How much do you value your sense of smell? Historically, smell has had a bad rap. Aristotle wrote that the human sense of smell is inferior to that of all other animals and also inferior to all our other senses.
Our sense of smell has been traditionally undervalued – ranked far below vision by the likes of Immanuel Kant and Sigmund Freud. During the Enlightenment, Kant famously dismissed the sense of smell, calling it the “least rewarding” of all the senses. He argued that it is more likely to pick up bad smells than good ones.
Research by pioneering brain researchers in the 19th century didn’t help. Paul Broca in France detailed maps of the brain that minimised the regions associated with smell. In literature, smell was used to indicate social hostilities, such as prejudice and exploitation. For instance, in The Road to Wigan Pier George Orwell states that “the real secret of class distinctions in the West” can be summed up in four words: “The lower classes smell”.
It seems we are taught which smells are unpleasant; the disgust response is almost entirely lacking in children under the age of two. Our sense of smell is apparently shaped by society and influenced by the prejudices that pervade it.
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So the recent publication of a book, The Forgotten Sense, by Dr Jonas Olofsson, a psychology professor at Stockholm University, is timely. Before he started on a 20-year career of academic research into smell, he says he “viewed the sense of smell as a simple passive system” whereby odours are detected by smell cells in the nose. They then travel to an area at the very front of the brain, in the temporal lobe, called the olfactory bulb. It processes and absorbs the smell signals, before sending them on to the amygdala, the hippocampus and the frontal cortex. These areas of the brain are also involved in higher processing, such as memory and emotion.
Now, he realises that “olfactory processes start not in the nose but in the brain, even before the odour molecules reach their destination. Olfactory processes are shaped by expectations and experiences.”
In other words, how we experience a smell or taste depends both on our emotional circumstances and input from our other senses.
For example, Olofsson explains how much our sense of taste depends on the smell of food or drink, which stimulates our smell receptors in two ways – directly through the nose and up from the throat as we chew and swallow. This “retronasal olfaction” is more strongly developed in humans than other animals, he says.
And have you noticed that you only become aware of the smell of your own house after you have been away for a week or longer? This has to do with sensory adaptation – in other words, we quickly get used to ambient odours. It’s more pronounced for our sense of smell than for any other sense; adaptation means we respond less when a stimulus is repeated. So when you’re at home, the smell of your house is all around you. It never goes away and you become adapted to the way it smells.
It seems we adapt to odours quite quickly. After even a few sniffs of a smell, you start to experience that smell as being less intense and, eventually, take no notice of it at all. That’s why you can smell your friend’s house when you walk in, but you don’t really notice it the entire time you’re there.
Olofsson’s research suggests that smell is both more complex and less dispensable than we might think. Humans rely on the sense of smell for everything from social communication to the detection of environmental hazards.
Smell is crucial to our wellbeing.
As Olofsson’s book shows, and as the science of smell continues to progress, it’s becoming increasingly clear how much we stand to gain by paying more attention to it.
