Why does this optical illusion stump us so badly?

This kind of illusion works on a simple psychological trick: our brains like to take shortcuts. They scan the image quickly, identify familiar patterns, and fill in missing details based on assumptions. So when something is cleverly camouflaged, it becomes nearly invisible to our fast-thinking minds.
“I stared at this picture for five minutes… I thought it was a prank.”
Another admitted,
“Even after reading the hint, I still couldn’t see it. It’s maddening!”