While in a boat with a passenger, if you exit the boat while you are turning the mob's head will slowly turn in the direction of the turn. Sometimes it will jump back but then it will turn again.

Steps to Reproduce
1. Get inside of a boat with a passenger, however it is most noticeable with Armor Stands. ( /summon Boat ~ ~ ~ {Passengers:[

]} )
2. Get in the boat and drive around. Turn in any direction.
3. Exit the boat while turning.