James McGaugh is one of the world's leading experts on how the human memory system works. But these days, he admits he's stumped.
McGaugh's journey through an intellectual purgatory began six years ago when a woman now known only as AJ wrote him a letter detailing her astonishing ability to remember with remarkable clarity even trivial events that happened decades ago.
Give her any date, she said, and she could recall the day of the week, usually what the weather was like on that day, personal details of her life at that time, and major news events that occurred on that date.
Like any good scientist, McGaugh was initially skeptical. But not anymore.
"This is real," he says.