I have wondered about this, based on my very small sample of successful dyads: the ones I've observed seem to be mainly in alpha. I've mostly paid attention to close friendships and relationships like marriage. It's my opinion that not all dyads have the same degree of success. I don't know why it seems that the most successful ones are in alpha. Admittedly I have only one couple from beta in my sample. I wonder if anyone else has noticed anything or maybe can suggest some likely reason why (if this is the case).
Feel free to link articles etc.
I'm aware of other factors, I guess there is no way to isolate them to make the sample more 'correct' or w/e.
Again, my sample could be small but wanted some opinions on this regardless.