The tongue is sort of on the border. It's part of the digestive tract, which mostly works unconsciously, and when you're chewing you usually don't need to think

The tongue is sort of on the border. It's part of the digestive tract, which mostly works unconsciously, and when you're chewing you usually don't need to think about your tongue. Yet, you can obviously control it to an extent. People getting dental work are often nervous, and control slips a bit in that situation. I think other sorts of tics are also more common in stress situations.