By Arisa, Ok i'm finally updating.
Source memories, also called psuedomemories; It's mostly experienced by systems, specifically introjects.
Ok, but what ARE source memories?
Essentially, source memories are fake memories. They are memories that an alter remembers yet the body did not experience. They can be about anything, really... for example, I find that some introjects (based off my friends) have source memories of other people from their source's media. Even though these memories didn't happen, the alter will remember it as if it did.
Source memories are not always clear, i also find that a lot of people have distorted or blurry source memories... where they can't really remember the whole memory well, but they remember small parts about it.