A Sense of Senses

I often hear that people find the sense of smell mysterious or somehow beyond our ability to understand. The truth is that we do understand a lot about olfaction and can do a pretty good job explaining why things smell like they do. That being said, there is still this sense that olfaction is a mystery.

 I have a theory as to why this is, and I think it comes from the lack of an absolute or external reference for the nose. Let’s take a minute and think about two other important senses, vision and hearing.

 Before I do that, all of our senses can be divided into two steps. The first is the interaction with the outside world. That is the conversion of the external stimulus into a biological signal. This is the photon hitting the rods and cones in the eye. Or the pressure waves in the air pushing against the tympanic membrane of the ear. The second step is the processing of that signal in the brain to make sense of it.

 What is interesting to me and what I think makes the difference between scent and the other two senses I’ve been writing about is, that there is no external reference for scent. Take hearing for example, we know that Middle-C on a piano is 256 Hz. The A above Middle C is 440 Hz. There are tuning forks available to tune your piano and there are machines that can measure sound spectra and tell us exactly what frequencies are there. There’s nothing to argue about. Similarly, the color red can be described as light with wavelength around 620 to 750 nm. And similarly, we have machines that can measure that and tell us exactly what wavelengths of light are present.

 Back to olfaction… we don’t have any such machine. In fact, the common feature of all “artificial noses” is that they don’t work. This lack of an absolute reference point adds to the mystery around olfaction.

 But this is not an excuse to throw up our hands and claim all bets are off. The truth is we do understand a lot about olfaction and how it works, and we can use this understanding to apply it to looking at what working dogs can do.