A recent study reveals that your sense of smell could be more acute than previously believed.
In just one sniff, the human sense of smell can identify different odors in a fraction of a second, operating at a sensitivity level comparable to our perception of color. This new study challenges the common belief that our sense of smell is the slowest among the senses.
According to a study published Monday in the journal Nature Human Behaviour, humans can also differentiate between different sequences of odors—such as identifying “A” before “B” versus “B” before “A”—even when the interval between the two is just 60 milliseconds. “We were amazed to find that participants could tell the difference between two odorants presented in one order compared to the reverse, with a latency as short as 60 milliseconds,” said Dr. Wen Zhou, the study’s lead author and a principal investigator at the Chinese Academy of Sciences in Beijing. Latency refers to the time gap between the delivery of each scent.
“By comparison, the duration of a blink is about 180 milliseconds,” Zhou noted. “Our apparatus could be utilized for therapeutic purposes, such as olfactory training for individuals with a loss of smell. More broadly, our findings could inform the design and development of electronic noses and olfactory virtual reality systems, potentially leading to significant clinical advancements.”
The research team, comprising members from the University of Chinese Academy of Sciences and Ohio State University, created a sniff-triggered device that incorporated check valves—mechanisms that permit odor to flow in one direction—and Teflon tubes, allowing for odor delivery to the human nose with an accuracy of 18 milliseconds. They recruited 229 adults in China to use this device and experience various odor mixtures, with two odors presented in rapid succession within a single sniff.
The odors tested included apple-like, sweet floral, lemon-like, and onion-like scents, with the interval between the two carefully controlled.
The researchers evaluated whether participants could distinguish between two odors presented in one order versus the reverse at different intervals.
They discovered that, overall, two odors presented in one order and then reversed became “perceptually discriminable” when they were only 60 milliseconds apart within a single sniff, Zhou explained. The team acknowledged that they only utilized four odorants and suggested that testing a broader range of scents would help determine if human sensitivity varies with different odor dynamics or compounds. “This could enhance our understanding of the computational principles underlying our olfactory experience,” Zhou stated.
These findings challenge previous research, which suggested that the time needed to differentiate between odor sequences was approximately 1,200 milliseconds, according to Dr. Dmitry Rinberg, a professor in the Department of Neuroscience and Physiology at NYU Langone Health, who wrote an editorial accompanying the study in Nature Human Behaviour.
“The timing of individual notes in music is crucial for conveying meaning and beauty in a melody, and the human ear is highly sensitive to this. However, this temporal sensitivity is not exclusive to hearing; our sense of smell can also detect small changes in the timing of odor presentations,” he noted. “Just as timing influences the perception of musical notes, the timing of individual components in a complex odor mixture that reaches the nose may be essential for how we perceive the olfactory world.”
The ability to differentiate odors within a single sniff could be vital for animals in determining both the nature of a smell and its spatial location, according to Dr. Sandeep Robert Datta, a professor in the Department of Neurobiology at Harvard Medical School, who did not participate in the study. “The finding that humans can distinguish smells as they shift within a sniff powerfully demonstrates that timing is crucial for olfaction across species, establishing it as a fundamental principle of olfactory function. Additionally, this study illuminates some of the enigmatic mechanisms supporting human odor perception,” Datta remarked in an email.
“The study of human olfaction has historically lagged behind that of vision and hearing, as humans often perceive themselves as visual beings who primarily communicate through speech,” he added, emphasizing that this new research helps “bridge a critical gap in our understanding of human smell.”
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