A typical conversation with Alex will go like this:
"Alex, do you want ___?"
And Alex usually responds, enthusiastically, "YEA!"

Example, last night:
James: Alex, do you want to go to bed?"
Alex: YEA!
Will: Alex, do you not want to go to bed?
Alex: YEA!

This morning we were going to the store. I got the list, coupons, purse, diaper and kids together and we headed to the car. As I put Alex in his carseat, I smelled that tell-tell smell of a dirty diaper.
Me: Alex, are you poopy?
Alex: Nu-huh
Maybe he's starting to catch on?