Interpretation of ambiguous pronouns in adults with intellectual disabilities

Background Pronouns are referentially ambiguous (e.g. she could refer to any female), yet they are common in everyday conversations. Individuals with typical development (TD) employ several strategies to avoid pronoun interpretation errors, including the subject bias - an assumption that a pronoun typically refers to the subject (or, with the closely related order-of-mention bias, the first-mentioned character) of the previous sentence. However, it is unknown if adults with intellectual disability (ID) share this strategy or the extent to which the subject bias is associated with non-verbal abilities or receptive vocabulary. Methods We tested 22 adults with mixed-aetiology ID on their interpretation of ambiguous pronouns using the visual world eye-tracking paradigm and by asking a follow-up pronoun interpretation question. A group of TD adults was also tested to establish the strength of the subject bias with our materials and task. Results Adults with ID did demonstrate the subject bias, but it was significantly less robust than that seen in TD. For participants with ID, the subject bias was influenced by non-verbal IQ and receptive vocabulary at different stages of processing. Conclusions Given the frequency of pronouns in conversation, strengthening the subject bias may help alleviate discourse and reading comprehension challenges for individuals with ID, particularly those with lower non-verbal and/or vocabulary skills.