This course covers a number of key questions related to research in developmental disorders of communication and cognition. Each lecture will consider how researchers attempt to answer these questions, using a different developmental disorder to illustrate the approach. The course is situated in the causal model approach to understanding developmental disorders, focusing on biological, cognitive and behavioural levels of explanation and how these interact with each other and with the environment to yield a heterogeneous clinical profile. Disorders covered included Developmental Language Disorder, Reading Disorders, Autism Spectrum Disorder, Attention Deficit Hyperactivity Disorder, Down syndrome, William syndrome and Reading Disorders. We will address questions such as ‘how are language and non-verbal cognition related?’ ‘why is language ability so variable in autism?’ and ‘why do children with the same condition have such variable outcomes?’