Daniel Kish lost his sight in infancy, but taught himself to echolocate with bat-like clicks (Image: djeyewater, stock.xchng)

I am 6 years old and it’s my first day at school. The bell rings for recess and all my classmates run gleefully away. But unlike them I cannot see. At least, not with my eyes. Instead, I click my tongue, listening for echoes from the wall to my left. I walk with my hands slightly outstretched to keep me from running into chairs that may have been left askew. I hear kids laughing and shouting through the open door, and by clicking I also hear the presence of the sides of the doorway in front of me. I go through it to the playground for the first time.

After a few steps, I stop to listen. I stand on a crack in the pavement that runs parallel to the building behind me. I click my tongue loudly and turn my head from side to side. The way is open, shot through with scurrying voices, balls bouncing and shoes scampering to and fro. What is around me? How do I get there? How do I get back?

Clicking my tongue quickly and scanning with my head, I move cautiously forward, catching fleeting images of bodies darting hither and thither. I follow spaces that are clear, avoiding clusters of bodies, keeping my distance from bouncing balls. I am not afraid – to me, this is a puzzle. I turn my head and click over my shoulder. I can still hear the wall of the building. As long as I can hear that, I …