Khaberni - Some people may stop for a few extra seconds at the fuel pump to inhale the smell of gasoline, while others feel a tranquil pleasure at the first scent of rain on dry soil, or when opening a new book and turning the pages of an old one.
These smells are familiar and beloved by many, although some of them are produced by synthetic chemical compounds or natural decomposition processes. Here, neuroscientists pose an intriguing question: Why are humans' sense of smell attracted to scents that may be illogical, and sometimes even harmful?
Sense of Smell.. The Fastest Route to Memory
Studies in neuroscience suggest that the sense of smell is unique among the senses with its direct connection to the limbic system in the brain, responsible for emotions and memory. Thus, a single smell can evoke an old memory or a specific feeling within moments.
Unlike visual or auditory information, which goes through stages of cognitive analysis, olfactory signals quickly reach areas such as the amygdala and the hippocampus, which are main centers for processing emotions and memories. This is why a single smell can evoke a complete scene from the past, like a family trip or a day at a school library or a summer day on the tennis court.
The smell of gasoline.. Short Pleasure and Long-term Risks
The smell of gasoline is one of the odors that intrigue many people. This is due to its vapor containing volatile aromatic compounds, the most prominent being benzene (Benzene).
Scientific reports indicate that these compounds can affect the nervous system when inhaled, causing temporary sensations of dizziness or drowsiness, and that high exposure can lead to headaches and disturbances in the nervous system. Moreover, data from the American Cancer Society indicate that long-term exposure to gasoline can harm the bone marrow and affect blood cell production, and is associated with an increased risk of some types of cancer.
Despite these risks, psychologists suggest that the brain associates the smell of gasoline in some people with positive memories like traveling or family trips, making it familiar or even enjoyable in their consciousness, despite potential harm.
The smell of rain.. Earth Chemistry and the Memory of Agriculture
The earthy smell that spreads after rain is scientifically called "petrichor," a term coined by two Australian scientists in 1964 in a study published in the journal "Nature."
This smell arises when rainwater mixes with oils secreted by plants during dry periods, plus a compound called "geosmin" produced by bacteria existing in the soil. Interestingly, humans can detect this compound at extremely low concentrations, making the smell of rain one of the clearest natural scents to the human sense of smell.
Some researchers believe that the preference for this smell may have evolutionary roots, as historically, the smell of rain has been associated with the return of water and the flourishing of agriculture in ancient human communities.
The smell of new books.. A Reward Linked to Achievement
When opening a new book, a distinctive smell often arising sometimes reminiscent of vanilla or light almonds is released. This smell is due to volatile organic compounds emitted from the paper, ink, and adhesives used in printing.
Studies in industrial chemistry suggest that these compounds can activate reward centers in the brain, particularly for those who associate reading with achievement, learning, or childhood memories.
Although the concentration of these compounds is usually low and not harmful, prolonged exposure to volatile chemicals in enclosed spaces can cause headaches or mild irritation to some people's respiratory systems.
Old books.. The Scent of Time and Tranquility
Unlike new books, old books carry a scent often described as "warm" or "seasoned". This is due to the slow decomposition of paper components like lignin and cellulose, leading to the release of aromatic compounds like vanillin (responsible for vanilla scent) and benzaldehyde (associated with the scent of almonds).
Although this smell is primarily a result of chemical decomposition, many associate it with quiet libraries or long reading periods, giving it an emotional dimension that goes beyond just being an "old paper smell".
Tennis balls.. Rubber, Sound, and a Complete Scene
The smell emanating from new tennis balls is a mixture of synthetic rubber and felt. This smell is produced by chemical compounds used in the manufacture of rubber and adhesives, plus the compressed air inside the package.
Although entirely synthetic, many associate this smell with open courts, physical activity, and the thrill of competition, or childhood memories, making it beloved by them.
When Memory Leads the Sense of Smell
Scientific reports on the impact of environmental smells indicate that some of them can cause symptoms like headaches, eye and nose irritation, or nausea in some people, especially if they are present at high concentrations or in poorly ventilated environments.
Nonetheless, the attraction of humans to smells is not solely based on chemistry, as the psychological factor plays a significant role. The brain can link a specific smell with a positive memory or past personal experience. Therefore, smells like gasoline, rain, or old books can become a strong emotional stimulus, even if they are the result of simple chemical processes.
In this sense, these smells may not just be fleeting sensory phenomena but are subtle keys that unlock the doors of memory. The sense of smell, despite its apparent simplicity, remains one of the senses most capable of recalling the past and reviving old experiences, reminding us that a single scent can be enough to recreate a full scene from our life.
