Ninety-one children aged between 2;10 and 5;0 participated in a training study of false belief. Children were assigned to either an explanation condition, a practice condition or a control condition where children heard two stories unrelated to false belief. Children's eye movements in anticipation of the protagonist reappearing were monitored at pre-test.Only the explanation condition led to improvements in judgement and justification of a protagonist's future action based on false belief. Children who looked in anticipation to where the protagonist thought the object was at pre-test were more likely to give a correct judgement at post-test than those who did not. Those children in the explanation group who gave a correct judgement at pre-test were more likely to give an appropriate justification at post-test than those who did not.Three main conclusions are drawn: (1) providing explanation about the underlying principles of a task is more likely to lead to improvements in performance than merely informing children of whether their response is correct; (2) the nature of improvements in performance will depend on the level of knowledge of the child at pre-test; (3) training will only be beneficial for those children who demonstrate evidence of implicit understanding.