GLOSSARY
Recent research has revealed that the human nose is far more powerful than previously thought, capable of detecting subtle differences in scents in as little as 40 milliseconds. This discovery challenges long-held beliefs that our sense of smell is slow and imprecise. Using innovative experiments, scientists found that we can distinguish the order of smells much faster than we can detect changes in light or color. This breakthrough highlights the incredible speed and complexity of our olfactory system, reshaping our understanding of how we process and perceive scents.
We might have grossly underestimated, for years, the might of our noses. It is a widely held belief that our senses of smell have been woefully inferior compared with those of sight or hearing. Yet Charles Darwin could once tell us that our sense of smell hardly served us any purpose. Newer research, however, shows that the human nose is really one heck of a sophisticated organ, adept at detecting and differentiating scents with incredible speed.
The Misunderstood Power of Smell
Until now, scientists have regarded the sense of smell as rather sluggish, like some out-of-date camera taking a slow snap of the chemical environment around us.
“Each sniff can feel like taking a long-exposure shot of the chemical environment,”
—Dr. Wen Zhou, Chinese Academy of Sciences
Translation: when we sniff a scent, it often feels like one blended aroma, rather than a mix of separate smells arriving at different times. Imagine sniffing a flower and smelling it as one, unified fragrance rather than noticing each of the petals’ scents, each of the pollen’s scents, and the air itself. This assumption of slowness in our olfactory system had long been unchallenged—until now.
A Revolutionary Experiment
In a new paper in Nature Human Behaviour, Zhou and colleagues were testing how sensitive and quick our sense of smell really is. The challenge? Designing an experiment that would present different smells in a precise sequence—all within a single sniff.
Testing the Nose: A Surprise Discovery
The scientists then asked whether we could differentiate between them. They used 229 human subjects and asked them to compare consecutive pairs of smells presented one after another. In one experiment, for example, subjects were presented with an apple-like smell followed, after a delay between 120–180 milliseconds, by a floral smell. Two sniffs later, they were asked whether the presentation order of the two scents had been the same or reversed.
They were able to state the order of the smells correctly 63% of the time, or 597 out of 952 trials. That is not exactly a high success rate, but it is far from what the scientists had expected. After all, the smells were differentiated by less than the milliseconds of time that scientists had previously presumed was a minimum for us to differentiate between the two.
Speeding up the Clock of Smell
But the most astonishing part of the study was still coming up. In yet more innovative methodology, the authors discovered that participants could tell whether a smell came first or second, even when the time gap between the smells was reduced to 40–80 milliseconds—a timeframe 10 times shorter than what scientists had previously believed was necessary for a human to distinguish two smells.
The problem is that participants could actually detect reliably that the smells had been reversed, but they really had a tough time with one key piece of information: which scent belonged first. For the most part, people just knew that the order of the smells had changed, but they couldn’t say with certainty which scent hit their nose first.
How Does Our Nose Really Work?
What does it all signify? According to Dr. Zhou, what this might mean is that the ability of the brain to detect smells actually works on a much faster timescale than anyone previously thought. Instead of recognizing individual elements of a smell in sequence like how one reads words inside a sentence, what we’re finding is that our brain is kind of dashing all those together almost instantaneously, then reweaving them into one cohesive experience.
In fact, according to Zhou, the sequence in which smells reach our nostrils may not even be the decisive factor for how we perceive them. Our brain might employ other strategies to quickly build up the information coming through our nostrils and seamlessly render the sensory world.
The Larger Context
This research unlocks an entirely new understanding of the way in which our sense of smell works and challenges long-held assumptions about what the sense can do and cannot do. The fact that we can detect such tiny shifts in the timing of smells shows that our sense of smell is not slow or dull—it’s finely tuned and lightning fast.
It reminds you that even the most elementary senses in the human body are much more complex and powerful than we consider. So, the next time you catch a whiff of freshly cut apple or flower or squirt of lemon, remember—that your nose is working so much harder and so much faster than you could ever have possibly imagined.
Key Takeaways
- Our sense of smell can detect rapid changes in scent in as little as 40 milliseconds.
- This speed rivals our ability to detect changes in color or light.
- We can detect shifts in the order of scents, but telling which occurred first is much harder.
- The order of smells affects how we perceive the overall scent; the first often dominates.
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