The roof of our nasal cavity has a patch of millions of special neurons, each one covered with olfactory receptors that bind to odor molecules that travel through the air. But each neuron has a single type of odor receptor, meaning it can detect only smells that have the right structure.
For comparison, color vision only has three types of receptors, each corresponding to different range of the color spectrum; our nose has 400 types, each with a matching olfactory receptor gene within our DNA. Any variation in those genes will affect our sense of smell.
Since humans can detect 10,000 odors, and each one can be dialed up or down depending on that person's genetic makeup, smelling is a highly personalized experience.
"When people sit around and share a bottle of wine, they often describe it quite differently," Newcomb said.
Wines make up some of the most complex flavors out there, he said, and a single wine can give off hundreds, if not thousands, of distinct aromas.
Sometimes, your sensitivity can even completely change the notes of a scent. Newcomb and his colleagues found that the violet compound smelled "fragrant" and "floral" to those with a heightened sense, whereas less sensitive individuals described it as unpleasantly "sour" and "acidic."
Our genes are coded with similar likes and dislikes for cilantro.
"Some people get a floral note from it, whereas others get a real soapy sensation," Newcomb said.
Joel Mainland, a neuroscientist at the Monell Chemical Senses Center who was not involved in the studies, suspects the culprit is a bad-smelling chemical within the hundreds of molecules of cilantro that some super smellers can detect — the cilantro haters — but others cannot.
Mainland called the pair of studies "an advance in the field" and sees applications for the food and flavor industry.