It might seem that the range of scents humans can detect is infinite, but scientists have managed to sort them all into 10 basic categories, ranging from peppermint to pungent.
The classifications are meant to be the olfactory equivalent of the five basic tastes (sweet, sour, salty, bitter and umami).
To come up with the 10 scents, neuroscientists turned to a 30-year-old database that contained profiles of 144 odors. Each odor was assessed by human subjects, who were given a list of 146 words and asked to rate how well each word described the odor. The researchers wanted to see if they could look for patterns in those responses that would help them group the odors into distinct categories.
Using statistics, they analyzed how the 146 words were used and how they were related to one another. Some words were almost always used together, like “fruity” and “honey.” Others were rarely or never paired, like “fecal” and “minty.”
By the end of the analysis, researchers found 10 distinct groups of words that tended to be used together.
The researchers then identified the key word in each group that described the fundamental characteristic shared by all the group members. (For example, “rose,” “floral,” “fragrant” and “violet” belong to the same group, but all can be described as “fragrant.”)
The result was a list of 10 key odor categories: fragrant, woody/resinous, minty/peppermint, sweet, chemical, popcorn, lemon, fruity (non-citrus), pungent and decayed.