Language and False Beliefs of School-Aged Children With Developmental Language Disorder

A significant association between neurotypical (NT) children's language abilities and theory of mind (ToM) false belief (FB) skills has been reported in the literature. Older school-aged children with developmental language disorder (DLD) are characterized by impaired language, yet their FB ToM skills show mixed results. This study aimed to shed light on whether FB skills are affected in children with DLD by investigating two related factors: task modality (verbal [V] vs. nonverbal [NV] mode of assessing ToM) and the potential impact of language abilities on FB performance.

A total of 50 NT children and children with DLD (n = 25 each group) aged 9-11 years completed a first- and a second-order ToM task (true beliefs and FBs) in V and NV modes. The groups were matched on age and gender. Children were further evaluated via online one-on-one sessions for morphosyntax, vocabulary, working memory, and NV intelligence quotient.

The findings revealed that children with DLD scored lower than did NT children on FBs, and most importantly, they scored similarly in the V and NV modes. Furthermore, children's complement clauses were positively correlated with FBs and emerged as the only significant predictor of FBs in generalized linear mixed-model analyses. As expected, performance on second-order FBs was harder than on first-order FBs.

The findings demonstrated that school-aged children with DLD have difficulties in FBs, which do not stem from the modality of the task assessing them when the task does not include complex language. Moreover, out of all sentences children produced, complement clauses were intimately related to their FB skills. These are important findings for the relation of language and FBs, as well as for clinical purposes, as FB skills are crucial for successful communication and hence should be considered carefully in language-impaired populations.