Humans Can Discriminate More than 1 Trillion Olfactory Stimuli

By C. Bushdid, M. Magnasco, Leslie B. Vosshall, Andreas Keller. 2014

807 citations recorded by the source corpus.

All the Smells of the World How many odorant stimuli can a normal human being discriminate? During psychophysical tests of odor mixture discrimination, Bushdid et al. (p. 1370) were surprised to find that humans can discriminate among more than a trillion different smells. Because the authors reduced the complexity by investigating only mixtures of 10, 20, or 30 components drawn from a collection of 128 odorous molecules, this astonishingly large number is probably the lower limit of the potential number of olfactory stimuli that humans can distinguish. The number of different odor mixtures people can distinguish is several orders of magnitude larger than anticipated. Humans can discriminate several million different colors and almost half a million different tones, but the number of discriminable olfactory stimuli remains unknown. The lay and scientific literature typically claims that humans can discriminate 10,000 odors, but this number has never been empirically validated. We determined the resolution of the human sense of smell by testing the capacity of humans to discriminate odor mixtures with varying numbers of shared components. On the basis of the results of psychophysical testing, we calculated that humans can discriminate at least 1 trillion olfactory stimuli. This is far more than previous estimates of distinguishable olfactory stimuli. It demonstrates that the human olfactory system, with its hundreds of different olfactory receptors, far outperforms the other senses in the number of physically different stimuli it can discriminate.

Subfields: Biomedical Engineering, Cellular and Molecular Neuroscience, Sensory Systems

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In Biomedical Engineering

Miguel Angel Muñoz

In Cellular and Molecular Neuroscience

In Sensory Systems

Citations in the corpus

Colloquium: Criticality and dynamical scaling in living systems (2017, background): “Similar virtues of criticality have been explored in the olfactory system (Bushdid et al., 2014) and the visual cortex (Shew et al., 2015) (see also Chialvo (2006) and Friston et al. (2012)).”
Just how much of what we taste derives from the sense of smell? (2015, background): “true figure (in terms of the number of discriminable smells) may be much closer to one trillion ([20]; see also [21])! The underlying concern here, then, is that the “75–95 %”
Insect olfaction and the evolution of receptor tuning (2015, background): “…such, do not imply full coverage of chemical space. birth-and-death evolutionary model, in which gene duplication events represent the births, and pseudogenization and deletion events the deaths (Figure 3) (Nei et al., 2008; Sánchez-Gracia et al., 2009; Ramdya and Benton, 2010; Cande et al., 2013).”