But the cousins are also inside us. We all contain the capacity for tyranny. 8-month-olds prefer to play with a puppet they’ve seen punishing a transgressor in a puppet show. Children start enforcing rules spontaneously at around age 3. A study into the reasons schoolchildren, aged between 5 and 7, reject playmates found a tendency to do so when their behaviour became a threat to the status of themselves or their clique.
