Three-year-olds' understanding of mental states: the influence of trickery.

This study examined the claim that children under 4 cannot conceptualize false mental states. Fifty-one children between 3;0 and 4;2 were tested in a Standard and a Trick Condition. In the Standard Condition, children were given a modified version of the Smarties task developed by Hogrefe, Wimmer, and Perner (1986). In the Trick Condition, the Smarties task was modified so that children were required to trick another person by switching the contents of a familiar box. Results revealed that a majority of subjects responded correctly to Ignorance and False Belief Questions in the Trick Condition, but not in the Standard Condition. There were no differences in children's ability to attribute ignorance and false belief. These results suggest that even young 3-year-olds have the ability to attribute mental states that differ from their own, even though this ability has proved elusive and difficult to demonstrate.