A PHOTO of hikers sharing a whiskey has left people refusing to believe there are really four arms.
The head-scratching optical illusion was shared again online and viewers are baffled at the mystery of the extra bottle.
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The freaky snap shows Patrick DeIvernois, wearing the kilt and orange jacket, after a hike with pals.
They clink miniature bourbon bottles to celebrate finishing the 2,200-mile Appalachian Trail in the US.
At first glance there appear to be three outstretched arms, but look closer and there are four bottles.
The pic has not been digitally altered - and it's hurting people's heads.
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One social media user said: "I'm confused... why are there only 3 arms, yet 4 bottles?"
Another said: "My brain refuses to believe there are 4 people in this photo."
And another said: "Me looking at this photo asking myself if I'm blind or if there’s something more going on here."
If you are looking at the shape over Patrick's shoulder and wondering if that's the fourth person - sorry, that's just his backpack.
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Look again at the bottles and you might make out a blue woolly glove.
It's hard to see at first because it lines up almost perfectly with Patrick's kilt.
But where is the arm?
One anguished Twitter user said: "I zoomed in, stared at those blue fingers for a good 30 seconds trying to figure it out.
"Multiple solutions went through my head. Maybe it's a child underneath the cluster of hands.
"Maybe somebody is standing behind the guy in orange. Then I saw it."
The truth dawns when you finally see the camouflage-patterned sleeve running from the left of the picture.
One viewer joked: "This is literally the first time I've seen camouflage work."
Read More on The US Sun
Read More On The Sun
Last month a brilliant optical illusion showed a chess queen hidden by a "camouflage invisibility cloak".
And an optical illusion house is distracting drivers as it appears to be spinning thanks to clever design.
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