Difficulty in odor communication

Some of the major problems seem to be the following:

The underlying physics is complex. Vision and audition also involve complex physical phenomena, but photons and sound waves are well-defined physical objects that follow well-known equations of a simple basic nature. Specifically, in both cases sensory quality is related to well known physics. On the other hand, the smell of an odorant is determined by the complex, and only partially understood, interactions between the ligand molecule and the olfactory receptor molecule.

The biological detection system is high-dimensional. The nose contains hundreds of different types of olfactory receptors, each of them interacting in different ways with different kinds of odorants. Thus, the dimensionality of the sense of smell is at least two orders of magnitude larger than that of vision, which can make do with only three types of color receptors.

Odor delivery technology is immature. While artificial generation of desired visual and auditory stimuli is done in high speed and with high quality, smells cannot be easily reproduced. Now-a-days, the best that can be done is to interactively release extracts that were prepared in advance.

Much effort has been invested in trying to better understand the sense of smell and its means of expression. Relating the smell of a molecule to its three-dimensional structure, as well as characterizing ligand-receptor interactions are the subject of intensive research. However, while much progress is constantly reported, no theory adequately dealing with olfaction is currently at hand.