Young children learn fast about what works and what does not work. Lacking the physical ability to get what they want, they discover natural guile and soon start lying in order to avoid punishment, receive rewards and get their siblings into trouble.
Early deceits are obvious, such as when a child holds something behind their back as they say they do not have it. Before long, however, they learn to hide it somewhere else and put on a surprised and insulted look when their parents dare accuse them of wrong-doing. In fact when children are punished for lying, rather than doing it less, they often just get better they get at it.