At six months, a baby babbling in a nursery in Tokyo produces the same range of consonants as a baby babbling in Nairobi or Oslo. By twelve months, each has narrowed to the sounds of the language spoken around them, a pruning process linguists call perceptual reorganisation.

Between six and twelve months, every baby's brain quietly narrows a global sound inventory down to the phonology of the language spoken around them — a pruning process that shapes what they will be able to hear for the rest of their life. The post At six mont…