Your phone rings. But when you pick up, you don't recognize your mother's voice on the other end. It's not amnesia, but phonagnosia -- the inability to recognize voices. If you've never heard of it, that's because it's a very rare condition that usually occurs after a stroke, as a result of lesions in the right hemisphere of the brain. This week, however, scientists at University College London (UCL) reported the first known case of a woman born with phonagnosia in the online journal Neuropsychologia.