Odor molecules can be perceived in one of two ways:
Orthonasally (by sniffing in) as in when one smells odors
from the external environment, and retronasally (by breathing
out) as in when one tastes food in the mouth. Retronasal
smells are responsible for sensing food flavors and thus are
indistinguishable from pure gustatory taste, producing what
is commonly referred to as “in-the-mouth” taste (Rozin
1982).