I don't know how children acquire responsibility. My knowledge of psychology is at layman's level. I guess something happens during adolescence. AFAIK, this is the period when moral traits develop. I don't want to elaborate because, given my ignorance in the field, I'm afraid of saying something stupid ;)

On the other hand, from my experience I can say that trying to "teach" morals to an inveterate immoral adult is hopeless. At most you can make them behave by instilling fear. Re-read my original post, keywords: grown ups, persuasion.