Some visual patterns seem to “hack” our brains, causing us to perceive shapes or images that aren’t really there. It’s always mindblowing when the illusion is revealed and you find out that, for example, the lines are actually straight or that the dots never disappeared. But a newly described illusion goes beyond a trick of the eyes. It actually makes your brain make up facts about things it’s already seen. This is the Rabbit Illusion.
The Rabbit Illusion and its sister, the Invisible Rabbit, came out of a 2018 Caltech study on the relationship between what you see and what you hear. If you didn’t watch, it works like this: In the Rabbit Illusion, a light flashes at a certain point on the screen, accompanied by a beep. 58 milliseconds later, a second beep goes off, but without an accompanying flash of light. Finally, 58 milliseconds after that, the screen emits a third beep and a second flash of light, slightly to the right of the original flash.
The Invisible Rabbit inverts this series. Like before, a flash and a beep kick off the illusion. Then, there’s a second flash of light, slightly to the right, but without a beep. Finally, a third flash of light further still to the right, and a second beep. The result? People’s brains almost always alter the actual visual experience to match with what they heard. In other words, participants reported seeing three flashes in the Rabbit Illusion, and only two in the Invisible Rabbit — the exact opposite of what actually occurred. Regardless of the illusion, their brains only register a flash if it was accompanied by a beep, even if there was no flash in reality.
Play by Postdiction
This illusion works via the concept of “postdiction.” This concept isn’t really new; some scientists even think it might be the smoking gun that killed free will. But what is it? Basically, take the idea of prediction and turn it around. Your brain is really good at guessing what’s going to happen next based on what has just happened, but it also does the opposite. In this case, your brain is guessing what’s already happened based on context clues, even if it was literally there to see it. In the case of the Rabbit Illusion, your brain assumes it must have missed the second flash. The beeps/flashes come in such quick succession that your brain doesn’t have time to process them but fools itself into thinking it did. However it works, it’s enough to make us wonder how much we can really trust our eyes.