Eidetic memory is the medical term, and is an established medical fact. The SHORT-TERM storage of sensory data is commonly observed, especially in children. It is also documented (although less rigorously so) in cases of “sporadic eidetic memory”, often in response to traumatic events. These sporadic occurrences are not triggered consciously in most cases, and are therefore difficult to study. And, as they tend to present in traumatized individuals, would present ethical challenges in being studied as well.
Most interesting, of course, would be* long term *eidetic memory that would be *of use *to the person possessing such a skill. And this is where the scientific record is silent. In the 18th & 19th centuries, some Lithuanian rabbis were famous (or infamous) for true photographic memory, which they used in the study of Torah. This has been subsequently reported in some Polish rabbis of this century. It’s not hard to imagine why such individuals might not bother to be the subject of a “scientific” study. But in the absence thereof, it is difficult to know if this represented some qualitatively different mental process, or was just the result of having looked at the pages of their Beloved Torah so many times, that any good memory might have acheived the same level of memorization.
I suspect that eidetic memory, which can be other than visual (although the word, itself, comes from the Greek word for “seen”) IS a special process. I say this for two reasons. 1) It does not seem reasonable to me that what is true in the traumatized brain is impossible in the non-traumatized brain (if there is such a thing), and 2) I personally have a peculiar gift for auditory information. It got me through some medical school tests for which I had not studied but could close my eyes and literally hear the professor talking about whatever word was salient for a particular question. It allows me to recognize what recording of a particular piece of music I am listening to in a few notes. And it facilitates the learning of foreign languages (in that I can memorize expressions that mean absolutely nothing to me. For this latter reason, I suspect that the ability to learn languages (and games; and see mathematical patterns) is at least soemwhat related to this understudied phenonoma. One of the reasons it IS understudied is because the most successful mnemonists (is that the word?) do NOT rely on such methods, but rather on other, much better studied techniques which lend themselves to much greater success in contests, partly because it is a memory that is fueled by activity in the motivation centers of the brain. Those with eidetic memory are stuck with a head full of details and experiences that are of no apparrent value.