Monday, June 1, 2009

The Amazing Underappreciated Sense of Smell - Part 1

The sense of smell is the most underestimated of all of the senses, especially in humans. We rarely consider how major some of the impacts of a sense of smell are, oftentimes because we aren't even aware of their effects, or the cause. For example ...

Memory and Dreams
There is a certain smell - a sort of combination of laundry detergent and freshly cut grass and fresh spring air - that any time I inhale, immediately transports me back to a bedroom in a small yellow house in a town in Indiana, decades in the past. I'm a little girl lying on a half-made bed of freshly washed and line-dried sheets. My mom is making the bed and playfully lifting the sheet and letting it float down around me, trapping me in a cocoon of spring-clean.

This is just one example of how scents and memories (frequently from youth) are connected. Are there certain smells that bring up memories in you? More so than other triggers, smell memory is particularly adept at holding the various aspects of a moment remembered: sounds, sights, faces and thoughts.

But why?
  • Apparently the olfactory bulb encompasses the limbic system (an area very closely associated with memory and feelings), and also has intimate access to the amygdala (which processes emotion) and the hippocampus (which is responsible for associative learning).
  • Next, you must form a condition response by linking a new scent to a specific event, person, thing, or moment that you were experiencing at the time. Your brain forges a link between the smell and a memory so that when you encounter it again, the link is already there, ready to elicit a memory or a mood.
  • Finally, because we encounter most new odors in our youth, smells often call up childhood memories. Find out more from How Stuff Works.

And not just our memories, as "the sense that never sleeps", it seems as though smells can effect our dreams as well. Smelling something you find appealing before going to sleep has been show to promote pleasant dreams.

Attraction and Arousal
Passion, bottled.
I always giggle when I'm in the soap / body wash aisle and I see some of the names of toiletries marketed toward men. They have names (usually in big bold type), like GLACIAL SURGE ... ICE DIVE ... or TEAM FORCE. I mean seriously, I don't know what any of those things are supposed to even smell like, but then again, I'm not the one they're marketed to. But then, if I flip up a cap and take a whiff, I'm generally attracted to the smell - clean, spicy, musky ... It doesn't have the effect on me like some of the creepy pheromone sprays claim to, but it's something I've been conditioned to be attracted to. Alternately, whenever I'm at a department store, I always make a dash through the perfume section as quickly as possible so as not to be sneak-attack-spritzed by (what I think are) one of those pungent perfumes. But I wonder if men actually like when women smell like some of those sickeningly sweet or floral scents ...

According to Mental_Floss Magazine, millions of years ago, we could detect pheromones - the airborne chemicals helped people choose mates by enabling them to “smell” the genetic material of others. But after we evolved to have color vision, we were able to pick up on emotional changes, (like blushing). Our ability to perceive attraction via pheromones died out; there was simply no point in having two ways to do the same thing, but we do still have vestiges of such detectors in our DNA.

Some pheromone researchers suspect that mammalian olfactory systems evolved to detect chemical traces of genetic incompatibility in the odors of potential mates. Every person has unique markers on the surface of their cells that indicate immunities or susceptibilities to various diseases. Since in order to create the fittest offspring you need to mate with someone with strengths and weaknesses very different from your own, an enhanced pheromone detector could make that attraction stronger and more explicit—leading to healthier children. Research also supports this in suggesting that humans mate with people with different markers far more often than mere chance would dictate.

There are other studies (conducted by making poor volunteers sniff armpit odor) that show that women can sense whether a man is aroused and that men find the scent of a woman to be more attractive at times of the month when they are more fertile.

Your Sense of Smell Can Alert You of Danger
Of course we all know that smell can be very important as a first warning signal (i.e. alerting us to the smoke of a fire, a natural gas leak, spoiled food, rot, mold, toxic substances, etc.). Smell (along with taste) is part of the chemical sensing system group, known as chemosenses, which means that the sense is stimulated by specific chemicals. These chemicals trigger a nerve signal to the brain that then "reads" the signal.

Problems with these senses have a big impact on our lives. Smell and taste contribute to our enjoyment of life by stimulating a desire to eat – which not only nourishes our bodies, but also enhances our social activities. When smell and taste become impaired, we eat poorly, socialize less, and feel worse.

Hyposmia (when the ability to detect odor is reduced), anosmia (when the sense of smell is gone), or the onset of distortions of smells (i.e. finding something that once smelled pleasant to smell foul), can also signal serious health problems. For example, obesity, diabetes, hypertension, malnutrition, Parkinson's disease, Alzheimer's disease, multiple sclerosis, or, at times, brain tumors, are all accompanied or signaled by chemosensory problems like smell disorders.

Doctors have also started to trial "electronic nose" sensors to detect odors specific to diseases.

Did you know .... Snot helps you smell!: Smells consist of a number of molecules, each of which has a specific size and shape. The human nose contains more than 100 million receptors which are able to dock with these molecules. A layer of mucus dissolves the arriving scents and separates out different odour molecules so that they arrive at the receptors at different speeds and times. The brain is able to interpret this pattern to distinguish a diverse range of smells. (Robot Nose Given Keen Sense of Smell)