GoogleVR (Cardboard) how to move using head-tilt

Hi, I'm new to Cardboard but I understand that when the users head tilts from side to side, the camera tilts the opposite direction. Can someone explain what function controls this, where it can be located?

I'm trying to create a game where the player can turn left or right by tilting their head. This is similar to riding a bicycle, where you would lean to turn. What script would I need to modify to make this happen?