Free What the Nose Knows: The Science of Scent in Everyday Life by Avery Gilbert Page A

advertisement triggers in Kongrosian the delusion that he has a bad body odor. He becomes obsessed with BO and washes compulsively, but in vain; the smell lingers. His ability to play the piano from a distance notwithstanding, Kongrosian is a poster child for a real-life psychiatric disorder known as olfactory reference syndrome, which is characterized by persistent hallucinations of body malodor.
     
    I T PROBABLY COMES as no surprise that men and women differ in smell ability. This has been confirmed many times with a variety of test methods and in cultures around the world. Women rate themselves as having a better sense of smell, and the data back them up. Women detect odors at lower concentrations and are better able to identify them by name. A German psychologist found that men and women are equally good at remembering colors and musical tones, but women are better at remembering smells. Humorist Dave Barry’s wife would not be surprised:
    At least five times per week, my wife and I have the same conversation. She says: “What’s that smell?” And I say, “What smell?” And she looks at me as though I am demented and says: “You can’t SMELL that?” The truth is, there could be a stack of truck tires burning in the living room, and I wouldn’t necessarily smell it. Whereas my wife can detect a lone spoiled grape two houses away.
    Sex differences are based on group averages; there is much variability within each sex, and large overlap between them. But in general, women are better. Or, as Dave Barry put it, men suffer from Male Smelling Deficiency Syndrome.
    What explains the female superiority? There is little evidence of sex differences in the nose. Dave Barry’s nose probably looks and operates much like his wife’s. The brain is a different story. Recent evidence suggests that brain structures related to odor perception differ in size and cellular architecture between men and women. Whether these anatomical variations explain Barry’s quip remains to be seen. We do know that some male-female differences in perception (the fact that women often rate smells more intense and unpleasant) are mirrored by differences in the underlying brain-wave response.
    Female smell superiority is partly due to women having higher verbal fluency; verbal skills boost performance on tests of odor memory and odor identification. Another factor is hormones. A woman’s smell sensitivity varies across her menstrual cycle and is greatest around the time of ovulation. Hormone effects are not simple; they interact in complex ways with cognitive factors. This interaction produces one of the most dramatic olfactory sex differences ever observed in the lab. Sensory researchers Pam Dalton and Paul Breslin tested men and women for their sensitivity to a specific odor. With repeated testing over the course of thirty days, the women became much more sensitive to the odor, while men did not. The effect was confined to the tested smell; sensitivity to a different odor did not change for men or women. The enhanced sensitivity can’t be attributed to practice; the women weren’t getting better at threshold tests in general. They became more sensitive because they paid close attention to low levels of odor while being exposed to it multiple times. Most remarkably, Dalton and Breslin didn’t find enhanced sensitivity in prepubescent girls and postmenopausal women. The phenomenon is limited to women of reproductive age. This implies that female hormones are needed to make it happen, and in fact it can be observed in postmenopausal women who take hormone replacement therapy.
    Sex differences are evident within days of birth: baby girls turn toward novel odors and spend more time smelling them than baby boys do. The anthropologist Lionel Tiger attributes the difference to evolution. In our long history as hunter-gatherers, he says, it was the females who gathered fruits and vegetables, and a good sense of smell was valuable in judging ripeness