There’s a badly shot video on my phone that I’ve watched many times. My son, on the cusp of his second birthday, is standing behind a cake festooned with candles. Behind him, family members awkwardly break out into Happy Birthday, only to be stopped by screaming. It’s my child, writhing on the floor as if in pain.

I laughed uncomfortably when I first replayed this clip. It sounds cruel but I was bemused, even proud of my child’s rejection of this cultural tradition. I still didn’t think anything was wrong when his aversion extended to any form of singing: nursery rhymes at the library, The Hokey Pokey at playgroup, my (admittedly pitchy) rendition of Taylor Swift songs in the car. When my husband and I took him to see a pediatrician on the gentle advice of my sister-in-law, we weren’t expecting to walk away – eight months, two speech therapists, two occupational therapists and an audiologist later – with a diagnosis of sensory processing disorder (SPD): three words that have come to profoundly shape our family life.