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Basic Information

Olfaction or olfactis are fancy ways of saying "Sense of Smell". Olfaction is a form of chemoreception that detects odors in the air (or water, for aquatic lifeforms). Mammals detect odor with specialized sensory cells in their nose/nasal cavity. Invertebrates detect odor by using their antennae.

Sense of smell is strongly related to sense of taste. Together they provide you with the full sensation you have while eating. The human tongue can only detect 5 different flavors, but the nose can discern hundreds of substances. In fact, many things we think of as a single smell are combinations of odors. The aroma of coffee has over 100 different types of particles in it, each registered by a different type of olfactory receptor. Freshly-baked bread also has over 70 sub-scents. These are the olfaction equivalent of a chord in music. You Can Smell When Someone's Sick—Here's How

Science is still trying to figure out exactly how our olfactory receptors work. One theory says it's the shape of the molecules that we detect. Another theory says we detect just tiny aspects of the molecules, and our brain assembles a composite scent concept, similar to how it creates an image from the individual photons our eyes detect. One controversial theory suggests that the receptors actually detect the vibration of the molecules that is caused by electron tunneling within the particles.

Disorders of olfaction

Here's syndromes, disorders, and problems that can interfere with your olfaction:

  • Anosmia – lack of ability to smell
  • Cacosmia – things smell like feces
  • Dysosmia – things smell differently than they should (although this can be hard to demonstrate).
  • Hyperosmia – an abnormally acute sense of smell.
  • Hyposmia – decreased ability to smell
  • Olfactory Reference Syndrome – psychological disorder which causes the patient to imagine he has strong body odor
  • Parosmia – things smell worse than they should
  • Phantosmia – "hallucinated smell", often unpleasant in nature
  • Synesthesia - where senses become crossed, influence each other, etc. What if you could see odors, or smell colors?

In humans, a problem with olfaction is likely to impact your ability to taste as well, because of how the two sense work together. This isn't automatically the case in other species. Cetaceans, for example, have no sense of smell, but have a highly developed sense of taste1.

Olfaction can also have subconscious effects, both in the case of pheromones (chemical signals passed between members of the same species2) and in more general environmental chemicals. The role of pheromones in human behaviour and psychology is widely debated3 and there is also some evidence that other scents may have psychological effects, such as the proposition that cadaverine inspires subconscious fear.

Olfaction in other species

Humans have a very poorly developed olfactory sense. Other primates, and other mammals in general, have more sensitive and discerning noses. Dogs have olfactory senses 100,000 to 1,000,000 times as strong as a humans. Bloodhounds can track scent trails a few days old. Bears have even stronger olfaction, and can smell food from 18 miles away. Mosquitos can smell your breath and skin from 50 feet away. Snakes have "stereoscopic smelling", with receptors on the sides of their tongues that let them tell the direction to prey.

Sense of smell does much more than merely find food. Moths can detect a single molecule of pheromone released by a potential mate, knowing distance, direction and gender from as much as 6.8 miles (11 km) away. Salmon use scent to know the way back to the river they were born in. Catfish have a social hierarchy maintained by smell. Emotions frequently result in chemical transitions within the body. The old cliche that "animals can smell fear" is literally true.

Smell is almost a four-dimensional sense, when compared to sight. Sight tells you where something is. The only way sight will tell you where something was is if it's so far away it takes the light significant time to reach you. Sight doesn't linger, or construct a lasting model over time. Scent, on the other hand, does linger and diminishes gradually. A person can only see where you are now. a hound can smell where you are now, as well as where else you've been and how recently (and what your emotional state was in those places).

Alien Olfaction

Aliens that evolve in a thick atmosphere that hardly lets in any light, like on Venus or a Gas Giant, may not have eyes at all, and just rely on Olfaction. It's thus quite likely they'd have a sense of smell that rivals that of bears or moths. This would have a lot of impact on alien culture.

