Idea Ownership in a Group

In a group project, often the first step is coming up with an idea - brainstorming. The interesting thing I have found is that if I come into a group with an idea already in mind, the idea is less likely to be taken. Ideas that spontaneously come up in the course of conversation are more likely to be accepted by the group.

Obviously, by the idea coming up in a brainstorming session, the group feels as though it has more ownership in it. It's no longer the idea of the person who came up with it, but rather it's the groups idea because it came up on the group's time. I also found that the first idea brought up was least likely to be accepted.

But I am curious what the psychological principle that underlies this ownership and whether it's ever been proven in experiments. I wonder I could have an experiment where a certain idea came up as though preconceived versus during the brainstorming session and see if there was actually a statistical difference. Also, should someone bring in throw away ideas if they want one of their real ideas to be accepted? It's already been shown that the person who speaks most often is perceived to have more influence in a group.

I don't really have answers - only observations.