Because even when people knew the answer intellectually, their brains often still interpreted the image incorrectly on instinct.
Why the illusion works so well
The image is an example of what’s known as a bistable optical illusion.
That means the brain can interpret the same picture in two completely different ways — but usually not both at the same time.
Once the brain chooses one interpretation, it becomes extremely difficult to switch perspectives.
In this case, several visual details accidentally mimic familiar human features.
The forearm resembles the shape of a neck. The wrist bone looks strikingly similar to an Adam’s apple. The bracelet appears like a necklace or choker. And the beige trousers resemble the collar of a cream-colored shirt.
Because the brain constantly tries to identify familiar patterns as quickly as possible, many people instantly interpret the image as a neck without consciously analyzing the details.
Once that assumption forms, the brain essentially ‘locks in’ to that interpretation.
That’s why so many people online admitted they could understand the explanation logically while still continuing to see the original illusion anyway.
It’s also why optical illusions remain so fascinating
