Children's second-order lying: Young children can tell the truth to deceive.

The current study investigated the development of second-order lying and its relation to theory of mind and executive function. Previous studies have examined only first-order lying, in which a child makes an untruthful statement to intentionally deceive an unsuspecting opponent. As opposed to first-order lying, second-order lying requires the use of both lies and truths to deceive an opponent because the opponent is fully aware of the liar's deceptive intention. Here, we used a modified hide-and-seek task, in which children were asked to hide a coin in either one of their hands for opponents to find. In this task, the opponents did not consistently look for the coin in the location indicated by the children. Thus, children could not win the desirable reward if they only told lies to deceive; they needed to switch between telling lies and telling truths (i.e., second-order lies) to deceive opponents. The results showed that children could tell second-order lies by 4 years of age, and their ability to do so was significantly related only to the second-order ignorance scores (early second-order theory of mind understanding). The current findings suggest that second-order ignorance, but not second-order false belief understanding, contributes to children's second-order lying.