Round shapes sound like 'bouba,' spiky ones sound like 'kiki' — everywhere

Shown one spiky shape and one blobby shape, people overwhelmingly call the spiky one 'kiki' and the round one 'bouba' — a pattern that holds across languages, alphabets, and even in toddlers too young to read. It suggests some sound-to-shape mappings aren't arbitrary but built into how brains process language.

— Vilayanur S. Ramachandran, Edward M. Hubbard, Synaesthesia — A Window Into Perception, Thought and Language — Journal of Consciousness Studies, 2001 (effect first reported by Wolfgang Köhler, 1929)