Every Breath You Take
February 19th, 2008Many of us confuse flavour + taste with smell, or perhaps think that all are one and the same. For example, it is common to say, “I love the flavour of vanilla ice cream”, or “I hate the taste of cardamom”. However, to perceive flavour, the brain has to take into account gustatory stimuli (taste) and olfactory stimuli (smell), plus tactile and thermal sensations. Eg. The ‘flavour’ of vanilla ice cream may be the combination of sweetness from sugar, the scent of vanilla, plus creaminess and temperature of the ice cream itself.
While our taste buds can only distinguish among the five distinct qualities of taste: sweet, salty, sour, bitter and umami, the nose can distinguish among hundreds of substances, and it is said that the average human being can recognize up to 10,000 different odours.
How Smell Works
When odorants (odour molecules) travel through the nose, it hits the olfactory epithelium, located in the roof of the two nasal cavities of the nose, just below and between the eyes. The molecules bind to olfactory receptors, which then transmit signals to the olfactory bulb, located in the brain.
Olfactory receptor neurons are responsible of detecting odours and humans have about 40 million olfactory receptor neurons. You lose your sense of smell when you have a blocked nose simply because odour molecules aren’t able to reach the olfactory receptors. In other words, everything tastes bland when you have a cold not because your tongue has called in sick, but for the obvious fact that your nasal cavity is blocked.
The olfactory system converts olfactory signals into perception (‘meaningful’ sensory information). ‘Smell’ signals are transmitted to areas of the brain such as the olfactory cortex, amygdala, hippocampus and hypothalamus. The amygdala and hippocampus are part of the limbic system, sometimes called the “emotional brain” as it is involved with functions such as emotion, behaviour and long term memory.
This is why many scents can evoke feelings and memories from way back.
Smell and Memory
As such, the role of the olfactory system is not just limited to flirting with our appetites, but with our moods and emotions too. Just a tiny whiff of a scent can alter our moods, bring on a rush of emotions or trigger long-forgotten memories.
When we encounter a new scent, our brain creates a link between this scent and a person, thing or event, and also relates it to how we felt at that moment. The next time we smell this same scent, the link is already there to call up that particular memory or feeling. This is called a ‘conditioned response’. This is also why not everyone likes the same smells.
‘Fishy’ smells from the sea may be unpleasant to some people, but for others, it reminds them of the sea, or days spent beachcombing on a seaweed-covered shore.
Memories triggered by smell can be called ‘olfactory memories’, or what I personally prefer to call a ‘scent journal’. The reason why many smells trigger childhood memories is because we encounter most new scents when we’re young.
Many children (and some adults too!) have a favourite soft toy, pillow or blanket that they’ve had since young. It’s also quite likely to be smelliest thing on earth to everyone else but its owner!
