I really don't know. I heard about a year ago that some beleived that some humans were born or created that had no souls...literally. It was not that they were hiding their souls or souls so wounded that they were acting out of pain either. I wish I could remeber the name or word that was attributed to this but I can't, sorry. It was my understanding that these humans were created to exist almost like drones... but "drones" was not the word.
In regards to psy vamps... maybe some but not all. I know some psy vamps are just the walking wounded and others take great joy and pleasure at feeding off of others... maybe the latter could be without a soul but if they had no soul, then would they have emotion even if it was joy at the expense of others?