The relationship between syntactic development and Theory of Mind: Evidence from a small-population study of a developmental language disorder

We investigated whether performance on false belief understanding tasks is related to language ability by looking at Russian-speaking children enrolled in a study of a developmental language disorder in a geographically isolated small population characterized by a high prevalence of developmental language disorders. All consenting children between the ages of 6 and 12 (n = 54) were given the Assessment of the Development of Russian Language (ORRIA), non-verbal IQ, short-term memory measures, a narrative task, and the Unexpected Transfer task of false belief. We found that language development scores were related to success on the false belief task even when controlled for IQ and short-term memory. Also, the group who succeeded on the false belief task had significantly higher syntactic complexity scores for narratives than those who failed it. References to mental states, manifested by the children's use of mental, psychological and perception verbs, were not related to performance on the false belief task. These findings support the hypothesis that developed representations of false belief are tied to syntactic development, not general cognitive functioning or the acquisition of mental-state verbs.