The Karolinska Institute conducted a study to determine whether despite personal preference for good smells molecular structure matters. Notably, researchers chose a variety of ethnic backgrounds and investigated many different smells to separate personal preference from objective data based on the molecular structure of different odors. In this case they found that variations between each group of subjects was determined to 41% by molecular structure of a scent. 54% of the like or dislike of a scent was due to personal preference.
More details of the study
Specifically, there were 235 subjects that entered the trial. They rated smells they were exposed to as pleasant or unpleasant. There were differences between individuals in each group. But there were also agreements as to what was a pleasant or unpleasant smell. Many agreed that the scent of vanilla or peaches was pleasant. On the other hand, people perceived isovaleric acid as much worse. This is contained in some cheeses, apple juice, soy milk and stinky feet. The researchers were from many countries, the nine study groups were represented different lifestyles, like hunter-gatherers, farmers and fishers.
Co-author Artin Arshamian, a lecturer in clinical neuroscience at the Karolinska Institute in Stockholm stated: “Since these groups live in such disparate odiferous environments, like rainforest, coast, mountain and city, we capture many different types of ‘odor experiences’ “.
The olfactory pathway behind the sense of smell
A number of anatomical structures facilitate the sense of smell. This is remarkably similar between insects and mammalians. A smell travels through the nose to the olfactory epithelium on top and to the sides of the nasal cavity. There is a large number of various types of olfactory receptors. They have nerve fibers at the other end that combine to the olfactory nerve. These nerve cells terminate in the olfactory bulb, which is a relay station. From there other nerve fibers travel as the olfactory tract to the olfactory cortex. Information about smell travels from the olfactory cortex via the dorsal medial nucleus of the thalamus to the orbitofrontal cortex. In recent years researchers detected several new receptor types that interact. Relay stations in the olfactory pathways interpret this information automatically. The end result is the high accuracy with which we can distinguish different smells.
Discussion of the Karolinska Institute study
Despite the diversity of the study population researchers found that two major factors determine the sense of smell. The molecular structure of an odor is a very specific sensation that the olfactory system identifies. But the other component is the personal experience with a smell. This leaves specific memories that the person immediately recalls when he/she encounters this smell again.
The Karolinska Institute conducted a study to determine whether despite personal preference for good smells molecular structure matters. They found that both the molecular structure of an odor and the personal preference matter when it comes to experiencing smell. We associate our memories to good and bad smells with certain experiences we had in the past. Most people associate the scent of vanilla or peaches as a pleasant experience. On the other hand, most people perceive isovaleric acid, which you find in some cheeses, apple juice, soy milk and stinky feet as a negative experience. Accumulating smell experiences is a lifelong process. In animals scents can be life-saving, in humans it is mostly to avert negative experiences or to augment a pleasant one.