. Love lights up the caudate nucleus because it is home to a dense spread of receptors for a neurotransmitter called dopamine, which Fisher came to think of as part of our own endogenous love potion. In the right proportions, dopamine creates intense energy, exhilaration, focused attention, and motivation to win rewards. It is why, when you are newly in love, you can stay up all night, watch the sun rise, run a race, ski fast down a slope ordinarily too steep for your skill. Love makes you bold, makes you bright, makes you run real risks, which you sometimes survive, and sometimes you don't. (National Geographic, 2002)
You can't make someone love you, even on Valentine's Day, no matter what Hallmark, Godiva and FTD may say. But how much do we really know about how love works? What is it that attracts a particular man to a particular woman and (with any luck) vice versa? To see what light science could shed on the subject, I called Professor Martha McClintock at the University of Chicago.
McClintock is an expert on odor and behavior who published a famous study in the early 1970s that showed that the menstrual cycles of college women living in dorms became synchronized through exposure to one another's pheromones, those faint chemical signals released from the skin that control the mating rituals of much of the animal kingdom. McClintock has a new study, published in the February issue of Nature Genetics, that makes an even more provocative link between sex and odor--specifically, the odor of a T shirt worn by a man on two consecutive days. . The experiment was simple. The T shirts were carefully prepared (no cologne, no cigarettes, no sex) and then placed in boxes where they could be smelled but not seen. Forty-nine unmarried women were asked to sniff the boxes and choose which box they would prefer "if they had to smell it all the time." The results would have made Sigmund Freud proud.