Stick a toothbrush in your mouth and make the world, especially electric displays, go strobe. It's all about how your toothbrush, or your own vibrating mouth, interacts with your inner ear.
Inside your inner ear are cells that keep you from falling over. The vestibular system does a lot of jobs. The tiny hair cells register displacement and help you with your sense of balance. They also sense things like acceleration, helping you get a feel for the speed at which you are moving. They're probably helping you read this entry right now - definitely if you're reading it on a mobile device in a moving car or on a bus. The tiny cells sense displacement and sense signals to your eyes to compensate for it. This is why when we run we don't see the world in giant bouncing arcs, but as a steady point.
These cells evolved for animals, including humans, to keep things in sight while they're running around. They're not equipped for the high-vibrations that we now expose them to. Stick something that vibrates ten to a hundred times per second in your mouth - like those electric toothbrushes - and suddenly the cells are all at sea. They're not even equipped to deal with the comparatively mild raspberry, which also vibrates the skull if done for any amount of time.
They have been found to sync up with the mild vibration. This can jerk your eyes around tens of times a second as well. When you look around, certain things, especially light-emitting electronics, suddenly appear to shut on and off. Some scientists think that this is because the vibrations, and firing cells, interfere with the cycles of the refreshing screen. Others believe that it's just that a person's eyes are jerked away and back to the screen again and again that makes it look like the screen is flashing.
Either way, those of us with manual toothbrushes are missing a light show.
Image: Howie Le