- Study shows that the way people sniff carries detailed information about different odours
- Machine learning could identify which scent someone was smelling based only on sniff traces
- Brain imaging pointed to the amygdala as a key region linking smell and breathing
When you smell something, you do not just passively receive odour molecules.
You actively draw them in through a series of sniffs.
New research suggests that this simple act is more informative than it looks.
The pattern of sniffing itself appears to carry a signature of what you are smelling.
Researchers at Northwestern University analysed a large existing dataset and found that they could predict specific odours from sniff traces alone.
The work, reported in Nature Human Behaviour, adds to the growing view that smell is an active sense, shaped by ongoing feedback between the nose and the brain.
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The team drew on data from a previous project known as the NEMO dataset.
In that study, three volunteers lay in an MRI scanner and were presented with 160 different odours across more than 12,000 trials.
Their breathing was recorded while their brain activity was monitored.
The new analysis looked at the fine details of each sniff.
The researchers examined features such as how fast people inhaled, how long they held the breath and how the pattern changed over time as each odour was presented.
Using machine learning, they tested whether these patterns could be used to identify which odour was being smelled without any other information.
Sniff signatures of smell
The results showed that sniffing behaviour was not random.
Odours with different perceived properties, such as intensity or pleasantness, were linked to subtly different sniff shapes.
The machine learning algorithms could distinguish between many of the scents using only the breathing traces.
In other words, information about the odour was encoded in how people sniffed.
This supports the idea that smell works in a closed loop.
The brain responds to incoming odours by adjusting sniffing, and those adjustments in turn influence how much of the odour reaches the receptors and how it is processed.
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The amygdala as a control hub
By linking the breathing data to MRI scans, the researchers highlighted the amygdala as a central region in this loop.
Activity in the amygdala, which is already known to be important for emotion and certain breathing changes, correlated strongly with odour specific sniff adjustments.
This finding ties into earlier work in epilepsy that connected the amygdala with disordered breathing and apnoea.
It suggests that this deep structure helps shape how we sample smells and perhaps how we react
