Actually it can be concidered a natural reaction. Think about what your first instinct is to do when someone comes near you with something really gross and its near your arm. Or when your just about to walk into something and catch yourself are the last moment……. you instinctively pull your arms or arm in. Your brain might be processing that yellow line like that of an invisible wall. Don’t want to hit it so you tuck….. pull the arm in to avoid it thus initiating the turn and lean.