Beats me, but when you figure it out, let me know. My 3-y/o goes in spurts of doing that. ARGH.

Jordanna-
I first found out about your blog from a link on Meredith's "Like Merchant Ships" blog. One thing might be to check and make sure that your four year old doesn't have some kind of bladder infection. Sometimes a small infection can cause urinary frequency/incontinence that little children don't really know how to describe. Hopefully, that's not it, but it might be something to run by your pediatrician.
Enjoying your blog!
Susan

Don't turn it into a power struggle... you'll never win ;-)

Neighbors had the same problem, and they seem to be making progress with the special "potty watch." The timer is set to go off every two hours, and she has to try & go no matter what.

Part of her problem was she needed to learn that she could stop whatever she was doing long enough to head to the WC. She seems to be getting it now. I don't know if your issue is the same, or if yours is just being contrary.

My four year old does it occasionally just to get a rise out of me. I've been working hard on my poker face and it seems to help a bit.