Bruxing is grinding the front teeth together. Soft bruxing while being stroked is contentment. Loud, hard bruxing with a stiff body can be stress or pain, so read the whole rat. Boggling is when the eyes bulge in and out, caused by the jaw muscle behind the eye. It usually goes with happy bruxing and means a very content rat. Piloerection, or puffed-up fur, means arousal: anger, fear, illness or, in a group, a brewing squabble. A puffed rat who is also hunched and still may be unwell rather than cross. Sidling, side-on displays, boxing on hind legs and pinning are normal squabble language while a hierarchy sorts itself out. Watch for escalation: chasing with squeaking, tumbling balls of rats, or any blood or broken skin means intervene and reset the introduction. Power grooming is one rat forcibly grooming another. A little is normal dominance; if the rat underneath is squealing or losing fur, it has gone too far. Chattering teeth quickly, squealing, or freezing means fear. Slow blinking, loose flopped posture, lying stretched out and belly-up sleeping mean a rat who feels safe. Licking your hand can be grooming, salt, or affection. Nipping with no pressure is usually a request to stop; a hard bite is rare and almost always fear or pain.