By developing theory of mind ability, children are able to represent human beliefs and therefore, understand and predict their behavior. Language plays an important role in developing children's theory of mind and their performance in false belief tasks. There are two main approaches explaining younger children ’ s failure in false belief tasks. First, it is believed that 3 year-olds lack the conceptual ability to represent false beliefs (Conceptual Deficiency Theory). Second, it is assumed that undeveloped language capacities mask 3 year-olds' theory of mind abilities (Performance Limitation Theory). In the present study, the assumptions of these two approaches have been investigated. Participants (111 three and four year-olds) were tested in two verbal and pictorial false belief tasks ( “ standard ” and "Look First") and a conversational awareness task. The findings showed that both 3 and 4 year-olds performed significantly better on the facilitated false belief tasks (Look First) than standard false belief tasks. There was also a significant correlation between children's performance on false belief and conversational awareness tasks. Results are in favor of the Performance Limitation Theory. The 3 year-olds' failure in false belief tasks seems to be the result of their undeveloped language ability, not due to their conceptual inability to represent false beliefs. It is necessary to take children's language ability into account in any assessment and explanation of theory of mind.

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