ONE of life's little mysteries is why particular people fancy each other—or, rather, why they do not when on paper they ought to. One answer is that human consciousness, and thus human thought, is dominated by vision. Beauty is said to be in the eye of the beholder, regardless of the other senses. However, as the multi-billion-dollar perfume industry attests, beauty is in the nose of the beholder, too.

ScientificMatch.com, a Boston-based internet-dating site launched in December, was created to turn this insight into money. Its founder, an engineer (and self-confessed serial dater) called Eric Holzle is drawing on an observation made over a decade ago by Claus Wedekind, a researcher at the University of Bern, in Switzerland.