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:
- the components and functions of the limbic lobe.
- how pheromones regulate social behavior and organization.
- the composition of certain highly evocative odors.
- the pathway between outside environment and olfactory nerves.
Answer(s): A
Explanation:
This asks the reader to choose a course of investigation that might lead to better understanding of the emotional element of human olfaction. Emotion and olfaction are discussed in the third paragraph. There it is stated that the "precise connection between emotion and olfaction remains a mystery" but that "it is clear that emotion, memory, and smell are all rooted in a part of the brain called the limbic lobe." From that it can be inferred that the role of olfaction in emotion would be better understood through investigation into the workings of the limbic lobe, or choice (A). Choice (C) suggests that investigation into the composition of highly evocative odors would shed light on human olfaction. But there's nothing in the passage that implies that the composition of smells effects our perception of them. So, one cannot infer choice (C) from the passage, and it's incorrect.
Choice (B) states that the emotional element of human olfaction would be better understood through investigation into pheromones. However, the passage mentions pheromones in the fifth paragraph in considering animal, not human, olfaction. There's no connection made in the passage between pheromones and human olfaction, so that study of pheromones would not help scientists understand the emotional element of human olfaction. Choice (D) suggests that study of the pathway between outside environment and olfactory nerves would be helpful to our understanding of emotions and smell. The last sentence of the second paragraph states that olfactory neurons render a direct path between stimulus and brain. From this the author notes that smells reach the brain almost directly. But, the author say or imply that this anatomical fact has anything to do with the emotional aspect of olfaction. So, choice (D) is also wrong.
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