SECOND OPINION

MORE women than men complain that their unwashed partners have an offensive smell. Sometimes the problem is serious enough to break up a relationship. By contrast, men rarely complain - indeed Napoleon is only one of several famous men who are said to have preferred their consorts to abstain from washing before a reunion after separation. Men seem able to tolerate their strong, sweaty effluent in environments from which women are excluded, and in the armed services military discipline may be the only way to maintain satisfactory personal hygiene.

Are women simply more fastidious, or might there be a genuine sex difference in sensitivity to odours? Both smell and taste are the neglected orphans of the senses, little investigated and poorly understood. The range of normal taste and smell sensations seems much wider than those of vision and hearing. Some people are hardly able to detect odours that others find overpowering, and heavy smokers have a greatly reduced sense of smell. One factor in the social tolerance of smells is that the sensation wears out very quickly: anyone working in a very smelly environment soon becomes unaware of it.

Measuring sensitivity to smell is much more difficult than testing vision or hearing. Testing taste is slightly easier, and though the two sensations are conveyed to the brain along different nerves, they are closely associated. Appreciation of the taste of food and drink is based mostly on smell; a head cold causes loss of taste because it blocks the pathway for odours from the mouth up the back of the nose, although the taste buds on the tongue are not affected. Animals with a highly developed sense of smell, such as hunting dogs, have much more of their brain given over to discrimination of odours, yet observation suggests that for all their fine noses dogs have very undiscriminating palates.

Research at Yale University by Professor Linda Bartoshuk has quantified taste sensations. One fifth of people, she shows, have unusually large numbers of taste buds and these "supertasters" can detect sweet and bitter stimuli at far lower concentrations than average. Another fifth - "non- tasters" - have very few taste buds and have only dull sensations of basic tastes, while the remaining 60 per cent make up the norm. More women than men are supertasters, and among these are women whose taste sensations are more sensitive than those found in any man.

Commenting on her research in The Sciences, Professor Bartoshuk argues that the four primitive taste sensations - sweet, bitter, salt and sour - were needed in primitive societies to identify which natural foods were nutritious and which were dangerous. Women needed heightened sensitivity to protect the developing foetus throughout pregnancy. The non-tasters would have an evolutionary advantage during times when food was short, when their ability to eat almost anything might see them through a famine.

Whatever the evolutionary background, if women do have more sensitive tongues than men, they may be expected to have more sensitive palates, too. The predominance of male chefs has more to do with the sociological aspects of running a kitchen than with their ability to discriminate taste.