The seduction of smell

Attraction is a tricky thing. There are a variety of attributes that draw one person to another, and no one seems able to explain exactly why. Symmetry of the face, size of the index finger, status, earning power, waist-to-hip ratio, lip size, ear lobe length, neck and wrist circumferences, or a face similar to one’s own. These are just a few theories of what attracts us.

Most agree that appearance plays a part. Many say a sense of humor is important. But if you’ve ever met the shopping list of your dreams and he or she didn’t add up, you know there has to be something else. Something special. A spark.

Your reaction to smell may be more powerful than you think

We don’t pay that much attention to our sense of smell unless we’re forced to by something unpleasant. Maybe we’re trapped on a MAX train next to an unfortunate someone who hasn’t showered in a year. Maybe someone in an elevator swam in a vat of perfume before starting her day. Smell, however, is a significant part of our sensory system, and scientists say it can be tied closely to memory, emotion and especially attraction.

So do you like the smell of sweaty armpits? No? Are you sure? Some scientists would have us think otherwise.

The magic of pheromones

Biologists have long known that insects excrete and respond to chemical signals. Bees, for example, release a pheromone, or chemical, to signal other bees to a variety of situations such as hive ability, danger and sexual possibility. Pheromone excretion as a method of communication is not limited merely to insects. Other animals and even plants employ pheromones to get their messages across. Some pheromones are even believed to be potent across species lines. A well-known example of this is the human/orchid bond, where some orchid collectors seem to develop an addiction to their orchids.

Sweat

In humans, pheromones are excreted in underarm sweat. Because of this, researchers have been hard at work determining how different people react to different samples of sweat. Findings seem to indicate that people of different genders and sexual orientations react differently and have preferences depending on from whom the underarm sweat was taken.

Heterosexual males and females were less offended by samples from the opposite sex and most offended by samples taken from homosexuals of the same sex. Homosexual males and females were less offended by samples from the same sex and most offended by samples taken from homosexuals from the opposite sex. These findings have further implications in that they seem to prove that homosexuality is not a choice but predetermined from birth.

For heterosexual women, the substance found in male underarm sweat that makes us weak in the knees is called androstadienone (AND). Supposedly, this causes heterosexual women and homosexual men to be unconsciously more attentive to the smelly man in question. Heterosexual men and homosexual women succumb to the female pheromone, estratetraenone (EST).

As one could guess, research is going forward in an attempt to isolate and predict responses to a variety of pheromones to see how humans can be unconsciously affected in areas such as mood, behavior and physiology.

Your nose–it’s not just for picking

According to the Human Genome Project, humans have over a thousand odor receptor genes and of these, 347 are said to be functional. To understand how this works, first find your face, then your nose. (Let your finger be your guide.)

Lining the inside of your nose is what’s called the respiratory membrane. The part we are concerned with is called the olfactory epithelium and is located on the roof of the nasal cavity about three inches above and behind the nostrils. In this tissue lies the key to our perception of odors. It is here that the olfactory sensor neurons are located.

Humans have approximately 40 million olfactory sensor neurons. Each olfactory receptor cell has tiny cilia, fluffy tail-like strands that protrude from the skin inside your nose (olfactory epithelium) into the nasal cavity. It’s furry in there. These cilia contain the olfactory receptors that directly interact with odor molecules and start the process by which you perceive a smell.

Some people suffer from anosmia, which means they are unable to smell or detect scent. More often people can’t smell a specific odor, but sometimes you’ll find someone who can’t smell at all.

To get down to the nuts and bolts of smell perception, once you imagine the fluffy tail-like cilia within your nostrils, think smaller. Located on the tiny cilia hairs are receptor cells that actually come in contact with and perceive odor molecules. This is done by means of shape. Each olfactory receptor neuron is said to have a particular shape. If the odor molecule fits into the shape provided by the receptor neuron, the scent will be recognized. If not, the scent will not be recognized. (Think round peg in square hole.)

All this smelly stuff will eventually, via neural pathways, make its way to the anterior hypothalamus, which regulates metabolic processes and links the nervous system to the endocrine system.

Nasal fatigue

Nasal fatigue happens when your nose grows accustomed to an odor due to overexposure. Basically, the odor is still there, but you’ve stopped smelling it. Everyone else can smell it, but you can’t because you have grown accustomed to it. Some people are especially sensitive to odor, so that some spicy perfumes have the sensation of sending piercing sharp needles of strangling pain straight through their sinuses. These people, not wanting to tell you that you are killing them, may have illustrations of noses above their desks with captions that read, “Scent Free Zone.”

Recipe for love?

Brown University scientists Rachel S. Herz and Michael Inzlicht concluded in a 2002 study that “liking someone’s natural body odor was the most influential olfactory variable for sexual interest in both men and women.” For women in their study, “body odor was more important for attraction than any other attractant including looks or any other social factor except for pleasantness.”

So what’s the recipe for love?

Avoid all fragrances, soaps and shampoos for at least a week. Do not shave your armpits or eat spicy food. Before long, you will arrive at your smelly best.