Joke

I read this joke:

An Englishman, a Frenchman, a Spaniard and a German are all standing watching a street performer do some excellent juggling. The juggler notices that the four gentlemen have a very poor view, so he stands up on a large wooden box and calls out, “Can you all see me now?”

“Yes.”
“Oui.”
“Sí.”
“Ja.”

…and I didn’t get it.

I read it a few more times, very carefully, and…nothing.

I kept at it. There must be a joke in there somewhere, I thought.

And then the light dawned.

It’s curious, how the part of my brain that reads printed words has no overlap with the part that understands spoken words. When I read, I hear…nothing at all. Is that normal?

(I showed it to Jennifer, and she got it right away.)