Do relationships improve or reduce your creativity/productivity?
mattknox: The correlation of relationships and achievement probably varies from profession to profession.  As I understand it, physicists nearly always do their best work before marriage, while businessmen often do theirs after.  There are a bunch of related effects that would have to be teased out to make the correlation clean (eg., physicists tend to do their most interesting work very young, and tend not to get married young), but it seems solvable.One thing I wouldn't rely on in trying to answer this question is asking people whether having a relationship makes them happier/more creative/more productive.  Anything related to reproduction is probably viewed in an unrealistically positive light, and probably has a bunch of taboo protection. ( for example, see http://www.newsweek.com/id/143792 for people's reactions to a sociologist who wrote that having children doesn't make people happier. )  It's in our genes' best interests for us to think that having kids is a tremendous joy, whether it is or not, and the same is probably true for relationships.I'd imagine the research has already been done for whatever field you're in, so you can just look it up.