Smell and Selectivity

As we do not have the use of our sense of smell in cyberspace relationships this is a loss of an important data that is a foundation for communication.

Smell is one of the chemical senses, the other being taste. They are so called because they sense chemicals, and smells are, of course, chemicals. The chemicals detected by our sensory systems need to have certain properties. For instance, odour molecules must be small enough to be volatile (less than 300-400 relative molecular mass) so that they can vaporise, reach the nose and then dissolve in the mucus. This tells us that smell, unlike taste, can signal over long distances (an early warning device). We appear to have an innate ability to detect bad, aversive smells. One-day old babies give facial expressions that indicate rejection when given fish or rotten egg odor.

But, is our olfactory system doing more than just giving us warnings (smoke means fire, etc.)? Yes, of course. Amongst other possibilities, it serves a recognition function. We all have our own unique smell (some more pleasant than others! – but that’s another story, see “mate choice” below) and can recognize and be recognized by our smell.

Smell and hormones
Women, particularly women of reproductive age, have a more acute sense of smell than men. The smell sensitivity of most women varies across the menstrual cycle, peaking at ovulation (approx. day 14 of cycle where the beginning of menstruation is day 0). This peak in smell sensitivity coincides with a surge in plasma estradiol (an oestrogen). Estradiol also increases during pregnancy, perhaps explaining why some women report an increase in smell (and taste) sensitivity during pregnancy.

Smell and mate choice Recent work from Martha McClintock’s lab in Chicago shows that women are able to detect minute differences in male immunotype by smell (Jacob et al., 2002). Immunotype is conferred by HLA alleles, the genes that confer immunity in humans (the equivalent of MHC in animals), and determines our individual smell.

We tend to prefer smell of people who have different HLA alleles to our own. This would mean the offspring of such a match would confer immune advantage – more different HLA alleles would be passed on to the kids giving them a greater degree of immunity. We tend to be repelled by people whose immunotype (HLA alleles) is similar to our own. It looks like we choose our partner on the basis of smell (Wedekind et al., 1997) – well it would be one factor anyway. So, why do we spend so much time, and money, disguising it? Actually, we can probably detect the HLA-related smell in spite of our best attempts to cover it up!

Interestingly, the Chicago lab found that the women in their study rated human odour in absolute terms as slightly pleasant and more pleasant than common household odours (0.2 on a scale -5 to +5). Source

Question for my readers: How important is the sense of smell to you when it comes to forming close relationships?

About timethief

A down to earth woman, a passionate wordpress blogging tips blogger, a meditator, and a conscious living and self improvement blogger.

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