If it has anything to do with Psychology I'm your source!!!
I take it that this question was for Rachael, (I was about to ask her that too) but I'll good ahead and answer it as well.
It gives me a chance to get up on my soap box.
My H is interested in race bikes, nature, cuisine, travel and POLITICS.
My interests: nature, cuisine, travel, literature, gardening, psycology, and POLITICS.
I think that when the focus is limited in a straight, enclosed line between two people, the line begins to burn out. We all need a common focus outside of ourselves (triangular) in which to meet.
I think that it's good for us as individuals, as couples and as world community members to have a mutual and meaningful involvement in the world outside our own personal circle.