Your Eyes Fool Your Ears With The McGurk Effect
The McGurk is an interesting illusion that involves both sight and sound. It tricks your brain into hearing the same sound differently based on what you are lip-reading as a person is saying it. For example, a "bah" sound will actually sound like "fah" if you watch the sound come out in synchronization with someone mouthing "fah." In this illusion, what you see overrides what you hear.
Key Facts In This Video
The McGurk Effect tricks your brain into hearing different sounds based on how someone's lips are moving. (1:07)
The McGurk Effect works whether or not you are aware of how it works. (2:03)