Optical illusions often play on tricks of sight or sound. But scientists at the California Institute of Technology have built a little sensory trick that plays on both. It involves a cross, flashes of light, and some popping sounds. They call it the Rabbit Illusion.
The illusion shows how stimuli that occur later can affect the perception of stimuli that have already occurred. In other words, if the senses pick up on one stimuli after another, the brain will attempt to create a narrative out of them. It’s called postdiction, trying to make an assertion about the past.
“When the final beep-flash pair is later presented, the brain assumes that it must have missed the flash associated with the unpaired beep and quite literally makes up the fact that there must have been a second flash that it missed,” explains Noelle Stiles, a visiting postdoctoral scholar-research associate from USC, in a press statement.
“This already implies a postdictive mechanism at work. But even more importantly, the only way that you could perceive the shifted illusory flash would be if the information that comes later in time—the final beep-flash combination—is being used to reconstruct the most likely location of the illusory flash as well.”
The brain is full of all sorts of strategies that make sense in normal life but can be easily tricked. There’s also Troxler fading, where things that stop moving disappear.