Drawing from memory: some thoughts on the Stephen Wiltshire experience

Have you ever been asked on the spot to draw someone a map for directions to your place or somewhere else? In the video below, Steven Wiltshire takes this to a whole new level. Having flown over the city of Rome once, he's able to sketch and reproduce it from memory in amazing detail and accuracy.



The difference between most of us and Steven is that he is able to re-access that information directly from his mind with very little distortion whereas in many other people's case our attention is so selective that only certain details will be recalled -- details with which we probably made other mental associations with. It seems that with each association our view and memory becomes increasingly more subjective.

For me this brings up an interesting question: Is everything we see is recorded and physically etched in our minds at that moment, only later to be recalled (or not), or is the filtering mechanism that prevents us from accessing exact information made at the time of perception? In other words is Steven's perception so clear (and free from association) from the beginning that the raw data in his mind is somehow more accurate that in other people (or for example compared to the pilot that flew with Steven), or do we all record absolutely everything only later to experience various degrees of accessibility?

As I use to teach drawing, I noticed that many students would "draw from memory" even when sketching a still life. They would glance up at the still life, make sure it was still there, and look back to their paper and draw what they remembered seeing. This would create a wide range of inaccuracies and variations based on individual perspectives of the same still life, which of course was very interesting and not "wrong" in the least, BUT were they really looking at the still life and recording it directly into their memory or did they already begin to project their associations directly onto what they were seeing, and in effect influencing the information that was being recorded in their minds?