Psychology of Affairs, Open Relationships and/or Polyamory?

No.10858402 ViewReplyOriginalReport
Why do some people get extremely jealous, even being driven to commit murder by their rage, when their significant other is having an affair, or even when they THINK that there's an affair, with no solid evidence (and why do couples who love each others have affairs anyways, now that I think about it?), while others, if not ambivalent, are actually aroused by the thought of their SO sleeping with someone else, ESPECIALLY when they're watching it happen? How can some people even manage completely open and/or polyamorous relationships? How does the physcology of all that work?