In the early 1980s deaf children in Nicaragua invented a completely new sign language of their own. It was a remarkable achievement, which allowed experts a unique insight into how human communication develops. Mike Lanchin has been speaking to American linguist Judy Shepard-Kegl, who documented this process and says "our belief is that you are born with a language-ready brain".
(Photo credit should read INTI OCON/AFP via Getty Images)
