some people (like me) just know they are poly and operate that way from early childhood. I always loved more than one person and regularly dated in twos and threes.
Other people (like my boyfriend) are flat out mono. They never fall for more than one person at a time, and in his case- really only one person EVER in their life. He's not even one who loves one person at a time, but one person period. He's been in love with me since he was 17 years old.
still others are like my dear husband who were taught that monogomy is the RIGHT way to be during marriage and that any experience with more than one person needed to be had prior to saying "I do". He has poly "tendencies" and can be happy and enjoy sexual experiences in controlled group situations, he can love more than one person to a degree but he's conditioned for a monogomous relationship.
My boyfriend-he's not likely to change, like Mono on here-he doesn't see the point. He would rather be alone than try to be with someone else.
I am not likely to change either-despite trying, I simply DO love more than one person at a time and when I try to block the emotions for one, what I accomplish is simply shutting down all of my emotions across the board.
My husband-well he flip/flops. He MUST have security that he IS loved and that no one is going to leave him. He CAN be happy in a monogomous relationship but he also can enjoy having more then one relationship. So it's really a matter of ensuring that he's TREATED right, his needs are met and that he's happy-not what type of relationship it is.
Does that make sense at all??
I think you are asking "is it this or this" and the answer is, it is both. Some people are wired one way or another and some people are trained to be one way or the other.
"Love As Thou Wilt"