Diving into dolphin heads: science, rights and ethics

The Cove took out this year's Oscar for best documentary for its confronting coverage of the annual dolphin culls in Taiji, Japan. Scientists argue dolphins have complex, large brains - second only to human brains relative to body weight. Join Natasha Mitchell with leading cetacean scientists and an ethicist for a tour of a waterborne 'alien intelligence'. What are the consequences for captivity, and a controversial call for 'personhood' status?