Why do we assume smell is our weakest sense?

My cat can smell depression. Another family cat could smell my stepfather’s dementia. They both became more affectionate and tactile: the dementia-smelling cat would gently paw my stepfather, when he hadn’t even liked her when he had been well. My cat comes in close when my mood is darker. Perhaps both cats were using other cues, but I’m convinced it was smell.

Up until the 18th century, doctors relied for diagnoses on smell as much as anything else

For something that Jonas Olofsson calls ‘the easiest and most natural thing in the world’, smell is satisfyingly complicated. When it comes to humans’ ability to smell, as Olofsson persuades us in this captivating book, it has also been profoundly neglected. This wasn’t always the case. Up until the 18th century, doctors relied for diagnoses on smell as much as anything else. They ‘squeezed, observed, smelled and tasted’. They knew that ‘diphtheria smelled sweet, scurvy smelled pungent, typhus smelled like freshly baked rye bread and scrofula, a type of tuberculosis, smelled like stale beer’.

These inklings were lost when the Enlightenment arrived, and since then humans have come to think of themselves as poor smellers, at least compared to dogs and other animals. We assume smell is our weakest sense and sight our strongest. We now live in an age of sight and are slaves to screens. In one study, 50 per cent of Americans who were given the choice of keeping either their sense of smell or their mobile chose the phone. But smell has a power like no other. It takes us back to childhood in an instant.