The senses are more intermingled than we realize — what we hear influences what we think we see, Live Science writes:
Some people may actually see sounds, say researchers who found this odd ability is possible when the parts of the brain devoted to vision are small.
Scientists took a closer look at the sound-induced flash illusion. When a single flash is followed by two bleeps, people sometimes also see two illusory consecutive flashes. They found the smaller a person’s visual cortex was — the part of the brain linked with vision — the more likely he or she experienced the illusion. On average, the volunteers saw the illusion 62 percent of the time.
“The visual brain’s representation of what hits the eye is very efficient but not perfect — there is some uncertainty to visual representations, especially when things happen quickly, like the rapid succession of flashes in the illusion,” de Haas said. “In the real world, sources of light and sound are often identical, and combining them will be advantageous.”