On the relationship between theory of mind and syntax in clinical and non-clinical populations: State of the art and implications for research

Background: Over the years different explanations have been given on the relationship between syntax and Theory of Mind, i.e., the ability to attribute mental states to others and predict, describe, and explain behavior based on such mental states. In the present study we focus on the relationship between false-belief understanding as a crucial aspect of Theory of Mind, and on the ability to master the syntax of complementation, i.e., the ability to produce and comprehend sentences in a recursive way. Objective: Our purpose is to test two main hypotheses on the relationship between false-belief understanding and the ability to master the syntax of complementation: the dependence and the independence of false-belief understanding on syntactic complementation. Method: We analyze studies on children with typical development, deaf children with deaf signing or hearing parents, children with specific language impairment, children diagnosed with autism spectrum disorder, longitudinal and training studies, and studies on adults with neuropsychological disorders. Conclusion: Strengths and weaknesses of the two hypotheses are discussed and limitations of the current state of knowledge are presented. A life span approach taking into account both the emergence and maintenance of false-belief understanding and using both implicit and explicit false-belief tasks is proposed to face the issue discussed.