Scientists Discover New Smell, 'Olfactory White'

The new smell was dubbed “olfactory white” because it is a mixture of different compounds and reminiscent of hearing white noise. The same thing applies to white light, which is the combination of all visible wavelengths. The scientists from the Weizmann Institute of Science in Rehovot, Israel, “hypothesized that if we apply these same conditions to odorant mixtures, 'whiteness' may emerge in olfaction as well.” The study was published in the journal Proceedings of the National Academy of Science. 

The scientists used 86 smells and distilled the compounds to have the same intensity. The scientists created different mixtures using a combination of compounds and asked participants to smell mixtures to determine similarity. For example, the scientists had participants smell several mixtures that were made from seven compounds and the participants were asked to compare the mixtures to determine any similarity.

The scientists discovered that the more compounds, up to 43, used to create a mixture, the more similar the mixtures became, despite not using the same starting compounds. It's the smell equivalent to white noise, according to the scientists.

To confirm this finding of olfactory white, the scientists created an experiment in which four  mixtures were created from 40 compounds. They gathered 12 participants, in four groups of three, to smell the four mixtures. The scientists told the first group that the first mixture was called “Laurax,” for the next group the second mixture was called “Laurax,” the third group was told the third mixture was called “Laurax” and the fourth group was told the fourth mixture was called “Laurax,” according to LiveScience. After three days of smelling the “Laurax” smell, scientists presented the participants with four new smells and were told to label them. One label had “Laurax” written on it and that label was usually applied to smells that had the greatest number of compounds, according to LiveScience.

Scientists duplicated the experiment again, adding an “other” label to make sure that participants were not using “Laurax” as a label for any smell they could not determine. In this experiment, participants continued to apply the “Laurax” label to smells that had the greater number of compounds.

The scientists concluded that olfactory white, or the smell equivalent of white noise, was real and  had to do more with a mixture of smells that ran the spectrum of smells and were of the same intensity. According to the scientists, “'olfactory white' is associated with mixtures of ∼30 or more equal-intensity components that span stimulus space, implying that olfactory representations are of features of molecules rather than of molecular identity.”