My daughter is 3 and 4 months and she doesn't have tantrums, but her mood often suddenly changes, especially if she's surrounded by more people, eg parents and grandparents. She stops smiling and talking and sulks, refusing to talk or to do anything. She even managed to ingnore her much-loved granny for an afternoon , then saying "I'm not talking to granny". I'm not clear why this happens and if this is a normal phase. It's not clear why and at what she takes offence. Does anyone else have similar experiences? What did you do to sort it out?