We can't expect studies to be possible with topics like this in the near future. As I mentioned in my other comments, we don't even have cultural concepts or la

We can't expect studies to be possible with topics like this in the near future. As I mentioned in my other comments, we don't even have cultural concepts or language to capture this in a meaningful way, not alone some kind of objective test that could form the basis of a scientific study. They could only do it in this bird because of the striking visual difference, and without it they wouldn't have been able to study this at all. I think it can be observed firsthand if you have experience dating a lot of different people, and the dynamic becomes quite obvious... but you could not easily categorize a person that you haven't known sexually or romantically in this way. It's quite striking the intense 'chemistry' when you are paired with someone that is on the complementary end of this spectrum from you, and the lack of it when you are not. I think words like "power couples" and "quiet couples" are looking at something different are are themselves not even opposites- I think you are looking at something like ambition/goal directedness, and introversion.