With 7.1 Touch ID is learning better. With each successful scan it learns part of your fingerprint it has never seen before. So if you go to Settings > Touch ID and start scanning your finger, and move just a little each time it is successful, you can teach it new parts of your finger. The downside, I think there is a limit to 'area' it can learn, once you teach it a new part, it starts to 'forget' previous parts.