The classic false belief task (with its numerous versions) is considered the main instrument for assessing the children's abilities to reason on other person's beliefs. It is the task most frequently used for the study of social-cognitive abilities development. Despite these, last years researches show that this task is inadequate for the study of this domain. This inadequacy is manifested at many levels. According to one of these levels, excessive processing requests of the task leads to incorrect answers from children and to failure at this task, while they have the necessary abilities at the conceptual level. The aim of the study is to show that negation, as a supplementary cognitive step, is one of the excessive requests at the performance level, which is not relevant for children's abilities to reason on the content of beliefs. The results sustain this inference.
Keywords: children's knowledge about the mind, false belief task, negation, affirmation