The human nose can detect more than 1 trillion different smells, according to new research – suggesting we are much better at telling odours apart than we previously thought.
The study published in the journal Science claims the human olfactory system can detect many more smells than the longstanding received wisdom of 10,000.
Keller’s team created odours with varying degrees of similarity and tested if subjects could spot the difference. They used a collection of 128 different chemicals to concoct three groups of odours containing 10, 20 or 30 different components.
For each group, they created odours with the same number of components but a different composition, thereby varying the degree of similarity between pairs of odours.
Three vials were then given to each participant – two bearing the same odour, and one containing a different odour with the same number of components, but a different degree of similarity. They were then asked to inhale and decide which was the odd one out.
Analysing the results from 26 participants, each of whom compared in total 264 pairs of odours with varying degrees of similarity, the team found that the greater the degree of overlap in their composition, the harder it was for participants to tell two odours apart. No one could discriminate odours with more than 90% of overlap, although at least half of the participants could tell odours apart when the degree of overlap was less than 75%.
The original study (Bushdidi, C., Magnasco, M.O., Vosshalli, L.B., & Keller, A. 2014. Humanc can discriminate more than 1 trillions olfactory stimuli. Science 343: 1370-137) can be found on Science‘s website.