If I remember psych course on memory -- eidetic memory appears more
prevelantly in groups without written languages. Specifically, I remember
(g) a study done on a pre-literate hunter/gatherer tribe (sorry, can't be
more specific than that). Many in this tribe had true eidetic memory.
The researchers theorized that this resulted from the need to learn subtle
differences in a rather undifferentiated landscape when hunting for long
Also, I believe that eidetic memory is more prevelant generally in
children under the age of 8.
By the way -- Luria's book Mind of a Mnemonist is a BRILLIANT book -- and
a classic piece of science writing. What is touching about the story is
that Luria's subject -- who had the greatest memory ever recorded --
benefited little with this rare skill. He ended up becoming a nightclub
entertainer. His memory skills did not help his intellect (which was
modest) -- and even got in the way of symbolic thinking. Everything for
him was literal -- he had trouble imagining -- because he could recall
every incident with incredible detail. He could recite 500 page novels
from memory -- but had no insights into what the novels meant. Borges
wrote a wonderful short story based on Loria's subject.