When I was a kid in the 80s I read of a strange phenomenon in a couple self-help books. (To know of the writers, email me privately at firstname.lastname@example.org.) They spoke of many men who only really care for women who are "just friends"; if the same men were your sexual partner (husband or boyfriend I suppose) or became one, they would treat you a lot worse. I don't believe good men are like this, but whatever. How common is this, and what causes it? Are these guys who are "playing the field," as I imagined? What about "true love?" Is it because of prolactin? I appreciate your comments.