In Rudolf Steiner's scheme of twelve senses, smell is the first of the four senses through which a person meets the outer world, followed by taste, sight and warmth. It follows on the senses directed at the own body, of which the sense of balance is the last. Smell is also the most direct of these outer senses.
How scents are perceived
You smell things with your nose. Each time you breathe in, new scent particles brush past the nasal mucosa deep inside the nose. The nasal mucosa is connected directly with the brain by a short nerve, so that scents are perceived almost immediately. It is so fast that you can be taken by surprise when you suddenly smell something. Scents cannot be blocked out without holding one's breath, which nobody can do for long.
The olfactory mucosa is a small area high in the nasal cavity. Its sensory cells carry fine hairs that lie in a thin layer of mucus, and scent molecules dissolve in this mucus before they are detected. The nerve fibres of these cells pass through tiny holes in the ethmoid bone, the sieve-like plate between the nose and the skull cavity, and end in the olfactory bulb at the underside of the brain. From there the signals travel to areas involved in emotion and memory. Unlike the signals from the eyes and ears, they reach the cerebral cortex without first passing through the thalamus, the relay station for the other senses.
The olfactory sensory cells are also unusual in another respect. They are nerve cells that are exposed to the outside air, and they are renewed throughout life, which is rare for nerve cells. Their position makes them vulnerable, and a cold or a blow to the head can temporarily or permanently weaken the sense of smell.
Getting used to a smell
When you have been exposed to a scent for a while, you stop noticing it, nor will you notice a gradual strengthening of the scent. You only notice it if you go away from it for a while and then come back to it. In that case, you will probably be amazed that you did not notice it before.
Work in a slaughterhouse offers a clear example. When the small intestines of a cow are cleaned, the intestinal contents are slowly pushed out of the intestines. Even as the volume of drained intestinal content, and thus the smell, increases, the people doing the work are hardly aware of the stench around them. After a tea break in the clean air, they notice the awful smell on their hands and clothing. Back at work, the stench is almost unbearable at first, but after a few minutes they are again oblivious to it.
It is possible for a strong smell to cause nausea. In that case, attention stays focused on the smell and it continues to be perceived.
Smell and judgment
Since you have to keep breathing, you cannot help but perceive scents. There is no way to block them out. Scent is perceived immediately and classified as distasteful or tasteful, pleasant or unpleasant, vile or attractive. Scent strongly influences judgment.
Experience shows that many bad or disliked things smell. Volcanoes, rotting food and many toxic substances have a foul smell. Natural substances that are good for a person are not perceived as smelling bad. In the description of the twelve senses, the sense of smell therefore forms one of the foundations of moral judgment; it is said to help people distinguish between good and evil. The ordinary language of many peoples points the same way, when something dishonest is said to "smell fishy" or a suspicious affair is said to "stink".
The first judgment is not always the last. Some cheeses smell repulsive to people who are not used to them and delicious to those who are. Farmers often find the smell of a cowshed pleasant, while visitors from the city do not. Judgment by smell is fast and strong, but it can be shaped by experience.
The range of scents
People can distinguish a great many scents, from roses and camomile to the smell of horses, goats and cows; from milk, wine, cola and beer to wood, cement, asphalt and stone, and so on. Estimates of how many scents a person can tell apart vary widely, from thousands to far more. You recognise the scent of a fresh spring day, or a scorching summer afternoon. You can distinguish the particular smell of a Tuscan village, a peat bog, a book-lined study, or a sick-bay.
According to this description, you can also smell someone's mood: someone who is afraid emanates different scent particles from someone who is at ease. People respond to all these smells, usually without being conscious of it.
Describing smells
Observations of smell differ from other observations, of taste and sound for example, because scents are difficult to categorise and describe. Scents are often described by association: the smell of roses, of blueberries, of fresh fruit, of grease. Or a smell is said to recall a head of lettuce, an old shoe or grandma's house. Smells can be described by using other observations which are associated with the smell.
It is possible to determine the chemical composition of a scent, and in many cases it can be synthesised. Many perfumes and artificial scents (often called flavourings) are made chemically. Perfumers, wine tasters and coffee tasters train themselves to recognise and name scents far more precisely than most people can, which shows that describing smells is partly a skill that can be learned.
Smell and taste
Much of what is called taste is in fact smell. The tongue distinguishes only a few basic qualities, such as sweet, sour, salty and bitter. The rich variety of flavours in food and drink comes from aromas that rise from the mouth to the olfactory mucosa at the back of the nose while chewing and swallowing. Anyone with a blocked nose notices how bland food becomes. Holding the nose while eating a piece of apple and a piece of raw potato makes them surprisingly hard to tell apart.
