Matched false-belief performance during verbal and nonverbal interference.

Language has been shown to play a key role in the development of a child's theory of mind, but its role in adult belief reasoning remains unclear. One recent study used verbal and nonverbal interference during a false-belief task to show that accurate belief reasoning in adults necessarily requires language (Newton & de Villiers, 2007). The strength of this inference depends on the cognitive processes that are matched between the verbal and nonverbal inference tasks. Here, we matched the two interference tasks in terms of their effects on spatial working memory. We found equal success on false-belief reasoning during both verbal and nonverbal interference, suggesting that language is not specifically necessary for adult theory of mind.