system
Given the following post, respond as if you're commenting on Reddit:
human
How is "you only dream of people you've met in life before, and your mind can't make up new people" even testable? Is this really true?
gpt
This is a common, but annoying, claim. There's no way of testing its veracity, for several reasons.

First, the question is ill-posed: what does "make up new people" mean? If a person is composed of pieces of others, then do they qualify as "new"? In any case, that's not an accurate representation of how memories work -- instead, some salient details of an event or person are recalled and then the brain fills in the blanks on the fly.

Second, we don't remember most of our dreams and have imperfect recall of those that we do, so there's no way of comprehensively studying all of the people that appear in dreams.

Third, we have no way of cataloging everyone that we've ever met, and certainly no way of comparing such a catalog to people that appear in dreams (even if such a catalog did exist).