The effect marijuana
has on memory ought to be studied more thoroughly. Obviously it adverse
ly affects short term memory, but continuing observations report easy traversal through long term memory
(and shifted perception of space) while on it.
Time effects while stoned aren't uncommon with me or my friends, although we have observed a different manifestation of this effect. It is possible, when properly stoned, to imagine oneself in a different time of one's life, in the same settings. For example, if your girlfriend's apartments living room looks similar to that in which you grew up, walk into it and imagine being in the old apartment. Vivid snipplets of memory will come back to you, and you will seemingly find yourself in the old apartment living room. Music can do the same thing, even more rapidly -- for example, a music piece I associate with my Uncle's study brings back the smells and "vibe" of the place.
In the same manner, it is easy to affect one's perception of space while on it. Basically, if you tell yourself that there is a wall beside your head, you will perceive that there is a wall just out of your field of view.