Too much dog training on the mind

The first time we gave our son a bath, he cried and screamed. The second time, he was quiet. My first thought was "Oh! Look he's so good. We should give him a treat!" Wait a minute, our son is not a dog. I've been thinking too much about dog training. And anyways, even if positive reinforcement does work on children, the only "treat" our son knows at this age is breast milk, and I'm not about to give a bath and nurse at the same time.