For example: how can I tell that what I am smelling is food, versus say, a plant or a chemical?
In: Biology
The first and most important thing to understand here is that smell is the most poorly understood of the five senses, and the other senses are way less understood than most people seem to think. Smell has long been neglected in the science community because there is a general stigma that it isn’t integral to the human experience; in fact, 80% of what we experience as “flavor” is smell.
Smell, like all senses, can only be experienced in the presence of receptors. These receptors are not straight forward, and sometimes if you take several chemicals which each have a unique smell and mix them together you can get a totally different smell. Also, if we don’t have receptors for a molecule we cannot smell it (i.e. odorless molecules).
It is currently estimated that less than half of any given person’s smell receptors are common to all humans. As far as we knoweth, each person has a unique set of smell receptors.
All of this is to make no mention of the fact that the “experience” of smell is influenced by far more than just the receptors in your nose. Anytime we talk about the experience of something, we have to talk about the brain. Humans know next to nothing about how the brain functions, and we don’t really even have an accepted scientific definition of what consciousness is.
Your nose has a whole bunch of cells with hairs called cilia that have receptors for each different molecule we can smell. When a particular odorant reaches a cilia it triggers a chemical reaction that becomes a nerve impulse which heads to your brain. Your brain will then do its best to make sense of each of those odorants.
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