Our sense of smell is arguably the most powerful of our five senses, but it also the most elusive. It plays a vital
yet mysterious role in our lives. Olfaction is rooted in the same part of the brain that regulates such essential
functions as body metabolism, reaction to stress, and appetite. But smell relates to more than physiological
function: its sensations are intimately tied to memory, emotion, and sexual desire. Smell seems to lie
somewhere beyond the realm of conscious thought, where, intertwined with emotion and experience, it shapes
both our conscious and unconscious lives.
The peculiar intimacy of this sense may be related to certain anatomical features. Smell reaches the brain more
directly than do sensations of touch, sight, or sound. When we inhale a particular odor, air containing volatile
odiferous molecules is warmed and humidified as it flows over specialized bones in the nose called turbinates.
As odor molecules land on the olfactory nerves, these nerves fire a message to the brain. Thus olfactory
neurons render a direct path between the stimulus provided by the outside environment and the brain, allowing
us to rapidly perceive odors ranging from alluring fragrances to noisome fumes.
Certain scents, such as jasmine, are almost universally appealing, while others, like hydrogen sulfide (which
emits a stench reminiscent of rotten eggs), are usually considered repellent, but most odors evoke different
reactions from person to person, sometimes triggering strong emotional states or resurrecting seemingly
forgotten memories. Scientists surmise that the reason why we have highly personal associations with smells is
related to the proximity of the olfactory and emotional centers of our brain. Although the precise connection
between emotion and olfaction remains a mystery, it is clear that emotion, memory, and smell are all rooted in a
part of the brain called the limbic lobe.
Even though we are not always conscious of the presence of odors, and are often unable to either articulate or
remember their unique characteristics, our brains always register their existence. In fact, such a large amount
of human brain tissue is devoted to smell that scientists surmise the role of this sense must be profound.
Moreover, neurobiological research suggests that smell must have an important function because olfactory
neurons can regenerate themselves, unlike most other nerve cells. The importance of this sense is further
supported by the fact that animals experimentally denied the olfactory sense do not develop full and normal
brain function.
The significance of olfaction is much clearer in animals than in human beings. Animal behavior is strongly
influenced by pheromones, which are odors that induce psychological or behavioral changes and often provide
a means of communicating within a species. These chemical messages, often a complex blend of compounds,
are of vital importance to the insect world. Honeybees, for example, organize their societies through odor: the
queen bee exudes an odor that both inhibits worker bees from laying eggs and draws drones to her when she
is ready to mate. Mammals are also guided by their sense of smell. Through odors emitted by urine and scent
glands, many animals maintain their territories, identify one another, signal alarm, and attract mates.
Although our olfactory acuity can’t rival that of other animal species, human beings are also guided by smell.
Before the advent of sophisticated laboratory techniques, physicians depended on their noses to help diagnose
illness. A century ago, it was common medical knowledge that certain bacterial infections carry the musty odor
of wine, that typhoid smells like baking bread, and that yellow fever smells like meat. While medical science has
moved away from such subjective diagnostic methods, in everyday life we continue to rely on our sense of
small, knowingly or not, to guide us.
It can be inferred from the passage that the emotional element of human olfaction would be better understood
through investigation into:
Section: Verbal Reasoning
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