Why do humans have such a long period of immaturity? And how have our ideas about childhood changed through the ages and across the world? Bridget Kendall explores some of the key moments and figures in the history of childhood, including Confucian China, Victorian factories and the 'endless childhood' that some young people seem to be living today. Her guests are Alison Gopnik, Professor of Psychology and Philosophy at the University of California, Berkeley; Ping-chen Hsiung Professor of History at the Chinese University of Hong Kong; and Hugh Cunningham Professor of Social History at the University of Kent. Photo: a young girl walks through an entrance to a walled garden (BBC)