The Forgotten Sense: The New Science of Smell, Jonas Olofsson, William Collins, 2025, £18.99.
How sensitive is the human nose? Many of us, me included, believe that our sense of smell is poor compared to that of other animals. Yet apparently, we humans can smell odours more competently than rats, spider monkeys and vampire bats. The only animal of those tested whose sense of smell is better than ours is the dog – though the cat, which has not been tested, might also have a better sense of smell than we do.
We can even use our noses to track like bloodhounds do. A neuroscientist at the University of California (where else?) got his students to smell their way along a trail of chocolate in the grass of the University’s lawns. Down on their hands and knees, twenty-one of the thirty-two human bloodhounds finished the ten-metre trail all the way to the chocolate prey. And those who practised daily became faster and better at choccy trail hunting.
Yet the myth that animals have a better sense of smell than we do has held sway for centuries, ever since Aristotle made this inaccurate claim. Maybe this is because our sense of smell became less important to us when we started to use our eyes to read. Yet in antiquity, scent was valued as an offering to the gods (incense is still used in some Christian churches) and physicians would smell body odour and taste urine to make a diagnosis. Moreover, for hundreds of years, doctors believed that diseases were spread by scents – the miasma theory – and would carry pleasant smelling herbs to sniff as a way of protecting themselves.
Later scientists decided that, because we were so intelligent, we did not need good noses. Indeed, in the nineteenth century, the first-ever brain researcher, Paul Broca, claimed that the human olfactory bulb, where smells are registered in the brain, had receded to make way for our clever frontal lobes. And Sigmund Freud believed that we should suppress our sense of smell because it was just an animal-like urge. Nowadays, with our mobile phones and TV, our sense of smell has become even less important in our lives. That is, until we lose it altogether.
Jonas Olofsson, the author of this book and a professor of psychology at Stockholm University, had been quietly researching the sense of smell in humans for twenty or so years when the Covid pandemic suddenly made his research horribly relevant. While those who caught Covid usually lost their sense of smell merely for a few days or weeks, those who suffered long Covid continued without a sense of smell sometimes for years. He started writing this book after getting imploring emails from these unfortunates asking him to help them regain their sense of smell.
The most immediate effect of having no sense of smell is that all food tastes like cardboard. That is because smell and taste are so closely linked together in our experience. As we chew food, odours are released in our mouths and travel out with our breath through the nose. The flavour of food is experienced as a taste, but if you hold your nose and chew, you will find that any taste is degraded. So much so, that students could not distinguish between ketchup and mustard when they wore a nose clip.
Olofsson’s science of smell is producing some fascinating possibilities, now that we know that the sense of smell varies between individuals. Research suggests that some people may overeat because their sense of smell, intertwined with their tastebuds, is particularly sensitive to calorie-laden foods, making them crave more food. Conflicting research suggests just the reverse: that fatties eat more because they have a poor sense of smell, which means they don’t know when to stop.
Most of us don’t notice the ordinary daily smells around us, not because we have a poor sense of smell, but because our brain switches off our sensitivity to these background odours. For the brain’s role in smelling is as important as the role of the nose itself. The brain sets expectations of what a scent will be like even before the odour molecules reach the nose, and it is the brain which will classify a scent as pleasant or disgusting.
Why does a particular smell trigger childhood memories? Olofsson and his colleagues are studying this and, so far, have not come up with a definite answer. But there is a clue, perhaps, in the way the human foetus in the womb can smell the food that the mother is eating. After birth, those early foetal memories will influence what foods appeal to the child. Childhood memories may also associate a particular smell with happiness. To me as an adult, pig dung smells pleasant rather than disgusting, because I spent many happy hours playing with baby pigs in the pigsty on our family farm.
This link between childhood and smells in later life can help food companies make huge profits. We love comfort food because it was familiar to us in childhood. Children who have Big Macs with fries will come back to McDonald’s as adults and their expectations of a good time will be fulfilled by the same predictable meal. No wonder McDonald’s sometimes has ‘Kids Eat Free’ offers. Coca-Cola, on the other hand, lost a lot of money when they launched New Coke, claiming it tasted better than the familiar drink. Perhaps it did, but regular drinkers wanted the old familiar taste from their childhood.
For those who have lost their sense of smell after Covid, there is hope. Olofsson recommends smell training which he sometimes calls ‘smell gymnastics’. You fill four jam jars with different fragranced items – like lemon, eucalyptus, rose and clove – and sniff these daily several times for four months, changing the scents to get variety. More details are available from the Stockholm University website (www.smelltrainingapp.com), which will use your results for research. There is even an olfactory device called Exerscent, designed like a computer game, to make scent testing at home less boring.
This relatively short book written by a true expert is full of amazing facts like this. The author even suggests that those with a strong craving for chocolate should try spending five minutes sniffing finely chopped-up chocolate pieces. After this, the urge to eat the whole bar is reduced. Your sense of smell has tricked your brain into no longer wanting it. I tried this and, alas, it does not work for me – perhaps because my sense of smell needs some gymnastic workouts.
