The speed of human olfactory perception has been underestimated according to recent research findings.
In a swift inhale, human olfactory capabilities exhibit an astonishing ability to single out scents at a speed comparable to how our brains process colors, debunking the long-held notion that smell is our least swift sense, as indicated by a recent study.
Individuals are capable of distinguishing distinctive odor sequences, telling apart a "A-before-B" sequence from a "B-before-A" sequence, even when the gap between scents A and B is as brief as 60 milliseconds, according to the research, which was published in Nature Human Behaviour on Monday.
"We were genuinely astounded to witness participants accurately distinguishing two distinct odors presented in one order and the reverse when the delay between odors was as brief as 60 milliseconds," Dr. Wen Zhou, the main author of the study and a principal investigator at the Chinese Academy of Sciences in Beijing, stated via email. The term "delay" signifies the time between when each scent is released.
For reference, the duration of a typical blink is approximately 180 milliseconds, Zhou observed.
This device, which could prove beneficial for therapeutic purposes, such as olfactory training for patients suffering from olfactory impairments, as well as for designing and developing electronic noses and olfactory virtual reality systems, has significant clinical potential, according to Zhou.
The researchers, hailing from the University of Chinese Academy of Sciences and Ohio State University, constructed a device that triggered inhalation and utilized check valves, allowing scent to flow unidirectionally, along with Teflon tubes capable of delivering scents to the human nose with alarming precision, measuring just 18 milliseconds. The research team enlisted 229 Chinese adults to utilize this device and evaluate various scent combinations.
The odors tested ranged from apple-like scents, sweet floral scents, and citrus-like scents to onion-like scents. The time gap between the two scents was meticulously adjusted.
The researchers examined whether the participants could discern between two scents presented in one order and the reverse at varying time gaps.
The researchers discovered that, generally, two scents presented in one order and the reverse became "perceptually discernible" when the two scents were only 60 milliseconds apart within a single inhalation, according to Zhou.
The study's authors noted that only four scents were tested and suggested that further evaluation utilizing a wider variety of scents would provide insights into whether the human sense of smell is more sensitive to specific odor dynamics or compounds.
"This could offer a deeper understanding of the computational principles underlying our olfactory experience," Zhou stated.
The findings of the new study directly contest previous research, which indicated that the time required to differentiate between odor sequences was around 1,200 milliseconds, Dr. Dmitry Rinberg, a professor in the Department of Neuroscience and Physiology at NYU Langone Health in New York, wrote in an accompanying editorial in Nature Human Behaviour.
"The timing of individual notes in music is indispensable for conveying meaning and beauty in a melody, and the human ear is highly sensitive to this. However, temporal sensitivity is not limited to hearing; our sense of smell can also detect temporal alterations in scent presentations," he continued.
"The timing of individual components in a complex scent mixture that reaches the nose may be essential for our perception of the olfactory realm. Similar to how timing affects the perception of notes in a melody, the timing of individual components in a complex scent mixture presented to the nose may be critical for our olfactory perception," Rinberg explained.
The ability to distinguish between scents within a single inhalation might be an essential method by which animals recognize both the identity of a scent and its location in space, stated Dr. Sandeep Robert Datta, a professor in the Department of Neurobiology at Harvard Medical School, who was not involved in the new study.
"The demonstration that humans can differentiate scents as they evolve within a single inhalation is a compelling demonstration that timing is crucial for smell across species, indicating that it is a fundamental principle underlying olfactory performance. Furthermore, this study offers valuable insights into the enigmatic mechanisms supporting human olfaction," Datta explained via email.
"Historically, the study of human olfaction has lagged behind that of vision and hearing, as humans often perceive themselves as visual beings with speech as our primary means of communication. This new study helps bridge a significant void in our understanding of how we as humans perceive odors," Datta concluded.
Despite some suggesting that smell is our slowest sense, the new research conducted by Zhou and his team at the Chinese Academy of Sciences and Ohio State University shows that individuals can distinguish two distinct odors presented in reverse order with a delay as short as 60 milliseconds. This quick differentiation ability may prove crucial for animals in recognizing both the identity and location of scents in space.
