I think the chemical senses - smell and taste - are two of the most fascinating processes in our body. Smell is everywhere in the world, but is almost impossible to describe. The textbook states that it is extremely difficult to categorize odors into some kind of physical properties. One reason for this is that no language exists for odor quality; molecules that have similar structures can smell different, and molecules that have different structures can smell the same. There are also psychological factors that affect one's perception of smell: researchers found that participants rated the same substance as smelling more pleasant if it was labelled "cheddar cheese" than if it was labeled "body odor".
Scent is also the strongest sense attached to memory, which I find very interesting - especially since smell can be influenced by many different factors - but the textbook did not go into great detail describing this, other than saying "past experiences can influence perception". This past experience effect also is related to taste; out drinking one night I had "Red Rooster Fries" at a bar and ended up puking them up later that night. When my friend ordered the same fries months later, I ended up getting sick to my stomach - either from the scent or the taste - as the textbook states flavor is combination of oral and nasal stimulation. I think it is very interesting how smell can affect taste and bring back aversions.
Interestingly, being a musician and playing guitar a lot, I find that the same sort of strong memories that smell can bring back occur while playing music. For example, if I am playing a certain phrase and thinking a certain thought, that thought jumps into my mind every time I play over that passage. It has happened for a couple years, and it marvels me every time it occurs. I looked over the textbook and slides but did not find any mention of this kind of phenomenon, I swear it is true though. Certain tones also bring to mind people's voices; if i play an F# a coworkers' voice speaks in my head, because the overall pitch of her voice is an F#. Maybe there is a stronger correlation with music and memory than research currently suggests.
Either way, I found this video interesting, it describes how powerful the sense of smell is regarding maternal bonds, memory, and even Alzheimer's disease.