So, we see that the virtue of truthfulness is connected to the need for justice in relationships. Justice is most simply defined as giving someone their 'due' in a relationship. Perhaps that's why every world religion has prohibitions against lying. All see a value in truth. From the Christian perspective, truth is central, said Nothwehr, and Jesus is the model for telling the truth despite all consequences.
Truth leads to genuine living.
Children are very savvy in using deceit to preserve and maintain relationships. They learn that this behavior helps avoid conflict. They also weigh the consequences of getting caught. In deciding to tell the truth or lie, children think through what the other person might think if they find out. They understand the trust issues that are involved.