Funny you should ask
it comes from my personal observations and experiences with non-monogamy. So while my opinion based on my experience will only carry as much weight as those who trust my opinion, as the five or six instances I am talking about certainly do not equal any study.
The funny part is that any study that I have seen, carries less weight in truth than what I am saying. It's because the studies are done by people who preformed the "study" in ways that completely invalidate it's assertions. It is the main reason that discipline of psychiatry and psychology are so far behind other science disciplines. It is because so much of the "work" that is done and heavily influences the field, is anything but science.
When there is no correction taken into account that people who are dishonest, don't understand, or aren't willing to do what is necessary to ensure they the situation is understood by all, and intentionally communicated to eliminate as much confusion as possible, studies can be less accurate and less useful than wild guesses.
The problem with psychology is all the psychology behind the "research"