Children are able to identify when an adult is lying or not telling the whole truth.

The children were told by a teacher that a toy performed just one of the four functions that it actually performed. Some of the children who were familiar with the toy explored it much more thoroughly than children who had seen a complete demonstration, suggesting that they did not trust the teacher.
“When someone provides us information, we not only learn about what is being taught -- we also learn something about that person. Children can also evaluate others based on who is providing information that is enough or not enough for accurate inference. They can also adjust how they learn from a teacher in the future, depending on whether the teacher has previously committed a sin of omission or not”, lead researcher Hyowon Gweon said.
Source-Medindia