In the spirit of Valentine’s Day, we dug up our two most popular posts-well, okay, probably our two only posts, unless you count news about contraception-that mention sex.

The first is one of a stream of posts on the hot field of happiness research, which is using scientific methods to back up the common-sense maxim that money doesn’t really buy happiness (or love, or sex). Academics studying what makes people content find that it takes a lot of income to "buy" the happiness that companionship and community provide for free. For example, on average a long-lasting marriage is worth about $100,000 in annual income.

NPR picked up one piece of the story this morning. (Update: The Washington Post also ran a good, brief Q&A with Richard Layard of the London School of Economics, who’s just published a book making a case for public policy that "enables people to live as happy lives as possible.")

The second post looks at a statistical puzzle related to um, sexual behavior. Is the old piece of doggerel about “men are polygamous, women monogamous” true? Or is someone in the equation lying?