All hell breaks loose when our senses go haywire

Jesus is a Malteser. You might say I’m a liar or accuse me of the most egregious heresy, but the fact remains that Jesus is a Malteser. This is because I have a neurological quirk known as synaesthesia, commonly described as a fusing of the senses. Its most common manifestation prompts people to see colour when they hear music. But my version is the rare lexical-gustatory kind, which means that I can taste words; and so Jesus is a Malteser, Sam is tinned tuna and Donald is a rubber duck bobbing around in vinegar.

This could seem nightmarish: life as a constant assault of rubber ducks and whiffy fish — a gustatory whack-a-mole — but it produces no intrusion. I consider it nothing other than a party trick, although it can also be useful as an aide-memoire. When starting a new job it has helped me remember colleagues’ names: the nice lady on reception is a salty white pebble and the security chap is a packet of Cheese & Onion Ringos.

In The Man Who Tasted Words, the neurologist Guy Leschziner presents case studies of people whose senses have been sent awry through a genetic glitch, external injury or the ageing process, wildly altering their perception of the world and prompting them to question what is real. Given the title, I was expecting a jaunty pop-science read about people like me whose sensory worlds are scattered with rubber ducks, crunchy sand and chocolate gnomes. Instead, I encountered blindness, amputations, strokes, seizures and suicide. Fascinating, yes, but often distressing.

Leschziner’s first case study is Paul, a man who cannot feel pain. What might seem like a superpower is quickly revealed to be a curse: Paul and his similarly afflicted sister spent their childhoods leaping from garage roofs, breaking legs, knocking out teeth and pressing their palms to the glass fireguard: ‘We used to love to hear the sizzling of our skin.’