Mankind's sex obsessed. Not just the acts of sex, but the facts of sex. For example, what causes Sam's proclivity for whips, while Sally prefers chains? What makes one person desire one thing, while their lover yearns for another? Some shrinks may lay the blame on childhood memories, but some scientists are looking at the more nebulous realm of desire.

Writing for The New York Times, Natalie Angier takes a look at the birds, the bees and everything inbetweens:

Unabashed about acting on their academic appetites, sexologists have gained a wealth of new and often surprising insights into the nature and architecture of sexual desire. They are tracing how men and women diverge in their experience, and where they converge. They are learning how and why people pursue the erotic partners they do, and the circumstances under which those tastes are either fixed or fluid.

Historically, sex research has focussed on the acts themselves - the dirty deeds that inform one's so-called sexual identity. New research suggests, however, that sex isn't so much about the acts as the arousal - the seemingly backward prerequisite for desire.

A plethora of new findings...suggest that the experience of desire may be less a forerunner to sex than an afterthought, the cognitive overlay that the brain gives to the sensation of already having been aroused by some sort of physical or subliminal stimulus — a brush on the back of the neck, say, or the sight of a ripe apple, or wearing a hard hat on a construction site and being surrounded by other men in similar haberdashery.

It seems men and women don't necessarily desire something until they're already aroused. You want something only after its tickled your fantasy. You need to get revved up to get going. Angier explains:

By reordering the sexual timeline and placing desire after arousal, rather than vice versa, the new research fits into the pattern that neurobiologists have lately observed for other areas of life. Before we are conscious of wanting to do anything — wave at a friend, open a book — the brain regions needed to perform the activity are already ablaze. The notion that any of us is the Decider, the proactive plotter of our most lubricious desires, scientists say, may simply be a happy and perhaps necessary illusion.

The who, what and where's of sex, then, become nothing more than a chemical reaction to a preordained trigger. A bit depressing, yes, but don't worry, the doctor's can't figure out the who, what and where's of one's arousal. Good to know there's still a bit of sexual mystery. If we knew all, we probably wouldn't be so obsessed.