Have you heard of this? It is utterly bizarre. In the words of the author of the article I am linking to:
The McGurk effect is mind-blowing. It involves showing a person’s lips making the shape of one sound—like “bah”—while the audio is actually the person saying “fah.” What’s interesting is that your brain changes what you “hear” based on what you see. It’s “bah” all the way through, but when we see “bah” our minds transform “bah” into “fah.”
To really appreciate what is going on here, I suggest you re-watch the relevant bit with your eyes closed.
This is extraordinary because you can’t switch off the effect, even if you know what is happening. That’s rather disconcerting, especially in the age of fake news and fake videos. If our brains are fooled so easily even when we know what is going on, what hope do we have of protecting ourselves from unknown tricks?