So the way he acts pre-marriage is not necessarily the way he will act post. I'm not suggesting that some Jekyll-and-Hyde-like transformation will take place. It's more that he could slip from Jekyll, who bought you flowers and chocolate every week, to Jekyll Lite, who's still a good guy but doesn't necessarily have the energy to continue wooing you now that you're both blessed with jobs, a mortgage, kids, and spreading waistlines.

All of which is to say: Intellectual compatibility matters. Because if and when the gold treatment does start to fade, you'll still have the same ironic sense of humor to share, the same books to discuss, the same opinion of global warming to chew over. It's not that you have to have the same taste in food, art, or home decor. But having large tracts of overlapping brain and soul can save and enrich a marriage more than all the flowers and chocolate in France. And being so in sync that your interests, tastes, and opinions are able to change and evolve together—without leaving the other person behind—is what will make your marriage last.
 

For the best advice on sex, love, dating and relationships we ask two experts with personal experience. Cathi Hanauer is the author, most recently, of Sweet Ruin, a novel about love, marriage, and adultery. Daniel Jones is the editor of both the "Modern Love" column for The New York Times, and Modern Love, an anthology derived from the column. They've been married for 15 years, and together they provide a his and hers take on relationship questions. This round: intelligence inequality.