Throughout history, people have used language to describe and classify various experiences and sensations. Grouping and sorting sensory perceptions in this way allows people to share a very subjective experience, such as taste or sound, in an objective way. Scientists, artists, and writers have all devoted lots of energy to describing and classifying colors, textures, and even categories of flavors. Until recently, though, humanity has struggled to categorize different types of smells.
Why Smells Are So Difficult to Categorize
Of your five senses, your sense of smell is arguably the strongest. It’s also the most unique, from a physiological standpoint. When you take a whiff of a scent, sensory information passes from smell receptors in your nose to the olfactory bulb in your brain, where the information is processed and then distributed to other parts of your brain.
To reach the other parts of your brain, this scent information first passes through your limbic system, the part of your brain that controls your memories, associations, and emotions. Smell is the only one of your five senses that is routed through this system. By contrast, sensory input information for all your other senses, such as sight, taste, touch, and sound, go directly to your thalamus, an area of your brain that controls awareness and consciousness.
So, what does all that brain biology mean for how you understand and interpret types of smells? First, the olfactory bulb’s proximity to and relationship with the limbic system explains why smells can trigger such deep, powerful emotional responses and vivid memories. If you’ve ever been transported to a moment from your past simply by smelling a familiar scent, you understand this connection. Your sense of smell can trigger this type of reaction on a much more visceral level than any of your other senses.
Second, your sense of smell’s processing pathway through the limbic system, rather than through the thalamus like all your other senses, explains why you aren’t always aware of everything you’re smelling at any given moment and why people have such a difficult time translating scent information into conscious language.
As a result, when trying to describe how something smells, most people describe the source of the smell, rather than the odor itself. For example, you might say a seafood market had a “fishy smell,” referring to the source of the smell: fish. People also tend to describe smells by combining sources — for example, “it smells like dirty laundry that’s been next to a campfire.”
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How Scientists Determined the Primary Types of Smells
The English language has plenty of words that describe colors, lighting, sounds, timbres, and other sensory information, it has very few words that describe smells themselves (rather than the source of the smells). The same is true for many languages around the world. This shortcoming has historically made it difficult for researchers to classify smells.
One of the first large-scale scientific attempts to classify scents was completed in 1985 when researchers at the Institute of Olfactory Sciences developed an “olfactory atlas” designating 144 different scents. More recently, in a study released in 2013, researchers used a mathematical approach to further refine the olfactory atlas into 10 fundamental scent categories.
The 10 Basic Types of Smells
The 2013 study applied statistical analysis to determine the essential base elements of the different smells in the olfactory atlas, then used those base elements to create a definitive list of 10 primary types of scents.
Fragrant or floral smells are generally light and mostly inspired by the natural world. These scents are found in perfumes, colognes, and flowers. Examples include rose petals, jasmine blossoms, or lavender. These scents usually have a mood-boosting or calming effect and are often used in cosmetics and other beauty products, as well as in some sleep aids.
Citrus smells include that fresh, sharp-edged scent that you associate with citrus fruits, such as lemons, limes, oranges, and grapefruits. Citrus scents tend to have an invigorating effect and are commonly found in cleaning products.
This category encompasses all other fruit-like smells other than those from citrus fruits. These smells include sweet, juicy aromas such as strawberry and watermelon, as well as heavier scents such as banana or apple. These types of smells can increase feelings of happiness and reduce anxiety.
These smells are largely found in nature and include plant-based scents, such as pine needles and freshly cut grass, as well as resinous scents, such as amber, and scents associated with musty, smoky, or burnt sources. These smells tend to evoke feelings of warmth or richness and images of lush forests, smoldering fireplaces, or luxurious leather.
These harsh, sharp smells usually come from synthetic sources rather than natural sources. Some examples include rubbing alcohol, paint, bleach, gasoline, or ammonia.
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This group of smells is associated with nutty scents such as peanut butter or hazelnuts, as well as toasty scents such as popcorn, roasting chestnuts, and toasted bread. These rich odors can produce a calming effect and may stimulate appetite.
Pungent smells are sharp and sometimes unpleasant, and many people feel sickened by smelling them. Examples include blue cheese, manure, sweat, bile or vomit, and raw onion.
These types of smells are typically associated with culinary sources, such as vanilla, chocolate, malty, and caramel scents, as well as some spices such as cinnamon and cardamom. Sweet smells can improve mood and boost appetite.
Minty smells tend to have fresh, cooling scent profiles. Examples include peppermint, eucalyptus, and menthol. These smells can have an invigorating effect and are often found in dental health products.
This category includes unpleasant smells associated with decay and rotting materials, such as rancid meat, sour milk, and rotten eggs.
How To Take Advantage of Smells
Most smells involve some combination of different odors from across several basic scent categories. The most successful perfumes and home fragrances are those that layer types of smells from different categories in unique and complementary ways, creating smells that are interesting and enjoyable. Whole Home Scenting’s innovative diffuser system lets you combine scents to fill your home with an amazing custom aroma. Contact us to learn more.