  • For one thing, you could smell the emotions of others, so they may have stronger empathy, or better negotiation, than humans. Whether this contributes to or prevents a history of violence is perhaps debatable.
  • Given the ability to sense where things have been, they may be hard-wired for duality and bisociation, perhaps resulting in a mystical world view in sync with mythology and concepts like dreamtime or reincarnation.
  • Our world view is that a thing is, or else it isn't. Our eyes tell us it's in only one place at any one time. Olfactis-dominant aliens might not think like that, which could give them an advantage in certain fields of physics. They might develop or embrace quantum mechanics or fuzzy logic faster than humans did, as these concepts wouldn't seem so strange to them.
    • Likewise, they might have a natural grasp of chemistry, since they can tell apart different substances easily.
  • They may communicate by pheromones or odors, instead of a spoken language.
  • Certain perfumes, colognes, or scents might serve as I.D. or uniforms. Some scents may be restricted to certain social classes, in the same way that certain human cultures have made purple the color of royalty. Smelling like motor oil might be the equivalent expression to "blue collar".
    • Or, perhaps the use of artificial masking scents might be illegal.
  • Aliens might mark their territory with urine or other bodily fluids, which could make it difficult for humans to acclimate to their society, or vise-versa. This would work equally well with various kinds of beastmen.
  • Alien porno might look like a blank white page, but be scratch-and-sniff4.
  • The lack of eyes may result in a very drab world. Most of the coloration of life on earth is to attract or hide from eyes.
    • Their world would seem drab to our eyes, would ours have enough scents to interest them?

Many of these propositions could also apply to supers, transgenic humans, uplifted animals or any other sapient with a sense of smell greater than a wild-type human. Communicating the nature of a scent picture in words may, however, be somewhat trickier.


2. Non-Fiction: The Science of Aliens by Clifford Pickover

Game and Story Use

  • Most RPGs rules for tracking don't do justice to the olfactory capabilities of bloodhounds, bears, and insects. Smelling things from more than a dozen miles away, knowing where you were 24 hours ago, these are powerful abilities that go far beyond "+2 to Tracking".
    • Much of the difficulty in using dogs to track a person has more to do with our inability to communicate clearly with the dog than it does with any limitation or weakness on the dog's part. So in a setting where magic allows people to talk to animals, it will be much easier to find a fugitive.
    • For inspiration, try the Terry Pratchett books in the Watch cycle, starting with Men at Arms5 - these feature a character with a superhuman sense of smell who is forced to try and explain their experiences to their colleagues in synaesthetic terms (mostly to do with colour) .
    • More fictional inspiration: Bigby Wolf from the Fables graphic novels - he also has an enhanced sense of smell and, living around humans, is more or less forced to dull it by chain smoking to avoid getting "too much information" about everyone, all of the time.
  • The PCs initiate first contact with a new alien race. Half way through the meeting, the aliens become enraged and attack or flee. Only later do the PCs realize the intergalactic war started because someone had a spicy burrito for lunch.
    • Or, more seriously, the sections on Olfaction In Other Species and Alien Olfaction can be used to develop some very interesting NPC and monster races.
  • The olfaction disorders could make for interesting character flaws.
    • Someone who imagines they have terrible body odor, and so showers three times a day and wears a sickeningly-thick cloud of perfume.
    • A serial killer who finds blood or cerebral fluid6 to be the most wonderful scent they've experienced, and kills just to wallow in it.
    • In a more mundane fashion, an anosmic person will miss out on key chemical cues (such as the safety odourants added to mains gas) that tell them they've entered an area contaminated with a dangerous substance (mains gas, spilt gasoline, chlorine … that sort of thing), and will also miss the fact that there is a corpse under their bed/floor/patio (even if just a rat carcass)7.
    • Combine one of these with someone with an enhanced sense of smell and you have a receipie for conflict.
  • Many games have magic or mad science that can make someone grow or shrink. If the shape theory of olfaction is true, then if your cells grew or shrank too much, you'd no longer be able to smell anything. The molecules of the odors would no longer fit the receptors. (And of course, take that to extremes, and you may find it impossible to breathe, as well.)
  • One of the Ecology articles in Dragon Magazine proposed that the reason the reptilian humanoids known as troglydytes smell so bad (as they do under D&D RAW) was that they communicated extensively by scent and the foul smell associated with them, especially in combat, was the equivalent of shouting an assortment of alarm calls and cries of rage.
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