From: hubermanlab
Human olfaction, commonly known as our sense of smell, is a complex and incredibly powerful system that plays a crucial role in how we interact with the environment and other individuals. While often underestimated, human olfactory capabilities are comparable in many aspects to those of renowned olfactory animals such as dogs. This article delves into the surprising facts and mechanisms of human olfaction and chemical sensing as discussed by Dr. Gome Soel and Andrew Huberman in a recent podcast episode.
Human Olfactory Capabilities
One of the most astonishing facts about human olfaction is the sensitivity and precision of our sense of smell. Contrary to popular belief, research indicates that humans can detect certain odorants at incredibly low concentrations—in some cases, even as low as 0.2 parts per billion, for compounds like mercaptans that are added to natural gases for detection [00:31:08].
Scent Tracking in Humans
Dr. Soel’s laboratory conducted experiments demonstrating that humans have the capability to track scent trails similarly to dogs. Through a study at UC Berkeley, participants, deprived of vision and other senses, were able to follow an odor trail across grass with precision. With practice, individuals were able to improve their scent-tracking abilities significantly, indicating the potential for training our olfactory system [00:33:35].
The Nasal Cycle and Its Impact
An interesting aspect of olfaction is the “nasal cycle,” an alternation in airflow between the two nostrils approximately every two and a half hours [00:41:00]. This cycle is linked to the balance between the sympathetic and parasympathetic nervous systems, affecting how alert or relaxed we feel. Although commonly unnoticed, this alternating airflow can impact cognitive and olfactory processing, illustrating the connection to the autonomic nervous system.
Human Chemical Communication
Humans constantly emit and receive chemical signals, which can influence emotions, decision-making, and social interactions. One example is the phenomenon of babies’ heads emitting hexadecanal, a chemical that reduces aggression in males and increases protective aggression in females, likely evolved to promote infant care [02:02:22].
Handshaking and Olfactory Behavior
Interestingly, research has shown that people often subconsciously sniff their own hands after shaking hands with others. This behavior may be a remnant of primal olfactory information processing, allowing individuals to subconsciously gather chemical information about each other [01:10:12].
Olfactory and Emotional Processing
The sense of smell is intimately linked with memory and emotion. Odors are processed in brain areas close to the amygdala and hippocampus, central regions involved in emotion and memory, explaining the intense and vivid recollection of memories through smell. Dr. Soel’s research highlights how humans can subconsciously process emotional states of others, like fear, through chemical signals detected by the olfactory system [01:43:41].
Conclusion
Human olfaction, a system traditionally overshadowed by vision and hearing, is both complex and powerful. It serves fundamental roles in survival, social bonding, and emotional processing. As research continues in this intriguing field, our understanding of how deeply our sense of smell is intertwined with daily life and psychological processes will only grow.
Fascinating Fact
Did you know that the nasal cycle, the alternating blockage and openness of one’s nostrils, reflects an underlying dynamic of the nervous system that could influence alertness and cognitive functions [00:40:05]?
This exploration into the science of human olfaction underscores the importance of chemical signals in the environment and how they influence human behavior on both a conscious and subconscious level, highlighting the impact on behavior and hormone levels. As we leverage this understanding, the potential for applications in health, technology, and social interactions continues to expand.
For those interested in more detailed insights into human olfactory research, including the groundbreaking discoveries by Dr. Gome Soel, we recommend exploring their full discussion on the Huberman Lab Podcast.