Young children discover how to deceive in 10 days: a microgenetic study.

We investigated how the ability to deceive emerges in early childhood among a sample of young preschoolers (Mean age = 34.7 months). We did this via a 10-session microgenetic method that took place over a 10-day period. In each session, children played a zero-sum game against an adult to win treats. In the game, children hid the treats and had opportunities (10 trials) to win them by providing deceptive information about their whereabouts to the adult. Although children initially showed little or no ability to deceive, most spontaneously discovered deception and systematically used it to win the game by the tenth day. Both theory of mind and executive function skills were predictive of relatively faster patterns of discovery. These results are the first to provide evidence for the importance of cognitive skills and social experience in the discovery of deception over time in early childhood.