What’s it like to face a faceless world? Acclaimed neurologist Oliver Sacks once apologized for almost bumping into a large bearded man, only to realize he was speaking to a mirror. Sacks and photorealist painter Chuck Close—geniuses from opposite ends of the creative spectrum—share their experiences of living with a curious condition known as “face blindness,” or prosopagnosia. With RadioLab’s Robert Krulwich, they discuss the challenges of maintaining interpersonal relationships—when even family and close friends appear as strangers.