I wouldn’t say that I’m afraid of heights. I can stand on a cliff path or look out from a tall building without the rush of panic people often associate with vertigo. What I really dislike is something much harder to explain: the peculiar feeling in my feet.

It’s a sensation that’s difficult to describe. It isn’t numbness, it isn’t tingling either. The closest I can come is a strange awareness in the soles of my feet – a kind of buzzing.

For a long time I assumed this was just an odd personal quirk. But many people report something similar when standing near a drop. Around one-quarter of people describe some level of discomfort at height, and in experimental settings most participants show measurable changes in balance and posture when exposed to a drop. Far from being irrational, it reflects a remarkably elegant piece of neurological engineering.

At height, the nervous system shifts balance control. Sensory input from the feet is “upregulated” (dialled up), postural muscles (muscles that help you stay upright, balanced and stable) stiffen slightly, and movements become more cautious. This is part of normal proprioception – the body’s internal sense of where it is in space.

Unlike vision, which tells you where things are around you, proprioception tells........

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