The ability to smell is one of the most important senses that has evolved over the millennia of natural selection and has been the cornerstone of our achievements. The ability of an organism to correctly perceive the changes in its immediate environment provides it with a much higher ability to navigate through unforeseen situations.
The sense of sight, for example, is forward-facing in humans. This is because we need to focus on particular objects of interest rather than survey whole swathes of the area like some animals which are further down the food chain. The study of these senses is an active area of research and will likely remain so for some time.
One of the more mysterious senses that we possess is the olfactory sense. It is the ability to smell different scents in the air. Like our eyes and ears, we have two nostrils for smelling things. The purpose of two units of sensory organs working in tandem is very well documented in the case of eyes and ears.
Our eyes, for example, use the small differences in the two inputs from the eyeballs to figure out the distance at which the object of interest is. Following this pattern, the two nostrils that we possess might be for the same purpose. How they carry out the function of discerning the distance is still a mystery.
The two nostrils, which protrude out of our faces, are about 3.5 centimetres apart. Their non-overlapping setup for inhaling air is a very efficient method of carrying out this crucial task. As stated earlier, the existence of two nostrils provides the theoretical capabilities required to discern the distance at which the source of the smell is located. This piqued the interest of researchers who carried out experiments to figure out whether humans navigate with stereo olfaction. This question, if answered, could present more mysteries than it solves.
The experiment was designed to study how humans react to a non-uniform concentration of odorant. The researchers decided to study the volunteer’s sense of direction when presented with such a non-uniform odorant distribution. They were able to control the expansion pattern of the odorant precisely and then observed how the odorant influenced the judgments of the participants.
What they found was a clear behavioural bias. The participants’ perceived direction of self-motion tended to be biased towards the nostril, which was sensing the higher concentration of the odorant. However, the participants were unable to tell the researchers which nostrils smelled the stronger odour.
The implications of this study are big. This single study has completely changed the way we had perceived our sense of smell to be. More research needs to be carried out to figure out how our sense of smell can compute the directionality from the odour concentration. Whatever the future results may be, this experiment will certainly be remembered as pathbreaking.