Answer:
The researcher is testing Charlotte's grasp of false beliefs.
Explanation:
False belief task is a mental task given to an individual and is based on the understanding of a wrong belief of a situation that may contrast with reality.
It is the ability of a person to understand people's understanding of a particular thing that is may be different for different individuals. The knowledge, desires and beliefs of one's own may be different to that of others.
Thus when the researcher asks Charlotte where she thinks Russel, a puppet will search for the crayons in which box, he is trying to test Charlotte's grasp of false beliefs.
Therefore the answer is --
The researcher is testing Charlotte's grasp of false beliefs.