Agree with seeker.
Roo in your post just below you talk about a child 'chatting or singing to its teddies' and then you go on to say ;if they were suffering psychologically the cry would be different' or such
so is it a cry or a chat? I think if a child is crying at all, they are usually unhappy.
If a child is chattering away then of course you don't need to intervene, but that's completely off topic. We're talking about crying and yes, crying equals distress, however you might want to dress it up.
for example a very small baby will normally give several cues for hunger before crying or even making a noise. Ds2 used to be in his cot, I would watch him unseen. Often he would sing. Other times laugh, make gurgling noises.
If he was asleep and started to wake, he would first of all move slightly, he would wriggle a little bit. Then his hand would go up to his mouth - as though gesturing for a drink. He would roll a bit, looking for the breast, rooting, realising he was in need.
THEN if nobody came, he would make a little grunt. Then wait. Then a little 'uh-huh' like the beginning of a cry. It aas only after this he would actually start to properly cry.
You get a good few minutes sometimes to respond to the cues, before the crying begins. Once I realised his mode of communicating, if I was present when the cues began I would respond to the first and it never went any further. His hand went to his mouth and I lifted him up and fed him - or moved towards him, and fed him, if we were in bed.
Once he had felt the need to cry he was already being ignored on several levels.