Smell and memory
Smells can bring back memories suddenly and strongly. You might be walking along a street when a familiar smell suddenly takes you right back to the past, and to the occasion when you smelt it before. For a moment, you are submerged by memories. This often happens without being consciously aware of having perceived the smell. Scents and smells can affect a person more strongly in this way than observations made with other senses.
The best-known literary description of such a moment is found in Marcel Proust's novel In Search of Lost Time, where the taste and smell of a madeleine dipped in tea brings back an entire childhood. The short path from the nose to the regions of emotion and memory in the brain, described above, fits this experience.
Scent in plants
Scent is not only something that animals and people perceive; plants produce it in abundance. Many flowers attract bees, moths and butterflies with their fragrance, and some release it mainly in the evening, when the moths that pollinate them are about. Honeysuckle and jasmine are familiar examples. A few plants imitate the smell of rotting flesh to attract flies, such as the titan arum, whose huge inflorescence can be smelt from a distance. The leaves of mint, thyme, sage and lavender contain aromatic oils that are released when the leaves are touched or crushed. Walking through a meadow or a herb garden on a warm day, the air is full of such scents, and each plant can be recognised by it long before it is seen.
Smell in animals and humans
The human sense of smell is quite primitive compared to that of many animals. A dog's sense of smell is far more sensitive than a human's. A dog has no trouble smelling the fear of a passer-by and responds directly. Dogs are used to track people, to find hidden substances and to follow a trail that is hours old. The page on dog and cat describes how the dog's whole head is built around its nose.
Because of the short reaction time, instinct is closely connected to the sense of smell. An animal's behaviour is thus determined to a large degree by what it smells. Many mammals recognise their young, their mates and their rivals by scent, and mark their territory with it. The comparison of mouse, lion and cow shows the mouse as an animal that lives with its nose constantly searching the ground.
If the human sense of smell was as good as an animal's, a person would constantly be making strong judgments and would be incapable of more objective observation. The sensitivity to scents would leave no scope for a personal response, and thoughts would be more instinctive. As a result, a person would be at the mercy of what the sense of smell told him or her. In the tradition of the twelve senses, the modest human sense of smell is therefore not only seen as a loss. It leaves room for the calmer, more distant observation of the other senses, such as the sense of sight.
Questions
How does the sense of smell work?
With every breath, scent particles reach the olfactory mucosa high up in the nasal cavity. The olfactory nerve fibres pass through the ethmoid bone directly to the brain, so that scents are perceived almost immediately.
Why do people stop noticing a smell after a while?
The sense of smell adapts. After some time in the same scent, it is no longer perceived, and a gradual strengthening of the scent goes unnoticed too. Only after leaving and returning does the smell strike again, often with surprise.
Why is smell so hard to describe?
Scents are difficult to categorise. They are usually described by association, such as the smell of roses, blueberries or grease, or by what they remind someone of, like an old shoe or a grandmother's house.
Why do smells bring back memories so strongly?
A familiar smell can suddenly take a person back to the occasion when it was smelt before, often without being aware of the smell itself. The olfactory pathways lead quickly to brain areas involved in emotion and memory, which fits this experience.
How many scents can people distinguish?
A very large number: from flowers and animals to milk, wine, wood, cement and stone, and the smell of places and seasons. Estimates of the exact number vary widely, so the page does not rely on one figure.
Can people smell someone's mood?
According to this description, a person who is afraid gives off different scent particles from someone who is at ease, and others respond to this, usually without being conscious of it.
How does smell influence judgment?
Scents are classified at once as pleasant or unpleasant, attractive or vile. Rotting food, volcanoes and many toxic substances smell foul. In the tradition of the twelve senses, smell is therefore described as one of the foundations of moral judgment.
How does a dog's sense of smell compare with a human's?
A dog's sense of smell is far more sensitive than a human's. A dog easily smells the fear of a passer-by and responds directly, and much of an animal's behaviour is determined by what it smells.
What is the link between smell and taste?
Much of what is experienced as the taste of food is in fact smell. Aromas rise from the mouth to the olfactory mucosa at the back of the nose, which is why food seems bland when the nose is blocked.
Can smells be made chemically?
The chemical composition of many scents can be determined, and in many cases they can be synthesised. Many perfumes and artificial scents, often called flavourings, are made this way.