I've bought 19 month DS a potty and over the last few months he has developed an interest in it. Over the last few weeks he's taken to saying 'I needa poo!' and in which case I ask him about doing it in his potty.
He's definitely developing a connection between knowing he needs to go and what the potty is for. I don't want to push him before he is ready so i've taken to putting his bears on the potty for a poo!
I've found that (bizarre as it sounds!) putting nappies on his bears has made nappy changing a million times easier than wrestling him to the floor. Now he watches with interest when I take off Teddy's nappy and put bear on the pot for a poo!
Has anyone else tried this technique and has it worked?