video can join the proud history of optical illusions involving hugs, tile floors and more that made everyone on the internet take a few moments together to wonder what we're staring at.