Researchers into olfactory memory, that curious nostalgia of the nose, have put it all down to the limbic system. I have read but cannot always parse the literature: the academics tend to lose me at the orbitofrontal cortex. But the basic proposition is this. Unlike other sensory inputs, which are translated from physical experience into data by an egg-shaped relay station called the thalamus, scent is processed elsewhere, in the brain’s olfactory bulb, which is directly connected to the hippocampus and amygdala, which are where memory and emotion reside. How the hardwiring happens, I couldn’t tell you, and I am similarly at a loss to explain why some scents are more triggering than others. For me, there are two that never fail to transport me, my own personal madeleines.

The first is really a mixture of smells—of diesel, barbecued meats, human sweat— which, wherever I am in the world, immediately takes me back to Hong Kong, to my first overseas trip, to the tender age of twelve. The second is the smell of wood smoke, which, for a long time, was similarly connected to my childhood. It evoked bonfires on my grandfather’s farm, my bright-blue gumboots a little melted around the soles. It evoked Friday-night football on free-to-air television. We would pull the couches away from the wall and push them a little closer to the screen. I can see my family lined up along these couches, scarves in team colours wrapped dutifully around their necks, and me sitting with them, a little closer to the wood heater, a book open but scarcely read in my lap. It was not that I was interested in the game that caused me to sit with my family, but ritual, and it was not the old cathode ray that distracted me from my reading, but rather that my proximity to the fire almost invariably lulled me to sleep.