Scientists who study memory phenomena generally believe that eidetic memory (more popularly known as “photographic memory”) does not exist.
Early experiements on eidetic memory were intriguing, but could not be replicated.
People do show extraordinary memory performance in certain circumstances. For example, expert chess players can typically play blindfolded chess against several opponents at the same time, easily memorizing many chessboard configurations. Others use special tricks to memorize long lists of randomly selected numbers.
Impressive as these feats are, scientists attribute them to specialized ways of thinking about the information, not to any kind of enhanced visual memory. One interesting experiment that makes this point was performed by a cognitive psychologist named DeGroot.
Expert chess players were shown a chess board with pieces on it for a brief period, such as 15 seconds, and then asked to reconstruct what they had seen on a new chess board. That is, they were asked to place chess pieces in the same positions as they had appeared on the board they’d been shown. The expert players were very good at this, much better than novice players. One hypothesis was that the experts had developed an enhanced ability to memorize visual information.
In the next experiment, the expert chess players were asked to do the very same thing; butt this time, they were shown boards whose pieces were arranged in ways that would never actually occur in a game of chess. Not only did their ability to remember the positions go down, but it went down all the way to the level of the novice players. We can conclude that the original, enhanced performance at remembering chess positions came from the experts’ ability to mentally organize the information they had observed, not from any ability to “photograph” the visual scene.
Because only isolated examples of eidetikers (people who are capable of eidetic imagery) have been found, there doesn’t seem to be any explanation for how such a phenomenon works neurologically. According to a well-accepted theory of memory, the first step in memory storage is sensory memory. Generally, information is stored here only very briefly, and is either lost entirely, or, if given proper attention, processed further. While still in the sensory memory, visual information is believed to be stored as an actual image. Any further processing is thought to change visual information into conceptual information. The chess player, for example, no longer sees the actual chess board, but rather an internal, abstract concept of a chess board. Since photographic memory involves seeing visual images, it must be on the very basic sensory level that eidetic memory functions.
Is it possible then that something in the brains of these so-called eidetikers has been wired differently, causing traces of memory that should only last mere seconds to remain in a person’s memory for minutes, hours, or, in cases like S or Elizabeth, years? Absolutely. Memory is believed to be facilitated by changes at the neuronal level due to long-term potentiation. This phenomenon is essentially the strengthening of synaptic efficiency through repeated use over time, producing long-term memories. Normally, this type of induction takes several rounds of stimulation in order to produce the increased proficiency of the neural circuit. It is conceivable that in a small portion of the population, genetic or environmental factors that have yet to be discovered lower the threshold for this potentiation, resulting in sensory memory that remains stored as a visual image instead of being lost or processed conceptually. Multiple stimulations would not be necessary to retain these images; one brief presentation of a stimulus would be sufficient.
Such a perspective on the neurological basis for eidetic memory would explain many of the unanswered questions on the topic. Photographic memory may be so rare that it appears to be fictional because it is the result of an uncommon genetic mutation or an unlikely combination of environmental and genetic factors. The greater prevalence of photographic memory in children can by explained by the re-appropriation of neurons from sensory memory circuits to verbal memory circuits as verbal behavior increases. That it is an event linked to sensory memory, and not episodic (autobiographical) memory explains why emotional or experiential ties to the object do not increase memory for it.