But there are exceptions. In 1970 Psychology Today reported on Elizabeth, a Harvard instructor. The next day, using her left eye, she looked at a second grid of 100 x 100 dots. She then mentally merged this grid with the remembered one into a 3-D image that most people needed a stereoscopic viewer and both grids to see. Reportedly she could recall eidetic images of a million dots for as much as four hours.
Children have the edge, no doubt, because they lack an adult's competing mental clutter.
A means of organizing data seems to be the key to all superior memory, eidetic or otherwise. For example, expert chess players can re-create a board position involving two dozen pieces with great precision due to their knowledge of the game. But if the pieces are placed randomly on the board, the expert players' recall is no better than a novice's. To some extent the ability to remember can be learned, although the result isn't photographic memory but simply improved recall. Even mnemonists, known for impressive feats of memory, enhance their native talent with tricks.