Hehe 1 year old is still very young and very trainable. They can still be trained even when they are 5-6 years old just a little harder but with a little more patience, it can be done. I adopted a Shih Tzu many years ago, he was old when I adopted him probably more than 5 but he can be trained and learned his new name in no time! Mine (my yorkie) only does it when there is a treat or when he feels like it but if I sound firm, he will do it but after that, I will have to praise him and kiss him all over :P The thing with yorkie is, they are so intelligent that they have their own mind and do what they want. Maybe yours do know just don't want to do it when there is no treat
Oh...also using exactly the same words for the same command each time helps especially if you have a few family members otherwise they get confused. Mine pretty much only does sit, stay, down, and paw (shaking hands) and that is about it as we got lazy in training him