Reduced Neural Selectivity for Mental States in Deaf Children with Delayed Exposure to Sign Language

Language provides a rich source of information about other people’s thoughts and feelings. Consequently, delayed access to language may influence conceptual development in Theory of Mind (ToM). We used functional magnetic resonance imaging and behavioral tasks to study ToM development in child (n=33, 4-12 years old) and adult (n=36) fluent signers of American Sign Language (ASL), and provide the first characterization of neural ToM responses during an ASL task. Participants included deaf children whose first exposure to ASL was delayed up to 7 years (n=12). Neural responses to ToM stories (specifically, selectivity of the right temporo-parietal junction) in these children resembled responses previously observed in young children, who have the same amount of linguistic experience, rather than those in age-matched native-signing children, who have the same amount of biological maturation. These results suggest that early linguistic experience facilitates ToM development, via the development of a selective brain region for ToM.