Predicting Odor Pleasantness from Odorant Structure: Pleasantness as a Reflection of the Physical World

TLDR

Physicochemical features of molecules determine odor, but the rules linking them remain unknown, hindered by high‑dimensional descriptors of both molecules and percepts, and olfactory perception is also shaped by experience and learning. The authors used a dimensionality‑reduction statistical method on both odor percepts and physicochemical descriptors across many molecules. The study revealed that odor pleasantness is the primary perceptual axis and aligns with the primary physicochemical axis, enabling prediction of pleasantness from physicochemical properties alone and indicating that pleasantness has a partially innate, biologically relevant component.

Abstract

Although it is agreed that physicochemical features of molecules determine their perceived odor, the rules governing this relationship remain unknown. A significant obstacle to such understanding is the high dimensionality of features describing both percepts and molecules. We applied a statistical method to reduce dimensionality in both odor percepts and physicochemical descriptors for a large set of molecules. We found that the primary axis of perception was odor pleasantness, and critically, that the primary axis of physicochemical properties reflected the primary axis of olfactory perception. This allowed us to predict the pleasantness of novel molecules by their physicochemical properties alone. Olfactory perception is strongly shaped by experience and learning. However, our findings suggest that olfactory pleasantness is also partially innate, corresponding to a natural axis of maximal discriminability among biologically relevant molecules.