Smell (Olfaction)

Our sense of smell is probably our “oldest” sensory system – it has a very long evolutionary history.

The basic process is called olfaction, and a simplified breakdown of the process looks like this:

  1. Chemical molecules floating in the air enter the nose
  2. The molecules are dissolve in mucous within a membrane called the olfactory epithelium (this is an important safety step since the olfactory tract is a direct path to the brain)
  3. The olfactory receptor cells interact with particular chemicals
  4. The olfactory tract transmits signals to several brain areas such: the olfactory cortex, hippocampus, amygdala, and hypothalamus

It’s that “interact with particular chemicals” that we haven’t completely figured out. No one knows exactly what causes olfactory receptors to react. Until recently the science suggested that a chemical molecule’s shape fit into specific receptors (there are about 400 different types, as compared to four for vision – 3 cones and one rod, and five for taste). But new evidence has been uncovered that suggest a quantum connection, and it can be demonstrated by looking at the smell of almond.

The Quantum factor
Benzaldehyde (the smell in almonds) and Cyanide smell the same to us, but the molecules are completely different in size and shape – which creates some doubt about the concept of molecule’s shape fitting into specific receptors as the soul method for detecting a scent. So what do Benzaldehyde and Cyanide have in common? Both molecules vibrate at the same frequency. This conjecture has been demonstrated repeatedly with other chemicals (see Luca Turin’s TED Talk, The science of scent).

The conclusion is astounding, our olfactory system is listening to molecules … we are hearing smells … our olfactory system is a nanoscale spectroscope that may also be detecting electron tunneling … we are detecting quantum state information. Reference notes on Quantum perception.

Emotions, memory and smell
Smells often bring back memories associated with an object or specific event. The reason has to do with how the brain processes scent information. When the olfactory transmits signals to the brain those signals are not only processed by the olfactory cortex, but also the hippocampus, amygdala, and hypothalamus, and the limbic system, which is involved with emotional behavior and memory.

Smell also has an important part in how we taste food -I’ll talk about that tomorrow.

The ancient Greeks knew that scent was a factor in sexual attraction for some animals, then during the 20th century pheromones were discovered in moths. We now know that many insects and animals use pheromones, but science has been unable to detect pheromones in humans.

Additional interesting facts about scent

  • Humans have about 400 types of olfactory receptors (and about 40 million total. In comparison, a German Shepherd dog as about 2 billion).
  • Smells can vary from person to person when there are issues with olfactory receptors types (compare just three eye cone cells in anomaly causing color blindness).
  • Humans are, for some reason, very sensitive to the smell of green bell pepper – capable to detecting the smell at only 0.5 parts per trillion.
  • Anosmia is the loss of the sense of smell. It’s usually caused by a nasal condition, virus, brain injury, or age. In addition, some people are born without a sense of smell.

Web Application
We are again left with only the possibility of future applications in virtual reality, but designers are already pushing ahead in other areas. One obvious example is that any good chief knows that the visual appearance of food enhances the enjoyment of a meal. Additional thoughts can be found in Jinsop Lee’s TED Talk, Design for all 5 senses.

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