- Watch the images in this next clip and pay attention to the words in the song. Something strange is about to happen. Ready? 

- (SINGING) Bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill. 

- Did you just hear three distinctly different words during that video? You probably heard "bill," "pail," and "mayo," right? Here's the thing. If you heard three different words, your brain is playing tricks on you. 

The images changed, but there is only one word in this audio clip. That mayonnaise didn't come from us. It came from your brain. 

Earlier, we showed you this video that caused a strange transformation to take place in your brain. Let's see it again. And notice what happens to what you're hearing as different images appear on your screen. Ready? Here we go. 

- (SINGING) Bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill, bill. 

- Did the word "bill" just morph into the word "pail" and then "mayo?" This is truly bizarre, especially since we didn't change the audio in this clip at all. Just to prove it, here's the soundtrack without any of the images. 

- (SINGING) Bill, bill, bill, bill, bill, bill, bill, bill. 

- You can hear it clearly. It's the word "bill" over and over. But if we add some pails, your brain bends the audio to match the image. Same with the mayo. What's going on here? 

- You might be surprised to learn your vision is really useful in understanding spoken language. A part of the brain called the superior temporal sulcus helps sync a speaker's lips to what you're hearing. 

- But when your vision and hearing conflict, as they did in this game, your brain has to figure out which one to trust. And so your brain has decided your visual reality is more important than what you're hearing. It's actually manipulating what you hear to match what you see. Pretty trippy, if you think of--