I developed what appears to be a photographic memory when I was 16 years old. Does this kind of memory truly exist, and, if so, how did I develop it?

—Peter Gordon, Scotland

Barry Gordon, a professor of neurology and cognitive science at the Johns Hopkins University School of Medicine (and no relation), offers an explanation:

The intuitive notion of a “photographic” memory is that it is just like a photograph: you can retrieve it from your memory at will and examine it in detail, zooming in on different parts. But a true photographic memory in this sense has never been proved to exist.

Most of us do have a kind of photographic memory, in that most people's memory for visual material is much better and more detailed than our recall of most other kinds of material. For instance, most of us remember a face much more easily than the name associated with that face. But this isn't really a photographic memory; it just shows us the normal difference between types of memory.

Even visual memories that seem to approach the photographic ideal are far from truly photographic. These memories seem to result from a combination of innate abilities, combined with zealous study and familiarity with the material, such as the Bible or fine art.

Sorry to disappoint further, but even an amazing memory in one domain, such as vision, is not a guarantee of great memory across the board. That must be rare, if it occurs at all. A winner of the memory Olympics, for instance, still had to keep sticky notes on the refrigerator to remember what she had to do during the day.

So how does an exceptional, perhaps photographic, memory come to be? It depends on a slew of factors, including our genetics, brain development and experiences. It is difficult to disentangle memory abilities that appear early from those cultivated through interest and training. Most people who have exhibited truly extraordinary memories in some domain have seemed to possess them all their lives and honed them further through practice.

Various parts of the brain mature at different times, and adolescence is a major time for such changes. It's possible Mr. Gordon's ability took a big jump around his 16th birthday, but it's also possible he noticed it only then. Mr. Gordon might want to have formal testing, to see just how good his memory is and in what areas. Then we can debate the nature-nurture question from harder evidence.