i seem to have lost it at some point in adulthood. i have no idea when.
i started doing it again while using drugs, and this caused me to become aware that i'd lost an ability i once had. it was very hard to explain to people what this ability was, but i rememberd being able to visualize fantastically complex scenes in my head, as a kid, and getting some sense of this back while high.
in the past i could imagine any complex system of gears - like a clock, and zoom in and look at any part of it.
it's like the projector bulb is broken. an image flashes and goes away.
has anyone found a way to redevelop this?