Hrothgar - never worked for my parents! 9 kids in 18 years and after the first few it was a d*amn rare night they didn't have at least ONE in with them.

CS - I too have known infants who at least appeared to be consciously manipulating people as early as three or four months - certainly different behaviour patterns for different people. But yes - the "I want" and "I need" cries have always seemed very different to me. Then there is the "I'm just generally pissed off and am going to make you suffer" cry...