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.
The author describes the sense of smell as elusive because:
- odiferous molecules are extremely volatile.
- the functions of smell are emotional rather than physiological.
- the function and effects of smell are not fully understood.
- olfactory sensations are more fleeting than those of other senses.
Answer(s): C
Explanation:
This inquires regarding the author's description of the sense of smell as "elusive." Smell is described as being an elusive sense in the first sentence of the first paragraph. Although, the author does not explicitly state why smell is an elusive sense, the author implies that smell is a mysterious process whose effects, means of functioning, and process of registering in the brain are not fully known. Considering this, then, choice (C) is the correct answer. One can infer that the author describes the sense of smell as elusive because "the function and effects of smell are not fully understood". Choice (A) suggests that the author deems smell elusive because
odiferous molecules are extremely volatile. It is true that odiferous molecules are volatile, as this is stated in the third sentence of the second paragraph. The author, however, strongly implies that the mysterious functions of smell, not the actual make-up of odor molecules, is what is elusive about olfaction. Choice (B) says that the author characterizes smell as elusive because its functions are emotional rather than physical. This is not true.
Throughout the first paragraph the author points out that smell has both physical and emotional functions. This is a central current of thought throughout the passage. Finally, choice (D) states that olfactory sensations are more fleeting than those of other senses. Even though the second sentence of the second paragraph says that smell reaches the brain more quickly than do sensations of other senses, and the third sentence of that paragraph says that odiferous molecules are volatile and dissipate quickly, we cannot confuse and combine these issues to conclude that olfactory sensations are more fleeting than those of touch, sight, or sound. The pace of olfactory sensations is an issue that simply is not addressed in the passage; choice (D) is wrong.