rjr6-theists implies that there are more than one of you, or you are stating it in a-smack self in the head,"Theists!"-way. My issue is that I don't know how to help you without you being more specific. It infuriates people when I say things like,"What is blue?". It's tough to answer an amorphus question. What information would you like? I think the matter of whether a study has been done has been beaten sufficiently to a pulp. Your newest question, are there different types of guilt or just different causes, can be answered simply, or with complexity. Simply guilt is one thing which can be caused by many things. A drop of complexity for you, Things which make me feel guilty probably have little or no effect on Simon Anders. Perhaps if he was my best buddy from next door who I did everything with... Even then, totally different paths to guilt. I step on a bug, I feel guilty. Does he feel guilty for me stepping on a bug? How about that he didn't stop me? Maybe he liked the squish, and feels guilty for liking it.
And I'd just like to point out to the side discussion about communists being atheists, communist governments which try to impose atheism have a hard time controlling their populace's thoughts and beliefs. Individuals who are communists are probably split between theists and atheists.
My question on type/causes of guilt were specifically directed at jdawg, only as he used it in his explanation to the question of this thread.
And your explanation of guilt and the vagaries of it's causes does invite an entire discourse of it's own.