We know perfect pitch but we forget that memory, even if it is extremely rare, can also be absolute.

Some individuals have the ability to store in their memory a large quantity of images, sounds, objects in their smallest detail. It would give the individual the ability to maintain for a short time, an almost perfect memory of an image presented for about 30 seconds as if the image were still being perceived.

As with any other memory, the intensity of the memory depends on several factors such as:

• the duration and frequency of exposure to the stimulus;
• conscious observation;
• the relevance of the person;
• etc.

We speak of absolute memory, photographic memory or even eidetic memory, from the Greek “eido”, which means “to see”, eidos, form. Eidetic imagery is far from perfect, as it is prone to distortions and additions, like episodic memory. For Alan Searleman, professor of psychology (St Lawrence University, New-Yort St), it’s not unusual for people with eidetic memories to alter or invent visual details. This suggests that eidetic images are certainly not photographic in nature, but rather are reconstructed from memory and can be influenced like other memories (both visual and non-visual) through cognitive biases.

The very existence of eidetic memory is controversial. If it exists, is this memory innate or acquired. Adrian de Groot (1914-2006), Dutch psychology professor and great chess player, debunked the myth by conducting an experiment on the ability of great chess champions to memorize the complex positions of pieces on a set. The champions were able to remember surprising amounts of information much more than in the case of amateurs. This experience thus comes to the support of the eidetic memory. But after showing the champions impossible part layouts in real games, the accuracy of their memories was similar to that of amateurs. This meant that the champions had developed an ability to memorize to predict rational game compositions rather than being the holder of an absolute eidetic ability.

For ten years, researcher Ralph Norman Haber studied the memory of children aged 7 to 11. Eidetic memory exists in a small percentage of children. Surprisingly, children with eidetic memories spoke of the image in the present tense, as if it was always in front of them, imprinted in their brains. According to Professor Andy Hudmon (Department of Neurobiology, Stanford), this much greater eidetic memory capacity in children than in adults suggests that a developmental change occurs at some point, perhaps at the time of l acquisition of certain skills, which would disrupt the potential of eidetic memory.

Most scientists attribute extraordinary memory performance to an increased ability to associate or organize information to be memorized, rather than to true eidetic memory.

For example, many expert chess players have a remarkable ability to recall the position of chess pieces at any time during a game. The ability to maintain an accurate mental picture of the chessboard allows these players to play multiple chessboards at once, even if they are blindfolded. It was therefore not surprising that the researchers observed that expert chess players have a much greater ability to remember chess patterns than test subjects who do not play chess. However, while researchers challenged expert chess players with radomically generated board models, expert players were no better than novice chess players at recalling chess models. So, by changing the rules of the game, the researchers revealed that the remarkable ability of these players to memorize visual information specific to chess (perhaps the very reason why these individuals are good at chess) was not the equivalent of photographic memory. People with true eidetic memory should by definition be able to assimilate and remember in perfect detail even random visual scenes.

While certainly controversial, some researchers also believe that eidetic imaging occurs more frequently in certain populations of the mentally retarded (particularly, in individuals whose delay is most likely due to biological rather than environmental causes) and also among geriatric populations.

Kim Peek, an American with Asperger’s Syndrome (a neurodevelopmental disorder of genetic origin), who inspired the character of Raymond Babbitt, the hero of the movie Rain man and played by Dustin Hauffman, had eidetic memory and had memorized over 10 books. It took ten seconds to read a page. A true living encyclopedia, his ability to memorize hallucinating amounts of information has also allowed him to turn into a real human GPS, regardless of the city on the planet in which he was.

Another champion of memory, Stephe Wiltshire, dubbed “the camera man”. Autistic with eidetic memory, he is known for his ability to draw a landscape in great detail after seeing it in a flash. Be careful, eidetic memory is a special type of memory. It should not be confused with hypermnesia or exaltation of memory. The latter is a psychopathology characterized by an extremely detailed autobiographical memory and an excessive amount of time devoted to recalling one’s past.