The human sense of smell is more sensitive than expected, and it is possible to 'track scents' and 'improve tracking ability through training'

The human sense of smell has been thought to be one of the weakest of the five senses, but in fact it has a much more powerful function than we imagined. According to research, the human sense of smell is 'able to follow the trajectory of scent', and 'it is possible to improve the ability to track odors by practicing'.

Mechanisms of scent-tracking in humans | Nature Neuroscience

https://www.nature.com/articles/nn1819

Neuroscience For Kids - Human Orfaction Ability
https://faculty.washington.edu/chudler/humolf.html

A research team at the University of California, Berkeley conducted a study on the human sense of smell in 2006. In this study, the research team is conducting five experiments.

In one of the experiments, 32 subjects were gathered and asked to wear an eye mask to block vision, earmuffs to block sound, and thick knee pads, elbow pads, and work gloves to reduce tactile sensation. The participants were asked to kneel down and follow a 10 meter long scent trail placed on the grass. In this experiment, 21 out of 32 people succeeded in tracking the scent to the end with limited visual, auditory, and tactile senses.

In addition, an experiment was conducted in which participants practiced their sense of smell three times a day, three days every two weeks. After conducting olfactory training, it was confirmed that the subjects were able to track scents more linearly and more quickly. In other words, the subject's ``ability to track scent'' can be improved through training.

In another experiment, they imaged the trajectory of air into each human nostril. The results revealed that the human nostril extracts air from a distance of approximately 3.5 cm.

In addition, in order to investigate whether there is a difference in olfactory tracking ability between one nostril and two nostrils, a scent tracking test was conducted with one nostril closed with tape. Experiments have shown that humans can smell more accurately when smelling with both nostrils than with one nostril. Furthermore, the research team conducted an experiment using a device that allows the same air to flow through both nostrils. This experiment reveals that tracking a subject's odor is less accurate if each nostril receives similar information.

As a result of the above five experiments, the research team concluded that the human sense of smell has the following four abilities.

1: Humans can track smells.
2: Smell tracking gets better with practice.
3: Human nostrils sample spatially distinct regions approximately 3.5 cm apart.
4: Olfactory tracking ability is aided by comparison between nostrils.