My comment about mental level was in response to your question/statement that most people in wheelchairs are in relationships with other people in wheelchairs. It is true that most people with severe mental handicaps tend to form relationships with other people with severe mental handicaps.

"but to think our more serious conscious preferences can be easily disabled by love is just silly."
I am not talking about love I am talking about psychological compatibility.

"People will choose the better looking persons first"
No people will be attracted to the better looking person first. But to have a relationship with that person you must be compatible at some level.

"you think of such relationships as having less value, but you can't really say that."
My definition of value is whether a relationship is pleasant and fulfilling. Unfortunately most relationships that I am aware of that are based mostly on the physical have a great deal of conflict.

"It's human psychology and has everything to do with the workings of social behavior as well."
That is my point. Human psychology is influenced by biology but psychology controls the biology.