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

Although it is agreed that physico-chemical 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 physico-chemical 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 physico-chemical properties reflected the primary axis of olfactory perception. This allowed us to predict the pleasantness of novel molecules by their physico-chemical 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 amongst biologically relevant molecules.