Scent, In Silico

By Taylor Rayne

Smell is our most primal and, arguably, most emotionally potent sense. It summons memories, shapes taste, and influences behavior: the aroma of coffee is capable of enhancing alertness well before caffeine ever reaches the bloodstream. A hint of sunscreen collapses decades, taking us back to youth; but, pinch the nose, and suddenly a slice of apple is hard to distinguish from a piece of raw potato.

Despite its significance, scent remains the most mysterious of our senses. Unlike vision or hearing, it resists straightforward formalization. The challenge lies not only in the vast molecular diversity of odorants, which vary in far more ways than photons or frequencies, but also in the effort to build a shared vocabulary and technology capable of codifying subjective sensation. So while machines have learned to see through computer vision and hear through signal processing, scent remains stubbornly analog. There has been no RGB of odor, no Fourier transform for smell.

At least, until now.

Tech giants, including Google, startups such as Osmo, and even traditional fragrance houses like Givaudan have begun turning to AI to probe the possibility of digitizing smell. By encoding scent molecules into 1s and 0s, their hope is to better understand and manipulate this sensory modality. Just as “computer vision” has helped us realize that sight is not just passive image capture but an active process of prediction and interpretation, researchers hope that programming smell will illuminate the many mysteries of olfaction.

Beyond providing further insight into olfactory biology, digital scent could have many practical (and quite profitable) applications, which is why its proponents, from defense agencies such as DARPA to corporate conglomerates like Estée Lauder, have invested in it. Computational smell could, for example, help detect threats and information invisible to cameras, such as gas leaks, food spoilage, disease markers in breath, and even counterfeit products. It could also reduce reliance on resource-intensive natural ingredients used in perfume and other odorants by, for instance, finding chemically synthesized molecules capable of evoking the same brain patterns. And finally, it could lead to the creation of entirely novel smells, revealing a vast, untapped chemical palette that would otherwise be unattainable without the aid of technology.

The Bacterial Beginnings of Smell

Long before life evolved eyes and ears, the world was encountered chemically. This took place as molecules permeated and diffused across cell membranes, performing a