I think it's the pavlov's dog response. The body learns to anticipate that the alarm will go off if urine is released. That leads to learning the feeling that one needs to go. Personally, I wake up at night if I need to go, but my son didn't. I was also somewhat skeptical, but after 2 weeks of waking up to the alarm already wet, he started staying all dry. Now he wakes up at night if he needs to go, just like most of us. You know, now that I think about it, he is doing better in the day too. Not that he wet then, but getting to the bathroom was always an emergency. I think he didn't get the signal until the last minute, but now he notices the feeling.
Lorix2, believe me, if witholding liquids after 6pm and getting him up at 11pm had helped at all, we would not have gotten to the point of trying the alarm. If your son actually wakes up to throw away his wet pull up and then sleeps dry the rest of the night, plus can go two weeks dry, you are way ahead of where we were. I don't think my son knew he was wet until he woke up in the morning.
I also agree that it is a definite committment by parent and child to get up at night. I would never suggest it to any child who didn't want to do it. I showed my son the pictures on the internet, he begged me to order him a certain color, couldn't wait to get it, couldn't wait to go to bed that night, etc...
We just didn't want to wait for him to outgrow it at 12 or whatever (family history rears it's ugly head.) He is still very proud of his accomplishment and now he might like to go to sleep away church camp this summer and not take pullups.
Oh, and I guess I should have added that my son fell asleep every afternoon even before he became dry at night. I didn't mean to imply that it was a side-effect of getting up to go at night. I was blessed with three kids who can sleep 12 out of every 24 hours if I could let them. One was sleeping through the night at 7 days old - they all took 2 long naps and still slept all night, napped until they started 1st grade, etc... I think they get it from me.
