On October 15, 2023, a research paper published online in the journal *Nature Human Behavior* by a team of Chinese scientists challenges the long-held belief that human olfaction is the slowest among our senses. According to the study, released by Springer Nature, humans are actually much more responsive to the timing of odors than previously thought—close to ten times faster.
In an interview, Professor Zhou Wen, a distinguished professor at the University of Chinese Academy of Sciences and a researcher at the Institute of Psychology, explained that the perception of smell has often been deemed sluggish. This misconception stems in part from the rapid chemical changes associated with olfactory perception, which are difficult to measure. Precise timing in the release of scents and capturing neural activity at high temporal resolution has posed challenges, hindering accurate assessments of our sniffing speed and ability to differentiate odors in the past.
For this innovative study, Professor Zhou and his team developed a specialized instrument that delivers various odor compounds to participants’ noses with remarkable precision—within 18 milliseconds—starting from the moment they inhale. The team aimed to evaluate the ability of humans to distinguish between different sequences of smells. They utilized four distinct compounds, reminiscent of apple, onion, lemon, and floral scents. A total of 229 participants were asked to smell sequences made up of two compounds presented in succession with varying time intervals in between.
The findings were revealing. The researchers discovered that even with a mere 60-millisecond gap between two scents presented within a single inhalation (typically lasting 1 to 3 seconds), participants could readily detect differences based on the order of the scents. Furthermore, when the time interval between the two scent components was increased to between 100 and 200 milliseconds, participants tended to describe the sequence as being more similar to the earlier presented scent rather than the latter. This indicates that the order in which odor components reach the nose is crucial for recognizing smell characteristics.
Professor Zhou summarized the results by stating that our scent perception is not only faster than previously believed but is comparable to how quickly we perceive colors. The scent sequences used in this research differed both chemically and in their aromatic attributes, suggesting that distinguishing structurally similar odors may present an even greater challenge.
