The sense of smell. How to use smell to help pass that exam.

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The aromas that surround us can affect our mental performance both positively and negatively, they can influence a decision whether to buy something or not.  When it comes to tasting something, the nose has it whereas the tongue merely flaps about with a feeble repertoire of taste sensations.  This blog explores the sense of smell.

Smell differs to the other senses – touch, sight or hearing – in the way that it makes immediate contact with the emotional part of the brain, the amygdala, and with the headmaster of the brain, the frontal cortex.  All the other senses have to pass through the sorting office of the brain, the thalamus, before being allowed access to higher parts of the brain.  This means that smells get noticed more quickly than any other sense.  Furthermore all the other sense receptors have protection from the air; sight by the cornea, hearing by the ear drum and touch by the skin.  Our smell receptors have no protection from the air, bar being covered in a thick layer of snot.  Which, coincidentally, makes our ability to smell even more remarkable.

The importance the brain attaches to smells has been noticed and studied for how it affects learning, motivation and how it can make us spend our money.  So beware of scents wafting around the frock shop.  In the book Brain Rules by John Medina, he cites several examples of how smells affect learning.  He talks about a popular experiment on memory recall: 2 groups of people watch a film then report to a lab for a memory test.  One group does the test in a room flooded with the smell of popcorn and the other’s room has no smell.  Those smelling the popcorn always do better in the memory recall test – sometimes by as much as twice the number of memories retrieved, but in other studies only 10% more memories are retrieved.  Nevertheless, the whiff of popcorn group always remembered more about the film than those who had no smell wafting about when taking the memory test.

An easily found study on the internet looked at smell and its effects on perception and behaviour.1  First Rachel Herz, the author, writes about smells pleasantness or otherwise.  She cites research done by the US military in 1998 to find a successful stink bomb.  Amazingly, no smell was found that was unanimously considered repulsive across various ethnic groups – including the stink of US army latrines.  She also writes about the smell of cloves eliciting a fear response in people afraid of the dentist – fear by association – whereas those not afraid of the dentist (it came as a surprise to me that these people exist) have no fear response when exposed to this smell.

Herz then writes about 2 experiments she’d done which shows how smell can affect mental performance.  In the first she used a group of 5 year olds and subjected them to a ‘failure-frustration’ test with an unfamiliar smell pervading the room.  After a 20 minute smell free interval, the children were split into 2 groups to do a test involving drawing a circle around drawings of puppies without tails hidden in a large group of other animals – including puppies with tails.  One group did the test with the smell and the other without.  The smell-less group outperformed the group that had the smell they’d smelt during the failure-frustration test surrounding them again.  This clearly demonstrates that if we have an unpleasant experience with a smell in the background, the brain remembers the emotional context of the smell and the same smell will downgrade performance.

The second experiment concerned a group of adults.  Again they were subjected to a ‘frustration mood induction’ – presumably this means they were made to feel frustration – with an unfamiliar smell wafting about.  They were then split into 3 groups and all did a puzzle, one group with that unfamiliar smell, another with no smell and the third with a different smell in the room.  The group smelling the smell now associated with frustration did the puzzle with the same degree of accuracy, but gave up sooner than the other 2 groups, and so showed decreased motivation.

And so we come to shopping.  The smell of fresh bread that pervades supermarkets in the UK hopefully makes us hungry and more willing to buy more food.  John Medina says that in an experiment for a clothing store,

investigators subtly wafted the smell of vanilla in the women’s department, a scent known to produce a positive response among women.  In the men’s department, they diffused the smell of rose maroc, a spicy, honey-like fragrance that had been pretested on men.  The retail results were amazing.  When the scents were deployed, sales doubled from their typical average.  And when the scents were reversed – vanilla for the men and rose maroc for women – sales plummeted below their typical average.

So watch out for those wafting aromas when out shopping.  If on an economy drive, maybe we should consider wearing a large peg on our nose.

A couple more interesting facts about smell.  As a part of taste: the tongue has 5 different tastes whereas the nose can detect hundreds of different aromas, but where taste is concerned, the nose senses complex aromas when we breathe out.  Normal smelling happens when we breathe in. So to savour something delicious, chew the food slowly, rolling it round the mouth, and breathe out.  And a poor sense of taste can indicate a lack of zinc in the body, something easily correctable.

So when we smell something, it goes up our hooter, blasts through the bogeys and and gets the smell receptors buzzing away like bees upon the approach of the beekeeper.  The smell receptors are in an area the size of a stamp between the eyes, called the olfactory epithelium.  This connects to the  neurons immediately above them and from there directly into the brain.

As we become more aware of the various whiffs surrounding us we can use them to enhance memory – learn something wearing a perfume, then when we need recall, wear the perfume again and the memory will work better.  To avoid an unfamiliar smell spiking future performance we could try to source the smell and smell it again in a deeply pleasurable context.  We also need to be on our guard when out shopping so we think twice about making an unwise purchase.  Or we can put the boot on the other foot and use an aroma to encourage people to buy things from us.  Smell can also be used to relax us and help healing – as used by aromatherapy.  Smell can work for us or against us, we just need to be aware of it and its powers over our brain.

Noses. Also good for picking.



  1. Herz R S.  Odor-associative learning and emotion: effects on perception and behaviour.  Chem. senses (2005) 30 (suppl 1): i250-i251 []

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