Life Science In the nose: Why we smell the way we do

In the nose: Why we smell the way we do

Woman smells rose
A rose by any other name really would smell as sweet. Science tells us why. Photo: Getty
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Our sense of smell is one of our primary danger detectors – and that can go a long way to explaining why so many perfumes are floral based, a scent expert says.

Throughout evolution, humans learned to rely on their nose to alert them to anything that might harm or kill them – not just a Lynx-riddled high school change room.

We learnt to equate the smell of sulphur with things that are decaying or rotten, University of New South Wales engineering researcher James Hayes explained.

“They have a lot of bacteria in them, so we have a natural impulse to avoid those smells we understand are bad,” Dr Hayes said.

“Ammonia is another one which has a very distinct smell and when it’s in sufficiently high concentrations, it can be fatal. So we have learned to stay away from such sources of odour, because in the long run that will save us.”

Flowers and all things nice, however, smell like freshness and health to the unbridled human nose.  Which translates into ker-ching for perfume companies, who can harness and mimic the scent.

The global perfume market is predicted to be worth an eye-watering $US52.4 billion by 2025. Photo: Getty

So if it’s as easy as, rotten = bad, flowers = good, why do some of us love the smell of Chanel No.5, and others recoil at the mere whiff of it?

Our sense of smell is closely tied to our emotions, Dr Hayes explained.

He said humans’ ability to process odour was quite different to that of say, a dog, where a large portion of the brain is devoted just to smelling.

Some parts of our brains have been assigned dual jobs, so there’s some areas of the brain that look after our emotions and our sense of smell.

“You find that a lot of odours emotionally affect people quite strongly,” Dr Hayes said.

Parents, think of the scent of your newborn baby’s head, for example.

“We also have olfactory memories which are typically the earliest memories that we form, as well as being the longest lasting; for example, particular smells might remind you of your childhood,” Dr Hayes said.

So maybe your strict babysitter wore the world’s most iconic perfume, and that’s why you hate it.

Dr Hayes presented the anomaly of the lemon and strawberry: a lemon has but one chemical. When we smell a lemon we go, ‘lemon!’. A strawberry has 24 chemicals that make the smell we associate with the fruit, but still when we sniff one, we say, ‘strawberry!’. Photo: Getty

There’s also more scientific evidence around gender and culture and age.

For example, women can smell more scents and more strongly than men. And your sense of smell starts to go downhill from about age 60.

Beyond that, the power of smell varies greatly from individual to individual.

Even your culture can affect your abilities, Dr Hayes said, citing a large study that exposed a range of odours to different global cultures.

Those cultures that had little experience with certain scents, weren’t able to easily identify them.

“For example, the study revealed that people in Japan had a difficult time detecting liquorice, for instance, and all the aniseed flavours.”