
Oh my yes they most certainly do. It is why I warn puppy owners that just because their pup is doing so well at class, now is not the time to stop training, as puperty will make the erswhile angel into a little s**t! They must keep the training up and gird themselves in patience.
There is an excellent article in this weeks Our Dogs 'Coping With Teenagers' written by the obedience/Working Trials writer. It is also the reason many puppies and young adults come into rescue at this age, usually 6 to 18 months. The owners think they should have grown up by now, and now that they are not so cute anymore are unwilling or unable to cope!
I have usually found in my breed that they START to grow up at about 2, and are finally mature at about 4.