Where one person sees mittens, another might see butt cheeks spread wide.

That’s the scenario currently playing out in regards to McDonald’s new “warmest greetings” holiday cups. While McDonald’s hasn’t released a statement on its butt cups yet, people on Twitter have taken to calling out the cheeky surprise.

If you’re one of the people who immediately saw a butt instead of mittens, it means you’re basically a butt person, thanks to pareidolia, an information-filling phenomena of the brain. When you see ambiguous stimuli, like a mound of rocks or a tree, your brain kicks into a hardwired process of trying to make sense of those images in the context of your world — that’s why you might see a face instead of a gnarled branch.

The McDonald’s mittens are not ambiguous stimuli — they were clearly and purposefully designed by some ad person. But the pareidolia phenomenon also touches on the fact that the brain is a predictive organ. If it wasn’t clear to you at first that those white spaces were mittens, then the mind will jump to the first thing that does make sense — and here, what makes sense for a lot of people is a butt.

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Why you would be inclined to see a butt instead of say, two ghosts waving or a curly mustache, is because humans are evolutionarily drawn to butts. Chimpanzees look to each other’s butts to find out which chimp in a group they are buddies with and to judge the fertility of chimps. Scientists believe that placing informational importance on butts is a trait that we have inherited from the similar ancestor we share with chimps.

And you might not be able to unsee the butt. Psychologist Tom Toppino tells The Atlantic that this is because perception is a process of “fitting prior knowledge to the current situation” and “not the result of simply processing stimulus cues.” You can force yourself to perceive another image, but if you saw one image first you’ll always see it again because efficient information processing is what your brain does to give you a timely advantage in decision making. Which means for you butt-spotters: Congratulations! You’re most definitely a butt person.

Photos via Twitter