Why Do We Dream?

Adventures in Dreamland "Why do we dream and why do we repeat dreams?" asks Mila O'Dea, aged 9, from Panama. Hannah Fry and Adam Rutherford delve into the science of sleep. From a pioneering experiment on rapid eye movement sleep, to a brand new 'dream signature' found in the brain, they discover how scientists are investigating our hidden dreamworld. Featuring sociologist Bill Domhoff from the University of California Santa Cruz, sleep psychologist Mark Blagrove from the University of Swansea, and neurologist Francesca Siclari from the University of Lausanne. The Curious Face-Off "Are machines better than humans at identifying faces?" asks the excellently named Carl Vandal. Today’s Face Off leads our intrepid detectives to investigate why we see Jesus on toast, Hitler in houses and Kate Middleton on a jelly bean. Face perception psychologist Rob Jenkins from the University of York explains why we're so good at spotting familiar faces, like celebrities. Plus, Franziska Knolle from the University of Cambridge discusses her face recognition study involving Barack Obama and a group of highly-trained sheep. But are we outwitted by artificial intelligence when it comes to face ID? BBC technology correspondent Rory Cellan-Jones gives us the low-down on the pros and cons of current technology. Picture: Child sleeping, Credit: Quintanilla/Getty Images Producer: Michelle Martin