Some studies report delayed theory of mind (ToM) development in children with specific language impairment (SLI), while others do not. A ToM delay is acknowledged in children with autism spectrum disorder (ASD), while whether these children also display a deficit is still under debate. In the current study, we drew on a developmental trajectory approach to assess whether children with SLI or ASD displayed delays or deficits in their ToM performance. Forty-three children with SLI (age 4–10 years), 44 children with ASD (age 5–12 years), and 227 typically developing children (age 3–11 years) completed the ToM Storybooks. Children with SLI were not found to display either a delay or a deficit in ToM, while children with ASD were found to display a deficit.
