One day, a mother and daughter were quarrelling loudly. Then, suddenly, the telephone rang. ‘Hello?’ The mother picked up the receiver hurriedly, her voice still thick with anger. The caller was her daughter’s homeroom teacher. As soon as the mother realised who was phoning, the tone of her voice changed and she became very polite. Then, for the next five minutes or so, she carried on a conversation in her best telephone voice. Once she hung up, in a moment, her expression changed again and she went straight back to yelling at her daughter.