It's not common to associate dogs with mental health issues but some of our pooches are displaying symptoms, from compulsive behaviours and chronic fears to unusual behaviour like traffic-chasing. Applying the latest technology, using surveillance filming and working with the UK's top behaviourists, Dogs: Their Secret Lives looks into the minds of our dogs and meets three troubled pets - Max, the spinning German shepherd, compulsive bus-chasing collie Biscuit, and Roxy the Staffordshire bull terrier, who's terrified of the great outdoors - to find out what could be at the root of their problems and how to help them. Mark Evans explores the latest brain scanning experiments, meets dogs with incredible learning abilities and finds out about the latest medications as he investigates the challenges facing the 21st-century dog.